Oxandrolone, an anabolic agent, has been administered for 1 year post burn with beneficial effects in pediatric patients. However, the long-lasting effects of this treatment have not been studied. This single-center prospective trial determined the long-term effects of 1 year of oxandrolone administration in severely burned children; assessments were continued for up to 4 years post-therapy.
Study Design
Patients 0–18 years old with burns covering >30% of the total body surface area were randomized to receive placebo (n=152) or oxandrolone, 0.1 mg/kg twice daily for 12 months (n=70). At hospital discharge, patients were randomized to a 12 week exercise program or to standard of care. Resting energy expenditure (REE), standing height, weight, lean body mass, muscle strength, bone mineral content (BMC), cardiac work, rate pressure product (RPP), sexual maturation, and concentrations of serum inflammatory cytokines, hormones, and liver enzymes were monitored.
Results
Oxandrolone significantly decreased REE, RPP, and increased IGF-1 secretion during the first year after burn injury, and in combination with exercise significantly increased lean body mass and muscle strength. Oxandrolone-treated children exhibited improved height percentile and BMC content compared to controls. The maximal effect of oxandrolone was found in children aged 7–18 years. No deleterious side effects were attributed to long-term administration.
Conclusions
Administration of oxandrolone improves the long-term recovery of severely burned children in height, BMC, cardiac work and muscle strength; the increase in BMC is likely to occur by means of IGF 1. These benefits persist for up to 5 years post burn.
Keywords: Burn, oxandrolone, children, height, bone mineral content, hypermetabolic response, hypercatabolic response, resting energy expenditure
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INTRODUCTION
Burn injury induces a hypermetabolic response that is characterized by elevations in cardiac work, metabolic rate, and muscle catabolism. Increased protein breakdown coupled with inadequate protein synthesis leads to muscle weakness and a loss of lean body mass (LBM). [1] Post-burn catabolic effects are not limited to muscle, as bone mineral content (BMC) and fat mass are decreased as well. This hypermetabolic response persists for up to 2 years after burn injury, greatly reducing the quality of life of severely burned patients. [2]
Oxandrolone, a synthetic oral non-aromatizable testosterone derivative, has only 5% of the virilizing activity and lower hepatotoxicity when compared to testosterone. Following administration, oxandrolone reaches peak serum concentrations within one hour and is excreted through the urine. Oxandrolone binds to androgen receptors in the skeletal muscle to initiate protein synthesis and anabolism. Because oxandrolone cannot be aromatized to estrogen, the likelihood of estrogen-dependent bone age advancement is reduced, making oxandrolone a safe therapeutic approach for growing children. [3–5]
In children with Turner’s syndrome and other growth-related conditions, oxandrolone has been successfully for many decades to safely treat growth delays. [6–10] More recently, oxandrolone has been used to induce anabolism in patients experiencing muscle wasting associated with AIDS, major surgery, infections, malnutrition, neuromuscular disorders, or thermal injury. [11–12] Oxandrolone is the only androgenic steroid approved by the Food and Drug Administration to maintain body weight in these catabolic states. [3] These studies have demonstrated that oxandrolone has an excellent safety profile and is well tolerated by patients.
We have previously shown in severely burned children that short-term administration of oxandrolone during the acute phase of burn injury increases net muscle protein balance, maintains LBM, and shortens intensive care unit (ICU) stay. [1,13–15] Additionally, short term oxandrolone use was associated with elevation of liver enzymes aspartate aminotransrferase (AST) and alanine aminotransferase (ALT) from 17 – 40 days post burn.[13] Amino acid utilization was improved for up to 6 months post-burn in patients randomized to oxandrolone treatment.[16] In a small group of severely burned children, the administration of oxandrolone for 1 year post-burn increased LBM, BMC, muscle strength, heights, and weights. These benefits lasted for at least a full year after discontinuation of oxandrolone. [17–18] The addition of a 12-week exercise program to 1 year of oxandrolone therapy provided an even greater increase in weight and LBM. [19]
We conducted a single-center prospective randomized controlled trial in massively burned pediatric patients to investigate the effects of oxandrolone administration for 1 year post burn on growth, body composition, muscle strength, REE, liver and cardiac function, serum markers, hormones, bone mass, and sexual maturation. We present the data from this trial, including data gathered up to 5 years post-burn to determine the safety and efficacy of the drug. A subset of these patients also underwent a 12-week exercise program to determine if exercise, in combination with oxandrolone, further affects LBM and BMC. These data are presented as well.
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METHODS
Patients
Two thousand eight-hundred twenty one severely burned children were admitted to our institution from 2000 to 2010. Of these, 516 patients with burns over 30% of the total body surface area (TBSA) were consented and randomized to studies of various anabolic agents administered acutely and long-term post injury. Seventy patients were randomized to receive oxandrolone, 152 to the control group, and 294 to other ongoing studies (Figure 1). Control patients outnumbered oxandrolone-treated patients due to the balanced design of the randomization schedule, in order to share control subjects with all studies in a time contiguous fast.
Patients 0–18 years of age at the time of the burn, with >30% of TBSA burned, and the need for at least one surgical intervention were included in the study. Exclusion criteria were the decision not to treat due to severity of the burn injury; anoxic brain injury; the presence of preexisting conditions such as HIV, AIDS, hepatitis, 5 year history of malignancy, or diabetes; and an inability to obtain informed consent. The administration of oxandrolone was started within 48 hours after the first operation and given orally at a dose of 0.1 mg/kg twice a day for one full year (BTG Pharmaceuticals, Iselin, NJ). Four Patients over 50 kg received 5 mg twice daily. Patients were assessed at admission; during acute hospitalization; at discharge; at 6, 9, 12, 18, and 24 months after burn; and annually thereafter. Patients who withdrew from the study were included in the data analysis up to the time of the withdrawal. This study was part of a large clinical trial (www.clinicaltrials.gov, NCT00675714) evaluating the outcomes of burn survivors after administration of therapeutic agents such as oxandrolone, propranolol, insulin, and the combination of oxandrolone and propranolol. Informed written consent approved by the Institutional Review Board of The University of Texas Medical Branch (Galveston, TX) was obtained from a legal guardian before enrollment in the study. Children older than 7 years assented to participate. This study adhered to ethical standards set forth by the Declaration of Helsinki (1975, revised 1983–2008).
Nutritional Support
Patients were resuscitated at admission according to the Galveston formula (a total of 5,000 ml/m2 TBSA burned + 2, 000 ml/m2 TBSA lactated Ringer’s solution given during the first 24 hours). Within 48 hours of admission, all patients underwent burn wound excision and autograft / allograft application. After excision and grafting procedures, patients remained on bed rest for 3 days and then ambulated daily thereafter until the next procedure. Sequential staged excision and grafting were performed until the wounds healed.
Each patient received Vivonex TEN® enteral nutrition composed of 82% carbohydrate, 15% protein, and 6% fat, by nasoduodenal tube. During the first week of hospitalization, intake was calculated to deliver 1,500 kcal/m2 TBSA + 1,500 kcal/m2 TBSA burned. The dietary replacement was then modified after the first week of treatment to 1.4 times the resting energy expenditure (REE) (see Indirect Calorimetry below). Caloric intakes remained constant throughout hospitalization. Albumin, pre-albumin, and retinol-binding protein served as indicators of nutritional status during the acute hospitalization period. Parents received nutritional counseling from the hospital nutritionist prior to discharge. In the outpatient setting, the patient’s caretakers were interviewed regarding intake every day when the patient returned to the tub room, weekly while the patient remained in apartments and residencies in the hospital vicinity, and during each long term follow-up visit. After discharge from the ICU, patients received the commercial formula Boost® (Nestle Health Care Nutrition, Nestlé S.A., Vevey, Switzerland), which is composed of 41 grams of carbohydrate, 10 grams of protein, and 4 grams of fat, three times per day. Supplementation continued until the nutritionist confirmed that the regular diet met the patient’s caloric requirements.
Patient Demographics and Injury Characteristics
Patient age, sex, and injury characteristics including the size and depth of the burn were recorded at the time of admission. Age-appropriate diagrams were used to determine burn size. [20] Conditions such as inhalation injury, sepsis, morbidity, and mortality were also recorded during the acute hospitalization. Inhalation injury was diagnosed by confirmation of the presence of soot, charring, mucosal necrosis, airway edema, or inflammation during fiber optic bronchoscopy, which was performed on all patients 24 hours after admission. Chest scintiphotograms, estimation of extra vascular lung water, and measurements of serum carboxyhemoglobin were also used for diagnostic purposes.
Indirect Calorimetry
All patients underwent weekly REE measurements during their acute hospitalization using the Sensor-Medics Vmax 29 metabolic cart (Yorba Linda, CA). Studies were performed while the patients were asleep between midnight and 5 AM. Inspired and expired gas compositions were sampled and analyzed at 60-second intervals. Values for carbon dioxide production and oxygen volume consumption were recorded when they were at a steady state for 5 min. Measured values were compared with predicted normal values based on the Harris-Benedict equation and body mass index (BMI). [21–23]
Anthropometric Measures
Measurements of height and body weight were obtained at admission, throughout the acute stay, and at all follow-up visits out to 5 years post injury. A standard calibrated scale was used to measure body weight. A wall-mounted stadiometer was used to measure height to the nearest 0.1 cm. Height and weight percentiles were calculated using growth charts specific for age and sex (obtained from the Centers for Disease Control and Prevention or National Center for Health Statistics, respectively). [24] Percent change in height- or weight- for-age percentiles was used to compare and interpret the results.
In order to eliminate seasonal differences in growth between children, height and weight velocities were calculated as whole year increments. Percentiles for those individual increments were obtained for age to determine whether the growth rate was within normal ranges. Maximal yearly height gains were used to determine annual height velocity for each patient, which were then plotted on standard and gender-specific growth velocity charts [25] at 1, 2, 3, 4, and 5 years post burn. In addition, the percentages of patients with growth velocities more than two standard deviations (SDs) below the mean (<3rd percentile) were determined at each time point.
Body Composition
Dual energy x-ray absorptiometry (DEXA) was used to measure whole body fat, LBM, BMC, and bone mineral density (BMD) (QDR-4500W Hologic, Waltham, MA). Calibration was performed daily using a spinal phantom in the lateral, anteroposterior, and single beam modes. A tissue bar phantom was used to calibrate individual pixels to accurately identify air, lean mass, bone, or fat. [26]
Measurement of Hormones, Proteins, and Cytokines
Blood and urine were collected from each patient for analysis of hormone, protein, liver enzyme, and cytokine levels at admission; during the acute stay; at discharge; and at follow-up appointments. Blood was collected in serum-separator collection tubes and centrifuged for 10 minutes at 1,320 rpm. The serum was removed and stored at −80°C until assayed. IGF-I, IGFBP-3, testosterone, parathyroid hormone (PTH), osteocalcin, albumin, and total protein were determined using HPLC and ELISA as previously published. [27–29] The Bio-Plex Human Cytokine 17-Plex panel was used with the Bio-Plex Suspension Array System (Bio-Rad, Hercules, CA) to profile expression of the following seventeen inflammatory mediators: IL-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-17, granulocyte colony-stimulating factor, granulocyte-macrophage colony stimulating factor, interferon-γ, monocyte chemoattractant protein-1, macrophage inflammatory protein-1β, and tumor necrosis factor. The manufacturer's protocol was followed as previously published. [27–29] Catecholamines were measured as previously published. [27–29]
Cardiac and Liver Measures
Heart rate (HR), stroke volume (SV), cardiac index (CI), mean arterial pressure (MAP), and cardiac output (CO) were determined for each patient. Cardiac and liver ultrasound measurements were made with a HP SONOS 100 CF echocardiogram (Hewlett Packard Imaging System, Andover, MA) equipped with a 3.5-MHz transducer. M-mode tracings were obtained at the level of the tips of the mitral leaflets in the parasternal long axis position, and measurements were performed according to the American Society of Echocardiography recommendations. Stroke volume and CO were calculated using left ventricular end-systolic and end-diastolic volumes measures. Rate pressure product (RPP) was obtained as a correlate of the myocardial oxygen consumption by multiplying Mean Arterial Pressure (MAP) × HR. The MAP was obtained by continuous arterial monitoring during the ICU stay, and RPP was calculated during the long term period using blood pressure measurements obtained at each follow up visit. The liver was scanned using an Eskoline B-scanner, a modified HP diagnostic sounder 7214A, and a modified 3.5-MHz transducer probe. Liver size and weight were calculated using a previously published formula. [30] Measurements were performed during the acute stay and at follow-up time points.
Rehabilitation Program
Because we have previously shown that completion of an exercise program improves LBM, muscle strength, and cardiovascular function, patients aged 7–18 years were also randomized to receive the standard of care (SOC) or to participate in an exercise program within 6 months of discharge per our published protocol. [31] The SOC consisted of a home based physical and occupational therapy instructions without exercise. The exercise program consisted of 12 weeks of in-hospital, supervised, and individualized aerobic and resistance exercise training carried out five days a week in addition to standard occupational and physical therapy regimens. Aerobic conditioning exercises were performed on a treadmill or cycle ergometer five times a week. A standardized treadmill exercise test was conducted using the modified Bruce protocol to assess cardiovascular fitness and peak aerobic endurance time. Patients exercised at 70% to 80% of their previously determined peak aerobic capacity (VO2 peak). Patients also performed resistance exercises such as bench press, leg press, and leg curls three times a week. Strength assessments were performed using the Biodex System 3 dynamometer (Biodex Medical Systems, Shirley, NY) according to instructions provided by the manufacturer. Peak torque values were calculated with the Biodex software system and were corrected for gravitational movements of the lower leg and the lever arm.
Additional Measurements
At each follow-up time point, X-rays of the patient’s hand and knee were obtained for bone age assessments and monitoring of the closure of the epiphyseal plate. In addition, psychosocial function was assessed at each follow-up time point. Patients participated in a structured clinical interview and were administered several self-report inventories.
Statistical Analysis
The distribution of the data was evaluated using QQ plots and the Kolmogorov-Smirnov normality test. Normally distributed data are presented as the mean ± standard deviation (SD) or standard error of the mean (SEM). Non-normally distributed data (i.e., cytokines) are presented as the median ± median absolute deviation (median±MAD). Frequency data are expressed as counts or percentages. We did not control for differences between the groups in sex, age, or weight, except in the case of muscle strength, which is corrected for body weight. Two-sided equal-variance t-tests were used to compare normally distributed continuous data. All trends in the data were calculated using the loess smoother. [32] Standard errors were calculated using the loess functionality in R. To test for differences between the curves, we calculated and tested the maximum t-statistic using the permutation distribution. [33] A step-down procedure was used to adjust the family-wise error rate. [34] Two-sided Wilcoxon exact tests were used for non-normally distributed. Repeated measures Friedman’s test was used to determine differences between intervals; if a difference were detected, a post hoc pairwise multiple comparisons (Dunn’s) test was also performed. SAS (version 9.2) was used for data analysis and hypothesis testing. Fisher’s exact test was used for frequency data. P values less than 0.05 were considered significant.
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RESULTS
Patient Disposition and Demographics
Of the 222 patients enrolled in this study, 29 were lost to follow-up (control, n=20; oxandrolone, n=9), and 39 withdrew from study participation (control, n=28; oxandrolone, n=11). Demographics did not differ significantly between the oxandrolone and control groups (Table 1). Two-thirds of the patients were male, which is typical of burn injury in children. Almost half of the patients in each group were diagnosed with inhalation injuries. The length of hospital stay was approximately a half day per percent TBSA burned for patients in both groups. Mortality was low in both groups. No differences were noted in the number or time between operations when comparing the oxandrolone and control groups. Thirty-five patients participated in a 12-week exercise program during the rehabilitation period (control, n=21; oxandrolone, n=14), and 187 patients received SOC (controls n=131; oxandrolone n=56).
TABLE 1
TABLE 1
Patient Demographics
Indirect Calorimetry
Oxandrolone significantly decreased percent of predicted REE (P<0.01), and this effect was sustained until approximately 6 months post burn, indicating that hypermetabolism was significantly decreased. Although REE decreased over time in both groups, these values remained elevated for over 12 months after burn in the control group (Figure 2).
FIGURE 2
FIGURE 2
Effect of oxandrolone on percent predicted resting energy expenditure. Data are represented the loess-smoothed trend in resting energy expenditure (REE) with shading indicating +/− standard error. Hatch marks across the bottom represent the density ...
Anthropometric Measures
In the control group, the percentage of children below two standard deviations (SDs) of the mean for height velocity was 48% at 1 year post burn; 32% at 2 years post burn; and ~20% at 3, 4, and 5 years post burn (Table 2). In the oxandrolone group, the percentage of patients falling more than two SDs below the mean for height velocity was only 8% at 1 year post burn and 7% at 2 years post burn. These values were significantly lower than those in controls (Table 2); however, this difference was not significant at 3, 4, or 5 years post burn.
TABLE 2
TABLE 2
Growth Distribution at Admission and 1–5 Years Post Burn
Patients in the oxandrolone group exhibited a positive percent change in height percentiles at 1 year post burn, with a maximal change of ~40% seen at the second year (Figure 3A). These changes were significantly higher than those seen in controls at corresponding time points. In contrast to oxandrolone-treated patients, controls exhibited a negative percent change in height percentiles that was maximal at 1 and 2 years post burn, and these values remained negative at all time points. No significant differences were detected between groups at 3, 4 and 5 years post burn. As shown in Figure 3B, the effect of oxandrolone was maximal in children between the ages of 7 and 18 years, and the percent change in height percentile was significantly different up to 4 years post burn (P<0.05). Controls, on the other hand, showed a loss in height percentile over time.
FIGURE 3
FIGURE 3
Percent change in height percentile from 1 to 5 years post burn in (A) all patients and in (B) patients aged 7–18 years. Data are expressed as mean ± SEM. *p<0.05 vs control.
An analysis of the percentage of children with weight velocities more than two SDs below the mean revealed that this percentage was lower in the oxandrolone group than in the control group at 1 year post burn, but not at 2, 3, 4, or 5 years post burn (Table 2).
Body Composition
Oxandrolone-treated patients who were 7–18 years old at the time of the injury had a significantly higher percent change in BMC than their control counterparts, beginning 2 years after injury and lasting until 5 years post burn (P<0.001) (Figure 4). No significant differences were detected between groups for children less than 7 years of age. Significant differences in BMC were also seen between children who received oxandrolone and participated in the exercise program and exercising control patients (P<0.01). BMD did not significantly differ between oxandrolone-treated patients and controls, regardless of age (data not shown). LBM approached significance at all time points (P=0.06). However, significance was reached only in exercising, oxandrolone-treated children, with differences between this group and exercising control patients at 2 years post burn, remaining significant throughout the remainder of the study period (P=0.01) (Figure 5B). No significant correlation was detected between percent change in LBM and percent change in BMC at any time post burn.
FIGURE 4
FIGURE 4
Percent change in (A) total body bone mineral content and (B) lean body mass. Data are represented as the loess-smoothed trend in BMC and in LBM with shading indicating +/− standard error. Hatch marks across the bottom represent the density of ...
FIGURE 5
FIGURE 5
Exercise
Hormones, Proteins, and Cytokines
Although catecholamines were elevated by burn injury, there were no differences between the groups. Serum constitutive proteins, pre-albumin, retinol-binding protein, and transferrin were significantly higher in oxandrolone-treated patients than controls from 2 to 12 months after burn injury (Figure 6 J, L, M). Serum albumin and total protein remained within normal limits and were not significantly different between groups (Figure 7D, H). Acute-phase proteins were significantly elevated in both groups during acute hospitalization (Figure 6). Complement C3 was markedly increased in the control group when compared to the oxandrolone group from discharge until 6 months post burn. Haptoglobin levels were significantly elevated in both groups until 6 months post burn, with oxandrolone-treated patients showing significant differences for 1 year following discharge when compared to controls. No differences were detected between the groups in α-2 macroglobulin and free fatty acid levels. In both groups, levels of C-reactive protein and α-1 acid glycoprotein returned to normal levels by 6 months after burn injury.
FIGURE 6
FIGURE 6
Effect of oxandrolone on serum levels of (A) free T4, (B) free thyroid index, (C) T3 uptake, (D) total T4, (E) IGF-1, (F) IGFBP-3, (G) growth hormone, (H) haptoglobin, (I) C3 complement, (J) retinol-binding protein, (K) α1 acid glycoprotein, (L) ...
FIGURE 7
FIGURE 7
Effect of oxandrolone on levels of (A) serum creatinine, (B) BUN, (C) alkaline phosphatase, (D) total protein, (E) total bilirubin, (F) aspartate aminotransferase, (G) alanine aminotransferase, (H) albumin, and (I) glucose. Data are expressed as mean±SEM. ...
Confirming previous studies [2, 13, 35], IGF-1, IGFBP-3, testosterone, growth hormone, β-estradiol, and total T4 levels were decreased after injury (Figure 6). Oxandrolone induced significant positive and persistent up-regulation of IGF-1 (Figure 6E); IGF-I was significantly higher in the oxandrolone group than the control group from discharge to 2 years post burn, with no differences in IGFBP-3 between the groups (Figure 6F). Exercise did not alter IGF-1 levels. Serum i-PTH and osteocalcin levels were dramatically decreased in both groups compared to normal values for over 2 years post burn and did not significantly differ between the groups (Figure 6P, Q). Free thyroid index and T3 uptake remained constant over time and did not differ between the groups (Figure 6B, C). Free T4 was significantly higher during the acute period in the oxandrolone group, although free T4 levels fell within normal range. Progesterone was consistently elevated in both groups but was not significantly different between them. All blood chemistry values were within normal limits, and no differences between the groups were detected. As in previous studies, [2, 36] glucose and insulin levels were above normal limits during acute hospitalization in both groups, with no significant differences detected between oxandrolone-treated and controls.
At most, serum cytokine levels significantly differed between the two groups at one or two time points after burn injury. These alterations were not sustained; therefore the overall inflammatory response did not differ between the groups.
Cardiac and Liver Changes
Absolute and percent of predicted CO, SV, and HR as well as CI and RPP were assessed up to 2 years following burn injury (Table 3). At 1 year post burn, CO, percent of predicted CO, and percent of predicted HR were significantly lower in the oxandrolone group compared to the control group (P<0.05). A significant decrease in RPP was observed in the oxandrolone group up to 1 year post burn (p<0.05). At 2 years post burn, percent of predicted CO and HR were significantly lower in the oxandrolone group than in the control group (P<0.05 for both). Liver length and weight were not significantly different between the control and oxandrolone groups (Table 3).
TABLE 3
TABLE 3
Cardiac and Liver Ultrasound Measurements
Rehabilitation Program
Significant increases in LBM, BMC, and muscle strength were seen in the oxandrolone + exercise group when compared to the control + exercise, control + SOC, or the oxandrolone + SOC groups. These effects persisted for up to 5 years post burn (Figure 5). Muscle strength, expressed as peak torque/kg body weight, was significantly greater in the oxandrolone + exercise group than the control + exercise group, the control + SOC group, or the oxandrolone + SOC group (P<0.05) at 9, 12, 18, and 24 months post burn. No significant difference in muscle strength was detected between oxandrolone + SOC and control + SOC.
Safety Profile
Our patients were closely monitored for adverse events for up to 1 year after discontinuation of oxandrolone. Thereafter, patients were assessed during annual follow-up visits. No signs of virilization were noted. Three female patients who had perineal burns developed clitoral hood edema, which resolved within 3 months. Chi-Square analyses revealed that oxandrolone did not affect acute and long-term psychosocial outcomes, including the prevalence of post-traumatic stress disorder, general anxiety, and depression between groups. Monitoring of liver and renal function included measures of serum creatinine, BUN, total protein, liver enzymes, total bilirubin, liver size, and liver weight (Table 3) (Figure 7). Alanine aminotransaminase and gamma glutamyl transpeptidase were elevated during the acute period in the control and oxandrolone groups, returning to normal levels 3 to 6 months post burn. However, levels of constitutive proteins were significantly increased in the oxandrolone group, indicating that liver function was not affected. The control group showed significantly higher levels of serum creatinine, total bilirubin, and BUN during the acute period than the oxandrolone group. Although these values were statistically significant, some fell within normal ranges. Alkaline phosphatase and total protein tended to increase with time in both groups and were not different between the groups. The rest of the parameters did not differ between the groups at any of the time points. There was no significant advancement in bone age versus chronological age over the post burn observation period, and no difference between oxandrolone-treated patients (0.93±0.16) and controls (0.94±0.24) was detected.
Study Design
Patients 0–18 years old with burns covering >30% of the total body surface area were randomized to receive placebo (n=152) or oxandrolone, 0.1 mg/kg twice daily for 12 months (n=70). At hospital discharge, patients were randomized to a 12 week exercise program or to standard of care. Resting energy expenditure (REE), standing height, weight, lean body mass, muscle strength, bone mineral content (BMC), cardiac work, rate pressure product (RPP), sexual maturation, and concentrations of serum inflammatory cytokines, hormones, and liver enzymes were monitored.
Results
Oxandrolone significantly decreased REE, RPP, and increased IGF-1 secretion during the first year after burn injury, and in combination with exercise significantly increased lean body mass and muscle strength. Oxandrolone-treated children exhibited improved height percentile and BMC content compared to controls. The maximal effect of oxandrolone was found in children aged 7–18 years. No deleterious side effects were attributed to long-term administration.
Conclusions
Administration of oxandrolone improves the long-term recovery of severely burned children in height, BMC, cardiac work and muscle strength; the increase in BMC is likely to occur by means of IGF 1. These benefits persist for up to 5 years post burn.
Keywords: Burn, oxandrolone, children, height, bone mineral content, hypermetabolic response, hypercatabolic response, resting energy expenditure
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INTRODUCTION
Burn injury induces a hypermetabolic response that is characterized by elevations in cardiac work, metabolic rate, and muscle catabolism. Increased protein breakdown coupled with inadequate protein synthesis leads to muscle weakness and a loss of lean body mass (LBM). [1] Post-burn catabolic effects are not limited to muscle, as bone mineral content (BMC) and fat mass are decreased as well. This hypermetabolic response persists for up to 2 years after burn injury, greatly reducing the quality of life of severely burned patients. [2]
Oxandrolone, a synthetic oral non-aromatizable testosterone derivative, has only 5% of the virilizing activity and lower hepatotoxicity when compared to testosterone. Following administration, oxandrolone reaches peak serum concentrations within one hour and is excreted through the urine. Oxandrolone binds to androgen receptors in the skeletal muscle to initiate protein synthesis and anabolism. Because oxandrolone cannot be aromatized to estrogen, the likelihood of estrogen-dependent bone age advancement is reduced, making oxandrolone a safe therapeutic approach for growing children. [3–5]
In children with Turner’s syndrome and other growth-related conditions, oxandrolone has been successfully for many decades to safely treat growth delays. [6–10] More recently, oxandrolone has been used to induce anabolism in patients experiencing muscle wasting associated with AIDS, major surgery, infections, malnutrition, neuromuscular disorders, or thermal injury. [11–12] Oxandrolone is the only androgenic steroid approved by the Food and Drug Administration to maintain body weight in these catabolic states. [3] These studies have demonstrated that oxandrolone has an excellent safety profile and is well tolerated by patients.
We have previously shown in severely burned children that short-term administration of oxandrolone during the acute phase of burn injury increases net muscle protein balance, maintains LBM, and shortens intensive care unit (ICU) stay. [1,13–15] Additionally, short term oxandrolone use was associated with elevation of liver enzymes aspartate aminotransrferase (AST) and alanine aminotransferase (ALT) from 17 – 40 days post burn.[13] Amino acid utilization was improved for up to 6 months post-burn in patients randomized to oxandrolone treatment.[16] In a small group of severely burned children, the administration of oxandrolone for 1 year post-burn increased LBM, BMC, muscle strength, heights, and weights. These benefits lasted for at least a full year after discontinuation of oxandrolone. [17–18] The addition of a 12-week exercise program to 1 year of oxandrolone therapy provided an even greater increase in weight and LBM. [19]
We conducted a single-center prospective randomized controlled trial in massively burned pediatric patients to investigate the effects of oxandrolone administration for 1 year post burn on growth, body composition, muscle strength, REE, liver and cardiac function, serum markers, hormones, bone mass, and sexual maturation. We present the data from this trial, including data gathered up to 5 years post-burn to determine the safety and efficacy of the drug. A subset of these patients also underwent a 12-week exercise program to determine if exercise, in combination with oxandrolone, further affects LBM and BMC. These data are presented as well.
Go to:
METHODS
Patients
Two thousand eight-hundred twenty one severely burned children were admitted to our institution from 2000 to 2010. Of these, 516 patients with burns over 30% of the total body surface area (TBSA) were consented and randomized to studies of various anabolic agents administered acutely and long-term post injury. Seventy patients were randomized to receive oxandrolone, 152 to the control group, and 294 to other ongoing studies (Figure 1). Control patients outnumbered oxandrolone-treated patients due to the balanced design of the randomization schedule, in order to share control subjects with all studies in a time contiguous fast.
Patients 0–18 years of age at the time of the burn, with >30% of TBSA burned, and the need for at least one surgical intervention were included in the study. Exclusion criteria were the decision not to treat due to severity of the burn injury; anoxic brain injury; the presence of preexisting conditions such as HIV, AIDS, hepatitis, 5 year history of malignancy, or diabetes; and an inability to obtain informed consent. The administration of oxandrolone was started within 48 hours after the first operation and given orally at a dose of 0.1 mg/kg twice a day for one full year (BTG Pharmaceuticals, Iselin, NJ). Four Patients over 50 kg received 5 mg twice daily. Patients were assessed at admission; during acute hospitalization; at discharge; at 6, 9, 12, 18, and 24 months after burn; and annually thereafter. Patients who withdrew from the study were included in the data analysis up to the time of the withdrawal. This study was part of a large clinical trial (www.clinicaltrials.gov, NCT00675714) evaluating the outcomes of burn survivors after administration of therapeutic agents such as oxandrolone, propranolol, insulin, and the combination of oxandrolone and propranolol. Informed written consent approved by the Institutional Review Board of The University of Texas Medical Branch (Galveston, TX) was obtained from a legal guardian before enrollment in the study. Children older than 7 years assented to participate. This study adhered to ethical standards set forth by the Declaration of Helsinki (1975, revised 1983–2008).
Nutritional Support
Patients were resuscitated at admission according to the Galveston formula (a total of 5,000 ml/m2 TBSA burned + 2, 000 ml/m2 TBSA lactated Ringer’s solution given during the first 24 hours). Within 48 hours of admission, all patients underwent burn wound excision and autograft / allograft application. After excision and grafting procedures, patients remained on bed rest for 3 days and then ambulated daily thereafter until the next procedure. Sequential staged excision and grafting were performed until the wounds healed.
Each patient received Vivonex TEN® enteral nutrition composed of 82% carbohydrate, 15% protein, and 6% fat, by nasoduodenal tube. During the first week of hospitalization, intake was calculated to deliver 1,500 kcal/m2 TBSA + 1,500 kcal/m2 TBSA burned. The dietary replacement was then modified after the first week of treatment to 1.4 times the resting energy expenditure (REE) (see Indirect Calorimetry below). Caloric intakes remained constant throughout hospitalization. Albumin, pre-albumin, and retinol-binding protein served as indicators of nutritional status during the acute hospitalization period. Parents received nutritional counseling from the hospital nutritionist prior to discharge. In the outpatient setting, the patient’s caretakers were interviewed regarding intake every day when the patient returned to the tub room, weekly while the patient remained in apartments and residencies in the hospital vicinity, and during each long term follow-up visit. After discharge from the ICU, patients received the commercial formula Boost® (Nestle Health Care Nutrition, Nestlé S.A., Vevey, Switzerland), which is composed of 41 grams of carbohydrate, 10 grams of protein, and 4 grams of fat, three times per day. Supplementation continued until the nutritionist confirmed that the regular diet met the patient’s caloric requirements.
Patient Demographics and Injury Characteristics
Patient age, sex, and injury characteristics including the size and depth of the burn were recorded at the time of admission. Age-appropriate diagrams were used to determine burn size. [20] Conditions such as inhalation injury, sepsis, morbidity, and mortality were also recorded during the acute hospitalization. Inhalation injury was diagnosed by confirmation of the presence of soot, charring, mucosal necrosis, airway edema, or inflammation during fiber optic bronchoscopy, which was performed on all patients 24 hours after admission. Chest scintiphotograms, estimation of extra vascular lung water, and measurements of serum carboxyhemoglobin were also used for diagnostic purposes.
Indirect Calorimetry
All patients underwent weekly REE measurements during their acute hospitalization using the Sensor-Medics Vmax 29 metabolic cart (Yorba Linda, CA). Studies were performed while the patients were asleep between midnight and 5 AM. Inspired and expired gas compositions were sampled and analyzed at 60-second intervals. Values for carbon dioxide production and oxygen volume consumption were recorded when they were at a steady state for 5 min. Measured values were compared with predicted normal values based on the Harris-Benedict equation and body mass index (BMI). [21–23]
Anthropometric Measures
Measurements of height and body weight were obtained at admission, throughout the acute stay, and at all follow-up visits out to 5 years post injury. A standard calibrated scale was used to measure body weight. A wall-mounted stadiometer was used to measure height to the nearest 0.1 cm. Height and weight percentiles were calculated using growth charts specific for age and sex (obtained from the Centers for Disease Control and Prevention or National Center for Health Statistics, respectively). [24] Percent change in height- or weight- for-age percentiles was used to compare and interpret the results.
In order to eliminate seasonal differences in growth between children, height and weight velocities were calculated as whole year increments. Percentiles for those individual increments were obtained for age to determine whether the growth rate was within normal ranges. Maximal yearly height gains were used to determine annual height velocity for each patient, which were then plotted on standard and gender-specific growth velocity charts [25] at 1, 2, 3, 4, and 5 years post burn. In addition, the percentages of patients with growth velocities more than two standard deviations (SDs) below the mean (<3rd percentile) were determined at each time point.
Body Composition
Dual energy x-ray absorptiometry (DEXA) was used to measure whole body fat, LBM, BMC, and bone mineral density (BMD) (QDR-4500W Hologic, Waltham, MA). Calibration was performed daily using a spinal phantom in the lateral, anteroposterior, and single beam modes. A tissue bar phantom was used to calibrate individual pixels to accurately identify air, lean mass, bone, or fat. [26]
Measurement of Hormones, Proteins, and Cytokines
Blood and urine were collected from each patient for analysis of hormone, protein, liver enzyme, and cytokine levels at admission; during the acute stay; at discharge; and at follow-up appointments. Blood was collected in serum-separator collection tubes and centrifuged for 10 minutes at 1,320 rpm. The serum was removed and stored at −80°C until assayed. IGF-I, IGFBP-3, testosterone, parathyroid hormone (PTH), osteocalcin, albumin, and total protein were determined using HPLC and ELISA as previously published. [27–29] The Bio-Plex Human Cytokine 17-Plex panel was used with the Bio-Plex Suspension Array System (Bio-Rad, Hercules, CA) to profile expression of the following seventeen inflammatory mediators: IL-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-17, granulocyte colony-stimulating factor, granulocyte-macrophage colony stimulating factor, interferon-γ, monocyte chemoattractant protein-1, macrophage inflammatory protein-1β, and tumor necrosis factor. The manufacturer's protocol was followed as previously published. [27–29] Catecholamines were measured as previously published. [27–29]
Cardiac and Liver Measures
Heart rate (HR), stroke volume (SV), cardiac index (CI), mean arterial pressure (MAP), and cardiac output (CO) were determined for each patient. Cardiac and liver ultrasound measurements were made with a HP SONOS 100 CF echocardiogram (Hewlett Packard Imaging System, Andover, MA) equipped with a 3.5-MHz transducer. M-mode tracings were obtained at the level of the tips of the mitral leaflets in the parasternal long axis position, and measurements were performed according to the American Society of Echocardiography recommendations. Stroke volume and CO were calculated using left ventricular end-systolic and end-diastolic volumes measures. Rate pressure product (RPP) was obtained as a correlate of the myocardial oxygen consumption by multiplying Mean Arterial Pressure (MAP) × HR. The MAP was obtained by continuous arterial monitoring during the ICU stay, and RPP was calculated during the long term period using blood pressure measurements obtained at each follow up visit. The liver was scanned using an Eskoline B-scanner, a modified HP diagnostic sounder 7214A, and a modified 3.5-MHz transducer probe. Liver size and weight were calculated using a previously published formula. [30] Measurements were performed during the acute stay and at follow-up time points.
Rehabilitation Program
Because we have previously shown that completion of an exercise program improves LBM, muscle strength, and cardiovascular function, patients aged 7–18 years were also randomized to receive the standard of care (SOC) or to participate in an exercise program within 6 months of discharge per our published protocol. [31] The SOC consisted of a home based physical and occupational therapy instructions without exercise. The exercise program consisted of 12 weeks of in-hospital, supervised, and individualized aerobic and resistance exercise training carried out five days a week in addition to standard occupational and physical therapy regimens. Aerobic conditioning exercises were performed on a treadmill or cycle ergometer five times a week. A standardized treadmill exercise test was conducted using the modified Bruce protocol to assess cardiovascular fitness and peak aerobic endurance time. Patients exercised at 70% to 80% of their previously determined peak aerobic capacity (VO2 peak). Patients also performed resistance exercises such as bench press, leg press, and leg curls three times a week. Strength assessments were performed using the Biodex System 3 dynamometer (Biodex Medical Systems, Shirley, NY) according to instructions provided by the manufacturer. Peak torque values were calculated with the Biodex software system and were corrected for gravitational movements of the lower leg and the lever arm.
Additional Measurements
At each follow-up time point, X-rays of the patient’s hand and knee were obtained for bone age assessments and monitoring of the closure of the epiphyseal plate. In addition, psychosocial function was assessed at each follow-up time point. Patients participated in a structured clinical interview and were administered several self-report inventories.
Statistical Analysis
The distribution of the data was evaluated using QQ plots and the Kolmogorov-Smirnov normality test. Normally distributed data are presented as the mean ± standard deviation (SD) or standard error of the mean (SEM). Non-normally distributed data (i.e., cytokines) are presented as the median ± median absolute deviation (median±MAD). Frequency data are expressed as counts or percentages. We did not control for differences between the groups in sex, age, or weight, except in the case of muscle strength, which is corrected for body weight. Two-sided equal-variance t-tests were used to compare normally distributed continuous data. All trends in the data were calculated using the loess smoother. [32] Standard errors were calculated using the loess functionality in R. To test for differences between the curves, we calculated and tested the maximum t-statistic using the permutation distribution. [33] A step-down procedure was used to adjust the family-wise error rate. [34] Two-sided Wilcoxon exact tests were used for non-normally distributed. Repeated measures Friedman’s test was used to determine differences between intervals; if a difference were detected, a post hoc pairwise multiple comparisons (Dunn’s) test was also performed. SAS (version 9.2) was used for data analysis and hypothesis testing. Fisher’s exact test was used for frequency data. P values less than 0.05 were considered significant.
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RESULTS
Patient Disposition and Demographics
Of the 222 patients enrolled in this study, 29 were lost to follow-up (control, n=20; oxandrolone, n=9), and 39 withdrew from study participation (control, n=28; oxandrolone, n=11). Demographics did not differ significantly between the oxandrolone and control groups (Table 1). Two-thirds of the patients were male, which is typical of burn injury in children. Almost half of the patients in each group were diagnosed with inhalation injuries. The length of hospital stay was approximately a half day per percent TBSA burned for patients in both groups. Mortality was low in both groups. No differences were noted in the number or time between operations when comparing the oxandrolone and control groups. Thirty-five patients participated in a 12-week exercise program during the rehabilitation period (control, n=21; oxandrolone, n=14), and 187 patients received SOC (controls n=131; oxandrolone n=56).
TABLE 1
TABLE 1
Patient Demographics
Indirect Calorimetry
Oxandrolone significantly decreased percent of predicted REE (P<0.01), and this effect was sustained until approximately 6 months post burn, indicating that hypermetabolism was significantly decreased. Although REE decreased over time in both groups, these values remained elevated for over 12 months after burn in the control group (Figure 2).
FIGURE 2
FIGURE 2
Effect of oxandrolone on percent predicted resting energy expenditure. Data are represented the loess-smoothed trend in resting energy expenditure (REE) with shading indicating +/− standard error. Hatch marks across the bottom represent the density ...
Anthropometric Measures
In the control group, the percentage of children below two standard deviations (SDs) of the mean for height velocity was 48% at 1 year post burn; 32% at 2 years post burn; and ~20% at 3, 4, and 5 years post burn (Table 2). In the oxandrolone group, the percentage of patients falling more than two SDs below the mean for height velocity was only 8% at 1 year post burn and 7% at 2 years post burn. These values were significantly lower than those in controls (Table 2); however, this difference was not significant at 3, 4, or 5 years post burn.
TABLE 2
TABLE 2
Growth Distribution at Admission and 1–5 Years Post Burn
Patients in the oxandrolone group exhibited a positive percent change in height percentiles at 1 year post burn, with a maximal change of ~40% seen at the second year (Figure 3A). These changes were significantly higher than those seen in controls at corresponding time points. In contrast to oxandrolone-treated patients, controls exhibited a negative percent change in height percentiles that was maximal at 1 and 2 years post burn, and these values remained negative at all time points. No significant differences were detected between groups at 3, 4 and 5 years post burn. As shown in Figure 3B, the effect of oxandrolone was maximal in children between the ages of 7 and 18 years, and the percent change in height percentile was significantly different up to 4 years post burn (P<0.05). Controls, on the other hand, showed a loss in height percentile over time.
FIGURE 3
FIGURE 3
Percent change in height percentile from 1 to 5 years post burn in (A) all patients and in (B) patients aged 7–18 years. Data are expressed as mean ± SEM. *p<0.05 vs control.
An analysis of the percentage of children with weight velocities more than two SDs below the mean revealed that this percentage was lower in the oxandrolone group than in the control group at 1 year post burn, but not at 2, 3, 4, or 5 years post burn (Table 2).
Body Composition
Oxandrolone-treated patients who were 7–18 years old at the time of the injury had a significantly higher percent change in BMC than their control counterparts, beginning 2 years after injury and lasting until 5 years post burn (P<0.001) (Figure 4). No significant differences were detected between groups for children less than 7 years of age. Significant differences in BMC were also seen between children who received oxandrolone and participated in the exercise program and exercising control patients (P<0.01). BMD did not significantly differ between oxandrolone-treated patients and controls, regardless of age (data not shown). LBM approached significance at all time points (P=0.06). However, significance was reached only in exercising, oxandrolone-treated children, with differences between this group and exercising control patients at 2 years post burn, remaining significant throughout the remainder of the study period (P=0.01) (Figure 5B). No significant correlation was detected between percent change in LBM and percent change in BMC at any time post burn.
FIGURE 4
FIGURE 4
Percent change in (A) total body bone mineral content and (B) lean body mass. Data are represented as the loess-smoothed trend in BMC and in LBM with shading indicating +/− standard error. Hatch marks across the bottom represent the density of ...
FIGURE 5
FIGURE 5
Exercise
Hormones, Proteins, and Cytokines
Although catecholamines were elevated by burn injury, there were no differences between the groups. Serum constitutive proteins, pre-albumin, retinol-binding protein, and transferrin were significantly higher in oxandrolone-treated patients than controls from 2 to 12 months after burn injury (Figure 6 J, L, M). Serum albumin and total protein remained within normal limits and were not significantly different between groups (Figure 7D, H). Acute-phase proteins were significantly elevated in both groups during acute hospitalization (Figure 6). Complement C3 was markedly increased in the control group when compared to the oxandrolone group from discharge until 6 months post burn. Haptoglobin levels were significantly elevated in both groups until 6 months post burn, with oxandrolone-treated patients showing significant differences for 1 year following discharge when compared to controls. No differences were detected between the groups in α-2 macroglobulin and free fatty acid levels. In both groups, levels of C-reactive protein and α-1 acid glycoprotein returned to normal levels by 6 months after burn injury.
FIGURE 6
FIGURE 6
Effect of oxandrolone on serum levels of (A) free T4, (B) free thyroid index, (C) T3 uptake, (D) total T4, (E) IGF-1, (F) IGFBP-3, (G) growth hormone, (H) haptoglobin, (I) C3 complement, (J) retinol-binding protein, (K) α1 acid glycoprotein, (L) ...
FIGURE 7
FIGURE 7
Effect of oxandrolone on levels of (A) serum creatinine, (B) BUN, (C) alkaline phosphatase, (D) total protein, (E) total bilirubin, (F) aspartate aminotransferase, (G) alanine aminotransferase, (H) albumin, and (I) glucose. Data are expressed as mean±SEM. ...
Confirming previous studies [2, 13, 35], IGF-1, IGFBP-3, testosterone, growth hormone, β-estradiol, and total T4 levels were decreased after injury (Figure 6). Oxandrolone induced significant positive and persistent up-regulation of IGF-1 (Figure 6E); IGF-I was significantly higher in the oxandrolone group than the control group from discharge to 2 years post burn, with no differences in IGFBP-3 between the groups (Figure 6F). Exercise did not alter IGF-1 levels. Serum i-PTH and osteocalcin levels were dramatically decreased in both groups compared to normal values for over 2 years post burn and did not significantly differ between the groups (Figure 6P, Q). Free thyroid index and T3 uptake remained constant over time and did not differ between the groups (Figure 6B, C). Free T4 was significantly higher during the acute period in the oxandrolone group, although free T4 levels fell within normal range. Progesterone was consistently elevated in both groups but was not significantly different between them. All blood chemistry values were within normal limits, and no differences between the groups were detected. As in previous studies, [2, 36] glucose and insulin levels were above normal limits during acute hospitalization in both groups, with no significant differences detected between oxandrolone-treated and controls.
At most, serum cytokine levels significantly differed between the two groups at one or two time points after burn injury. These alterations were not sustained; therefore the overall inflammatory response did not differ between the groups.
Cardiac and Liver Changes
Absolute and percent of predicted CO, SV, and HR as well as CI and RPP were assessed up to 2 years following burn injury (Table 3). At 1 year post burn, CO, percent of predicted CO, and percent of predicted HR were significantly lower in the oxandrolone group compared to the control group (P<0.05). A significant decrease in RPP was observed in the oxandrolone group up to 1 year post burn (p<0.05). At 2 years post burn, percent of predicted CO and HR were significantly lower in the oxandrolone group than in the control group (P<0.05 for both). Liver length and weight were not significantly different between the control and oxandrolone groups (Table 3).
TABLE 3
TABLE 3
Cardiac and Liver Ultrasound Measurements
Rehabilitation Program
Significant increases in LBM, BMC, and muscle strength were seen in the oxandrolone + exercise group when compared to the control + exercise, control + SOC, or the oxandrolone + SOC groups. These effects persisted for up to 5 years post burn (Figure 5). Muscle strength, expressed as peak torque/kg body weight, was significantly greater in the oxandrolone + exercise group than the control + exercise group, the control + SOC group, or the oxandrolone + SOC group (P<0.05) at 9, 12, 18, and 24 months post burn. No significant difference in muscle strength was detected between oxandrolone + SOC and control + SOC.
Safety Profile
Our patients were closely monitored for adverse events for up to 1 year after discontinuation of oxandrolone. Thereafter, patients were assessed during annual follow-up visits. No signs of virilization were noted. Three female patients who had perineal burns developed clitoral hood edema, which resolved within 3 months. Chi-Square analyses revealed that oxandrolone did not affect acute and long-term psychosocial outcomes, including the prevalence of post-traumatic stress disorder, general anxiety, and depression between groups. Monitoring of liver and renal function included measures of serum creatinine, BUN, total protein, liver enzymes, total bilirubin, liver size, and liver weight (Table 3) (Figure 7). Alanine aminotransaminase and gamma glutamyl transpeptidase were elevated during the acute period in the control and oxandrolone groups, returning to normal levels 3 to 6 months post burn. However, levels of constitutive proteins were significantly increased in the oxandrolone group, indicating that liver function was not affected. The control group showed significantly higher levels of serum creatinine, total bilirubin, and BUN during the acute period than the oxandrolone group. Although these values were statistically significant, some fell within normal ranges. Alkaline phosphatase and total protein tended to increase with time in both groups and were not different between the groups. The rest of the parameters did not differ between the groups at any of the time points. There was no significant advancement in bone age versus chronological age over the post burn observation period, and no difference between oxandrolone-treated patients (0.93±0.16) and controls (0.94±0.24) was detected.
