Overview

• The review pooled 67 randomized trials with 2,309 adults across ketamine and four other NMDA antagonists.
• Ketamine showed no clear reduction in chronic pain across conditions or routes of administration, with intravenous dosing tied to more adverse events.
• Reported harms included psychotomimetic effects such as delusions, delirium, and paranoia, plus nausea and vomiting.
• Investigators rated the evidence low to very low certainty due to small, short, and methodologically weak studies.
• No trials assessed whether ketamine reduced depressive symptoms or opioid use, even as off-label prescribing for chronic pain remains widespread.