Hot topic: Drug controversies involving finasteride, Zostavax

Boston – Two of the hottest controversies in today’s dermatologic drug therapy involve medical concerns surrounding finasteride (Propecia, Merck) and Zostavax (zoster vaccine live, Merck), said Stephen E. Wolverton, M.D., at the 2012 American Academy of Dermatology Summer Academy Meeting.

In the former area, recent publications attempt to link finasteride use with persistent sexual dysfunction (Irwig MS, Kolukula S. J Sex Med. 2011;8(6):1747-1753; Irwig MS. J Sex Med. 2012 Jul 12).

"Finasteride inhibits 5-alpha-reductase type 2, and increases - or at least leaves alone - the testosterone levels that are important to male sexual function," says Dr. Wolverton, Theodore Arlook Professor of Clinical Dermatology, Indiana University School of Medicine, Indianapolis.

In a review of all finasteride clinical trials involving 1,879 men, "The risk of sexual side effects including loss of libido, orgasmic abnormalities or erectile dysfunction in the group that took the drug was 3.8 percent, versus 2.1 percent for placebo (McClellan KJ, Markham A. Drugs. 1999;57(1):111-126)," Dr. Wolverton says. Study investigators reported, however, that these side effects resolved after patients discontinued the medication.

Therefore, excluding one small category, claims of persistent sexual side effects lack biologic plausibility, he says. "Testosterone influences sexual drive and erectile function, and testosterone levels should be the same or increased with finasteride, whereas the ejaculate volume theoretically would be reduced by finasteride due to the role of dihydrotestosterone in prostate function."

Because there's no routine diagnostic test in most areas of male sexual function, however, "It's all based on patient history, which potentially creates a strong financial incentive for patients to allege long-term harm when perhaps none occurred," he adds.

Zostavax debate
Another debate involves whether the herpes zoster vaccine paradoxically causes herpes zoster, Dr. Wolverton says. A live attenuated virus, Zostavax is essentially the same as the chickenpox vaccine but at least 14 times stronger, he says. It aims to boost patients' cell-mediated immunity to prevent reactivation of the varicella virus, which remains latent in the body after chickenpox has resolved.

A patient-safety advocate claims that the varicella-zoster vaccine actually has caused seven cases of shingles, Dr. Wolverton says.

In response, he points to a study involving 38,546 adults in which placebo-treated patients were twice as likely to develop herpes zoster, and three times as likely to have postherpetic neuralgia, as vaccinated patients (Oxman MN, Levin MJ, Johnson GR, et al. N Engl J Med. 2005;352(22):2271-2284).

Because the seven vaccinated patients who got shingles did not have the Oka virus strain that the vaccine contains, the vaccine did not cause the infection; it merely allowed it to happen as it would have in unvaccinated patients, Dr. Wolverton says. "That's an important distinction."

Disclosures: Dr. Wolverton reports no relevant financial interests.

Go back to the Dermatology Times eNews newsletter.