BERKELEY, CA (UroToday Inc.) - Since the arrival of sildenafil (Viagra®) for the treatment of male sexual dysfunction to the marketplace on March, 27, 1998, an estimated 16 million men worldwide have tried the drug. Although sildenafil, and the two newer agents, vardenafil and tadalafil, were approved by the FDA for the treatment of erectile dysfunction, recent information has arisen regarding the use of this class of drugs (PDE5 inhibitors) for the enhancement of sexual performance in men without a medical indication. In addition, the association of PDE5 inhibitors with increased sexual risk behavior and sexually transmitted diseases (STD's), including human immunodeficiency virus (HIV) infection has been suggested.

A review was performed by S. G. Swearingen and J. D. Klausner from the San Francisco Department of Public Health to determine the rates of sildenafil usage among different populations, primarily among men who have sex with men, and to measure the association of sildenafil use with increased sexual risk behavior and sexually transmitted diseases. The review is published in the June, 2005 issue of the American Journal of Medicine.

To perform the review, 14 different studies pertaining to usage of sildenafil and its association with sexual practices and STD's were examined and their results compiled in meta-analysis form. No specific articles were found on the use of tadalafil or vardenafil and their association with different sexual practices and risks of STD transmission. Eight of the 14 studies reviewed had sampled participants from San Francisco.

The results showed the prevalence of sildenafil use ranged from 3% use ever among men and women attending dance clubs in England in 1999, to 32% use ever among men who have sex with men in San Francisco from 2000-2001. Eleven of the 14 studies focused more specifically on sildenafil use among men who have had sex with men. 7 studies had found that > 10% of these men had used sildenafil, with particularly high levels of use (42%) among HIV-positive men who have sex with men.

Thirty-six percent of all men who had used sildenafil had combined it with the use of other drugs including methamphetamines (23%), ecstasy (18%) and poppers (15%). Most men (54%) reported that the combination of the drugs enhanced their sexual experience. Four studies examined the source of sildenafil used by the study participants and all found that the majority (56-84%) reported obtaining the drug without a prescription. The studies also found an increase in unprotected anal sex with unknown or discordant HIV status with sildenafil users being between twice and six times more likely to engage in this risky behavior. The incidence of STD's was almost twice as prevalent in those men who used sildenafil compared to those who did not, and the incidence of HIV positivity was more than twice as likely among the users of the drug.

The authors suggest that focused action should be taken to respond to this ongoing public health problem. They suggest the labeling for PDE5 inhibitors should be modified to warn users of an increased risk for STD's, including HIV infection, due to the increased incidence of risky sexual behavior that the drugs seem to promote.

Am J Med. 2005 Jun; 118(6):571-7