| Methods |
Randomised, double‐blind, placebo‐controlled, parallel, multi‐centre (16). PP analysis. Duration 3 months |
| Participants |
155 general practice patients with chronic bronchitis defined by MRC. 88% had smoked. Exclusions were those with other serious respiratory disease or peptic ulcer and those on long‐term antibiotics or requiring mucolytics. Mean age 63 years; 67% male. 34 dropped out |
| Interventions |
NAC 200 mg 3 times daily or placebo |
| Outcomes |
Exacerbations, subjective symptom scores, clinical signs, radiological appearance, global well‐being, adverse effects |
| Notes |
British. Excluded from original review, but with new comparison, "pts with no exacerbations" can now be included |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Random sequence generation (selection bias) |
Unclear risk |
Information not available |
| Allocation concealment (selection bias) |
Unclear risk |
Information not available |
| Blinding of participants and personnel (performance bias)
All outcomes |
Low risk |
Double‐blind; matching placebo |
| Blinding of outcome assessment (detection bias)
All outcomes |
Low risk |
Double‐blind |
| Incomplete outcome data (attrition bias)
All outcomes |
High risk |
22% overall dropout rate (34/155). 4 participants withdrew from the intervention arm due to adverse events and 5 from the placebo arm. Other reasons for withdrawal from each arm not given |
| Selective reporting (reporting bias) |
Unclear risk |
None detected |
