Abstract

In the article on drug interactions (November 10, p. 90) we correctly stated that propranolol can prolong insulin hypoglycaemia, but gave a wrong explanation. The release of glucose from the liver is an adrenergic α-effect; it is unaffected by propranolol but can be blocked by phentolamine.¹ However propranolol prevents the release of lactate from muscle, which seems to be mediated by β receptors.¹ This lactate is subsequently converted in the liver to glucose. If no lactate is there to be converted, hypoglycaemia may result, especially when the liver contains little or no glycogen.