Phenylpropanolamine
A sympathomimetic amine once ubiquitous in over-the-counter decongestants and appetite suppressants (e.g. Dexatrim, Acutrim). It was withdrawn from US human use around 2000 after a study linked it to hemorrhagic stroke, especially in young women using it for weight loss.
01 Overview
Phenylpropanolamine (PPA, dl-norephedrine) is a noradrenergic sympathomimetic that was sold for decades as a nasal decongestant and as the active ingredient in leading nonprescription diet pills. Its appetite-suppressing effect is modest.
The Hemorrhagic Stroke Project, published in 2000, found an association between PPA — particularly in appetite-suppressant use by women — and hemorrhagic stroke. The FDA moved to withdraw it from OTC products, and it was reclassified as unsafe for human use in the US; it survives mainly in veterinary medicine (canine urinary incontinence). It remains a cautionary example among OTC anorectics.
02 Mechanism
A sympathomimetic amine that releases noradrenaline and directly stimulates adrenergic receptors, causing vasoconstriction (decongestion) and appetite suppression.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Former anorectic dose | 25–75 mg/day | Oral | Diet-pill formulations commonly delivered ~75 mg/day; withdrawn for human use in the US. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Appetite suppressionSmall short-term reduction in appetite and weight. | modest | Clinical | |
| Nasal decongestionVasoconstriction relieves nasal congestion (its other historical use). | effective | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Hemorrhagic strokeIncreased risk of hemorrhagic stroke, particularly in women using it as an appetite suppressant. | Life-threatening | Rare but the reason for withdrawal | Observational | |
| Hypertension and palpitationsRaised blood pressure and heart rate. | Moderate | Common | Clinical |