Fenfluramine potentiation of antihypertensive effects of thiazides

Hydrochlorothiazide, a drug which is often initially prescribed for mild to moderate hypertension, failed to lower blood pressures in 9 of 43 patients but concomitantly elevated plasma norepinephrine (NE) levels in all patients with hypertension. The 9 obese hydrochlorothiazide-resistant patients were then given fenfluramine, an anorectic, in addition to the thiazide. They were reevaluated after 2 and 5 wk, at which times there were reductions in blood pressures and marked reductions in the plasma NE levels which had been elevated by the hydrochlorothiazide. Since iatrogenic sympathetic activation seems undesirable in treating hypertension, fenfluramine may be useful in obese thiazide-resistant hypertensive patients when used in combination with a thiazide diuretic.