Effect of Low dose Naltrexone versus Naproxen Extended-release for Pain Relief in knee osteoarthritis, a Triple-blinded, Non-inferiority Phase II Randomized Controlled Trial (FREEDOM) - Study Protocol

: Background and objectives: Osteoarthritis (OA) is a degenerative articular disease that affects approximately 240 million people worldwide, with knee OA accounting for 80% of this burden. One of the aims of pharmacological treatment in OA is to reduce pain. Non-steroidal anti-inflammatory drugs (NSAIDs) are effective for pain relief in OA but have considerable renal, hepatic, cardiovascular, and gastrointestinal adverse effects, with the resultant increase in morbidity and mortality. Naltrexone is an orally activated opioid antagonist that has varied dose-dependent pharmacodynamic effects: Analgesic and anti-inflammatory effects are exhibited only at low dosage ranges of 0.5mg to 4.5mg (Low Dose Naltrexone LDN) while retaining a favorable adverse effect profile. This study aims to test the non-inferiority of LDN against Naproxen. Methodology: This is a prospective phase II triple-blinded, two-arm, parallel-group, non-inferiority randomized controlled trial. The intervention group will receive low dose naltrexone 4.5 mg once daily, and the control group will receive extended-release naproxen 1000 mg once daily during the 12 week trial duration. Our sample size will be 118 patients recruited from a single Orthopedic referral center in the USA. Discussion: The use of LDN for pain relief in osteoarthritis (OA) may be beneficial due to its favorable adverse effect profile. To the best of our knowledge, there is no published data on LDN use in OA even though preliminary evidence has documented its safety and tolerability in a variety of chronic pain conditions.