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Proin Chewable Tablets (25 mg) (Canada)

This page contains information on Proin Chewable Tablets (25 mg) for veterinary use.
The information provided typically includes the following:
  • Proin Chewable Tablets (25 mg) Indications
  • Warnings and cautions for Proin Chewable Tablets (25 mg)
  • Direction and dosage information for Proin Chewable Tablets (25 mg)

Proin Chewable Tablets (25 mg)

This treatment applies to the following species:
Company: Virbac

Phenylpropanolamine Hydrochloride Chewable Tablets

For Veterinary Use Only

DIN 02397382 (25 mg)

DIN 02397390 (50 mg)

DIN 02397404 (75 mg)


PROIN Chewable Tablets are scored and contain the active ingredient phenylpropanolamine hydrochloride (PPA), USP, in three different strengths: 25 mg, 50 mg and 75 mg per tablet in a palatable formulation.

Therapeutic Classification: PROIN Chewable Tablets (phenylpropanolamine hydrochloride) is a sympathomimetic amine closely related to ephedrine. Phenylpropanolamine hydrochloride is the nonproprietary designation for benzenemethanol, α-(1-aminoethyl)-, hydrochloride, (R*, S*)-, (±).

Proin Chewable Tablets (25 mg) Indications

PROIN Chewable Tablets are indicated for the control of urinary incontinence due to urethral sphincter hypotonus in female dogs.

Dosage and Administration

The total recommended dosage for oral administration to dogs is 2 mg/kg of body weight twice daily. PROIN Chewable Tablets are scored and dosage should be calculated in half-tablet increments.


PROIN Chewable Tablets may cause hypertension; therefore, the use of this drug is contraindicated in dogs with high blood pressure due to chronic hypertension.

Cautions: PROIN Chewable Tablets should not be used in dogs with incontinence due to urinary tract infection; the administration of this drug will mask clinical signs of a urinary infection. PROIN Chewable Tablets are not effective in dogs with incontinence due to neurologic disease or malformations.

Since the safe use of PROIN Chewable Tablets has not been evaluated in dogs intended for reproductive purposes, during pregnancy or in lactating bitches, this drug should not be administered to breeding, pregnant or lactating dogs.

PROIN Chewable Tablets should be used with caution in dogs with pre-existing heart disease, liver disease, kidney insufficiency, diabetes, glaucoma, and conditions with a predilection for hypertension.

PROIN Chewable Tablets may interact with the use of other drugs. (Please see the Drug interactions section under Clinical Pharmacology). PROIN Chewable Tablets may cause increased thirst; therefore, provide ample fresh water. This drug should be stored out of reach of dogs in a secured area.


Not for human use. Keep out of reach of children. Consult a physician in case of accidental ingestion by humans.

Adverse Reactions

A placebo-controlled clinical study involving 123 PROIN-treated dogs and 61 placebo-treated dogs was conducted for 28 days. The most common adverse reactions are shown in Table 1 below. In addition, one dog exhibited disorientation, nervousness, a 7.7% loss of body weight, and hypertension with proteinuria. A second dog exhibited restless behaviour, lethargy, a 2.8% body weight loss and proteinuria.

Table 1: Number and percentage of dogs with adverse reactions in the 28-day placebo controlled clinical study

Adverse reactions

PROIN-treated (N=123)

Placebo-treated (N=61)




Hypertension (≥160 mmHg)1.






Body weight loss (>5%)2.






Anxiety/aggression/behaviour change












Musculoskeletal Disorder



Insomnia/Sleep Disorder



1. One or more systolic blood pressure readings of > 160 mmHg

2. The “N” for weight loss is PROIN-treated N=118 and placebo N=59 because seven dogs did not have a final weight at the time of withdrawal from the study.

One-hundred fifty seven dogs continued into the 6-month open-label clinical study. The most common adverse reactions are listed in Table 2 below. In addition, one dog exhibited progressively worsening hypertension with proteinuria. Five dogs enrolled in the study with pre-existing heart disease. Of these, one dog developed systolic failure with an unknown relation to treatment.

Table 2: Number and percentage of dogs with adverse reactions in the 6-month open-label clinical study

Adverse reactions

Total N=125

Hypertension (≥160 mmHg)1.


Body weight loss (≥5%)












Anxiety/aggressive/behaviour change


1. Percent of dogs with systolic blood pressures of ≥160 mmHg on day 7 were 30.2% and on day 0 were 33.3%.

Post-market Adverse Drug Reactions: Although all adverse drug reactions (ADRs) are not reported, the following adverse reaction information is based on voluntary post-approval drug experience reporting. It is generally recognized that this method of reporting results in significant under-reporting of adverse drug reactions. It should be noted that suspected ADRs listed here reflect reporting and not causality. The adverse reactions are listed in decreasing order of frequency: hypertension, vomiting, mydriasis, bradycardia, piloerection, agitation/hyperactivity, panting, lethargy, erythema and hyperthermia.

Reports of death in dogs treated with phenylpropanolamine have been received internationally. Vocalization, neurologic signs and collapse were also reported in some of these cases. A necropsy of one dog revealed subarachnoidal and intraventricular hemorrhage in the brain.

For a copy of the Material Safety Data Sheet (MSDS) or to report adverse reactions, call Pegasus Laboratories at 1-800-874-9764.

Information for Owner or Person Treating Animal: Always follow the dosage instructions for PROIN Chewable Tablets provided by your veterinarian. Monitor your dog after giving PROIN Chewable Tablets to be sure all of it was consumed. If you have difficulty giving this drug, contact your veterinarian. It may take several days of treatment with PROIN Chewable Tablets before urinary incontinence improves. If you miss a dose, give it as soon as you remember. If it is close to the time for the next dose, skip the dose you missed and go back to the regular dosing schedule. Do not give two doses at once. It should only be given to the dog for which it was prescribed. Because PROIN Chewable Tablets are flavoured, store in a secure area.

Contact your veterinarian if you notice restlessness or irritability, loss of appetite, persistence or worsening of the incontinence, or any other unusual signs.

Consult your veterinarian before using PROIN Chewable Tablets with any other medications.

Clinical Pharmacology

Phenylpropanolamine is a chemical analogue of the endogenous sympathomimetic amines. It is an α-adrenergic agent which has been reported to increase urethral tone in dogs.2 Its mechanism of action is not well determined, but it is believed to cause the release of norepinephrine by indirectly stimulating both the alpha and beta-adrenergic receptors of the smooth muscle to increase smooth muscle tone of the urethra, bladder neck, and the internal urethral sphincter.3,4

The pharmacokinetics of phenylpropanolamine in dogs has not been well studied. In humans, phenylpropanolamine is readily absorbed after oral administration of solid dosage forms and has an onset of action of approximately 15-30 minutes and duration of effect of about three hours. In a published study in dogs, phenylpropanolamine disposition was characterized in three dogs administered phenylpropanolamine intravenously and orally in immediate-release and controlled-release formulations.5 The terminal elimination half-life averaged 3.5 ± 0.5 hours after the intravenous dose. Oral absorption from the immediate-release capsule was rapid and bioavailability was 98.2 ± 6.9 percent. Absorption of phenylpropanolamine from the controlled-release dosage form was biphasic; an initial rapid phase was followed by a second, slower absorption phase which continued over 16 hours. Plasma concentrations then declined with a half-life roughly parallel to the intravenous and oral immediate-release half-lives. Oral bioavailability from the controlled-release tablet was 93.7 ± 5.9 percent.

Drug Interactions: This drug should be used with caution in dogs receiving sympathomimetic drugs, tricyclic antidepressants, or monoamine oxidase inhibitors, as increased toxicity may result. Use with caution in dogs administered halogenated gaseous anesthetics as this may increase the risk of cardiac arrhythmias. Interactions can also potentially occur with drugs in the same therapeutic class as PPA, such as NSAIDs (non-steroidal anti-inflammatory) drugs. A laboratory study on human blood revealed that PPA used in conjunction with aspirin may potentiate decreased platelet aggregation.1 Moreover, drugs that affect the urinary pH may modify the renal/urinary excretion of PPA and influence its effect.

Animal Safety Studies: In a target animal safety study, PROIN Chewable Tablets was administered to 32 healthy male and female Beagle dogs at 0, 2, 6 and 10 mg/kg of body weight (0, 1, 3 and 5 times the recommended dose; 8 dogs per group) twice daily for 26 consecutive weeks. The most pronounced finding was a dose-dependent increase in blood pressure. Mean systolic blood pressure was increased in all PPA-treated groups compared to the control, but mean values for all 4 groups were within the normal range. Mean diastolic and mean MAP (mean arterial pressure) were higher in the 3X and 5X groups, and in the 1X males. Dogs in the 3X and 5X groups had more individual systolic, diastolic, and MAP values above the normal range than the control group dogs. A dose-dependent decrease in heart rate was observed in the 3X and 5X dogs. In the 0, 1, 3, and 5X groups, 5%, 34%, 44%, and 40% of the total number of heart rates obtained from electrocardiograms for each group over the course of the study were below the normal range (70-120 beats per minute), with the lowest value being 51 bpm in 4 of the 1X group dogs. One dog in each of the 1X and 5X groups had an elevated heart rate between 150-180 beats per minute on at least 2 of the 13 physical exams. One dog in each of the 1X and 3X groups developed gallop heart sounds after treatment began that were noted in 12 of 13 and 6 of 13 physical exams respectively. Dogs in the PPA-treated groups exhibited anxious/restless behaviour more frequently than the control group. One dog each in the 1X and 3X groups were responsible for the majority of the observations. A decline in mean body weight and body condition was observed in females in all 4 groups, including the control. One female in the 1X group lost 33% body weight. Vomiting and loose stool occurred in a dose-related fashion, and most of the vomiting episodes took place within 1 hour of dosing. Mean platelet counts were higher in at least one of the PPA-treated groups, with individual values up to 1.4X the upper limit of normal (ULN) in the 3X and 5X groups. The 3X and 5X groups had higher mean serum ALT values compared to the control. Mean ALT was within the normal range for all 4 groups. There were more dogs with ALT levels above the normal range in the 3 PPA-treated groups compared to the control, but increased values were transient and less than 1.8X ULN. All dogs had ALT values in the normal range at the conclusion of the study.

In a separate tolerance study, 6 healthy female Beagle dogs were administered PROIN Chewable Tablets at 20 mg/kg body weight (10 times the recommended dose) twice daily for 21 consecutive days. Mean systolic blood pressure was increased in the 10X group compared to the control, but mean values were within the normal range for both groups. Mean diastolic pressures were above the normal range on days 7 and 21 for the 10X group, and day 14 for the control. The 10X dogs had hypertensive mean MAP values on days 7 and 21, whereas the control dog mean MAP values were in the normal range. There was a trend in 10X dogs for lower heart rates following initiation of PPA treatment. Four of 6 dogs in the 10X group had heart rates below the normal range on day 7, whereas none of the control dogs did. The 10X group dogs had increased hematocrit, hemoglobin, RBC counts, urine specific gravity, and water intake consistent with transient, sub-clinical dehydration that occurred shortly after PPA treatment was started. All 6 dogs in the 10X group vomited at least once during the treatment period, whereas only 1 of the control dogs did. Most of the vomiting episodes took place within 1 hour of dosing. Mean platelet counts were also higher in 10X dogs on all 3 exam days; mean values were above the normal range on day 7, with individual values up to 1.5X ULN. The 10X group had a higher mean serum ALT value on day 7 than the control. Mean ALT values for both groups were in the normal range on all 3 exam days, but 2 dogs in the 10X group had ALT values up to 1.4X ULN on day 7; these elevated values were transient, and all dogs had normal ALT values on days 14 and 21.

For either study, there was no evidence of chronic hypertension-induced target organ damage; there were no clinical finding attributable to PPA on the ophthalmic exams, electrocardiogram evaluation, or gross necropsy and histopathology.


A 28-day placebo-controlled clinical study was conducted in 21 study sites across the U.S. The study included 184 dogs with urinary incontinence due to sphincter hypotonus of which 127 dogs (100 female, 27 male) were evaluated for effectiveness. Dogs were randomly assigned either to receive 2 mg/kg PROIN Chewable Tablets (123 dogs) or placebo (61 dogs) administered orally twice daily for 28 days. This product was found effective in controlling urinary incontinence in females dogs, based on a decrease in urinary accidents per week. Effectiveness was not demonstrated in male dogs. Changes to hematology and serum chemistry were not considered clinically significant or related to treatment.

Table 3: Mean urinary accidents per week by treatment group, females


Mean Urinary Accidents

(PROIN-treated, N=66)

Mean Urinary Accidents

(Placebo, N=34)
















One-hundred fifty seven dogs continued into the 6-month open-label clinical study conducted in 21 study sites across the U.S. All the dogs had participated in the 28-day placebo-controlled clinical study and had urinary incontinence due to sphincter hypotonus. Dogs were administered 2 mg/kg PROIN Chewable Tablets orally twice daily for 180 days. This product was effective for the control of urinary incontinence for 180 days based on 98.1% owner satisfaction. The dogs averaged just over one accident per dog per week. Changes in hematology and serum chemistry were not considered clinically significant or related to treatment.

The dogs voluntarily consumed 53.9% of the doses and 33.7% of the doses in food. The owners pilled the dogs 12.1% of the doses and were unable to administer 0.3% of the doses.


Store at controlled room temperature.

How Supplied

PROIN Chewable Tablets are scored and contain 25, 50 or 75 mg phenylpropanolamine hydrochloride per tablet. Twenty-five and 50 mg tablets are packaged in bottles containing 60 or 180 tablets, and 75 mg tablets are packaged in bottles containing 60 tablets.


1. Watson R, et al. Ephedra alkaloids inhibit platelet aggregation. Blood Coagulation and Fibrinolysis, 2010, 21: 266-271.

2. Richter K.P., Ling G.V. Clinical response and urethral pressure profile changes after phenylpropanolamine in dogs with primary sphincter incompetence. JAVMA, Vol. 187, No 6, September 15, 1985. 605-611.

3. Scott, L., Leddy M. and Bernay, F. Evaluation of phenylpropanolamine in the treatment of urethral sphincter mechanism incompetence in the bitch. J. Small Anim. Pract. 2002; 43(11): 493-6.

4. Noel, S., et al. Combined pharmacokinetic and urodynamic study of the effects of oral administration of phenylpropanolamine in female Beagle dogs. Vet. Journal, 2010; 184(2): 201-207.

5. Hussain, M.A., Aungst, B.J., Lam, G. and Shefter, E. Phenylpropanolamine pharmacokinetics in dogs after intravenous, oral, and oral controlled-release doses. Biopharm Drug Dispos, Vol. 8, No. 5, September-October 1987. 497-505.

Manufactured by: Pegasus Laboratories, Inc., Pensacola, FL 32514, USA

Imported and Distributed by: Virbac Canada Inc., 340-1400 Albert Street, Ottawa, Ontario, Canada, K1R 0A5

PROIN is a registered trademark of Pegasus Laboratories, Inc. and is used under license.

REV: October 2012


CPN: 1177067.1

Toll-Free:   866-458-3350
Fax:   844-458-4004
Every effort has been made to ensure the accuracy of the Proin Chewable Tablets (25 mg) information published above. However, it remains the responsibility of the readers to familiarize themselves with the product information contained on the Canadian product label or package insert.

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