Saowalak Sawangdee. Effect of Phenylpropanolamine alone and in combination with Chlorpheniramine on blood pressure in rats . Master's Degree(Biopharmaceutical Sciences). Mahidol University. : Mahidol University, 2006.
Effect of Phenylpropanolamine alone and in combination with Chlorpheniramine on blood pressure in rats
Abstract:
Phenylpropanolamine (PPA) is a sympathomimetic drug that exerts its effect
mainly through the alpha-adrenergic receptor. It is used alone or in combination with
other compounds in prescription and over-the-counter (OTC) drug products as a nasal
decongestant. PPA alone in high doses is also used an appetite suppressant OTC
weight control drug. A pharmacoepidemiological study reported by The Hemorrhagic
Stroke Project in the year 2000 suggested an association between high dose PPA and
hemorrhagic stroke. However, the hemodynamic effect of PPA might be altered in the
presence of other compounds such as chlorpheniramine (CPM) as used in OTC cold
remedy (PPA, 0.3 mg/kg plus CPM, 0.04 mg/kg).
This study was designed to investigate the effect of PPA on blood pressure in
rats either administered alone or in combination with CPM. Blood pressure was
measured by indirect method at the rat’s tail. Before the test compound was orally
administered, as the baseline value, and then every 30 minutes for 120 minutes after
the administration. The results showed PPA at doses of 5, 15 and 30 times the used in
humans, a significantly increased in blood pressure in a dose-dependent manner.
When high dose PPA (30 times the dose used in humans, 9 mg/kg) was coadmininistered
with CPM at doses of 1, 3 and 6 times that used in humans (0.04, 0.12
mg/kg and 0.24 mg/kg, respectively), it was shown that CPM could reduce the
hypertensive effect of PPA in a dose dependent manner. This result suggests an
antagonistic effect of PPA and CPM on blood pressure. Our experiments also revealed
an antagonistic action of CPM on two hypertensive agents which act on different
receptors, i.e. α-methyl-hydroxytryptamine (a selective 5-HT2A agonist) and
phenylephrine (an alpha-adrenergic agonist). It was found that both the anti-alpha
adrenergic and antiserotonergic action of CPM might be involved in the hypertensive
effect of PPA.
A chronic experiment demonstrated a cumulative hypertension that could be
attenuated by CPM. In contrast, CPM failed to reduce the pressor response to PPA
especially on the 28th day. In addition, PPA elevated systolic blood pressure in the
proestrous group more than the non-estrous group and male group.