Animal & Veterinary

INCURIN (estriol) Tablets and PROIN (phenylpropanolamine hydrochloride) Chewable Tablets - Veterinarians

April 20, 2012

Dear Veterinarian:

The U.S. Food and Drug Administration (FDA) wants to tell you about the approvals of INCURIN (estriol) Tablets and PROIN (phenylpropanolamine hydrochloride) Chewable Tablets to control urinary incontinence in dogs. FDA also wants to remind you of the benefits of using FDA-approved drugs in your clinic and the legal requirements for compounding animal drugs.

Drug Information

 INCURIN Tablets PROIN Chewable Tablets
Manufacturer Intervet Inc.Pegasus Laboratories, Inc.
Application TypeNew Animal Drug Application (NADA)New Animal Drug Application (NADA)
Application Number141-325141-324
IndicationFor the control of estrogen-responsive urinary incontinence in ovariohysterectomized female dogsFor the control of urinary incontinence due to urethral sphincter hypotonus in dogs
Active IngredientEstriolPhenylpropanolamine hydrochloride
How Supplied1 mg tablets25, 50, and 75 mg tablets
Clinical PharmacologyEstriol is a natural estrogen. Estrogens increase the resting muscle tone of the urethra in females and can be used to treat female dogs with urinary incontinence due to estrogen depletion.Phenylpropanolamine is a chemical analogue of the endogenous sympathomimetic amines. It is an alpha-adrenergic agent which has been reported to increase urethral tone in dogs. 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 internal urethral sphincter.

Please see the approval notices for INCURIN and PROIN in the Federal Register.

FDA rigorously evaluates an animal drug before approving it. As part of the approval process, the drug company must prove to FDA that:

  • The drug is safe and effective for a specific use in a specific animal species;
  • The manufacturing process is adequate to preserve the drug’s identity, strength, quality, and purity; and
  • The drug’s labeling is truthful and complete.

FDA’s role does not stop after the agency approves an animal drug. As long as the drug company markets the animal drug, the agency continues to monitor the drug’s:

  • Safety and effectiveness to determine if concerns arise that were not known at the time of approval;
  • Manufacturing process to ensure quality and consistency are maintained; and
  • Labeling to make sure the information remains truthful and complete.

By prescribing FDA-approved INCURIN and PROIN, you provide your clients and their dogs with the only marketed estriol and phenylpropanolamine products shown to be safe and effective for controlling urinary incontinence in dogs. INCURIN and PROIN are also the only marketed estriol and phenylpropanolamine products that are manufactured to meet FDA’s strict standards for quality, purity, and potency.

Please be aware that estriol and phenylpropanolamine products should not be imported from other countries for use in animals. In addition, bulk estriol and phenylpropanolamine should not be used to compound animal drugs.

A compounded animal drug is not FDA-approved. This means FDA has not evaluated the safety and effectiveness of the compounded drug or the adequacy of the manufacturing process.

You may have specific patients that need estriol or phenylpropanolamine in strengths or dosage forms not offered by INCURIN or PROIN. In these limited cases, estriol or phenylpropanolamine can be legally compounded by using FDA-approved INCURIN or PROIN as the source of the active pharmaceutical ingredient. Please find additional requirements for legal animal drug compounding at Title 21, Code of Federal Regulations, Section 530.13.

FDA’s Center for Veterinary Medicine (CVM) is committed to promoting and protecting animal health by ensuring safe and effective drugs are available for animals. For more information, please contact the CVM Communications Staff at 240-276-9300 or


FDA’s Center for Veterinary Medicine

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