Evaluation of the safety of fexofenadine from experience gained in general practice use in England in 1997

Background: Fexofenadine is the active metabolite of the non-sedating anti-histamine terfenadine. Pre-licensing clinical trials in over 6000 patients suggested it was effective and well tolerated. Objective: To assess the tolerability and safety of fexofenadine immediately after its availability on the UK market in March 1997. Methods: Post-marketing non-interventional observational cohort study using the methodology of prescription-event monitoring. Exposure data derived from dispensed prescription details supplied in confidence by the Prescription Pricing Authority. Outcome data derived from questionnaires returned by general practitioners (GPs) in England between March and August 1997. Results: Of the 35,817 questionnaires sent, 18,238 (50.9%) were returned, of which 16,638 contained useful data. These included 40% male (mean age 36 +/- 19 years) and 59% female (mean age 39 +/- 19 years). Most common indications were allergic rhinitis (55%), not specified (28%), urticaria, pruritus or rash (10%) and other indications (7%). There were 40 reports of adverse drug reactions in 27 patients. Less than 2% of patients stopped the drug because of side effects. Events reported after exposure to fexofenadine were uncommon and already reported in clinical trials. There were eight reports of possible cardiac side effects (palpitations, three; chest pain, three; arrhythmia, one; and chest tightness, one). None was felt to be serious. There were no drug interactions reported. None of the 30 deaths was related to fexofenadine. None of the three adverse outcomes from the 47 pregnancies reported was related to fexofenadine. Conclusion: Within the limitations for an observational cohort study, fexofenadine was found to be well tolerated and safe in 16,638 users in general practice in England.