The effect of multiple doses of phenylpropanolamine on the blood pressure of patients whose hypertension was controlled with beta blockers.

Single-dose phenylpropanolamine (PPA) can cause blood pressure elevation in healthy volunteers and in patients whose hypertension is controlled with beta blockers. Few data exist on the effect of long-term PPA dosing on blood pressure in normotensive or hypertensive patients. Therefore, we studied the effect of multiple PPA doses in seven hypertensive men whose blood pressure was controlled with beta blockers. These patients had previously demonstrated a mean increase in blood pressure after 25 mg PPA compared to placebo. Each patient received 25 mg PPA 3 times a day for 6.3 days. Five patients completed the study. After drug therapy on days 1 and 7, statistically significant increases in the peak measured systolic and diastolic blood pressures from baseline were found, with ranges of maximum increase 3-22 mm Hg and 0-16 mm Hg, respectively. The peak measured blood pressures on days 1 and 7 were significantly different from placebo values for both systolic and diastolic pressures. The area under the blood pressure-time curve and the change between baseline and peak for systolic and diastolic blood pressures on days 1 and 7 were not significantly different. Tolerance and hypersensitivity were not detected. Several doses of PPA did not alter the blood pressure effect from the first-dose response, however, caution and close monitoring are still necessary for these patients.