[Comparison of the pA2 of various beta blocking agents]

The drug industry is now putting out specific beta 1 or beta 2 beta-blocking agents. The pA2 of various beta-blocking agents were determined on isolated organs-guinea pig atrium and trachea: practolol and acebutolol were considered as specific beta-1 inhibitors; butoxamine was a specific beta-2 inhibitor, while pindolol, oxprenolol, propranolol and alprenolol were specificity free. The pA2 quantifies the action exerted by an inhibitor. Cardioselectivity is expressed by the pA2 left atrium/pA2 trachea ratio. It exceeds 1 000 for practolol, it equals 30 for acebutolol, and is very slight for butoxamine. The pA2 therefore gives a good idea of the potential of the various drugs on the animal's isolated organ. However, these data cannot safely be extrapolated to man. Hence the necessity of conducting clinical pharmacological studies.