(For veterinary information only)
WARNING
The size of the tablet/medication is NOT an indication of a proper dose. Never administer any drug without your veterinarian's input. Serious side effects or death can occur if you give medications to your pet without your veterinarian's advice.
It is our policy not to give dosing information over the internet.
Brand Name: Proin
Available in 25mg, 50mg, and 75mg chewables; 18mg, 38mg, 74mg, and 145mg extended-release tablets
Background
The autonomic nervous system can be thought of as the “automatic” nervous system in that it controls physiologic functions that one is not aware of. Examples include sweating during anxiety, increases and decreases in heart rate or respiratory rate, dilation or constriction of the pupils, blood pressure changes, and other functions that enable humans to adapt to a changing environment. While the nervous system controls all these things, humans are unaware of when they happen, thanks to the autonomic nervous system. Phenylpropanolamine tightens the urinary bladder sphincter by providing extra stimulation to certain neurologic receptors. If this is all you need to know about how phenylpropanolamine works, then by all means, skip this section. If you want to know the longer version, be our guest and read it here.
The autonomic nervous system is divided into two portions: one for body maintenance and one to prepare for "fight or flight. "Phenylpropanolamine acts as a stimulant, promoting the 'fight or flight' reflexes within the body. This means that phenylpropanolamine has many effects and thus many uses in the treatment of different medical conditions.
This is best illustrated in the human medical market as phenylpropanolamine was widely used as an over-the-counter decongestant, an appetite suppressant to aid dieting, and a bladder sphincter tightener.
It was accessible in numerous forms on the shelves of every drug store in America, but two problems changed all that. The first problem is that this drug was found to increase the incidence of strokes and cerebral hemorrhage in people aged 18 to 49. The second problem is that phenylpropanolamine can be used in the illegal production of methamphetamine. The drug was withdrawn from the human market, and restrictions have been placed on quantities of the veterinary product that can be ordered. In some states, it is considered a controlled substance.
In veterinary medicine, phenylpropanolamine is used almost exclusively for the control of urinary incontinence in dogs and occasionally in cats. Phenylpropanolamine is able to increase sphincter tone in the urethra, thus curtailing inadvertent urine leakage. The increase in high blood pressure that was problematic in humans is not considered a significant issue to the pet population.
How this Medication is Used
Phenylpropanolamine is used to treat urinary incontinence. Regular phenylpropanolamine is generally given twice daily, while the extended-release version may be given once daily.
Only occasionally is this medication used as a decongestant in animals. If a dose is accidentally skipped, do not double up on the next dose. Give the medication when remembered and time the next dose according to the instructions.
An extended-release tablet that is given once a day has been recently approved.
Interactions with Other Drugs
In some cases of urinary incontinence, phenylpropanolamine is used in combination with estrogens, such as diethylstilbestrol or estriol. No harmful drug interactions are expected with this combination.
Phenylpropanolamine should not be used with L-Deprenyl (Anipryl) due to resulting unpredictable fluctuations in blood pressure. It is recommended that phenylpropanolamine be withdrawn for two weeks preceding the use of L-Deprenyl.
An increased risk of hypertension can also occur if phenylpropanolamine is given in conjunction with tricyclic antidepressants (such as amitriptyline or clomipramine), non-steroidal anti-inflammatory drugs (NSAIDs), or amitraz (the active ingredient of several tick control products).
Side Effects
Phenylpropanolamine stimulates a “fight or flight” response. This means that the following effects may be observed: rapid heart rate, elevation in blood pressure, and restlessness. Appetite loss or reduction may be a problem. An increase in thirst is also a common side effect.
Irritability and restlessness are documented side effects that can occur in humans. It is reasonable to consider that this medication may create similar effects in our pets. Other side effects generally not considered to be serious include a mild upset stomach (generally controlled by giving the medication with food), dilated pupils, panting, and increased thirst.
Potentially serious side effects would include high blood pressure (hypertension). This is rarely an issue in pets, but it could potentially happen. Urinary protein loss has also been reported.
Concerns and Cautions
When initiating therapy with phenylpropanolamine, it is important not to expect an immediate change in urinary incontinence. Several days of proper dosing will be needed before the effect can be assessed.
Before using phenylpropanolamine to control urinary incontinence, it is important to rule out other medical causes of incontinence, such as kidney disease and bladder infection.
These latter conditions are progressive and should be identified early in their course for meaningful treatment results.
Phenylpropanolamine should be stored in containers that protect it from light. Light exposure leads it to lose potency.
Phenylpropanolamine acts by causing the release of a hormone and neurotransmitter called norepinephrine. With chronic use, it is possible to deplete the body’s stores of norepinephrine, and the patient will appear to become resistant to the effects of the drug. This phenomenon is well described in people who use phenylpropanolamine as a decongestant, but it is unclear whether this occurs in dogs and cats.
The extended-release product is not approved for dogs weighing less than 10 lbs.
Regular phenylpropanolamine tablets are given twice daily. Extended-release tablets are given once daily. Extended-release tablets do not come in a size appropriate for dogs under 10 lbs. Extended-release tablets are not meant to be cut or split.
Because of its effects in elevating heart rate and blood pressure, phenylpropanolamine should not be used in patients with heart disease or pre-existing high blood pressure. This includes patients with glaucoma, hyperthyroidism, and diabetes mellitus, as well as those with certain types of cardiovascular disease. Check with your veterinarian if there are any questions.
It is our policy not to give dosing information over the Internet.