Examining the tolerability of the non-sedating antihistamine desloratadine: a prescription-event monitoring study in England.

Background: Desloratadine is a non-sedating, long-acting histamine H(1) receptor antagonist indicated for the symptomatic relief of allergic rhinitis (AR) and chronic idiopathic urticaria in patients aged>12 years.

Objective: To monitor the safety of desloratadine as prescribed in England, using the observational cohort technique of prescription event monitoring (PEM).

Methods: Exposure data were derived from dispensed prescriptions written by primary care physicians (general practitioners [GPs]) for desloratadine (March-May 2001); patient demographics, indication, pattern of use and outcome (event) data were obtained via simple questionnaires returned by GPs. Incidence density observation rates (IDobs) were calculated to compare the difference in event rates between months 1 and 2 (m1/m2) and were compared for the whole cohort and by groups defined by indication and pattern of use.

Results: The cohort comprised 11 828 patients (median age 37 years [interquartile range 22, 54]; 59.9% were female). The most frequent indication was AR (n=8001; 67.6%). After 2 months, 36.8% (n=2464) of patients were still taking desloratadine. 'Condition improved' was the most common event and reason for stopping. Headache/migraine was uncommon but associated with starting treatment (IDobs(m1/m2) ratio 3.99 [95% CI 1.70, 10.83]). Cardiovascular events occurred rarely or very rarely, as did central and peripheral nervous system events. No serious adverse drug reactions (ADRs) were reported. Events related to effectiveness were more frequent in month 1 than month 2 for all patient subgroups.

Conclusions: This postmarketing surveillance study shows that desloratadine is well tolerated when used in general practice in England. No previously unrecognized ADRs were detected. This study highlights how modifications to PEM are contributing to the evaluation of drug utilization factors in relation to risks.