Finasteride

Hirsutism

In women with hirsutism low doses of finasteride (2.5 mg/day) are generally well tolerated [ ]. However, in a randomized study in 38 hirsute women finasteride 2.5 mg every 3 days was as effective as 2.5 mg/day and better tolerated [ ].

Prostate cancer

The effect of adding finasteride 5 mg/day to high-dose bicalutamide 150 mg/day has been studied in 41 men with advanced prostate cancer treated over a mean of 3.9 years [ ]. The serum prostate-specific antigen (PSA) concentration was measured every 2 weeks until disease progression. At the first nadir of PSA, the median fall from baseline was 96.5%; a second nadir occurred in 30 of 41 patients, with a median fall of 98.5% from baseline. The median times to each nadir were 3.7 and 5.8 weeks respectively. The median time to treatment failure was 21 months. Adverse reactions were minor, including gynecomastia. Sex drive was normal in 17 of 29 men at baseline and in 12 of 24 men at the second PSA nadir, but one-third of the men had spontaneous erections at both times. The authors concluded that finasteride provided additional intracellular androgen blockade when added to bicalutamide. The duration of control was comparable to that achieved with castration, with preserved sexual function in some patients.

Androgenetic alopecia

In an open comparative study of androgenetic alopecia in 90 men oral finasteride (1 mg/day for 12 months; n = 65) was compared with 5% topical minoxidil solution twice daily (n = 25) [ ]. The cure rates were 80% for oral finasteride and 52% for topical minoxidil. The adverse reactions were all mild, and did not lead to withdrawal of treatment. Of the 65 men given oral finasteride, six had loss of libido, and one had an increase in body hair at other sites; irritation of the scalp was seen in one of those who used minoxidil. These adverse events disappeared as soon as the treatment was withdrawn. The laboratory data did not show any statistically or clinically significant changes from baseline values to the endpoint, except for the serum total testosterone concentration, which was increased, and free testosterone and serum prostate-specific antigen in the finasteride group which were reduced from baseline values.

Benign prostatic hyperplasia

The benefit of combining an alpha-adrenoceptor antagonist with a 5-alpha-reductase inhibitor has been assessed in men with benign prostatic hyperplasia [ ]. Modified-release alfuzosin was more effective than finasteride, with no additional benefit in combining the drugs. The adverse reactions to alpha-blockade were postural hypotension, hypotension, headache, dizziness, and malaise; adverse reactions to finasteride were ejaculatory disorders and impotence.

The therapeutic and adverse effects of dibenyline, finasteride, and a combination of the two in 190 patients with symptomatic benign prostatic hyperplasia have been evaluated [ ]. Adverse reactions were more common with dibenyline than with finasteride alone or in combination with dibenyline. The drop-out rate was higher with dibenyline (16%) than finasteride alone (7.5%) or the two in combination (4.6%). The reported adverse reactions are listed in Table 1 .

In short-term studies the herbal preparation saw palmetto ( Serenoa repens ) and finasteride seem to give a similar degree of relief in benign prostatic hyperplasia [ ]. However, in a prospective 1-year comparative randomized trial in 64 men with category III prostatitis or chronic pelvic pain syndrome, in which finasteride 5 mg/day was compared with saw palmetto 325 mg/day, the mean NIH Chronic Prostatitis Symptom Index score fell from 24 to 18 with finasteride, but scarcely or not at all with saw palmetto [ ]. Adverse events included headache (n = 3) with saw palmetto and reduced libido (n = 2) with finasteride. Although one might envisage even more prolonged studies, these findings hardly suggest that saw palmetto is a serious replacement for finasteride, even though it is well tolerated.

Polycystic ovary syndrome

In 44 women with polycystic ovary syndrome treated with finasteride or flutamide for 6 months adverse reactions to flutamide were reduced libido, gastrointestinal disorders, and dry skin [ ]. Finasteride caused reduced libido, headache, and dry skin. Dry skin was reported in 68% of users of flutamide and in only 27% of users of finasteride.

Dutasteride (Avodart®) inhibits both types 1 and 2 and is approved for the treatment of symptomatic benign prostatic hyperplasia in a dose of 0.5 mg/day. It is about three times more potent than finasteride at inhibiting 5α-reductase type 2 and more than 100 times more potent at inhibiting type 1. Of 416 subjects, 11 withdrew because adverse events including mild to moderate reduction in libido [ ].

Androgenetic alopecia

In an unusual study, finasteride 1 mg/day was used for 1 year to treat male-pattern baldness in nine subjects; each had an identical twin who received placebo [ ]. Finasteride significantly improved hair growth. There were no drug-related adverse events, either clinical or biochemical.

Of 1553 men with male-pattern baldness who took finasteride 1 mg/day, all of whom had initially taken part in one of two 1-year placebo-controlled studies, 1215 continued into further controlled studies over another 4 years [ ]. There was durable improvement in scalp hair over 5 years and no new safety concerns were identified.