Lysergic Acid Diethylamide (LSD) as Treatment for Cluster Headache

This double-blind, randomised, placebo-controlled two-phase crossover trial tests whether a pulse regimen of oral LSD (three 100 µg doses across three weeks) reduces frequency and intensity of cluster headache attacks compared with placebo.

Primary outcomes are changes in attack frequency and intensity recorded in a standardised headache diary; safety and tolerability are monitored throughout. Eligibility includes adults 25–75 years with chronic or predictable episodic cluster headache responsive to oxygen.