The diffusion of a novel therapy into clinical practice - The case of sildenafil

Background: Erectile dysfunction is a common condition, yet in the past mos t affected men did not seek medical treatment. Objective: To examine how sildenafil (Viagra), a new medication for the tre atment of erectile dysfunction, has been incorporated into general medical practice. Subjects and Methods: The study population consisted of all male members of a group-model Massachusetts health maintenance organization (HMO) whose fi rst prescription for sildenafil was dispensed during the first 24 weeks of its availability through the HMO as a plan benefit (April 24, 1998, through October 8, 1998). Data collected on each member in the study population in cluded age, specialty of the prescribing physician, initial dose, use of pr ior treatments for erectile dysfunction, receipt of medications known to pr edispose to impotence, filling of a second prescription for sildenafil, and concomitant medical conditions (including hypertension, ischemic heart dis ease, hyperlipidemia, diabetes mellitus, and history of radical prostatecto my). Cross tabulations and logistic regression models were constructed to e valuate the potential associations between filling a second prescription fo r sildenafil and other characteristics of sildenafil users. Results: We identified 899 members who filled a first-time sildenafil presc ription in the 24-week period of interest. The majority of sildenafil presc riptions that were filled for the first. time (85%) occurred in the first 1 2 weeks of its availability. Most sildenafil users (84%) were between 45 an d 74 years of age (average age, 61 years; age range, 23 to 90 years), and a pproximately 40% had documentation of prior treatment for erectile dysfunct ion. Use was highest among those aged 55 to 64 years, with almost 5% of all male HMO members in that age group having received at least 1 sildenafil p rescription. Our cohort of sildenafil users was significantly more likely t o have hypertension (P<.01), hyperlipidemia (P<.01), and diabetes mellitus (P<.01) than persons who participated in a widely publicized clinical trial of the medication. Prescribing physicians were predominantly primary care physicians (78% were internists, and 11% were family practitioners). More t han 60% of sildenafil users filled a second prescription within 3 months of the first prescription; in multivariate analyses, factors associated with filling a second prescription included younger age and prior treatment for erectile dysfunction. Conclusions: Sildenafil was rapidly adopted into the clinical practice of p rimary care physicians for the treatment of erectile dysfunction in the man aged care setting. The patients for whom the drug was prescribed in the gen eral practice setting differed across many medical characteristics from stu dy subjects who participated in clinical trials of the drug.