Side-effects with long-term labetalol: an open study of 251 patients in a single centre.

An open study was carried out in 251 hypertensive patients, all but 10 of whom had been treated previously, mainly with beta-blockers or dihydralazine, to collect data primarily on the incidence of side-effects when long-term treatment with labetalol was substituted. Dosage ranged from 100 to 2400 mg per day (mean 654 mg per day) and treatment was continued for between 6 and 18 months (mean 7.8 months) in 229 patients. Labetalol proved to be at least as effective as previous therapy in the majority of patients and, although side-effects were reported in approximately half the study population, most were mild and transient requiring withdrawal in only 10%, within a few days or weeks in 20 patients. Scalp tingling was the most frequent of the side-effects particular to this drug. Postural hypotension and bradycardia was usually not very marked and troubles with micturition or sexual problems did not occur often. There was an improvement in Raynaud's and similar syndromes and arteritis in patients with these symptoms who had previously been receiving beta-blocking agents.