A new selective beta-adrenoceptor antagonist with carbanilate structure.

Bl343 Ac antagonized the responses to isoprenaline in guinea pig left atrial preparations in a competitive manner, while in guinea pig tracheal preparations it inhibited the responses to isoprenaline non-competitively. The response to salbutamol were inhibited only by high concentrations of BL 343 Ac. The pA2 value and slope of the Schild plot, which was less than unity, suggest that BL 343 Ac has no competitive beta 2-adrenolytic properties, and thus appears to be a cardioselective beta 1-adrenoceptor blocking agent.