- USES: Cetirizine is used to treat allergic rhinitis and idiopathic urticaria. It is available alone as tablets, chewable tablets, and as an oral syrup. It is also available as a bilayer tablet containing immediate release cetirizine and extended release pseudoephedrine. PHARMACOLOGY: Cetirizine is an antihistamine; its principal effects are mediated via selective inhibition of peripheral H1 receptors. TOXICOLOGY: Anticholinergic (primarily antimuscarinic) effects develop in overdose. EPIDEMIOLOGY: Overdose is not common and serious toxicity is extremely rare. MILD TO MODERATE POISONING: Effects are generally mild and include sedation, somnolence, fatigue, restlessness, irritability, and tachycardia. Anticholinergic effects may theoretically occur but have not been reported. SEVERE POISONING: There is one report suggesting torsade de pointes following an ingestion, in a patient who had other risk factors (eg, hypokalemia, renal failure), but this has not been observed in other cases. ADVERSE EFFECTS: Reported effects following therapeutic administration include urticaria, constipation, diarrhea, abdominal pain, dry mouth, intrahepatic cholestasis, severe acute hepatitis, weight gain, asthenia, somnolence, sedation, fatigue, headache, and impaired cognition. No clinically significant prolongations of QTc have been observed.
Range of Toxicity:
- TOXICITY: No specific toxic dose has been established. ADULTS: Somnolence occurred after ingestion of 150 mg of cetirizine. CHILDREN: Doses of cetirizine up to 7.8 mg/kg in children resulted in minimal toxicity. An 18-month-old developed restlessness, irritability, and drowsiness after ingesting approximately 180 mg (approximately 50 times the prescribed dose), and a 4-year-old became drowsy after ingesting 60 mg. Serious toxicity and fatalities have not been reported after overdose of cetirizine. THERAPEUTIC DOSES: Adults and children (ages 6 to 11 years): 5 mg or 10 mg daily. Children 2 to 5 years: 2.5 mg once daily; MAX, 5 mg per day.
- Support: MANAGEMENT OF MILD TO MODERATE TOXICITY: Observation and supportive care is all that is required for the vast majority of overdoses. MANAGEMENT OF SEVERE TOXICITY: Serious toxicity is not expected after ingestion of cetirizine alone. Patients with CNS depression should be monitored to assure that they do not have respiratory depression or require airway management.
- Decontamination: PREHOSPITAL: Gastrointestinal decontamination is not routinely required. HOSPITAL: Activated charcoal should be considered after extremely large ingestions or if more toxic coingestants are involved within 2 hours from the ingestion.
- Airway management: Maintain open airway and perform orotracheal intubation if necessary.
- Antidote: There is no specific antidote.
- Monitoring of patient: No routine laboratory testing is needed unless otherwise clinically indicated. Cetirizine plasma concentrations are not readily available or clinically useful. Obtain serum electrolytes, and acetaminophen and salicylate concentrations in patients with self-harm ingestions.
- Enhanced elimination procedure: Cetirizine is not effectively removed by dialysis due to its high degree of protein binding.
- Patient disposition: HOME CRITERIA: Asymptomatic children and adults with inadvertent ingestions may be monitored at home. OBSERVATION CRITERIA: Symptomatic patients and those with deliberate ingestions should be referred to a healthcare facility for observation and treatment. CONSULT CRITERIA: Consult a poison center or medical toxicologist for assistance in managing patients with severe toxicity or in whom a diagnosis is not clear.