Sildenafil users engaged in unprotected sex with partners of unknown HIV status from twice as often to almost six times as often as non-users. HIV-positive MSM were almost twice as likely to be diagnosed with an STD if they were also Sildenafil users and the newly HIV infected were 2.5 times as likely to be users.
Further complicating the situation, 54% of users mixed Sildenafil with other drugs to enhance the sexual experience. One study reported that 36% of all Sildenafil users combined its use with other drugs, including methamphetamines (23%), ecstasy (18%), poppers (15%), ketamine (11%), and GHB (8%). A study among MSM seeking STD clinic services in San Francisco found Sildenafil to be used concurrently with ecstasy (43%), methamphetamines (28%), and amyl nitrate (15%).
Writing in the article, Jeffrey D. Klausner, MD, MPH, suggests that "Focused action is needed to target this ongoing public health problem. Although the current evidence of association exists only for Sildenafil, likely due to the relatively recent approval of Tadalafil and Vardenafil, the needed action should focus on all three phosphodiesterase inhibitors (PDIs), as the observed associations with Sildenafil use most likely would occur with drugs of identical nature. The labeling for PDIs should be modified to warn users of an increased risk for STDs, including HIV infection. Educational programs, particularly among physicians, MSM, and methamphetamine users, should be implemented to increase awareness as to the use of these medications and their association with STDs, including HIV infection."
In an accompanying editorial, Joseph S. Alpert, MD, University of Arizona Health Sciences Center, Tucson, is concerned about the public health implications when Sildenafil and its relatives are abused or used recreationally with illegal drugs. He points to a recent article published in The Lancet in which investigators from Rockefeller University reported on a patient who presented with a new strain of HIV virus that was considerably more virulent and progressed more rapidly to AIDS than any HIV virus previously found. Dr Alpert writes that "This patient had been abusing both Sildenafil and methamphetamine. The question that immediately leaped to mind was: What effect did the combined abuse of these drugs have on the patient? Could this have resulted in the development of the highly virulent HIV mutant? Does this combination drug abuse increase the likelihood of STD transmission and/or the propensity for unsafe sex?" Dr. Alpert also questions whether the risk of STD and unsafe sex is also increased in male heterosexual patients who use Sildenafil. He points to the need for increased physician and patient education as well as further exploration of the multiple implications surrounding abuse of Sildenafil.
The study is reported in "Sildenafil Use, Sexual Risk Behavior, and Risk for Sexually Transmitted Diseases, including HIV Infection: a Review" by Sean Swearingen, BA and Jeffrey D. Klausner, MD, MPH. It appears with the editorial, "Viagra: The Risks of Recreational Use" by Joseph S. Alpert, MD, in The American Journal of Medicine, Volume 118, Number 6, published by Elsevier.