A Cochrane review [Abstract] 1 included 23 studies with a total of 2 724 adult participants. Patients receiving combination inhaled therapy with short-acting anticholinergics (SAAC) and short-acting beta-agonists (SABA) were less likely to be hospitalised, were more likely to experience improved forced expiratory volume (FEV1) and peak expiratory flow (PEF), and were less likely to return to the emergency department for additional care than participants receiving SABA alone (table T1). In particular, combination inhaled therapy was more effective in preventing hospitalisation in adults with severe asthma exacerbations who are at increased risk of hospitalisation, compared to those with mild-moderate exacerbations. Adverse events, such as tremor, agitation, and palpitations, were more common with combination therapy compared to SABA alone (table T1).
| Outcome | Relative effect(95% CI) | Assumed risk with control - SABA alone | Risk difference with intervention - SABA + SAAC (95% CI) | No of Participants(studies) Quality of evidence |
|---|---|---|---|---|
| Hospitalisation | RR 0.72 (0.59 to 0.86) | 231 per 1000 | 65 fewer per 1000(from 30 fewer to 95 fewer) | 2120 (16) Moderate |
| Total adverse events | OR 2.03 (1.28 to 3.20) | 131 per 1000 | 103 more per 1000(from 31 more to 195 more) | 1392(11) Moderate |
| FEV1 | _ | Range 1.36 to 2.4 Litres | MD 0.25 higher(0.02 to 0.48 higher) | 687(6) Low |
| Peak expiratory flow (PEF) | _ | Range 190 to 313 litres/min | MD 36.58 higher(23.07 to 50.09 higher) | 1056(12) Moderate |
| Relapse rates | RR 0.8 (0.66 to 0.98) | 250 per 1000 | 50 fewer per 1000(from 5 fewer to 85 fewer) | 1180(5) Moderate |
Comment: The quality of evidence is downgraded by study limitations (unclear allocation concealment and blinding in most of the studies).
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