Yamada Y, Matsuyama K, Takayanagi R, Kotaki H, Sawada Y, Iga T
Department of Pharmacy, University of Tokyo Hospital, Faculty of Medicine, University of Tokyo, Japan.
Yakugaku Zasshi. 1999 Jul;119(7):495-501. doi: 10.1248/yakushi1947.119.7_495.
Beta-adrenoceptor blocking agents (beta-blockers) have been widely used for the treatment of angina pectoris. The average/standard therapeutic doses vary widely among beta-blockers with the maximum of about a 120-fold difference. In order to clarify the mechanism of this difference, we analyzed retrospectively the pharmacological effects of beta-blockers in consideration of the beta 1-receptor binding affinity and the vasodilative activity on the basis of pharmacokinetics and the receptor occupancy theory. The analysis was performed on eight beta-blockers without a vasodilative effect and on four beta-blockers with a vasodilative effect. The beta 1-receptor occupancies at the steady-state condition after oral administration of standard doses were calculated by the use of the data on the concentration of unbound agents in plasma and on the dissociation constant of receptors. The estimated receptor occupancies were 87 +/- 6% or 88 +/- 10% for the beta-blockers with or without a vasodilative effect, respectively, and a significant difference was not observed between these groups. These results suggest that the beta 1-receptor occupancies may be a principal indicator for the therapeutic effects for angina pectoris regardless of their vasodilative effects.
