Effect of Ketanserin After LSD Administration

This double-blind, random-order, two-period crossover study in healthy volunteers compares 100 µg LSD followed by ketanserin 40 mg versus 100 µg LSD followed by placebo to assess whether post-hoc 5-HT2A antagonism shortens and reduces psychedelic effects.

Primary purpose is basic science: to probe competitive antagonism at the 5-HT2A receptor and characterise acute subjective and physiological effects. Outcomes include subjective ratings, safety measures and pharmacodynamic observations.