Oxandrolone (Oxandrin) is an anabolic steroid created by Searle Laboratories under the trademark Anavar, and introduced into the US in 1964. It is taken orally, and unlike other steroids delivered in this manner, most of which are Class II steroids, the majority of its effects are due to reaction with the androgen receptor. In sufficient dosage, Oxandrolone is highly likely to bind well with the receptor, and is therefore a Class I steroid, while having few other side-effects.

As opposed to most other anabolic steroids Oxandrolone has two major advantages: First of all it does not aromatize (convert to estrogen which causes gynecomastia - breast tissue) and it does not significantly influence on low dosages (10mg) body's normal testosterone production (HPTA axis). When dosages are high (this goes for any anabolic steroid) then your body feels that it has enough testosterone and it reduces the production of LH (luteneizing hormone) which no longer stimulates Leydig cells in testicles to produce testosterone therefore causing testicular atrophy (shrinking).
Post Cycle Therapy (PCT) is of course needed for high dosages (40-50mg) of this synthetic derivative of testosterone because as the dosage increases the influence on HPTA is bigger. Lack of PCT will of course lead to protein catabolism until body's normal testosterone secretion is back to normal.

The drug was prescribed for a number of medical disorders causing involuntary weight loss, in order to promote muscle regrowth. It had also been shown to be partially successful in treating cases of osteoporosis. However, in part due to bad publicity from its abuses by bodybuilders, Oxandrolone was discontinued by Searle Laboratories in 1989. It was picked up by Bio-Technology General Corporation, now Savient Pharmaceuticals, Inc. who, following successful clinical trials in 1995, released it under the tradename Oxandrin.

It was approved for orphan drug status by the Food and Drug Administration (FDA) in treating alcoholic hepatitis, Turner's syndrome, and weight loss caused by HIV. In addition, the drug has shown positive results in treating anaemia and hereditary angioedema. Clinical studies however have shown links between prolonged use of the drug and problems of liver toxicity similar to those found with other 17\u03B1-alkylated steroids. Even in small dosages, many users reported gastro-intestinal problems such as bloating, nausea, skin rash and itching (hives), black, tarry stools or light-colored stools, depression, unusual bleeding, unusual swelling, yellowing of the eyes or skin, and diarrhoea.

In rare cases, serious and even fatal cases of liver problems have developed during treatment with oxandrolone. Oxandrolone may increase the amount of low density lipoprotein (LDL; 'bad cholesterol') and decrease the amount of high density lipoprotein (HDL; 'good cholesterol') in the blood. This may increase the risk of developing heart disease.