Opioids for the palliation of symptoms in people with serious respiratory illness: a systematic review and meta-analysis.

Background: People living with serious respiratory illness experience a high burden of distressing symptoms. Although opioids are prescribed for symptom management, they generate adverse events, and their benefits are unclear.

Methods: We examined the efficacy and safety of opioids for symptom management in people with serious respiratory illness. Embase, MEDLINE and the Cochrane Central Register of Controlled Trials were searched up to 11 July 2022. Reports of randomised controlled trials administering opioids to treat symptoms in people with serious respiratory illness were included. Key exclusion criteria included <80% of participants having a nonmalignant lung disease. Data were extracted regarding study characteristics, outcomes of breathlessness, cough, health-related quality of life (HRQoL) and adverse events. Treatment effects were pooled using a generic inverse variance model with random effects. Risk of bias was assessed using the Cochrane Risk of Bias tool version 1.

Results: Out of 17 included trials, six were laboratory-based exercise trials (n=70), 10 were home studies measuring breathlessness in daily life (n=788) and one (n=18) was conducted in both settings. Overall certainty of evidence was "very low" to "low". Opioids reduced breathlessness intensity during laboratory exercise testing (standardised mean difference (SMD) -0.37, 95% CI -0.67- -0.07), but not breathlessness measured in daily life (SMD -0.10, 95% CI -0.64-0.44). No effects on HRQoL (SMD -0.42, 95% CI -0.98-0.13) or cough (SMD -1.42, 95% CI -3.99-1.16) were detected. In at-home studies, opioids led to increased frequency of nausea/vomiting (OR 3.32, 95% CI 1.70-6.51), constipation (OR 3.08, 95% CI 1.69-5.61) and drowsiness (OR 1.37, 95% CI 1.01-1.86), with serious adverse events including hospitalisation and death identified.

Conclusions: Opioids improved exertional breathlessness in laboratory exercise studies, but did not improve breathlessness, cough or HRQoL measured in daily life at home. There were significant adverse events, which may outweigh any benefits.