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784 Phenylpropanolamine Toxicosis

Phenylpropanolamine Toxicosis Client Education
Sheet
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• Excessive catecholamines and sympathetic
BASIC INFORMATION
○ Do NOT use atropine to increase the
amines can cause myocardial necrosis in • Treatment of cardiac arrhythmias
Definition humans and animals. heart rate (bradycardia is a reflex from
Adverse effects are caused by exposure to • Disseminated intravascular coagulation hypertension and should resolve after the
phenylpropanolamine (PPA), a synthetic (DIC) has developed in critically ill patients. blood pressure is normalized)
sympathomimetic amine used to control urinary ○ A specific beta-1 blocker may be given
incontinence in dogs due to urinary sphincter DIAGNOSIS for significant supraventricular tachyar-
incompetence (p. 1011). rhythmias: esmolol 5-100 mcg/kg/min
Diagnostic Overview CRI
Synonyms Diagnosis is based on a history of exposure to ○ Ventricular premature contractions (VPCs)
PPA, Proin toxicosis PPA and supporting clinical signs. Diagnostics or ventricular tachycardia: lidocaine
are performed to evaluate the physiologic effects 2-4 mg/kg IV over 1-2 minutes, fol-
Epidemiology of PPA. There is no clinically relevant testing lowed by 0.5-2 mg/kg q 20-60 minutes
SPECIES, AGE, SEX available to determine exposure. Troponin 1 or 0.4-0.8 mg/kg/min CRI, if required
Exposure occurs more commonly in dogs than assays can be performed if myocardial necrosis (p. 1033)
cats. is suspected. • Central nervous system (CNS) stimulatory
signs: acepromazine (see above)
GENETICS, BREED PREDISPOSITION Differential Diagnosis • IV crystalloid fluids are used to maintain
Large-breed dogs and potentially greyhounds • Amphetamine and cocaine toxicosis: most hydration, meet maintenance needs, and
may have a higher risk of developing significant commonly with these agents, tachycardia is protect renal function. Avoid fluid loading
cardiac effects, including ventricular arrhythmias seen, and agitation or hyperactivity is more until hypertension is controlled.
and myocardial necrosis. pronounced.
• Phenylephrine toxicosis Chronic Treatment
RISK FACTORS • Sumatriptan and other selective serotonin If myocardial necrosis occurs, ongoing
Animals with pre-existing renal compromise subtype 1 agonist toxicosis treatment of heart disease may be necessary
(renal excretion) or pre-existing cardiac disease (p. 409).
may be at a higher risk. Initial Database
• CBC, clinical chemistry: often unremark- Behavior/Exercise
Clinical Presentation able, but thrombocytopenia possible with Exercise restriction may be indicated when
HISTORY, CHIEF COMPLAINT DIC, azotemia possible with renal injury myocardial necrosis is suspected or confirmed.
• History of exposure to PPA; onset of signs or dehydration, and hypoglycemia reported
most commonly occurs within 3 hours of • Urinalysis: ± myoglobinuria Drug Interactions
exposure. • Electrocardiogram (p. 1096): bradyarrhyth- • Caffeine seems a very important co-ingestant,
• Most common clinical signs on presentation: mia or tachyarrhythmia potentially triggering significant hypertensive
agitation or lethargy, vomiting, mydriasis, • Blood pressure (p. 1065): hypertension episodes.
piloerection, and dermal erythema • Any agent that can cause an increase in blood
Advanced or Confirmatory Testing pressure can worsen clinical signs.
PHYSICAL EXAM FINDINGS • Troponin 1 assay
Bradycardia (occasionally tachycardia), pilo- • Echocardiogram to evaluate cardiac function Possible Complications
erection, erythema, occasionally ventricular • DIC
arrhythmias, rarely hyphema and retinal TREATMENT • Myocardial necrosis
detachment due to hypertension • Retinal detachment
Treatment Overview • Renal damage
Etiology and Pathophysiology Treatment is focused on controlling the clinical
• PPA is a sympathomimetic that acts mainly signs and physiologic effects of PPA. Recommended Monitoring
by causing release of norepinephrine, but it Heart rate, blood pressure, renal parameters,
also has direct agonist activity at some adren- Acute General Treatment and ocular function
ergic receptors. Release of norepinephrine • Decontamination includes emesis (p. 1188)
indirectly stimulates alpha and beta receptors. and activated charcoal (p. 1087) if overdose PROGNOSIS & OUTCOME
Most effects are on the alpha receptors, with is suspected before onset of clinical signs.
weak effects on beta receptors. • Treatment of hypertension With prompt and appropriate treatment, a full
• Excessive amounts of norepinephrine can ○ Acepromazine 0.02 mg/kg IV, can repeat 2-3 recovery is expected for most patients.
have multisystemic effects: cardiovascular times, but if hypertension is not controlled
(hypertension, tachycardia or bradycar- use other pharmacologic intervention. PEARLS & CONSIDERATIONS
dia, arrhythmias, myocardial necrosis), ○ Nitroprusside continuous-rate infusion
musculoskeletal (rhabdomyolysis), renal (CRI) 1-2 mcg/kg/min initially, increas- Comments
(myoglobinuria), ocular (hyphema and retinal ing by 1 mcg/kg every 3-5 minutes until • Significant hypertension can be present even
detachment), and endocrine (hypoglycemia improvement is noted, or in patients that look relatively normal.
has been seen) ○ Phentolamine 0.02-1 mg/kg IV bolus • Severe signs can be seen in dogs at doses as low
• Animals are initially agitated and tachycardic; followed by a CRI, or as 3.5 mg/kg (therapeutic dose 1-2 mg/kg).
then as their blood pressure rises, they ○ Hydralazine 0.5-3 mg/kg IV q 12h or a
become lethargic, and a reflex bradycardia 0.1 mg/kg IV loading dose followed by Prevention
occurs. a CRI of 1.5-5 mcg/kg/min Prevent access to medication.

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