Oxandrolone, first sold as Anavar, is an oral anabolic steroid derived from dihydrotestosterone (DHT). G.D. Searle introduced it in 1964 as a drug to help patients regain weight lost to surgery, infection or trauma.
For decades it had a reputation as a “mild” steroid, and it was studied in burns, HIV wasting, Turner syndrome and older men. In June 2023 the FDA withdrew approval of every oxandrolone product in the US. FDA concluded that the drug’s benefit had never been shown to outweigh its risks.
This page summarizes what the label, the clinical trials and the FDA record report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | 17α-alkylated anabolic-androgenic steroid (DHT derivative) |
| Brands | Anavar (Searle, 1964); Oxandrin (later Savient / Gemini); generics |
| Route | Oral tablet |
| Former strengths | 2.5 mg and 10 mg |
| Former labeled adult dose | 2.5–20 mg/day in 2–4 divided doses, for 2–4 weeks |
| Half-life (label) | 10.4 h in younger adults; 13.3 h in the elderly |
| Aromatizes to estrogen | No |
| US status | FDA approval withdrawn June 28, 2023; still Schedule III |
What it is
Oxandrolone’s chemical name is 17β-hydroxy-17α-methyl-2-oxa-5α-androstan-3-one: formula C₁₉H₃₀O₃, molecular weight 306.4 g/mol (generic oxandrolone label). It differs from DHT in two ways:
| Change | What it does |
|---|---|
| 2-oxa substitution: an oxygen atom replaces carbon 2 in the A-ring | Makes it a “2-oxasteroid,” a new class when it was made. The ring structure cannot be converted to estrogen. |
| 17α-methyl group | Slows breakdown in the liver, so the drug survives oral dosing. The same group is tied to liver toxicity across this class of steroids. |
Raphael Pappo synthesized it at Searle and reported 2-oxasteroids in 1962. The patent was granted in 1964 (US 3,128,283). The first human study described it as having about six times the anabolic potency of methyltestosterone (Fox et al., JCEM 1962).
Because it is already a 5α-reduced DHT derivative and has no aromatizable A-ring, oxandrolone does not convert to estradiol. This is why it does not cause estrogen-driven water retention or gynecomastia the way testosterone can.
About anabolic:androgenic ratios. Online sources often quote figures like “10:1” or “322–633:24” for oxandrolone. We could not trace these to an original assay, so we do not repeat them here. The only primary potency figure is the 1962 human comparison above.
Pharmacokinetics
From the Oxandrin label (FDA, 2005):
| Parameter | Younger adults | Elderly |
|---|---|---|
| Mean elimination half-life (single dose) | 10.4 h | 13.3 h |
| Time to peak, peak level, total exposure (AUC) | No significant difference between groups | No significant difference between groups |
The half-life of about 10 hours explains why the label split the daily dose into 2–4 doses.
Former medical uses
The Oxandrin label approved oxandrolone for the following uses:
- as an add-on to promote weight gain after weight loss from extensive surgery, chronic infection or severe trauma;
- for some patients who fail to gain or keep a normal weight with no clear cause;
- to offset the protein breakdown caused by long-term corticosteroid use;
- to relieve bone pain that often comes with osteoporosis.
| Population | Labeled dose |
|---|---|
| Adults | 2.5–20 mg/day in 2–4 divided doses; 2–4 week courses, repeated if needed |
| Elderly | 5 mg twice daily |
| Children | Up to 0.1 mg/kg/day |
What the research shows
Severe burns
Burns are where oxandrolone was studied most. A 2016 meta-analysis pooled 15 randomized trials with 806 patients (Li et al., Burns 2016):
| Outcome | Effect of oxandrolone vs control |
|---|---|
| Hospital length of stay | −3.0 days |
| Weight loss during the catabolic phase | 5 kg less weight lost |
| Donor-site healing time | −4.4 days |
| Lean body mass at 12 months | +10.8% |
| Mortality | RR 0.85 (not significant) |
| Liver dysfunction | RR 1.15 (not significant) |
An updated 2025 meta-analysis found no mortality benefit. In adults, it found liver enzyme elevations in 19% vs 5% of patients (p = 0.002) (Lou et al., World J Emerg Surg 2025).
In children with burns over 30% of their body, oxandrolone at 0.1 mg/kg twice daily for 12 months was compared with no oxandrolone (Porro et al., J Am Coll Surg 2012). Results:
- Lean body mass: only a trend on oxandrolone alone (p = 0.06). The gain was significant when oxandrolone was combined with exercise.
- Bone mineral content: higher from year 2 to year 5 in children aged 7–18.
- Growth: fewer children fell more than 2 standard deviations below normal height velocity: 8% vs 48% at year 1, and 7% vs 32% at year 2.
Older men
The best-characterized trial in healthy older men randomized men aged 60–87 to 20 mg/day oxandrolone or placebo for 12 weeks. They were then followed for 12 more weeks off the drug. The trial was reported across three papers (Schroeder et al., J Appl Physiol 2004; JCEM 2004; J Gerontol 2005):
| Measure | After 12 weeks on oxandrolone | 12 weeks after stopping |
|---|---|---|
| Lean body mass | +3.0 kg | Back to baseline |
| Total fat mass | −1.9 kg | −1.5 kg (most of the loss kept) |
| Trunk fat | −1.3 kg | Largely kept |
| Leg press 1RM | +6.7% | Back to baseline |
| Chest press 1RM | +9.3% | Back to baseline |
| HDL cholesterol | −0.49 mmol/L (≈ −19 mg/dL) | Largely reversed |
| LDL cholesterol | +0.57 mmol/L (≈ +22 mg/dL) | Largely reversed |
Two other findings stand out:
- More than 90% of the lean-mass gain, 2.7 kg, had already appeared by week 6.
- Muscle and strength gains disappeared within 12 weeks of stopping, while the fat loss mostly remained.
HIV-associated weight loss
The largest dose-ranging trial randomized 262 men with HIV-associated weight loss to placebo or oxandrolone at 20, 40 or 80 mg/day for 12 weeks (Grunfeld et al., JAIDS 2006):
| Daily dose | Weight change | Body cell mass change |
|---|---|---|
| Placebo | +1.1 kg | +0.45 kg |
| 20 mg | +1.8 kg | +0.91 kg |
| 40 mg | +2.8 kg | +1.5 kg |
| 80 mg | +2.3 kg | +1.8 kg |
Only the 40 mg weight gain, and the 40 and 80 mg body-cell-mass gains, were significantly greater than placebo. Doubling the dose from 40 to 80 mg added little.
Across the oxandrolone arms, the trial also found that the drug:
- raised liver transaminases;
- raised LDL and lowered HDL;
- suppressed LH, FSH and the men’s own testosterone.
Turner syndrome
Girls with Turner syndrome are already treated with growth hormone. A trial in 133 such girls added oxandrolone or placebo (Menke et al., JCEM 2010):
| Arm | Adult height gain | Notes |
|---|---|---|
| Placebo | +7.2 cm | — |
| Oxandrolone 0.03 mg/kg/day | +9.5 cm | Significant (p = 0.02) |
| Oxandrolone 0.06 mg/kg/day | +8.3 cm | Not significant: faster bone maturation; more virilization |
A 2019 Cochrane review of 6 randomized trials estimated an average gain in final adult height of +2.7 cm (95% CI 1.3–4.1) (Mohamed et al., Cochrane 2019).
Why the FDA withdrew it
- Earlier doubts. A 1984 FDA advisory committee had already “unanimously concluded that there was no evidence of efficacy for oxandrolone.”
- 2019. The holder of the original application, Gemini, had stopped marketing the drug and asked for its approval to be withdrawn.
- December 2022. FDA told the company that a potential safety problem was serious enough to remove the drug from the market.
- June 28, 2023. FDA withdrew the original application and all generic approvals (Upsher-Smith, Sandoz, Par) (88 FR 41970).
- September 2023. FDA formally determined that the benefit-risk profile was “unfavorable without substantial evidence to support effectiveness.” Oxandrolone was removed from the Orange Book, and FDA will not approve new generics unless new clinical studies support them (88 FR 62799).
As a result, no FDA-approved oxandrolone is sold in the US. Oxandrolone remains a Schedule III controlled substance, and anything sold as “Anavar” today comes from outside the regulated drug supply.
Side effects and risks
Boxed warning
The Oxandrin label carried the boxed warning shared by anabolic steroids:
- Peliosis hepatis. Blood-filled cysts form in the liver and can cause liver failure or bleeding into the abdomen.
- Liver cell tumors. These are usually benign, but malignant and fatal tumors have been reported.
- Blood lipid changes. HDL falls and LDL sometimes rises, which is linked to atherosclerosis.
The NIH’s LiverTox database ties the 17α-alkylated steroids, the class oxandrolone belongs to, to several forms of liver damage (LiverTox: Androgenic Steroids):
- prolonged cholestatic jaundice;
- peliosis hepatis;
- nodular regeneration;
- adenomas;
- hepatocellular carcinoma.
Lipids
The cholesterol changes are the most consistent lab finding. In the older-men trial, 20 mg/day lowered HDL by about 19 mg/dL and raised LDL by about 22 mg/dL within 12 weeks. Both largely reversed after stopping. The HIV trial found the same direction of change.
Warfarin interaction
The label reported a large interaction with warfarin. In 15 healthy volunteers on warfarin, oxandrolone at 5–10 mg twice daily produced these changes:
| Measure | Warfarin alone | With oxandrolone |
|---|---|---|
| S-warfarin half-life | 26 h | 48 h |
| S-warfarin AUC | 4.55 ng·h/mL | 12.08 ng·h/mL |
| Warfarin dose needed for INR 1.5 | 6.13 mg/day | 1.13 mg/day (about 80% lower) |
Bleeding also occurred during the study: 9 of 15 volunteers had microscopic blood in the urine, and 1 had bleeding gums.
Hormonal suppression and virilization
“Mild” does not mean non-suppressive. In the HIV trial, oxandrolone suppressed LH, FSH and the men’s own testosterone. In girls with Turner syndrome, the higher dose (0.06 mg/kg/day) caused significantly more virilization than placebo (p under 0.001). Virilization in women can include voice deepening, facial hair growth and clitoral enlargement, and these changes may not reverse.
Key takeaways
- An oral DHT derivative that does not aromatize. The 17α-methyl group makes it orally active and links it to the class’s liver risks. The 2-oxa A-ring blocks conversion to estrogen.
- Short half-life. About 10 hours in adults and 13 hours in older adults, which is why the label split dosing through the day.
- Real but modest effects. About 3 kg of lean mass in 12 weeks in older men, and faster recovery in burns. The muscle gains disappeared within 12 weeks of stopping.
- Higher doses gave little extra. In the HIV trial, 80 mg/day did no better than 40 mg/day for weight gain.
- Lipids and liver are the main risks. HDL fell by about 19 mg/dL in older men, and liver enzyme rises were about four times more common than with control in adult burn trials.
- No longer an approved drug. FDA withdrew all US approvals in 2023 for lack of demonstrated benefit relative to risk.
Sources
- Fox M, Minot AS, Liddle GW. Oxandrolone: a potent anabolic steroid of novel chemical configuration. J Clin Endocrinol Metab. 1962;22:921–924. PubMed.
- Pappo R. US Patent 3,128,283, assigned to G.D. Searle; filed 1961, granted April 7, 1964. Google Patents.
- Savient Pharmaceuticals. Oxandrin (oxandrolone tablets, USP) prescribing information, NDA 013718/S-023, 2005. FDA; DailyMed.
- Sandoz. Oxandrolone tablets prescribing information. Label PDF.
- Food and Drug Administration. Notice withdrawing approval of Oxandrin (NDA 013718) and four oxandrolone ANDAs. Federal Register. June 28, 2023;88:41970 (FR Doc 2023-13733). govinfo.
- Food and Drug Administration. Determination on the withdrawal of Oxandrin (oxandrolone) tablets for reasons of safety or effectiveness. Federal Register. September 13, 2023;88:62799 (FR Doc 2023-19796). govinfo.
- Li H, Guo Y, Yang Z, et al. The efficacy and safety of oxandrolone treatment for patients with severe burns: a systematic review and meta-analysis. Burns. 2016;42(4):717–727. PubMed.
- Lou J, Xiang Z, Zhu X, et al. Oxandrolone for burn patients: a systematic review and updated meta-analysis of randomized controlled trials from 2005 to 2025. World J Emerg Surg. 2025;20(1):75. PubMed.
- Porro LJ, Herndon DN, Rodriguez NA, et al. Five-year outcomes after oxandrolone administration in severely burned children: a randomized clinical trial of safety and efficacy. J Am Coll Surg. 2012;214(4):489–502. PubMed.
- Schroeder ET, Zheng L, Yarasheski KE, et al. Treatment with oxandrolone and the durability of effects in older men. J Appl Physiol. 2004;96(3):1055–1062. PubMed.
- Schroeder ET, Zheng L, Ong MD, et al. Effects of androgen therapy on adipose tissue and metabolism in older men. J Clin Endocrinol Metab. 2004;89(10):4863–4872. PubMed.
- Schroeder ET, Vallejo AF, Zheng L, et al. Six-week improvements in muscle mass and strength during androgen therapy in older men. J Gerontol A Biol Sci Med Sci. 2005;60(12):1586–1592. PubMed.
- Grunfeld C, Kotler DP, Dobs A, et al. Oxandrolone in the treatment of HIV-associated weight loss in men: a randomized, double-blind, placebo-controlled study. J Acquir Immune Defic Syndr. 2006;41(3):304–314. PubMed.
- Menke LA, Sas TC, de Muinck Keizer-Schrama SM, et al. Efficacy and safety of oxandrolone in growth hormone-treated girls with Turner syndrome. J Clin Endocrinol Metab. 2010;95(3):1151–1160. PubMed.
- Mohamed S, Alkofide H, Adi YA, et al. Oxandrolone for growth hormone-treated girls aged up to 18 years with Turner syndrome. Cochrane Database Syst Rev. 2019;(10):CD010736. PubMed.
- National Institute of Diabetes and Digestive and Kidney Diseases. LiverTox: Androgenic Steroids. NCBI Bookshelf.