( - ) -alprenolol and ( - ) -dihydroalprenolol , however , acted as competitive antagonists at both sites ( pa2 values of 8.2 and 8.81 at beta-1 adrenoceptors and 6.47 and 6.43 at atypical beta adrenoceptors , respectively ) .
C0002334
alprenolol
C0012278
dihydroalprenolol