Evaluation of intrinsic sympathomimetic activity of beta-adrenoceptor blocking drugs in the treatment of patients with angina pectoris.

Beta-adrenoceptor blocking drugs with intrinsic sympathomimetic activity (ISA) may be less effective in the treatment of patients with angina pectoris than some others that lack this property. A review of 14 trials comparing beta-adrenoceptor blocking drug with ISA and those without ISA in angina pectoris has been made. The overall picture emerges from both acute and chronic studies using subjective and objective endpoints, that there is no striking difference in effectiveness between the two kinds of beta-adrenoceptor blocking drugs. The one exception is pindolol (a drug with ISA) which, at higher doses, has been shown to be consistently worse than propranolol (a drug without ISA). The reasons for the similarity between propranolol and other bets-blocking drugs with ISA in the trials cited are either that the trial design was defective (the trials were mainly fixed dose comparisons) or that the stimulant effects of those drugs with ISA is not of sufficient magnitude to make a difference. It is suggested that further carefully constructed clinical trials should be carried out before the second reason can be accepted.