Phenylpropanolamine Toxicosis

Phenylpropanolamine (PPA) is a sympathomimetic amine commonly prescribed for female dogs with urinary incontinence associated with primary urethral sphincter incompetence. Few adverse effects are reported in dogs given the recommended therapeutic dose of 1 to 1.5 mg/kg or total dose of 12.5 to 50 mg PO q8–12h. This retrospective study evaluated dogs with potential PPA toxicosis from the database of a poison control center. Of the 170 dogs included, 66 did not develop clinical signs. The remaining 104 developed 1 or more clinical signs, including agitation, vomiting, mydriasis, lethargy, tremor or twitching, panting, bradycardia, tachycardia, hypertension, erythema, and piloerection. Dogs with clinical signs had a much higher median ingestion dose (37.3 mg/kg) than did dogs without clinical signs (18 mg/kg). Time from ingestion to development of clinical signs was recorded for 72 dogs and ranged from <30 minutes to 24 hours. Most dogs developed signs within 8 hours of ingestion. Hospitalization time ranged from 4 to 72 hours, with time increasing as ingestion dose increased. The only dog that died may have ingested as much as 145 mg/kg of PPA, but it had also been exposed to multiple other medications in the garbage at a veterinary clinic. Most dogs did well with decontamination and supportive care.

CommentaryThis study drives home the point that dogs will eat all chewable medications available to them, sometimes with fatal consequences. Veterinarians should inform owners that PPA is safe at a therapeutic dose, but overdoses can cause clinical signs that may require treatment and hospitalization. Clinical signs fit with sympathomimetic agents and, depending on the time frame from ingestion to presentation, dogs may either present with bradycardia or tachycardia.—Tina Wismer, DVM, DABVT, DABT

SourcePhenylpropanolamine toxicosis in dogs: 170 cases (2004-2009). Peterson KL, Lee JA, Hovda LR. JAVMA 239:1463-1469, 2011.