Serotonin Antagonists

5-HT2A antagonists: they occupy the receptor the classical psychedelics agonise, and so blunt or end an experience that is already running. Ketanserin is the selective one and is essentially a research drug — it also blocks α₁ receptors, so it lowers blood pressure. What is actually to hand is rarely selective. The atypical antipsychotics antagonise 5-HT2A too, which is why an antipsychotic rather than a clean blocker is what tends to be reached for, and it brings D2 blockade, sedation and its own risks with it.

Filed here rather than under Antipsychotics because what defines the family is the serotonergic block, not dopamine. And an off-switch for the visuals is not an off-switch for the drug: nothing here addresses the cardiovascular and hyperthermic half of a stimulant-like overdose, which is the half that kills with the NBOMes.