Cetirizine

Cardiovascular

In a prospective, double-blind, parallel-group study for 18 months in 817 children with atopic dermatitis aged 12–24 months, cetirizine 0.25 mg/kg bd had no effect on the QT _c interval [ ].

In a double-blind, randomized, placebo-controlled study in 85 infants aged 6–11 months there were no differences in the frequencies of adverse events between those who were given cetirizine or placebo, and no electrocardiographic changes, particularly in the QT interval [ ].

The cardiotoxic effects of antihistamines are of concern in patients with long QT syndrome who also have allergies [ ]. In a randomized, single-blind study 15 asymptomatic patients with type 1 or type 2 long QT syndrome and 15 healthy volunteers were given placebo or cetirizine 10 mg [ ]. Electrocardiography was performed at rest and after exercise. Cetirizine did not prolong the QT intervals either at rest or during exercise and recovery in either group. Thus, it may be safe in carriers of the gene mutations that cause long QT syndrome.

Nervous system

Oculogyric crisis has been described in nine patients treated with cetirizine; eight cases occurred in children [ ].

The effects of cetirizine (5, 10, and 15 mg) on sleep latency, subjective sleepiness, and performance from 0.5 to 7.5 hours after ingestion have been studied [ ]. Cetirizine produced shortened sleep latencies, increased subjective sleepiness, and impaired tracking. The authors considered that cetirizine should not be used by personnel involved in critical occupations.

Drug-induced movement disorders are most commonly associated with neuroleptic drugs. However, there are a few reports of abnormal involuntary movements associated with antihistamines.

• A 4-year-old girl weighing 19.5 kg developed repetitive, stereotyped, involuntary dystonic movements after taking cetirizine syrup 5 mg/day for 18 days for allergic rhinitis [ ]. Her symptoms included a tic of the right eye with frequent shoulder shrugging, followed by intermittent retrocollis and arm abduction movements. These movements did not interfere with voluntary movements and were painless, aggravated by fatigue, and briefly suppressible. One week after the last dose of cetirizine, the movements were greatly improved. Similar movements also developed within a few days of exposure to mepyramine 10 mg in an expectorant for congestion. Three weeks later, she had occasional retrocollis and her arms would abduct when she was tired. All involuntary movements resolved 8 weeks after the last dose of cetirizine.

As a piperazine derivative, cetirizine has dopamine receptor blocking properties. The authors therefore postulated that cetirizine had caused the dystonic movements although this was not directly tested by rechallenge.