Repeated-dose effects of mequitazine, cetirizine and dexchlorpheniramine on driving and psychomotor performance.
OBJECTIVE
Previous studies have demonstrated that the antihistamines mequitazine, cetirizine and dexchlorpheniramine produce mild sedation after single doses. It is unknown, however, whether acute sedation persists after repeated dosing. Therefore, this study assessed the effects of repeated dosing of these antihistamines on driving and psychomotor performance.


METHODS
Sixteen healthy volunteers were treated with mequitazine 10 mg q.a.m., cetirizine 10 mg q.a.m., dexchlorpheniramine Repetab 6 mg b.i.d. and placebo for four separate 8-day periods. Drug effects were assessed on days 1 and 8 using on-the-road driving tests (highway driving and car following), psychomotor tests (tracking and divided attention) and subjective questionnaires.


RESULTS
Dexchlorpheniramine and mequitazine significantly impaired driving performance on the highway driving test on the first day; dexchlorpheniramine increased Standard Deviation of Lateral Position by 2 cm [95% confidence interval (CI) 0.5, 3.8] and mequitazine by 2.5 cm (CI 1.0, 4.3). These effects on driving performance disappeared after 8 days of treatment. No effect of treatment was found on car following, tracking and divided attention. Although subjective ratings confirmed that subjects knew their driving had been impaired in the mequitazine and dexchlorpheniramine condition after completion of the highway driving test on day 1, they did not expect their driving to be affected before the start of the test. Cetirizine did not impair performance on any of the tests.


CONCLUSIONS
Single doses of mequitazine 10 mg and dexchlorpheniramine Repetab 6 mg cause mild driving impairment. However, when taken over several days, the impairing effect wears off, possibly as a result of tolerance.
Theunissen
Eef L
EL
Experimental Psychopharmacology Unit, Brain and Behaviour Institute, Faculty of Psychology, Maastricht University, the Netherlands. e.theunissen@psychology.unimaas.nl
Vermeeren
Annemiek
A
Ramaekers
Johannes G
JG
D000284:Administration, Oral; D000328:Adult; D001334:Automobile Driving / Q000523:psychology; D017332:Cetirizine / Q000008:administration & dosage*; D002744:Chlorpheniramine / Q000008:administration & dosage*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D006634:Histamine H1 Antagonists / Q000008:administration & dosage*; D039563:Histamine H1 Antagonists, Non-Sedating / Q000008:administration & dosage; D006801:Humans; D008297:Male; D008875:Middle Aged; D010640:Phenothiazines / Q000008:administration & dosage*; D011597:Psychomotor Performance / Q000187:drug effects*; D012647:Self-Assessment
D006634:Histamine H1 Antagonists; D039563:Histamine H1 Antagonists, Non-Sedating; D010640:Phenothiazines; C018904:dexchlorpheniramine; D002744:Chlorpheniramine; C006069:mequitazine; D017332:Cetirizine