Databases and Data Treatment
Clinicaltrials.gov, CENTRAL, MEDLINE and PsycINFO were searched from October 2013 to May 2019. Randomized controlled trials comparing opioids with placebo and at least 4 weeks of double‐blinded duration were analysed. Primary outcomes were pain relief of 50% or greater, disability, tolerability and safety. Effects were summarized by a random effects model using risk differences or standardized mean differences. We added nine new studies with 2,980 participants for a total of 21 studies with 7,650 participants. Study duration ranged between 4 and 15 weeks. Studies with a parallel and cross‐over design: Based on very low to low‐quality evidence, opioids provided no clinically relevant pain relief of 50% or greater, but a clinically relevant reduction of disability compared to placebo. Enriched enrolment randomized withdrawal (EERW) design: Based on very low to low‐quality evidence, opioids provided a clinically relevant pain relief of 50% or greater, but not a clinically relevant reduction of disability compared to placebo. There was no clinically relevant harm with regard to serious adverse events by opioids compared to placebo in studies with parallel/cross‐over and EERW design. There was a relevant harm with regard to drop out rates due to adverse events in studies with parallel/cross‐over, but not in studies with EERW design.
Conclusions
Opioids may provide a safe and clinically relevant pain relief for 4–15 weeks in highly selected patients.