CARDIDSELECTIVE ~-BlDCKERS ARE BETTER FOR DIABETICS

The pharmacological selectivity and intrinsic sympathomimetic activity of ~·b lockers have little bearing on their clinical efficacy in hypertension and angina, but do affect their use in diabetics. As ~·blockers can delay recovery from h.ypoglycaemia, an agent with a mainly ~,-blocking elTect may be preferable to a non-selective agent like propranolol in diabetics prone to hypogtycaemic reactions. Atenolol has no effect on the rise of blood glucose after insulin-induced hypoglycaemia and aoebutolol snows less effect than propranolol. The effects of metoprolol on hypoglycaemia are less certain. The cardiovascular effects of hypoglycaemia are also altered difTerently by ~dioselective ~·blockers. Most o[lhe cardiovascular responses to hypoglycaemia are due to high serum levels of adrenaline (epinephrine). When both ~l and ~J receptors are blocked by propranolol. unapposed adrenaline vasoconshiction causes a rise of systolic and diastolic BP and reflex bradycardia. However. after selective blockade with metoprolol. adrenaline reduces diastolic BP and increases heart rate. It is also possible for patients on propranoloi lO have clinically important hypertensive responses to hypoglycaemia.

'When a beta·blocking drug is 10 be used in a diabetic polienllioble to hypoglycaemfc attacks, one a/the more

cardioselective drugs should be clwsen, bolh 10 lessen Ihe risk a/hypertensive anaeles and 10 allow more rapid recovery from low. blood.glucose leve/j , •

Editorial, woet I, 843 (r 6 Apr 1977)

'NPHARMA 7th May, 1917 p3