When taken by pregnant women, oxandrolone may have unintended effects such as masculinization on the fetus. Side effects
Women who are administered oxandrolone may experience virilization, irreversible development of masculine features such as voice deepening, hirsutism, menstruation abnormalities, male-pattern hair loss, and clitoral enlargement. Oxandrolone may disrupt growth in children, reducing their adult height. Because of these side effects, doses given to women and children are minimized and people are usually monitored for virilization and growth abnormalities. Like other androgens, oxandrolone can cause or worsen acne and priapism (unwanted or prolonged erections). Oxandrolone can also reduce males fertility, another side effect common among androgens. In an attempt to compensate for the exogenous increase in androgens, the body may reduce testosterone production via testicular atrophy and inhibition of gonadotropic activity.Unlike some AASs, oxandrolone does not generally cause gynecomastia because it is not aromatized into estrogenic metabolites. However, although no reports of gynecomastia were made in spite of widespread use, oxandrolone was reported in a publication in 1991 to have been associated with 33 cases of gynecomastia in adolescent boys treated with it for short stature. The gynecomastia developed during oxandrolone therapy in 19 of the boys and after the therapy was completed in 14 of the boys, and 10 of the boys had transient gynecomastia, while 23 had persistent gynecomastia that necessitated mastectomy. Though transient gynecomastia is a natural and common occurrence in pubertal boys, the gynecomastia associated with oxandrolone was of a late/delayed onset and was persistent in a high percentage of the cases.
The reduced ratio of anabolic to androgenic activity of oxandrolone often motivates its medical use in children and women because less androgenic effect implies less risk of virilization. The bodybuilding community also considers this fact when choosing between AASs.As oxandrolone is already 5α-reduced, it is not a substrate for 5α-reductase, hence is not potentiated in androgenic tissues such as the skin, hair follicles, and prostate gland. This is involved in its reduced ratio of anabolic to androgenic activity. Due to the substitution of one of the carbon atoms with an oxygen atom at the C2 position in the A ring, oxandrolone is resistant to inactivation by 3α-hydroxysteroid dehydrogenase in skeletal muscle. This is in contrast to DHT, and is thought to underlie the preserved anabolic potency with oxandrolone. Because it is 5α-reduced, oxandrolone is not a substrate for aromatase, hence cannot be aromatized into metabolites with estrogenic activity. Oxandrolone similarly possesses no progestogenic activity.Oxandrolone is, uniquely, far less hepatotoxic than other 17α-alkylated AASs, which may be due to differences in metabolism. Pharmacokinetics
The oral bioavailability of oxandrolone is 97%. Its plasma protein binding is 94 to 97%. The drug is metabolized primarily by the kidneys and to a lesser extent by the liver. Oxandrolone is the only AAS that is not primarily or extensively metabolized by the liver, and this is thought to be related to its diminished hepatotoxicity relative to other AASs. Its elimination half-life is reported as 9.4 to 10.4 hours, but is extended to 13.3 hours in the elderly.