Antiemetics

Nausea agents, defined by target rather than by structure: ondansetron blocks 5-HT3, metoclopramide, domperidone and prochlorperazine block D2, aprepitant blocks NK1. Which receptor a member hits decides what else it does to a person — the D2 blockers carry the antipsychotics' movement effects, acute dystonia and akathisia among them, and prochlorperazine is a phenothiazine in everything but the shelf it is sold from.

They are filed here because they are routinely co-used: taken deliberately alongside opioids, psychedelics and entactogens, and taken by people who do not count them as drugs at all. The class-level risk is cardiac. Ondansetron, domperidone and cisapride prolong QT — cisapride was withdrawn over it — and that adds to methadone, to the antipsychotics, and to anything else on board doing the same thing.