title: Randomised placebo-controlled study of the effect of paracetamol on asthma severity in adults.
abstract: OBJECTIVE
  To investigate the effect of regular paracetamol on bronchial hyper-responsiveness (BHR) and asthma control in adult asthma.
  
  
  METHODS
  Single research-based outpatient clinic.
  
  
  METHODS
  94 adults with mild-to-moderate asthma received randomised treatment; 85 completed the study. Key inclusion criteria were age 18-65 years, forced expiratory volume in 1 s (FEV1) >70% predicted, provocation concentration of methacholine causing a 20% reduction in FEV1 (PC20) between 0.125 and 16 mg/mL. Key exclusion criteria included an asthma exacerbation within the previous 2 months, current regular use of paracetamol, use of high-dose aspirin or non-steroidal anti-inflammatory drugs, current or past cigarette smoking >10 pack-years.
  
  
  METHODS
  In a 12-week randomised, double-blind, placebo-controlled, parallel-group study, participants received 12 weeks of 1 g paracetamol twice daily or placebo twice daily.
  
  
  METHODS
  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 12 weeks, 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 (-0.07 L (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.
  
  
  BACKGROUND
  Australia New Zealand Clinical Trials Registry Number: NZCTR12609000551291.
authors: Medical Research Institute of New Zealand, Wellington, New Zealand.
authors: Sally J
authors: SJ
authors: Ioannides
authors: Mathew
authors: M
authors: Williams
authors: Sarah
authors: S
authors: Jefferies
authors: Kyle
authors: K
authors: Perrin
authors: Mark
authors: M
authors: Weatherall
authors: Robert
authors: R
authors: Siebers
authors: Julian
authors: J
authors: Crane
authors: Mitesh
authors: M
authors: Patel
authors: Justin
authors: J
authors: Travers
authors: Philippa
authors: P
authors: Shirtcliffe
authors: Richard
authors: R
authors: Beasley
mesh_terms: D000082:Acetaminophen / Q000627:therapeutic use*; D000328:Adult; D018712:Analgesics, Non-Narcotic / Q000627:therapeutic use*; D001249:Asthma / Q000188:drug therapy* / Q000503:physiopathology; D001944:Breath Tests; D016535:Bronchial Hyperreactivity / Q000188:drug therapy* / Q000503:physiopathology; D001985:Bronchial Provocation Tests; D004311:Double-Blind Method; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000032:analysis; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires
chemical_list: D018712:Analgesics, Non-Narcotic; D009569:Nitric Oxide; D000082:Acetaminophen