White Paper - Finasteride (Propecia)

Basic Science

Finasteride (Propecia) is a synthetic 4-azasteroid compound that is a specific inhibitor of type II 5-alpha reductase. 5-alpha reductase is the enzyme that converts testosterone (T) to dihydrotesterone (DHT). With decrease in DHT, hair follicles that would be susceptible to hair loss via the presence of DHT would have a lower likelihood of loss and also conversion of vellus hairs back to terminal hairs. The type II 5-alpha reductase isoenzyme is found predominantly in the hair follicles (and prostate).

Finasteride Clinical Trials

Finasteride slowed the progression of hair loss and increased hair growth in 1553 men aged 18 to 41 years when treated with 1 mg of finasteride as compared with placebo with continued improvement observed in an extension of the study with 1215 men. Evaluating these men for an entire 5-year period showed improvement over placebo in all clinical endpoints including hair counts in a 1” circle, patient questionnaire, investigator assessment, and global photographic assessment. The long-term evaluation of side effects showed a 0.3% incidence of patients who had loss of libido or erectile dysfunction at 5 years.

Whiting found that finasteride was helpful in older men aged 41 to 60 with a 24-month double blind, randomized, placebo-controlled study of 424 men using clinical endpoints of global photography, patient self-assessments, and investigator assessments. Another study involved nine pairs of identical twins who received finasteride or placebo for 12 months and were evaluated with global photographic assessments, hair counts, and patient self-assessments and were found to have statistically significant improvement in the treated group versus placebo.

Studies have shown clinical improvement in hair regrowth in both vertex (crown) as well as frontal regions of the scalp.

Finasteride Dosage

In 1997, the FDA cleared finasteride for use in the United States at a dose of 1 mg/day for androgenetic alopecia. A study by Drake showed that the 1 mg and 5 mg dosage of finasteride were comparable in reduction of DHT. In addition, although reduction of DHT was found with a 0.2 mg dosage, the 1 mg was noted to be superior.

Finasteride is cleared by the liver and caution should be taken in individuals with liver dysfunction. Dosage need not be adjusted with kidney insufficiency. Finasteride does not affect the P450 system, and no drug interactions have been reported. Finasteride is available only by physician prescription in the United States. Upon cessation of the medication, over time all clinical benefits are lost and the individual returns to placebo baseline.

Finasteride Side Effects

Side effects occur in less than 2% of patients and include 1.8% decreased libido (1.3% in placebo), 1.3% erectile dysfunction (0.7% placebo), and 0.8% decreased ejaculate volume (0.4% placebo). There is no statistically significant difference between treated and placebo when taken separately, but there is a statistically significant difference when all side effects are considered together (3.8% versus 2.1%). Moreover, side effects resolve in 58% of individuals who continue treatment.

Finasteride is known to reduce the serum prostate-specific antigen (PSA) by 30 to 50%. Accordingly, men over 40 years of age should have their PSA doubled for interpretive value. Consultation with your primary physician regarding finasteride and PSA should be undertaken.

Finasteride and Prostate Cancer Risk 2008 Udpate

In 2005 the Prostate Cancer Prevention Trial (PCPT) showed that finasteride at a dosage of 5 mg per day intended for benign prostatic hypertrophy decreased the likelihood for prostate cancer by 25% as compared with placebo. However, it appeared that finasteride increased the specificity and selectivity of prostate cancer detection, thus, a perceived increased rate of high Gleason grade tumors. The 2008 update of this study showed that the reason that finasteride seemed to increase the rate of high-grade tumors was that the prostate size was reduced by the medication. Also, this study showed a 30% reduction in the risk of prostate cancer. With a review of 500 prostate samples, a pathologist found that finasteride did not increase the risk of high-grade prostate cancer.

Finasteride and Professional Athletes

Finasteride has been shown to mask the effect of steroid abuse. Therefore, finasteride is banned in many professional sporting societies and associations. It is important that if you are a professional athlete you ensure that finasteride is not a banned substance in your sport before deciding to take it.

Finasteride in Women

For more information on finasteride use in women.

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