Serum concentrations of phenylpropanolamine and associated effects on blood pressure in normotensive subjects: a...

This study was undertaken to investigate the effects of racemic phenylpropanolamine (PPA) on blood pressure (BP) in normotensive human subjects following the administration of three different dosages of PPA (25 mg, 50 mg and 100 mg) as single doses and to determine whether any relationship existed between the serum concentrations of PPA and its possible effects on BP. Blood was sampled and BP measured at specified times. Phenylpropanolamine was determined by HPLC with UV detection. No significant changes in BP occurred following the 25 mg dose (5 +/- 7/6 +/- 6 mm Hg), whereas statistically significant changes were found after the two higher doses of 50 mg (26 +/- 16/12 +/- 13 mm Hg) and 100 mg (30 +/- 13/15 +/- 8 mm Hg). Increases in systolic pressure following the 50 mg and 100 mg doses appeared to show a better correlation with peak serum concentrations of PPA than did diastolic effects. Although serum concentrations of PPA increased linearly with increasing dose, no clear-cut correlation could be found between serum concentrations and BP effects. The pressor effects, however, became more noticeable following the 50 mg dose and were markedly increased following the 100 mg dose. Side-effects which were reported were relatively minor even at the higher doses.