Phenylpropanolamine for Veterinary Use
by Barbara Forney, VMD
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Overview |
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Therapeutic Class
Sympathomimetic, alpha-adrenergic agonist |
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Species
Dogs and cats |
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Commonly Prescribed by Vets for:
Urinary incontinence | |
Basic Information
Phenylpropanolamine HCL (PPA) is a sympathomimetic amine that causes the release of norepinephrine by indirectly stimulating both the alpha and beta-adrenergic receptors. Its primary use in veterinary medicine is to increase smooth- muscle tone of the urethra and the bladder neck. Other pharmacologic effects of PPA include vasoconstriction, increased heart-rate and coronary blood-flow, increased blood pressure and mild CNS-stimulation.
In humans PPA was used as a nasal decongestant and for appetite suppression but it has been withdrawn from the human market. There are some restrictions to the purchase of large quantities of PPA because it may be used illegally in the manufacturing of methamphetamine.
Dogs and Cats
Urinary incontinence is a common clinical problem in both dogs and cats. It is seen more commonly in dogs than in cats and certain populations or breeds of dogs are affected more frequently. It is most common in older, female spayed dogs. Large and giant breeds are more at risk as are dogs with docked tails and dogs that are overweight. Urinary leakage is most likely to occur when the animal is tired, relaxed or sleeping.
Although PPA is an effective nasal decongestant and appetite-suppressant in humans, it is less effective for this purpose in companion animals.
PPA needs to be given for several days before the full effects are seen. Client compliance with regular dosing also is important for this drug to work fully. Diethylstilbestrol also is used to treat urinary incontinence (see DES).
Phenylpropanolamine Side Effects
Rare: Restlessness, excitability, hypertension, anorexia or decreased appetite.
Precautions
- PPA should be used with caution in animals with glaucoma, prostatic hypertrophy, hypertension, hyperthyroidism, diabetes mellitus and cardiovascular disorders.
- It is not known if PPA crosses the placenta or is excreted in milk. There is some clinical evidence that PPA may decrease ovum implantation. It should be used only during pregnancy or lactation when the benefits outweigh the risks.
Drug Interactions
- PPA should not be administered with other sympathomimetic drugs such as ephedrine or epinephrine.
- PPA should not be used within two weeks of treatment with monamine oxidase inhibitors.
- The risk of hypertension is increased if PPA is given with NSAIDs including aspirin, reserpine, tricyclic antidepressants or ganglionic blocking agents.
- There is an increased risk of cardiac arrhythmia if PPA is given with cyclopropane or halogenated hydrocarbon anesthetic agents.
Overdose
Signs of overdoses with PPA resemble more-severe side-effects. Central nervous system signs can range from stimulation to coma. Cardiovascular signs can include both hypertension and rebound hypotension, bradycardia to tachycardia and finally cardiovascular collapse. Supportive treatment including gastric emptying, cathartics and activated charcoal may be used if the overdose was recent.
About the Author
Dr. Barbara Forney is a veterinary practitioner in Chester County, Pennsylvania. She has a master's degree in animal science from the University of Delaware and graduated from the University of Pennsylvania School of Veterinary Medicine in 1982.
She began to develop her interest in client education and medical writing 1997. Recent publications include portions of The Pill Book Guide to Medication for Your Dog and Cat, and most recently Understanding Equine Medications published by the Bloodhorse.
Dr. Forney is an FEI veterinarian and an active member of the AAEP, AVMA, and AMWA.
You can purchase books by Dr. Forney at www.exclusivelyequine.com
The information contained on this site is general in nature and is intended for use as an informational aid. It does not cover all possible uses, actions, precautions, side effects, or interactions of the products shown, nor is the information intended as medical advice or diagnosis for individual health problems or for making an evaluation as to the risks and benefits of using a particular product. You should consult your doctor about diagnosis and treatment of any health problems. Information and statements have not been evaluated by the Food and Drug Administration ("FDA"), nor has the FDA approved the products to diagnose, cure or prevent disease.
Wedgewood compounded veterinary preparations are not intended for use in food and food-producing animals.