Prescription-event monitoring is a form of pharmacovigilance, an exercise which has its legal basis in European Union directives 65/65 and 75/319 and in regulation 2309/93.
The method of study (records only research) also complies with the guidelines on the practice of ethics committees in medical research involving human subjects issued by the Royal College of Physicians of London in August 1996.
General practitioners are also asked to indicate whether the event was considered to be related to the drug, although they are not required to make this connection.
Incidence densities were calculated for all of the events reported, to give an indication of which events were reported significantly more frequently in the first month of exposure.
We calculated non-adjusted and age and sex adjusted odds ratios for drowsiness or sedation for fexofenadine, cetirizine, and acrivastine using loratadine as baseline.
This means that first-generation antihistamines are more likely to cause side effects such as sedation, dry mouth, dizziness, low blood pressure, and a rapid heart-beat.
They are also more likely than second-generation antihistamines to impair a person’s ability to drive or operate machinery.
Table 1 gives the age and sex distribution of patients treated with each antihistamine.
The demographics of each cohort were roughly similar.Main outcome measure: Reporting of sedation or drowsiness.Results: The odds ratios (adjusted for age and sex) for the incidence of sedation were 0.63 (95% confidence interval 0.36 to 1.11; P=0.1) for fexofenadine; 2.79 (1.69 to 4.58; P Antihistamines are often used to treat the symptoms of allergies such as seasonal and perennial allergic rhinitis and urticaria.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.After three, six, or 12 months, “green form” questionnaires are sent to the general practitioners who wrote the original prescriptions.