The US Food and Drug Administration (FDA) last week approved Proin ER (phenylpropanolamine hydrochloride extended release), a tablet for the control of urinary incontinence in dogs.

The drug will aid with urethral sphincter hypotonus, which occurs due to a dog’s age and weakening muscles in the urethra.

The FDA had already approved Proin Chewable Tablets in 2011 (the same year they approved Incurin, an estrogen-based medication for canine urinary incontinence), which had to be administered two to three times a day.

Prion ER, however, is administered only once a day .

Is this a game changer for veterinarians and clients dealing with a pet suffering from urinary incontinence?

NEWStat asked Julie Byron, DVM, DACVIM, professor of small animal internal medicine in the Department of Veterinary Clinical Services at The Ohio State University and an expert in urinary tract disorders, what she thought.

“The game-changing aspect is that it makes [Prion] a once-a-day drug [like] Incurin,” Byron said. “So, for clients who can’t deliver medications twice a day, It brings it more into alignment with the convenience factor that they need.”

For the study, the FDA recruited 119 client-owned dogs who had been previously diagnosed with urethral sphincter hypotonus. All had been taking Proin Chewable Tablets before the study and their response to the medication (number and frequency of accidents, etc.) recorded.

The dogs were given Proin ER for 28 days. Their owners noted how many accidents the dogs had each day. After four weeks, 75 of the 104 dogs who completed the study had no accidents on either tablet. Nineteen of the dogs had fewer accidents on Proin ER, while ten of the dogs had more in comparison to when they were taking Proin Chewable Tablets.

Proin ER’s most common side effects were vomiting, weight loss, hypertension, and diarrhea.

Byron says when you examine the efficacy of the two versions of Proin in the FDA study, “It’s fairly comparable. But being a once-a-day drug, [the extended release version] certainly becomes much more convenient.”

Byron mentions that some of her research in the past has been sponsored by both Merck Animal Health and PRN Pharmacal, the makers of Incurin and Proin, respectively, but she adds that she has no conflicts of interest: “I don’t care which one you use.”

Although sometimes, she says, you might want to use both.

“I’m actually an advocate of that,” Byron said, noting that not all incontinence medications work for all dogs. Sometimes, it’s a matter of trial and error. “Generally I say, ‘Try one. If it works, great. If not, try the other one. If that doesn’t work, try both together.”

Byron’s reasoning: “They work in different ways. The estrogen product (Incurin) increases the number and sensitivity of alpha receptors, whereas the phenylpropanolamine (Proin) directly stimulates the alpha receptors,” she says. “If you think about the ways they work, it makes sense that combining them could lead to continence.”

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