Prescribed drug therapy and near-fatal asthma attacks

Abstract

Inhaled fenoterol has been associated with an increased risk of death in severe asthmatics, when compared to other adrenoceptor agonists. It is plausible that fenoterol may also increase the risk of near-fatal attacks. We have conducted a case-control study to investigate this hypothesis. The cases comprised Intensive Care Unit (ICU) admissions for asthma in the Wellington region during 1977-1988. For each of these cases, two age-matched controls were selected from asthma admissions to the same hospital during the same period. For the 155 cases and 305 controls, information on prescribed drug therapy was collected from the hospital admission records. The relative risk of a near-fatal asthma attack in patients prescribed inhaled fenoterol was 2.00 (95% confidence interval (CI) 1.35-2.97). An increased risk was also observed for oral theophylline (odds ratio (OR) = 1.88; 95% CI 1.26-2.79). For the 65 cases and 104 controls who had a previous admission for asthma in the previous 12 months, information relating to the previous admission was also collected; an increased risk was once again observed for inhaled fenoterol (OR = 2.18; 95% CI 1.10-4.33) and for oral theophylline (OR = 1.18; 95% CI 0.99-3.57). No other asthma drugs showed significantly increased risks. Although the ICU admission cases had generally been prescribed more asthma drugs than the hospital admission controls, and appeared to have more severe asthma, it is possible that the findings reported here are influenced by confounding by severity. We nevertheless estimate that our findings are consistent with the hypothesis that fenoterol increases the risk of near- fatal asthma attacks, and that they complement previous findings on fatal asthma attacks. They also provide some support to previous concerns about the safety of oral theophyllines, although the evidence for this is less consistent.