Effects of antihypertensive medications on carbohydrate metabolism

Propranolol, clonidine, and hydrochlorothiazide, three commonly used antihypertensives, have diabetogenic properties that lower insulin levels and raise growth hormone (GH) levels. In this prospective study, six-hour oral glucose tolerance tests (OGTTs) were performed before, at four weeks, and at eight weeks of therapy with the medications administered in standard therapeutic doses. Basal and postabsorptive glucose levels, insulin response to glucose, and the rise in GH induced by the declining glucose values in the last 3 hours of the OGTT were assessed. No changes due to therapy with any drug were noted in basal glucose levels, the area under the glucose response curve, or the area under the insulin response curve. The GH response was augmented modestly by propranolol at four weeks (13.4 ± 4.2 vs 5.9 ± 1.7 ng/ml, P < 0.05), but not by clonidine or hydrochlorothiazide. The findings of the present study suggest that all three antihypertensive agents are equally devoid of diabetogenic effect when given in conventional doses for up to eight weeks to hypertensive patients without preexisting glucose intolerance.