Therapeutic doses of phenylpropanolamine increase supine systolic blood pressure

The anorectic agent phenylpropanolamine (PPA) has a low therapeutic index and can cause severe hypertension at doses as low as 85 mg. To determine the effects of a therapeutic dose on blood pressure, PPA 37.5 mg (as commercially available immediate release formulation) or placebo was administered orally to ten normotensive subjects using a randomized double-blinded crossover design. The mean increase in supine systolic blood pressure (BP) was greater after PPA (18.5 ± 10.7 mmHg) than after placebo (5.1 ± 5.4 mmHg, P = 0.005). Increases in systolic BP after PPA ranged from 8 to 43 mmHg. The BP increase due to PPA was postural, and there was no change in sitting or standing BP. Doses of BP available in over-the-counter formulations can increase supine systolic BP. Recent use of products containing PPA should be considered when evaluating patients with hypertension.