Enhancement of insulin hypoglycaemia by beta adrenoceptor antagonists

Interaction of insulin with beta-adrenoceptor antagonists was studied in conscious rabbits. Propranolol and metoprolol did not modify the peak of insulin hypoglycaemia but delayed its recovery. Practolol, sotalol and 1-INPEA enhanced the peak effect and delayed the recovery of insulin-induced hypoglycaemia. H 35/25 and d-INPEA did not modify insulin hypoglycaemia. The beta-blockers did not produce significant hypoglycaemia per se. Since sotalol, 1-INPEA (specific beta-adrenoceptor antagonists devoid of local anaesthetic activity); practolol and metoprolol (selective cardiac beta-1 adrenoceptor antagonists) enhanced hypoglycaemic action of insulin and H 35/25 (a selective beta-2 adrenoceptor antagonist) failed to affect it, it seems that selective beta-adrenoceptor blockade (similar to cardiac beta-1 adrenoceptors) mediates enhancement of insulin hypoglycaemia. Caution should, therefore, be exercised in administering beta-adrenoceptor antagonists and insulin together. A reduction in the dose of insulin may be necessary.