Fexofenadine (Telfast) or loratadine (Clarityn) should be prescribed in preference to acrivastine (Semprex) or cetirizine (Zirtek) in situations when a second generation antihistamine is required and sedation is highly undesirable (eg, for flight crew). This is the conclusion of an analysis of prescription-event monitoring (PEM) studies carried out by Professor Ronald Mann and colleagues from the Drug Safety Research Unit in Southampton. They report in the British Medical Journal (2000;320:1184) that data for a total of 43,363 patients was assessed and the odds ratios calculated for drowsiness or sedation associated with each of the four drugs. In addition, they calculated the "incidence density", which was the number of reports of each event per thousand patient-months of exposure to the drug.
Loratadine and fexofenadine were associated with a lower incidence of sedation than acrivastine and cetirizine. The odds ratios for incidence of sedation were 1, 0.63, 2.79 and 3.53 and the incidence densities for drowsiness and sedation were 1.2, 1.5, 4.4 and 3.7, respectively. There was no increased risk of accident or injury related to sedation nor were any cardiotoxic events "of any relevance" noted, say the authors.
Dr Robin Ferner (West Midlands Centre for Adverse Drug Reaction Reporting, City hospital, Birmingham) says in a commentary on the article (ibid, p1186): "We should certainly be reassured by the low overall incidence of sedation with selective histamine H1 antagonists. . . .There are some differences between them, which may be relevant to people in safety critical jobs."

Flight crew and workers in other "safety critical" jobs should be prescribed fexofenadine or loratadine, say researchers