Objectives: To investigate the frequency with which sedation was reported in post-marketing surveillance studies of four second generation antihistamines: loratadine, cetirizine, fexofenadine, and acrivastine. Setting: Prescriptions were obtained for each cohort in the immediate post-marketing period.Subjects: Event data were obtained for a total of 43 363 patients.
Always read the label and all product packaging before use.
This reminder follows a report received by the Centre for Adverse Reactions Monitoring (CARM) concerning a three-year-old child who was given chlorphenamine for a lower respiratory tract infection and experienced a serious neurological disorder.
Excessive doses in children have led to respiratory depression, coma and death.
Symptomatic measures, such as increasing fluids, making sure children get enough rest and reducing the spread of the virus (including regular hand washing) should be practiced.
These studies correlated prescriptions issued in general practice with events reported by the patients to their general practitioners after the drug was dispensed.
By monitoring these events in a substantial population of allergy sufferers, without the restrictions imposed by clinical trials methodology, it was possible to measure differences in side effects between these drugs.
The first-genaration antihistamines have alpha adrenolytic activity which can decrease the vasoconstrictive effect of adrenaline and noradrenaline and an antimuscarinic effect with the corresponding adverse effects.
Certain H1 antagonists, such as promethazine, have a local anesthetic effect.
Main outcome measure: Reporting of sedation or drowsiness.