Effects of sustained-release oral phenylpropanolamine on the nasal mucosa of healthy subjects

Phenylpropanolamine (PPA) is widely used as a nasal decongestant administer ed orally in sustained release preparations and, in Sweden, the recommended dose nowadays is 50 mg twice daily for adults. The aim of this placebo-con trolled, cross-over study was to determine the onset and duration of the de congestive effect of 50 and 100 mg PPA in lj healthy subjects. All subjects arrived at the laboratory at 07.30 h. After an acclimatisation, the nasal mucosal baseline was established with rhinosterometry and the minimal cross -sectional area was measured using acoustic rhinometry. The systolic and di astolic blood pressures were also determined. Then all subjects were given their study drugs for the day and the measurements were repeated every hour for 8 h. This procedure was repeated for 3 days at 35 h intervals between the days. For purposes of comparison, the decongestive effect of oxymetazol ine nasal spray was studied on a separate day. The decongestive effect of 1 00 mg PPA was similar to that of topical oxymetazolins. It develops after 1 h and lasts for approximately 6 h. The decongestive effect of oxymetazolin e was significantly greater than that of 50 mg PPA and that of 100 mg PPA w as significantly greater than that of 50 mg PPA using rhinostereometry, but nor when using acoustic rhinometry. However, 50 mg PPA had no significant decongestive effect, compared with placebo, with rhinostereometry or acoust ic rhinometry. In the first 3h after administration of PPA, there was a dos e-response increase in the systolic and diastolic blood pressures, which th en returned to baseline. In conclusion, this study shows that PPA in double the recommended dose, i.e. 100 mg, has a significant decongestive effect o n the nasal mucosa in healthy subjects. However, when the dose of PPA is in creased the systolic and diastolic blood pressures also increase.