For many patients with refractory headache, ketamine treatment may provide short-term analgesia with tolerable adverse events, according to a study published in Regional Anesthesia and Pain Medicine.

For the study, a total of 61 patients admitted over 3 years for 5 days of intravenous therapy that included continuous ketamine were enrolled. Study participants were classified as immediate responders if they had a decrease ≥2 points in the numeric rating scale (0-10) from start to final pain in the hospital. Maintenance of ≥2-point improvement at follow-up office visits was indicative of a sustained response.

In total, 77% of participants (n=48) were classified as immediate responders. Demographics, opioid use, and fibromyalgia were comparable between immediate responders and nonresponders. The maximum improvement occurred at a mean of 4.56 days after treatment onset. At the first follow-up visit (mean, 38.1 days), 40% of responders had a sustained response. At the second follow-up visit (mean, 101.3 days), 29% of responders had a sustained response.

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Adverse events included nystagmus, sedation, nausea/vomiting, blurry vision, hallucinations, and vivid dreams. All adverse events were considered mild and improved when ketamine dosage was decreased.

“Prospective studies should focus on responder characteristics and optimal dosing strategies that minimize [adverse events] while providing optimal headache relief,” concluded the investigators.

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Schwenk ES, Dayan AC, Rangavajjula A, et al. Ketamine for refractory headache: a retrospective analysis [published online June 19, 2018]. Reg Anesth Pain Med. doi:10.1097/AAP.0000000000000827