teratogenesis
Finasteride (Propecia) Adverse Reactions
Adverse reactions to finasteride are generally mild and transient. In a long-term (4 years) clinical trial in men with benign prostatic hypertrophy, the most frequently reported adverse reactions to finasteride were related to sexual function. At 1 year, the adverse reactions reported to be drug-related were impotence (erectile dysfunction), decreased libido, decreased ejaculate volume, ejaculation dysfunction, breast enlargement, breast tenderness, and rash (unspecified). There was no significant difference between finasteride and placebo in the incidences of impotence, decreased libido, and ejaculation dysfunction in years 2 to 4 of the study. From June 1992, when finasteride was approved, until February 1995, the FDA received reports of gynecomastia in 214 men (median age: 71 yrs). Most were taking a dose of 5 mg/day PO. Gynecomastia has been the most frequently reported adverse effect of this drug since it was marketed. The onset of gynecomastia ranged from 14 days to 2.5 years (median: 180 days). Thirty percent had unilateral gynecomastia, 25% had bilateral involvement, and, in the remainder of reports, this information was not specified. Twenty-seven percent of patients were also taking other medications that are known to cause gynecomastia. Gynecomastia resolved either completely or partially in 80% of subjects after finasteride was discontinued, however, in at least 2 cases, a secondary malignancy of primary intraductal breast cancer subsequently developed. Other post-marketing adverse reactions have included testicular pain and hypersensitivity reactions including pruritus, urticaria, and swelling of the lips and face.
In controlled trials of finasteride for the treatment of male pattern hair loss, 1.4% of patients discontinued therapy due to adverse events, compared with 1.6% of placebo-treated patients. Discontinuation of therapy because of a drug-related sexual adverse experience occurred in 1.2% of patients on finasteride and 0.9% of patients on placebo. The following adverse events were reported as at least possibly drug-related in finasteride-treated patients: libido decrease (1.8%), impotence (1.3%), and ejaculation disorder (1.2%), primarily decreased ejaculate volume. The incidence of each of the above adverse effects decreased to <= 0.3% by the fifth year of treatment.
By inhibiting the conversion of testosterone to DHT, finasteride and other 5-alpha-reductase inhibitors have the ability to cause teratogenesis, specifically abnormalities in the external genitalia of the male fetus (e.g., hypospadias).
[ Last revised: 7/6/2004 4:35:00 PM ]
References
. Green L, Wysowski DK, Fourcroy JL. Gynecomastia and breast cancer during finasteride therapy. N Engl J Med 1996;335;823.
. McConnell JD, Bruskewitz R, Walsh P et al. The effect of finasteride on the risk of acute urinary retention and the need for surgical treatment among men with benign prostatic hyperplasia. N Engl J Med 1998;338:557 - 63.
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