Radioreceptor assay for serum levels of cetamolol, a new beta-adrenoceptor antagonist.

Cetamolol hydrochloride, viz 2-[2-[3-(1,1-dimethylethyl)amino-2-hydroxy-propoxy]phenoxy]-N- methylacetamide hydrochloride, is a potent beta-adrenoceptor antagonist with moderate cardioselectivity and intrinsic sympathomimetic activity. In support of ongoing clinical trials, a radioreceptor assay has been developed to measure serum drug levels. In this assay, serum extracts containing cetamolol compete with [3H]-dihydroalprenolol for rat lung binding sites. This method which is sensitive to 1 ng/mL has been validated with respect to stability, blank, specificity, accuracy, within-assay precision, between-assay precision and parallelism. This method has been applied to a preliminary clinical study where serum drug levels were detectable up to 24 h after a single oral dose of 10 or 25 mg cetamolol hydrochloride.