Sedating and non sedating antihistamines
Table 1 gives the age and sex distribution of patients treated with each antihistamine.The demographics of each cohort were roughly similar.After three, six, or 12 months, “green form” questionnaires are sent to the general practitioners who wrote the original prescriptions.These questionnaires seek to determine any event experienced by patients while they were taking the drug and for a period afterwards.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.
Additional information, such as use during pregnancy, can be monitored, and data on the use of certain drugs during the first trimester of pregnancy have been published.7 A disadvantage of the method is that it relies on general practitioners returning completed green forms.
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.
All reported pregnancies are followed up to determine the outcome and the cause of all deaths are established.
Both the exposure (prescription) and the outcome (event) data are computerised for analysis.