N-Acetylcysteine for Chronic Bronchitis
Verdict: Published with Warning
Across 5 PubMed studies, the evidence for N-Acetylcysteine in Chronic Bronchitis grades Tier B — preliminary evidence. Effective, but with safety or population caveats.
B 🟡 B Preliminary Evidence Published with Warning
Why this grade7-layer evidence engine
⚖️
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditableRaw score 0.67
D
C
B
A
S
← counter-evidence / ineffectiveeffective / strong evidence →
Final grade
B · Published with Warning
Confidence
79%
Broadly consistent
Evidence level
E1
Cochrane high-quality SR/MA
▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.666
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 positive (2 篇 > 1 negative)
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status
PubMed studies (5)L2 · primary research & systematic reviews
N-acetylcysteine Treatment in Chronic Obstructive Pulmonary Disease (COPD) and Chronic Bronchitis/Pre-COPD: Distinct Meta-analyses
Finding: NAC reduced exacerbation incidence in both COPD (IRR 0.76, 95% CI 0.59-0.99) and chronic bronchitis/pre-COPD (IRR 0.81, 95% CI 0.69-0.95). In CB/pre-COPD, NAC also improved symptoms/QoL (OR 3.47, 95% CI 1.92-6.26). Sensitivity analyses confirmed effect for trials >5 months.
View on PubMed Mucolytic agents versus placebo for chronic bronchitis or chronic obstructive pulmonary disease
Finding: Mucolytics reduce likelihood of exacerbation vs placebo (Peto OR 1.73, 95% CI 1.56-1.91 for being exacerbation-free; ~52/100 vs 39/100 exacerbation-free; NNT 8 over 9 months). Reduced disability ~0.43 days/month. No clear effect on mortality. Earlier (1970s-90s) trials showed larger benefits than recent trials.
View on PubMed Twice daily N-acetylcysteine 600 mg for exacerbations of chronic obstructive pulmonary disease (PANTHEON): a randomised, double-blind placebo-controlled trial
Finding: NAC group 1.16 exacerbations/patient-year vs placebo 1.49 (risk ratio 0.78, 95% CI 0.67-0.90; p=0.0011). Effect most pronounced in moderate (vs severe) COPD. Adverse events similar between groups (29% vs 26%).
View on PubMed The efficacy of N-acetylcysteine in chronic obstructive pulmonary disease patients: a meta-analysis
Finding: No significant difference in patients without acute exacerbations (OR 1.12, 95% CI 0.92-1.36; p=0.26). No significant change in FEV1 (MD 0.00, 95% CI -0.01 to 0.00; p=0.29) or FVC, SGRQ, GSH. Concludes NAC did NOT reduce exacerbation risk or slow lung function decline.
View on PubMed Effect of high-dose N-acetylcysteine on exacerbations and lung function in patients with mild-to-moderate COPD: a double-blind, parallel group, multicentre randomised clinical trial
Finding: Long-term high-dose NAC did NOT significantly reduce annual rate of total exacerbations and did NOT improve lung function in patients with mild-to-moderate COPD. Findings contrast with PANTHEON (moderate-to-severe COPD).
View on PubMed Regulatory & authoritative positionsL4/L5 · FDA / EMA / NIH ODS / Cochrane / Mayo …
L4a US FDA
Cautious
NAC is excluded from the dietary supplement definition under section 201(ff)(3)(B)(ii) of the Federal Food, Drug, and Cosmetic Act source↗
L4b EU EFSA
Against
a cause and effect relationship has not been established source↗
L4c UK NHS
Supportive
Acetylcysteine is the antidote used to treat paracetamol overdose source↗
L5a NIH Office of Dietary Supplements
Cautious
NAC has FDA approval for treating potentially hepatotoxic doses of acetaminophen. source↗
L5b Mayo Clinic
Cautious
Acetylcysteine is used for certain lung conditions when increased amounts of mucus make breathing difficult. source↗
L5c Cleveland Clinic
Cautious
Acetylcysteine inhalation is used to help thin mucus in patients with certain lung conditions source↗
L5e Specialty Society (condition-mapped)
Cautious
long-term treatment with N-acetylcysteine reduces exacerbations source↗