A comparison between propranolol, practolol and betaxolol (SL75212) on the circulatory and metabolic responses to insulin-induced hypoglycaemia.

1. Six healthy male volunteers received equivalent intravenous beta-blocking doses of propranolol, practolol and betaxolol (SL75212) or saline at weekly intervals Sixty minutes later 0.1 unit/kg insulin was given intravenously. 2. In all studies, maximum hypoglycaemia (mean 1.2 mmol/l) was reached thirty minutes after insulin. Recovery from hypoglycaemia was delayed with propranolol but practolol and betaxolol had no effect. 3. Propranolol blocked the tachycardia and widening of pulse pressure seen in saline treated subjects. It also blocked the rebound rise in free fatty acids (FFA) and glycerol concentrations that followed the nadir of hypoglycaemia. 4. Neither practolol nor betaxolol had significant effects on pulse rate or blood pressure but betaxolol resembled propranolol in blocking the rebound rise in FFA and glycerol, while practolol blocked the rise in glycerol alone. 5. The magnitude of the rise in growth hormone following hypoglycaemia was similar in all groups, but the peak was earlier after practolol and betaxolol.