Transient hypertension after two phenylpropanolamine diet aids and the effects of caffeine: a placebo-controlled follow-up study.

OBJECTIVE

Reports of severe adverse reactions following the ingestion of single (75 mg) or double doses of the sympathomimetic drug phenylpropanolamine (PPA), with and without caffeine, prompted us to undertake a study of the effects of five drug preparations (75 mg PPA, 150 mg PPA, 75 mg PPA plus 400 mg caffeine, 400 mg caffeine, and placebo) in 16 resting, normotensive subjects. The study was of a double-blind, randomized, crossover design. Each subject consented to take the five drug preparations on different study days, which were separated by at least 48 hours.

RESULTS

Compared with blood pressure (BP) values obtained after placebo ingestion, significant BP increases occurred over several hours following 150 mg PPA and after 75 mg PPA plus 400 mg caffeine. Significant BP increases after ingestion of 75 mg PPA and after 400 mg caffeine were less frequent. The mean peak BP following 150 mg PPA was 173 +/- 9/103 +/- 4 mm Hg, compared with 148 +/- 4/97 +/- 3 mm Hg after the other three active preparations; after placebo, peak BP reached 137 +/- 8/85 +/- 5 mm Hg.

CONCLUSIONS

These results indicate that 150 mg PPA (the amount in two diet aids) substantially elevates BP. Our findings may explain some of the recent case reports of nontraumatic intracranial hemorrhage in young, healthy persons ingesting PPA at recommended or minimally greater dosages. We suggest physicians inform patients who are likely consumers of PPA (i.e., those with allergies, those with eating disorders, overweight persons, women during the postpartum period) and patients at risk for stroke (i.e., the elderly and hypertensive patients) of the risks of taking more than the recommended amounts of PPA and of combining caffeine with PPA.