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Antiallergic and antitussive medications: extent of use and relationship to asthma exacerbations
E Van Ganse1, P Van der Linden, H G Leufkens
1Department of Pharmacoepidemiology and Pharmacotherapy, Utrecht University, The Netherlands.
Background:
Asthma patients are frequently exposed to antiallergic and antitussive medications, in addition to their respiratory treatment. These medications interfere with inflammatory pathways common to all atopic diseases and could affect asthma.
Objectives:
To investigate associations between antiallergic and antitussive medications and the occurrence of asthma exacerbations and to assess the extent of use of these medications in asthma.
Methods:
Regular users of anti-asthma medications were identified in a drug dispensing database. A base-cohort of asthma patients was identified using age and exposure criteria. A nested case-control study was performed within the base-cohort: the outcome was defined as a new dispensing of oral corticosteroids and matched cases and controls were compared regarding exposure to antiallergic medications. Odds ratios (OR) were computed by conditional logistic regression and adjustment incorporated markers for asthma severity.
Results:
680 asthma patients were followed in the base-cohort for an average duration of 1390 days. Antitussives, antihistamines and nasal corticosteroids were used by respectively 40, 30 and 13 per cent of the asthma population. Among the patients, 134 cases were pair matched with controls. In these pairs, antitussives showed a significant association with asthma exacerbations, with an OR of 3.1. The association had borderline significance for antihistamines and was not significant for nasal corticosteroids. The results were not modified by adjustment for disease severity.
Conclusions:
This study confirms that antitussives and antihistamines are commonly used by asthmatics and indicates that both classes are associated with increased occurrence of asthma exacerbations; assessing causality from present data is, however, difficult. Nasal corticosteroids are used less often and are not associated with the outcome. Antihistamine and antitussive medications should be more thoroughly investigated in asthma patients.