Pharmacology Update

Finasteride Tablets for Hair Growth

By William T. Elliott, MD, and James Chan, PharmD, PhD

In a classic example of making lemonade when life gives you lemons, Merck has turned its modestly effective benign prostatic hypertrophy (BPH) drug finasteride (Proscar) into a potential megamillion dollar hair growth drug called Propecia. Finasteride is the first oral hair growth product to be approved by the FDA, joining minoxidil (Rogaine), a topical product. Rogaine was recently approved for over-the-counter (OTC) use for male pattern baldness, leaving finasteride as the only prescription product for this indication.

Finasteride has been available for years in higher doses for the treatment of BPH. The drug is a competitive inhibitor of Type II 5 alpha-reductase, the enzyme that converts testosterone into dihydrotestosterone (DHT). It has been speculated that finasteride decreases scalp and serum DHT. In men with male-pattern hair loss, the balding scalp contains miniaturized hair follicles and increased amounts of DHT compared to hairy scalp.1

Indications

Finasteride as Propecia is indicated for the treatment of male pattern hair loss (adrogenetic alopecia) in men.

Potential Advantages

In contrast to minoxidil (Rogaine), finasteride is indicated for hair loss in the anterior mid-scalp area as well as the vertex. However, the hair growth effect in the anterior scalp is small compared to vertex hair growth, with studies showing a 6% increase for the anterior scalp compared to 11.6% at the vertex at 12 months.2

Potential Disadvantages

About 2% of patients in controlled clinical trials reported decreased libido, and about 1% reported erectile dysfunction and ejaculation disorders.1 In older men with benign prostatic hyperplasia, finasteride decreases serum prostatic-specific antigen by approximately 50%. In men 18-41 years of age, the mean decrease was from 0.7 ng/mL at baseline to 0.5 ng/mL at month 12.1 Until more data are available, considerations should be given to doubling the PSA levels in men undergoing this test while taking Propecia.

Propecia, unlike minoxidil, is not indicated for use in women. The drug may cause hypospadias in male fetuses; therefore, pregnant or possibly pregnant women should not handle crushed or broken tablets because of the possibility of absorption.1 Data suggest that finasteride may be more effective in Caucasians than Blacks or Asians.1

Dosing Information

Finasteride as Propecia is supplied in 1 mg tablets. The 1 mg tablet is taken once daily without regard to meals. It generally takes about three months or more of continuous administration before benefit is observed.1

Comments

Finasteride 5 mg was first introduced for the treatment of benign prostatic hyperplasia. Merck has now introduced a lower strength, 1 mg, for male-pattern hair loss. In clinical trials (men aged 18-41), finasteride produced significant mean hair counts in a one-inch diameter circle compared to placebo. The mean hair count changes from baseline compared to placebo at 12 months were 91 vs. -19 among Caucasians, 49 vs. -28 among blacks, 53 vs. -38 among Asians, and 67 vs. 5 among Hispanics.1 Hair count increased over the first year and leveled off the second year. Long-term effects are not known at this time. Discontinuation of treatment will result in reversal of increases in hair growth within 12 months. Finasteride has greater effect on vertex hair regrowth than on frontal hair growth. It is not clear how finasteride compares to minoxidil 2%. In the clinical trials, all patients received Neutrogena T/Gel.

Clinical Implications

Male pattern hair loss is not considered a disease but, rather, a normal course of aging, albeit with significant interindividual variations. Rogaine, a topical solution, was introduced in 1988. Pharmacia & Upjohn are launching a new Rogaine Extra Strength (minoxidil 5%, OTC) this year. Propecia will be joining this lucrative market in the next few months. It is unlikely that most health plans will cover Propecia. The cost to consumers is estimated to be $45-49 per month. Extensive direct to consumer advertising is expected for all male pattern baldness medications.

References

1. Propecia Product Information. Merck & Co., Inc. December 1997.

2. F-D-C Reports. The Pink Sheet. November 17, 1997.

In controlled clinical trials, side effects of finasteride included which of the following?

a. Erectile dysfunction

b. Ejaculation disorders

c. Decreased libido

d. All of the above