Pseudoephedrine is a sympathomimetic used as an oral decongestant in humans. In dogs it has been suggested for controlling urinary incontinence. It is available in 15 mg, 30 mg, 60 mg, 120 mg (12-hour extended release) or 240 mg (24-hour extended release) via tablet. It also comes in liquid in 3 or 6 mg/ml strengths.
While pseudoephedrine is an over-the-counter medication, its sales are restricted in the United States so it can only be purchased with ID and is kept behind the counter. This is helpful when a pet has chewed the label: asking the owner if they bought the medication off the shelf or had to ask for it from behind the counter and provide ID can help determine whether pseudoephedrine was present in the medication.
Being a sympathomimetic, pseudoephedrine causes stimulation to the nervous system and cardiovascular systems. Common signs include restlessness, agitation, hyperactivity, tremors, tachycardia, hypertension, hyperthermia, panting and mydriasis. DIC and rhabdomyolysis are uncommon but serious sequelae of clinical signs.
Onset of signs will depend on the formation of the pseudoephedrine. Liquids and immediate release tablet/capsules (15, 30 and 60 mg) can be very rapid with signs starting as soon as 15 to 30 minutes after ingestion. The extended release formations signs may take 3 to 6 hours or longer for signs to develop. With the extended release formulations the progression of signs may be more subtle – so it may take the owner even longer to realize there is something wrong with the pet.
Treating Pseudoephedrine Ingestion
Treating pseudoephedrine toxicity is similar to treating amphetamine toxicosis. CNS stimulation is commonly controlled with acepromazine or chlorpromazine. Valium is generally avoided for agitation and hyperactivity as it may potentially worsen the stimulation.
Cyproheptadine as a serotonin antagonist may be considered. A muscle relaxant such as methocarbamol may be used for tremors. Propranolol or another appropriate beta blocker may be considered for controlling tachycardia. Hypertension is often controlled through the use of acepromazine for CNS stimulation control; however, if that is insufficient, other vasodilators such as nitroprusside may be considered.
Stronger sedatives such as barbiturates, propofol or gas anesthesia may be considered if acepromazine is not enough. Alpha 2 adrenergic agonists such as medetomindine and dexmedetomindine should be avoided as they, as well as pseudoephedrine, cause peripheral vasoconstriction and have the potential to worsen the hypertension.