Clinical Pharmacology of α1-Adrenoceptor Antagonists

Abstract

Benign prostatic hyperplasia (BPH) is the most prevalent condition to affect men beyong middle age. α₁-adrenoceptor blockers have been used in the treatment of BPH for more than 20 years and their effect on the lower urinary tract is now well established. These agents as a class have produced consistent improvements in both symptom scores and urinary flow rates in around 60–70% of patients treated. This efficacy is balanced against a small, but significant, incidence of side-effects, that consist of headaches, dizziness, nasal stuffiness, tiredness and very occasionally postural hypotension. There are important other effects of α₁-adrenoceptor blockers; for example in men with hypertension, these agents generally produce a clinically significant reduction in both systolic and diastolic blood pressures. There is also well documented evidence of a reduction in LDL cholesterol levels as well as serum triglycerides. A new and interesting observation is that patients receiving certain α₁-adrenoceptor blockers notice improvement in their sexual function and in particular in the quality of their erectile response. This effect has been attributed to decreased sympathetic vasoconstrictor tone to the helicine arteries supplying the lacunar spaces of the corpora cavernosa in the penis. In summary α₁-adrenoceptor blockers produce significant improvements in symptoms and flow rates in patients with bladder outflow obstruction due to benign prostatic hyperplasia. This is balanced against a small but significant incidence of side-effects, but some of these side-effects, such as a reduction in blood pressure in hypertensive patients, improvement in lipid profile and improvement in erectile function could be construed as beneficial.