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Title: Adenosine A1-receptor occupancy predicts A1-receptor antagonist effects of N-0861. Author: Yasuda SU, Nagashima S, Douyon E, Benton RE, Woosley RL, Barbey JT. Journal: Clin Pharmacol Ther; 1998 Nov; 64(5):536-41. PubMed ID: 9834045. Abstract: OBJECTIVE: To evaluate the relationship between dose of N-0861 ([+/-]N6-endo-norbornan-2-yl-9-methyladenine), N-0861 plasma concentrations, and antagonism of adenosine-induced slowing of atrioventricular nodal conduction and to evaluate A1-receptor occupancy by antagonist present in plasma of subjects after administration of N-0861 to determine A1-selectivity of these effects. METHODS: The study was conducted in patients undergoing a clinically indicated electrophysiology study to evaluate atrioventricular nodal conduction. Nineteen subjects were enrolled in the study and received adenosine (60 to 140 microg/kg) before or during a bolus dose and maintenance infusion of specific doses of N-0861. Adenosine-induced slowing of atrioventricular nodal conduction was determined by measuring A-H intervals on the intracardiac electrocardiograms. Plasma concentrations of N-0861 were determined with an HPLC method. A1-Receptor occupancy by antagonist present in plasma from identical time points was determined with use of a radioreceptor assay. RESULTS: A linear relationship was shown between plasma concentration and dose of N-0861. A-H interval lengthening by 60 microg/kg adenosine was reduced by administration of N-0861. A linear relationship was observed between A1 occupancy and N-0861 concentration and between occupancy and antagonism of adenosine-induced A-H prolongation. CONCLUSION: The results suggest that the effect of N-0861 on antagonism of adenosine-induced prolongation of A-H interval, at the doses used in this study, were the result of effects at the A1 receptor.[Abstract] [Full Text] [Related] [New Search]