Drug interaction study of vardenafil 20mg and doxazosin 4mg or tamsulosin 0.2mg in patients with benign prostatic hyperplasia and erectile dysfunction to evaluate changes in blood pressure

Abstract

Purpose: This study aimed at evaluating the expected additive blood pressure (BP) lowering effect of vardenafil when administered in the background of chronic 1-blocker therapy. Materials and Methods: Patients (n=90) with symptomatic benign prostatic hypertrophy (BPH) and erectile dysfunction (ED) took vardenafil 20mg in the morning following repeated doxazosin gastrointestinal therapeutic system (GITS) 4mg (n=60) or tamsulosin 0.2mg (n=30) HS a day for 30 days. The standing and sitting BP at baseline, before taking the vardenafil and 30 minutes and 1 hour post vardenafil were measured 3 consecutive times. The data were analyzed by Student's t-test (paired), repeated measures of two-way ANOVA, chi-square tests and Pearson correlation analysis. Results: Doxazosin produced a significant reduction in systolic/ diastolic BP (- 12.3/ - 6.7mmHg), but tamsulosin did not. In the doxazosin group, the average reductions in BP from baseline (- 24.7/ - 15.8mmHg) were significantly higher than that for the tamsulosin group (- 14.6/ - 7.5mmHg However, the average BP change was not different in both group (- 12.4/ - 9.lmmHg in the doxazosin group and - 11.3/ - 6.4mm-Hg in the tamsulosin group) following a single dose of 20mg vardenafil. The higher the BP was at baseline, the more the reduction in BP was in both the doxazosin and tamsulosin groups. Two patients of tamsulosin showed a sitting systolic BP < 85mmHg, but they didn't experience dizziness. Conclusions: We recommend starting Vardenafil treatment in the background of chronic α1 blocker therapy, including tamsulosin, with a low dose and to increase the dose by monitoring the BP, particularly for the patients with hypertension.