PPA loss leaves veterinarians looking for alternatives

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On Nov 3, the FDA announced a decision to initiate rule making to classify phenylpropanolamine as not generally recognized as safe and effective, because of an association between PPA and hemorrhagic stroke in humans. The drug is currently available by prescription and over the counter as a nasal decongestant, and OTC for weight control.

A Yale University School of Medicine study showed that the number of people having strokes when taking PPA was greater than the number of people having strokes who were not taking PPA. Although the risk of hemorrhagic stroke is low, the FDA has concerns because of the seriousness of a stroke and the inability to predict who is at risk. The risk of hemorrhagic stroke was found mostly in women, but men may be at risk also. As a result, the FDA issued a public health advisory recommending consumers not use products containing the drug.

On Nov 7, the FDA Center for Drug Evaluation and Research announced it is taking steps to remove PPA from all drug products, and is urging voluntary measures to stop use of any product containing PPA. The FDA requested that drug companies cease marketing products containing the drug.

PPA is one of the drugs that have been widely used as treatment for canine urinary incontinence.

At press time, compounding pharmacies were beginning to prepare formulations containing PPA on the prescription of a veterinarian. Clinical pharmacologists are exploring the potential use of pseudoephedrine, a drug reportedly widely used by Australian and Canadian veterinarians.

Dr. Mark Papich, associate professor of clinical pharmacology at North Carolina State University College of Veterinary Medicine, said pseudoephedrine has been used in Canada for years, because of the lack of availability of PPA.

"When I was still up in Canada and treating patients, pseudoephedrine was pretty much all we used at the time," he said. "It comes as a 30 or 60 mg tablet and we would empirically give little dogs 30 mg and big dogs 60 mg. Although no one has ever done a controlled comparison, it was our subjective interpretation that it worked well with few side effects. As the stereoisomer of ephedrine, it produces less CNS stimulation, blood pressure damage, and tachycardia than ephedrine. Occasionally, some dogs got a bit excited from it, but a decrease in the dose usually fixed that, and veterinarians will have to evaluate each patient individually for this side effect."