Metabolic actions of a single atenolol and metoprolol dose.

Atenolol (CAS 29122-68-7) and metoprolol (CAS 37350-58-6) are beta 1-selective adrenoceptor antagonists without intrinsic sympathomimetic activity. beta-Receptor blockers influence carbohydrate- and lipid metabolism. Liver is a central organ of these processes. The metabolic fate of a single oral atenolol and metoprolol dose and their actions on carbohydrate- and lipid parameters have been investigated. Healthy male rats received a dose reducing heart beat/min by 25% (atenolol: 6 mg/kg; metoprolol: 10 mg/kg). About 9% of atenolol is metabolized by cytochrome P-450 (P-450). P-450-dependent functions (aminopyrine-N-demethylase, hexobarbital biotransformation time) were not inhibited. Serum bilirubin was normal. Triglyceride (TG), total cholesterol and HDL-cholesterol levels of the plasma were not affected. Transient blood glucose increase was measured returning to initial value at 120 min. Metoprolol is metabolized by hepatic monooxygenases. P-450-dependent functions were inhibited correlating to the lowered P-450-content of the microsomes. High TG level and decreased HDL-cholesterol content were measured. Blood glucose was significantly high. The liposoluble metroprolol affected the hepatic functions more than the hydrophilic atenolol. The monitoring of blood glucose during beta-receptor antagonist treatment may be suggested.