Recovery from acute hypoglycaemia induced by the injection of insulin has been examined in six human subjects under control conditions, under non-selective beta blockade (propranolol) and under selective beta 1 blockade (metoprolol). The normal blood glucose recovery was biphasic with an initial rapid and a slower subsequent phase of recovery. The early recovery mechanism was unaffected by either form of beta blockade, but with propranolol the late phase of recovery was significantly prolonged. Rises in blood lactate and plasma free fatty acids following hypoglycaemia were markedly reduced by propranolol but to a much lesser degree with metoprolol. The counterregulatory hormonal responses of glucagon, cortisol and growth hormone were augmented appropriately for the prolonged hypoglycaemia associated with propranolol. Non-selective beta adrenergic blockade with propranolol is associated with an impairment of the late phase of blood glucose recovery from hypoglycaemia. The possible mechanisms of this impairment are discussed.

The acute hypoglycaemic reaction is accompanied by a rise in systolic and a slight fall in diastolic blood pressure and a tachycardia. In contrast, during beta-blockade with propranolol there is a rise of both systolic and diastolic blood pressures and bradycardia. Restoration of blood glucose to normal is delayed. With metoprolol there is a lesser increase in diastolic blood pressure and a slight tachycardia. Restoration of the blood glucose to normal is little delayed. When patients liable to hypoglycaemia require a beta-blocking agent, it is suggested that a selective blocker such as metoprolol should be used.

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