The diffusion of a novel therapy into clinical practice: the case of sildenafil

Erectile dysfunction is a common condition, yet in the past most affected men did not seek medical treatment.

To examine how sildenafil (Viagra), a new medication for the treatment of erectile dysfunction, has been incorporated into general medical practice.

The study population consisted of all male members of a group-model Massachusetts health maintenance organization (HMO) whose first 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 included age, specialty of the prescribing physician, initial dose, use of prior treatments for erectile dysfunction, receipt of medications known to predispose to impotence, filling of a second prescription for sildenafil, and concomitant medical conditions (including hypertension, ischemic heart disease, hyperlipidemia, diabetes mellitus, and history of radical prostatectomy). Cross tabulations and logistic regression models were constructed to evaluate the potential associations between filling a second prescription for sildenafil and other characteristics of sildenafil users.

We identified 899 members who filled a first-time sildenafil prescription in the 24-week period of interest. The majority of sildenafil prescriptions that were filled for the first time (85%) occurred in the first 12 weeks of its availability. Most sildenafil users (84%) were between 45 and 74 years of age (average age, 61 years; age range, 23 to 90 years), and approximately 40% had documentation of prior treatment for erectile dysfunction. 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 prescription. Our cohort of sildenafil users was significantly more likely to 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 than 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.

Sildenafil was rapidly adopted into the clinical practice of primary care physicians for the treatment of erectile dysfunction in the managed care setting. The patients for whom the drug was prescribed in the general practice setting differed across many medical characteristics from study subjects who participated in clinical trials of the drug. Arch Intern Med. 2000;160:3401-3405.