Summary of evidence per mucolytic, per outcome
| Mucolytics/outcomes | N-Acetylcysteine | Ambroxol | Erdosteine | Bromhexine | Hypertonic saline | Hyaluronan |
| Treatment success | NA | N=50 (+) N with resolution or significant improvement of symptoms and laboratory findings [40] N=80 (+) N with clinical efficacy [41] | N=27 (+) N with clinical judgement of effectiveness [52] N=226 (+) N with resolution of symptoms [31] | NA | NA | NA |
| Patient reported | NA | 30 (−) Number of dyspnoea and cough attacks [37] | 226 (+) Global clinical assessment score [31] 200 (+) N with improvement [50] | NA | NA | NA |
| Overall symptom score | NA | 50 (+) Chinese medical symptom score, mean change [40] | 55 (+) Breathlessness–sputum–cough scale [46, 48] | NA | NA | |
| Breathlessness | 40 (−) N per severity [42] 88 (−) Likert score 0–7, nonvalidated [53, 54] | 50 (−) Chinese medical symptom score [40] | 226 (+) Nonvalidated score 0–3 [31] N with absence [31] | 27 (−) N with improvement [44] | 59 (−) Modified Borg scale [38] | NA |
| Cough | 38 (−) Nonvalidated score 0–7 [53] 95 (+) Nonvalidated score 0–3 [29] 122 (+) N with improvement in intensity [51] | 50 (+) N with severe cough affecting sleep, Chinese medical symptom score [40] 23 (−) Nonvalidated score 0–3 [33] | 253 (+) Nonvalidated score 0–3 [31, 52] 226 (+) N with absence [31] (same study as above) | NA | NA | NA |
| Ease of expectoration | 38 (−) Nonvalidated score 0–7 [53] 122 (+) N with improvement [51] | 50 (−) Chinese medical symptom score [40] 23 (+) Nonvalidated score 0–3 [33] | 253 (+) Nonvalidated score 0–3 [31, 52] 226 (+) N with absence [31] (same study as above) | 27 (−) N with improvement [44] | NA | NA |
| Sputum viscosity | 30 (+) Nonvalidated score 0–3 [35] | NA | 27 (+) Centipoises, mean % change, compared to pre-treatment [52] 226 (+) Nonvalidated score 0–3 [31] N with fluid saliva [31] | 27 (−) Centipoises and arbitrary units [44] | NA | NA |
| Health-related quality of life | 78 (+) Clinical COPD questionnaire, mean change [39] | |||||
| Hospitalisation duration | 166 (−) [39, 53, 54] | NA | 52 (−) [46, 47] | NA | NA | 36 (+) [36] |
| Indication for higher level of care | 42 (−) N with ICU admission and intubation [53] | NA | NA | NA | NA | 41 (−) N needing invasive ventilation [36] |
| Future exacerbations | 38 (−) Rate by 6 months [53] Time to first by 6 months [53] | NA | 40 (+) N by day 30 [46] Hazard ratio by day 60 [46] 15 (−) Rate by day 30 [49] (+) Rate by day 60 [49] | NA | NA | NA |
| Mortality | 42 (−) N [53] | NA | NA | 31 (−) N [44] | 59 (−) N up to 30 days [43] | 41 (−) N [36] |
| Serious adverse events | 50 (−) None [54] | NA | NA | NA | 59 (−) None [43] | NA |
Various measurement instruments were used for assessing some of the outcomes. Results are pooled per instrument and for each instrument we present the overall population in which it was tested and whether there was evidence (+) or no evidence (−) of a beneficial effect with mucolytics. ICU: intensive care unit; N: number of participants; NA: not assessed in any trial.