Toxicology Brief: Phenylpropanolamine toxicosis in dogs and cats - Veterinary Medicine
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Toxicology Brief: Phenylpropanolamine toxicosis in dogs and cats


VETERINARY MEDICINE


MONITORING AND TREATMENT

Observe for CNS signs such as agitation or restlessness. Heart rate and rhythm, blood pressure, and body temperature should be monitored carefully. If marked hyperthermia is present, monitor for the development of disseminated intravascular coagulation. When hyperthermia is marked, cooling techniques should be instituted. If ventricular arrhythmias are detected, an echocardiographic examination should be considered.

Nitroprusside can be used to treat hypertension (1 to 2 g/kg/min; increase the dose incrementally every three to five minutes, if necessary, until desirable blood pressure is achieved).1 If nitroprusside is unavailable, a low dosage of acepromazine may be given (0.02 mg/kg intravenously) and increased in small amounts to the desired effect.10 Phenothiazines are also effective for the anxiety or agitation that can be seen.

Bradycardia is usually a reflex mechanism that does not require specific intervention and is expected to resolve with correction of hypertension.

If marked supraventricular tachycardia is present, a beta-1-specific beta-blocker can be used, such as esmolol at 0.2 to 0.5 mg/kg given intravenously over one to two minutes or 25 to 200 g/kg/min as a constant-rate infusion.1 Propranolol, a nonspecific beta-blocker, should be avoided since blockade of beta-2 receptors may worsen any hypertension that is present. Ventricular arrhythmias may be treated with lidocaine or other appropriate antiarrhythmics. Intravenous fluids should be administered to maintain hydration, provide venous access, and promote adequate renal function. Fluids should be administered judiciously when hypertension is present. Other supportive measures should be instituted as needed.

Depending on the dose, clinical signs may persist up to 48 hours. Ideally, patients should be monitored in the hospital until they are not exhibiting any clinical abnormalities and are not receiving any medications for CNS or cardiovascular signs for six to eight hours. If a patient has experienced marked ventricular arrhythmias, follow-up echocardiographic and electrocardiographic examinations may be indicated. With appropriate symptomatic treatment, a full recovery is expected.

"Toxicology Brief" was contributed by Dr. Judy K. Holding, ASPCA Animal Poison Control Center, 1717 S. Philo Road, Suite 36, Urbana IL 61802. The department editor is Petra Volmer, DVM, MS, DABVT, DABT.

REFERENCES

1. Plumb DC. Plumb's veterinary drug handbook. 6th ed. Ames, Iowa: Blackwell Publishing, 2008;68,359,660,726-727.

2. FDA Talk Paper: FDA issues public health warning on phenylpropanolamine; Nov. 6, 2000. Available at http://www.fda.gov/Drugs/DrugSafety/InformationbyDrugClass/ucm150763.htm

3. Hussain M, Aungst B, Lam G, et al. Phenylpropanolamine pharmacokinetics in dogs after intravenous, oral, and oral controlled-released doses. Biopharm Drug Dispos 1987;8(5):497-505.

4. AnTox Database. Urbana, Ill: ASPCA Animal Poison Control Center, 2003-2011.

5. PRN Pharmacal: Proin product label. Pensacola, Fla.

6. Veterinary Product Laboratories: Cystolamine product label. Phoenix, Ariz.

7. Phenylpropanolamine. In: POISINDEX System [intranet database]. Version 5.1. Greenwood Village, Colo: Thomson Reuters (Healthcare) Inc.

8. Crandell JM, Ware WA. Cardiac toxicity from phenylpropanolamine overdose in a dog. J Am Anim Hosp Assoc 2005;41(6):413-420.

9. Poppenga R. Treatment. In: Plumlee KH, ed. Clinical veterinary toxicology. Mosby, St. Louis, Mo: Mosby, 2004;15.

10. Tranquilli WJ. College of Veterinary Medicine, University of Illinois, Champaign, Ill: Personal communication with Dr. Judy Holding, 2003.


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