Factors that predict changing the type of phosphodiesterase type 5 inhibitor medication among men in the UK


Philip Kell, Archway Sexual Health Clinic, Whittington Hospital, Highgate Hill, London N19 5NF, UK. e-mail: pdkell@hotmail.com



To evaluate predictors of changing the type of phosphodiesterase type 5 (PDE5) inhibitor (switching) among men with erectile dysfunction (ED) in the UK, the largest consumer of PDE5 inhibitors in Europe, as switching medication is often associated with higher resource use, and there are three oral PDE5 inhibitor medications currently available.


Patients were identified from The Health Improvement Network database in the UK; men initiating therapy with sildenafil, tadalafil or vardenafil from May 2003 to August 2004 with ≥ 6 months of prescription history before and after their initial PDE5 inhibitor prescription were included. Switching was evaluated as the proportion of second PDE5 inhibitor prescriptions that were for a drug differing from the first. Logistic regression was used to adjust for factors that might be associated with switching (dose, age and the presence of hypertension, dyslipidaemia, diabetes or depression).


Of the 2703 eligible men who initiated PDE5 inhibitor treatment during the study period, 91 (3.4%) switched to a different PDE5 inhibitor at their second prescription. The choice of initial PDE5 inhibitor therapy was a highly significant predictor of switching; men initiated on sildenafil were less likely to switch than those initiated on tadalafil (P < 0.001) or vardenafil (P < 0.003). Age and the presence of comorbidities were not significantly associated with switching (P > 0.05).


Initiating ED therapy with sildenafil was associated with the lowest rate of PDE5 inhibitor switching, which might reflect treatment satisfaction and patient preference.