Abstract
Objective To investigate the effect of regular paracetamol on bronchial hyper-responsiveness (BHR) and asthma control in adult asthma.
Setting Single research-based outpatient clinic.
Participants 94 adults with mild-to-moderate asthma received randomised treatment; 85 completed the study. Key inclusion criteria were age 18-65years, forced expiratory volume in 1s (FEV1) >70% predicted, provocation concentration of methacholine causing a 20% reduction in FEV1 (PC20) between 0.125 and 16mg/mL. Key exclusion criteria included an asthma exacerbation within the previous 2months, current regular use of paracetamol, use of high-dose aspirin or non-steroidal anti-inflammatory drugs, current or past cigarette smoking >10 pack-years.
Interventions In a 12-week randomised, double-blind, placebo-controlled, parallel-group study, participants received 12weeks of 1g paracetamol twice daily or placebo twice daily.
Primary and secondary outcome measures The primary outcome variable was BHR, measured as the PC20 at week 12. Secondary outcome variables included FEV1, fractional exhaled nitric oxide (FeNO) and asthma control questionnaire (ACQ) score.
Results At 12weeks, the mean (SD) logarithm base two PC20 was 1.07 (2.36) in the control group (N=54) and 0.62 (2.09) in the paracetamol group (N=31). After controlling for baseline PC20, the mean difference (paracetamol minus placebo) was -0.48 doubling dose worsening in BHR in the paracetamol group (95% CI -1.28 to 0.32), p=0.24. There were no statistically significant differences (paracetamol minus placebo) in log FeNO (0.09 (95% CI -0.097 to 0.27)), FEV1 (-0.07L (95% CI -0.15 to 0.01)) or ACQ score (-0.04 (95% CI -0.27 to 0.18)).
Conclusions There was no significant effect of paracetamol on BHR and asthma control in adults with mild-to-moderate asthma. However, the study findings are limited by low power and the upper confidence limits did not rule out clinically relevant adverse effects.
Trial Registration Australia New Zealand Clinical Trials Registry Number: NZCTR12609000551291.