Phenylpropanolamine

Phenylpropanolamine (PPA), sold under many brand names, is a sympathomimetic agent used as a decongestant and appetite suppressant. It was once common in prescription and over-the-counter cough and cold preparations. The medication is taken orally.

Side effects of phenylpropanolamine include increased heart rate and blood pressure. Rarely, PPA has been associated with hemorrhagic stroke. PPA acts as a norepinephrine releasing agent, indirectly activating adrenergic receptors. As such, it is an indirectly acting sympathomimetic. It was once thought to act as a sympathomimetic with additional direct agonist action on adrenergic receptors, but this proved wrong. Chemically, phenylpropanolamine is a substituted amphetamine and is closely related to ephedrine, pseudoephedrine, amphetamine, and cathinone. It is usually a racemic mixture of the (1R,2S)- and (1S,2R)-enantiomers of β-hydroxyamphetamine and is also known as dl-norephedrine.

Phenylpropanolamine was first synthesized around 1910 and its effects on blood pressure were characterized around 1930. It was introduced as medicine by the 1930s. It was withdrawn from many markets starting in 2000 after learning that it was associated with increased risk of hemorrhagic stroke. It was previously available both over-the-counter and by prescription. Phenylpropanolamine is available for both human and/or veterinary use in some countries.

Phenylpropanolamine is used as a decongestant to treat nasal congestion. It has also been used to suppress appetite and promote weight loss in the treatment of obesity and has shown effectiveness for this indication.

Phenylpropanolamine was previously available in the United States over-the-counter and in certain combination drug forms by prescription. One such example of the latter was a combination of phenylpropanolamine and chlorpheniramine, which dually contained decongestant and antihistamine effects, marketed by Tutag as 'Vernate'. These forms have all been discontinued in the U.S., although phenylpropanolamine remains available in some countries.

Phenylpropanolamine produces sympathomimetic effects and can cause side effects such as increased heart rate and blood pressure. It has been associated rarely with incidence of hemorrhagic stroke.

Certain drugs increase the chances of déjà vu occurring in the user, resulting in a strong sensation that an event or experience currently being experienced has already been experienced in the past. Some pharmaceutical drugs, when taken together, have also been implicated in the cause of déjà vu. The Journal of Clinical Neuroscience reported the case of an otherwise healthy male who started experiencing intense and recurrent sensations of déjà vu upon taking the drugs amantadine and phenylpropanolamine together to relieve flu symptoms. He found the experience so interesting that he completed the full course of his treatment and reported it to the psychologists to write up as a case study. Because of the dopaminergic action of the drugs and previous findings from electrode stimulation of the brain, it was speculated that déjà vu occurs as a result of hyperdopaminergic action in the mesial temporal areas of the brain.

There has been very little research on drug interactions with phenylpropanolamine. In one study, phenylpropanolamine taken with caffeine was found to quadruple caffeine levels. In another study, phenylpropanolamine reduced theophylline clearance by 50%.