Phenylpropanolamine
Phenylpropanolamine HCl
Also known as: Proin · Propalin · Cystolamine · Uricon · Uriflex-PT · Urilin · PPA · dl-norephedrine · Diphenylpyraline
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Urethral sphincter hypotonus | 12.5-50 mg (total dose) or 1-2 mg/kg PO q8h | PO | q8h | — | 🌎 NA |
| Urethral sphincter hypotonus | Dogs weighing less than 40 lbs: ½ capsule PO daily. Dogs 40-100 lbs: 1 capsule PO daily. Dogs weighing >100 lbs: 1.5 capsules PO per day. | PO | q24h | — | 🌎 NA |
| Urethral sphincter hypotonus | 1-1.5 mg/kg PO two to three times a day | PO | q8-12h | — | 🌎 NA |
| Urethral sphincter hypotonus | 5-50 mg per dog PO q8h or 1.5 mg/kg PO q8h-12h | PO | q8-12h | — | 🌎 NA |
| Retrograde ejaculation | 3-4 mg/kg PO twice daily | PO | q12h | — | 🌎 NA |
- Urethral sphincter hypotonus: Using the time-release 75 mg capsules
- Urethral sphincter hypotonus: Controls 74-92% of dogs with primary sphincter mechanism incontinence. Over half of dogs not responding to regular PPA will respond to sustained-release PPA.
- Retrograde ejaculation: May be tried
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Urethral sphincter hypotonus | 12.5 mg PO q8h | PO | q8h | — | 🌎 NA |
| Urethral sphincter hypotonus | 1-1.5 mg/kg PO q8h | PO | q8h | — | 🌎 NA |
| Urethral sphincter hypotonus | 1.1 -2.2 mg/kg PO two to three times daily | PO | q8-12h | — | 🌎 NA |
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Phenylpropanolamine (PPA) is a non-selective sympathomimetic amine primarily used in veterinary medicine to manage urinary incontinence associated with urethral sphincter mechanism incompetence (USMI), particularly in spayed female dogs.
While it has historically been used as a nasal decongestant, its principal veterinary indication relies on its ability to increase smooth muscle tone in the bladder neck and proximal urethra.
Clinical Pearls:
- PPA is highly effective for acquired urinary incontinence in dogs, with success rates often exceeding 75-85%.
- Because it is a sympathomimetic, it can cause systemic adrenergic effects, most notably hypertension and behavioral changes (restlessness, anxiety).
- It is classified as a List 1 chemical in the USA due to its potential use as a precursor in methamphetamine synthesis, which may subject it to specific purchasing restrictions.
Mechanism of action
Phenylpropanolamine acts primarily as an indirect-acting sympathomimetic, though it may have some direct receptor agonist activity.
- Mechanism: It stimulates the release of endogenous norepinephrine from presynaptic nerve terminals.
- Pathway: Released norepinephrine binds to alpha-1 adrenergic receptors located in the smooth muscle of the internal urethral sphincter and bladder neck → increased sphincter tone → prevention of urine leakage.
- It also stimulates beta-adrenergic receptors, which can contribute to systemic cardiovascular effects (e.g., increased heart rate and contractility).
- Note: Prolonged use or excessive dosing frequency can theoretically deplete norepinephrine from storage sites, leading to tachyphylaxis (decreased response), though this is rarely documented in dogs or cats treated for incontinence.
Safety & warnings
Contraindications
- Glaucoma
- Prostatic hypertrophy
- Hyperthyroidism
- Diabetes mellitus
- Cardiovascular disorders
- Hypertension
- Severe renal or hepatic disease
Adverse effects
- Restlessness
- Anxiety
- Irritability
- Urine retention
- Tachycardia
- Hypertension
- Anorexia
- Rare reports of 'stroke' in dogs
- Panting
Precautions
Use with caution in patients with glaucoma, prostatic hypertrophy, hyperthyroidism, diabetes mellitus, cardiovascular disorders, or hypertension. May cause decreased ovum implantation, though clinical experience has not demonstrated untoward effects during pregnancy.
Drug interactions
Increased risk of arrhythmias. Propranolol may be administered should these occur.
Should not be given within two weeks of receiving MAOIs due to risk of severe hypertension and toxicity.
Increased chance of hypertension if given concomitantly.
Increased chance of hypertension if given concomitantly.
Should not be administered together as increased toxicity may result.
Increased chance of hypertension if given concomitantly.
Increased risk of hypertension
Risk of severe hypertensive crisis
Increased sympathomimetic effects and risk of hypertension
Monitoring
- Clinical effectiveness (reduction in urine leakage)
- Adverse effects (restlessness, irritability, anorexia)
- Blood pressure
- Clinical response (reduction in urinary incontinence)
- Heart rate and rhythm
- Behavioral changes (restlessness, pacing)
Pharmacokinetics
Half-life
Absorption
In humans, readily absorbed after oral administration. Onset of action is about 15-30 minutes with a duration of effect lasting approximately 3 hours (regular capsules/tablets).
Distribution
Reportedly distributed into various tissues and fluids, including the CNS. Unknown if it crosses the placenta or enters milk.
Metabolism
Partially metabolized to an active metabolite.
Elimination
80-90% is excreted unchanged in the urine within 24 hours of dosing.
Overdose
Clinical signs of overdosage may consist of an exacerbation of adverse effects (restlessness, anxiety).
Severe Overdose Signs:
- Cardiovascular: Hypertension to rebound hypotension, bradycardias to tachycardias, and cardiovascular collapse.
- CNS: Stimulation progressing to coma.
- Case report: A dog ingesting 48 mg/kg developed ventricular tachycardia and myocardial necrosis (resolved within 6 months).
Treatment:
- If recent, empty the stomach using usual precautions and administer charcoal and a cathartic.
- Treat clinical signs supportively.
-
WARNING: Do NOT use propranolol to treat hypertension in bradycardic patients. Do NOT use atropine to treat bradycardia.
- Hypertension may be managed with a phenothiazine (e.g., acepromazine at very low doses such as 0.02 mg/kg IV or IM). If unsuccessful, consider a CRI of nitroprusside.
- Contact an animal poison control center for further guidance.
Available products
Formulations
- Chewable tablets
- Timed-release capsules
- Oral solution
- 40 mg/ml syrup
- 15 mg tablet
- 50 mg tablet
Veterinary
- Phenylpropanolamine Chewable Tablets: 25 mg, 50 mg, & 75 mg (Proin, Propalin, Uriflex-PT, Uricon)
- Phenylpropanolamine Timed-Release Capsules: 75 mg (Cystolamine)
- Phenylpropanolamine oral solution: 25 mg/mL in 60 mL bottles (Proin Drops); 50 mg/mL in 30 mL and 100 mL bottles
- Propalin 40 mg/ml syrup
- Urilin 40 mg/ml syrup
- Proin 15 mg tablets
- Proin 50 mg tablets
Human-labeled
- Removed from the US market due to potential adverse effects in humans.
Regulatory status
Classified as POM-V (Prescription Only Medicine - Veterinary).
Classified as POM-V.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store phenylpropanolamine products at room temperature in light-resistant, tight containers.
Client information
Important: In order for this drug to be effective, it must be administered exactly as directed by your veterinarian. Missed doses will negate its effect and lead to recurrent leaking.
- It may take several days for the full benefit of the drug to take place.
- This medication manages incontinence but does not cure it; long-term use is typically required.
- When to call the vet: Contact your veterinarian if your pet demonstrates ongoing changes in behavior (such as excessive panting, restlessness, pacing, or irritability), if they stop eating, or if the incontinence persists or worsens.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.