Memantine reduces opioid use but not pain in knee osteoarthritis patients after surgery

INTRODUCTION: Total knee arthroplasty (TKA) provides significant pain relief and improved function for patients with knee osteoarthritis. Despite its effectiveness, postoperative pain remains a major challenge. Effective management of this acute postoperative pain is critical for enhancing recovery. The study investigates the effectiveness of memantine in reducing postoperative pain in patients undergoing TKA. METHODS: This double-blind, randomized controlled trial aimed to evaluate the efficacy of memantine for managing postoperative pain after TKA. Conducted from April to September 2022, eligible participants over 18 years with ASA grades I or II were recruited. Exclusions included patients with substance abuse histories, chronic opioid use, significant comorbidities, or contraindications to memantine. Participants were randomly assigned to receive either memantine (20 mg daily preoperatively for three days and 10 mg daily postoperatively for two weeks) or a placebo. Both groups received standard analgesics during hospitalization and upon discharge. Pain levels were assessed using Visual Analog Scale (VAS) scores and Short-Form McGill Pain Questionnaire (SF-MPQ) at various time points. Secondary outcomes measured included opioid usage and nocturnal awakening. RESULTS: Memantine did not significantly lower pain levels compared to placebo, as measured by VAS (mean difference: 0.138, CI 95%: - 0.468-1.103, P = 0.418) and SF-MPQ (mean difference: 1.962, CI 95%: - 1.013-4.936, P = 0.190). Patients receiving memantine needed opioid analgesia (2.85 ± 0.67 times) significantly (P < 0.001) less frequently than the Placebo patients (4.14 ± 1.06 times). Nocturnal awakening did not differ significantly between the two groups (Memantine: 3.59 ± 2.15, Placebo: 2.33 ± 2.12, P = 0.067). CONCLUSION: The comparison of pain levels between oral memantine and placebo indicates that memantine does not significantly reduce pain in patients undergoing TKA. However, it significantly lowers the need for opioids postoperatively.