Beta-and alpha-adrenergic blockade and metabolic responses to insulin induced hypoglycaemia in diabetics.

The metabolic, autonomic and symptomatic effects of labetalol and metoprolol in comparison with placebo, were studied during insulin induced hypoglycaemia in 5 non-insulin dependent diabetics. Both drugs suppressed the expected increase in heart rate during hypoglycaemia, but did not affect awareness of hypoglycaemic symptoms. Neither drug produced a rise in blood pressure during hypoglycaemia nor delayed the recovery from insulin-induced hypoglycaemia. In both there was no inhibition of release of gluconeogenic substrates such as free fatty acids. The results indicate that both metoprolol, a selective beta-blocker, and labetalol, a combined alpha beta-blocker, do not impair awareness of hypoglycaemia nor alter the metabolic response to hypoglycaemia in diabetics.