- There is a strong association between men who use cannabis and men who obtain sildenafil from sources other than a prescribing physician.
Purpose This study examined the ways by which patients obtain nonprescription sildenafil and the patient predictors associated with nonprescribed use.
Methods We conducted this descriptive study via questionnaire-guided interviews with 231 male sildenafil users (ages 18 to 80) between December 1, 2002 and April 30, 2003 at outpatient Family Medicine and Urology Clinics at The Brooklyn Hospital Center, Brooklyn, NY. Patients were divided into 2 groups: those with erectile dysfunction (reported by the patients as defined by their physician) and those without.
Results The prevalence of erectile dysfunction in our total study population of sildenafil users (n=231) was 40.3% (n=93); 59.7% (n=138) did not have erectile dysfunction. Of those without erectile dysfunction, 76.1% (n=105) admitted to cannabis use, compared with 7.5% (n=7) of the subjects with erectile dysfunction. Patients without erectile dysfunction and history of cannabis abuse reported obtaining sildenafil from friends and street vendors significantly more often than non-cannabis users with erectile dysfunction (54.3%, n=57 vs 9.3%, n=8; P<.0001).
Conclusion Illicit use of cannabis is a strong predictor of recreational sildenafil use among patients without erectile dysfunction.
Published reports of improved sexual performance have prompted men without erectile dysfunction to use sildenafil inappropriately.1-4 Sildenafil has also been used to counteract the impotence-inducing effects of “club drugs” such as ecstasy.5
Cannabis, another widely abused street drug, is a known inhibitor of the cytochrome P450 3A4 isoenzyme pathway, the same pathway in which sildenafil is metabolized.6 Cannabis can thus potentiate the effect of sildenafil. A case report from 2002 has indicated that a young man using sildenafil and cannabis concomitantly suffered a myocardial infarction.7
In this study, we sought to answer the following questions:
- What methods did the men use to obtain sildenafil without a prescription?
- Why were the men taking sildenafil?
- Did these men increase the dose without physician supervision?
Setting, participants, and design
Two senior resident physicians from the Department of Family Practice at The Brooklyn Hospital Center asked male patients between the ages of 18 and 80 if they would be interested in participating in this descriptive study. Two hundred and thirty-one patients agreed to be interviewed during their outpatient clinic appointments in the Departments of Family Practice and Urology. We conducted these interviews between December 1, 2002 and April 30, 2003.
Patients with and without physician-diagnosed erectile dysfunction who were using sildenafil were included in this study. Patients were excluded if they were taking nitrates, had cognitive disabilities, were female, or if they could not read English.
The 1-page, 35-item questionnaire was read to the subjects by a resident, who provided additional explanations if needed. The researchers noted their responses to questions on demographics, medical history, social history, treatment duration of erectile dysfunction, method of procurement of sildenafil, and knowledge about the indications of sildenafil. The questionnaire was pretested on a small sample for comprehension prior to distribution.
We developed descriptive statistics and performed cross-tabulations using SPSS version 11.0 (SPSS, Inc, Chicago, Ill). We used a chi-square test to determine statistical significance between cannabis abuse and illicit sildenafil use. We established statistical significance at P<.05. The Institutional Review Board at the Brooklyn Hospital Center approved our research protocol, and we obtained consent from all the study participants.
Strong link between cannabis use and recreational sildenafil
TABLE 1 shows the demographic information of the entire study population (n=231). Our study found that patient predictors for recreational sildenafil use are a younger unmarried male who smokes cannabis. Of the men in the study, 138 (59.7%) reported erectile function prior to the use of sildenafil.
We decided to examine data from this subgroup of our study population. As shown in TABLE 2, patients with erectile function but with a history of cannabis abuse reported obtaining sildenafil from friends, street vendors, and the Internet significantly more often than those with erectile dysfunction who did not use cannabis.
Discussion: Is there a danger?
Our study showed a strong association between individuals who obtained sildenafil from sources other than a prescribing physician and those who used cannabis. These men purchased this prescription medication from street vendors, friends, family, or via the Internet. Illicit sildenafil users took the medication mainly to improve performance and increase desire–and they often increased the dose of the medication at will. The differences between patients with erectile dysfunction compared with those without were so great that much of our data proved to be statistically significant (TABLE 1).