Proof of concept study for evaluation of the effect of ketamine intranasal spray in treatment of chronic Cluster Headache (CCH)

This single‑site Danish open pilot study assessed whether intranasal ketamine hydrochloride spray administered at sub‑anesthetic doses reduces acute pain in adults with chronic cluster headache (n=20).

Primary endpoint was ≥50% reduction in pain on a 0–10 NRS at 15 minutes after administration; secondary endpoints included pain at 30 minutes, proportion achieving NRS <4, need for rescue medication, patient preference versus oxygen or injectable sumatriptan, and serious adverse events.