To examine the hemodynamic interactions of the phosphodiesterase type 5 (PDE-5) inhibitor tadalafil with the uroselective alpha_1-blocker alfuzosin (10 mg daily), commonly prescribed for benign prostatic hyperplasia-related lower urinary tract symptoms. Erectile dysfunction is commonly associated with lower urinary tract symptoms. PDE-5 inhibitors are the first-line treatment of choice for erectile dysfunction. When co-administered with alpha₁-blockers, PDE-5 inhibitors could induce orthostatic hypotension.

During each of the two periods of a randomized, double-blind, placebo-controlled, crossover study, 18 healthy middle-aged men received alfuzosin 10 mg daily for 7 days and either a single 20-mg dose of tadalafil or placebo on day 7. The blood pressure and heart rate were monitored before and for 24 hours after tadalafil or placebo.

The combination of tadalafil 20 mg with alfuzosin 10 mg daily elicited a maximal decrease in standing systolic blood pressure that was not significantly different from that after placebo (mean difference 4.35 mm Hg, P = nonsignificant). Analysis of the blood pressure outliers showed that only 1 subject had an asymptomatic standing systolic blood pressure of less than 85 mm Hg. No vasodilatory adverse events were observed with the combined medication.

In healthy, middle-aged men, tadalafil 20 mg showed no clinically relevant hemodynamic interactions with alfuzosin 10 mg daily.