Despite limited evidence of efficacy, opioid analgesics are frequently used by patients for chronic pain while awaiting total hip or knee arthroplasty (THA or TKA). Preoperative use of opioids is problematic as it increases the likelihood of postoperative opioid-related adverse drug events and postoperative complications and is the strongest predictor of persistent opioid use post surgery. Opioid tapering prior to elective surgery has been proposed as a strategy for mitigating harms and improving postoperative outcomes. This protocol describes a randomised clinical trial, which aims to determine the effectiveness of a preoperative pharmacist-partnered opioid tapering programme compared with standard care for patients awaiting elective THA or TKA on postoperative outcomes including persistent opioid use.

Eligible participants must be aged ≥18 years; awaiting elective unilateral or bilateral THA or TKA; speak and read English; use prescription opioid analgesics at least 4 days a week and have access to internet or telephone. The participants will be excluded if they are undergoing a repeat surgery (same procedure within 6 months), are using opioids for cancer, palliative care or substance use disorder; have previously or are currently undergoing an opioid tapering programme or active medication review or have cognitive impairment. Enrolled participants will be randomised in a 1:1 ratio in permuted blocks of two and four to: (1) intervention or (2) standard care. A total of 314 participants will be recruited into the study. The intervention will include a pharmacist-partnered opioid tapering programme in which a pharmacist will work with participants to reduce their opioid dose over a 3-month period before surgery. Standard care will involve review by the hospital preadmission clinic multidisciplinary team to assess medical, physical and psychological health prior to surgery and education sessions for preoperative and postoperative care. The primary outcome assessed is persistent opioid use 3 months post surgery. The key secondary outcome is total Western Ontario and McMaster Universities Arthritis Index score. Data analysis will be performed using an estimand framework, with a generalised estimating equation model for the primary outcome from 1 day to 3 days presurgery to 3 months post surgery and a multilevel model for the main secondary outcome from baseline to 3 months after surgery. Cost-effectiveness and cost-utility analyses will be conducted to determine whether the intervention is cost-effective from the healthcare system perspective.

Ethics approval for this study was granted by a Human Research Ethics Committee (approval number: 2023/ETH01042). Results will be disseminated in peer reviewed journals, at international scientific meetings as well as meetings with key stakeholders and via the media.

ACTRN12623000685617.