Silodosin is a highly selective α1A-adrenoceptor antagonist approved for the treatment of the signs and symptoms of benign prostatic hyperplasia. Its clinical pharmacology profile offers a number of advantages, including uroselectivity, once-daily (QD) dosing, a standard dose of 8 mg QD that does not need to be adjusted according to age, and the feasibility of concomitant treatment with phosphodiesterase type 5 (PDE5) inhibitors and antihypertensive agents. Three phase 3 double-blind, randomised trials using the dosage regimen of 8 mg QD in >800 patients have shown that silodosin is significantly more effective than placebo (p <0.001) and at least as effective as tamsulosin (0.4 mg QD) in improving International Prostate Symptom Score (IPSS) total score, storage subscore, and voiding subscore. It is significantly more effective than tamsulosin in inducing simultaneous improvement of bothersome lower urinary tract symptoms such as incomplete emptying, frequency, and nocturia (p = 0.03). Safety data collected in 1581 patients exposed to chronic treatment with silodosin 8 mg QD have shown that the drug is safe and well tolerated. As was to be expected with a uroselective compound, cardiovascular effects have been minimal. The most common adverse reaction is "retrograde ejaculation" (anejaculation), which led to treatment discontinuation in only 3.9% of patients. The rare, drug class-related safety issue of intraocular floppy iris syndrome can be satisfactorily managed by warning patients simply to inform their ophthalmologist that they are or were on treatment with an α1-adrenoceptor blocker.
- α1A-adrenoceptor antagonist
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