Study Design Characteristics and Endpoints for Enriched Enrollment Randomized Withdrawal Trials for Chronic Pain Patients: A Systematic Review

Abstract Enriched enrollment randomized withdrawal (EERW) pain trials are designed to include only responders with considerable pain relief without unacceptable side effects into the randomized phase. There are no recommendations for primary endpoints in such trials. Our objective was to propose recommendations based on assessment of trial characteristics, endpoints and effect sizes in EERW pain trials. We conducted a systematic review by searching electronic databases up to June 2020 for EERW trials comparing an analgesic with a placebo in adults