Study into antihistamines packaged as non-sedative reveals high level of drowsiness among users
Antihistamines sold as non-sedatives can cause drowsiness, a major research project by the Drug Safety Research Unit in Southampton has shown.
Researchers warned that the drugs, used most intensively at this time of year to combat hay fever, "may be dangerous in the workplace and when driving".
Of the four antihistamines investigated, acrivastine and cetirizine were most likely to cause sleepiness. Researchers said that loratadine and fexofenadine had lower incidence of sedation, but still had some effects.
So-called "second generation" antihistamines were introduced as having no or limited sedative effects. A meeting of international experts in Manchester last month raised concern over the issue.
Dr Charles Mercier-Guyon, a member of the European Commission's working group on alcohol, drugs and traffic safety, said,"Doctors should question their patients about their profession and activities when prescribing.
"They should choose the less sedative drugs for people who drive, and those whose work is demanding."
In the research, questionnaires were sent to GPs covering a total of about 40,000 patients prescribed the drugs, and the incidence of sedation was recorded. Full results were published in the British Medical Journal.
Several European countries, including France and Sweden, have implemented the European Union Directive on "red triangle" labelling of substances known to have a sedative effect, but the UK has not followed suit.