This figure shows the different sites of actions of anti-emetics. The agents used to treat emesis generally exert their effect by blocking one neurotransmitter receptor and can thus be grouped into classes of dopamine D2 antagonists, serotonin 5-HT3-antagonists and anticholinergics.
The exception to this is the drug metoclopramide which has both D2- and 5-HT3-antagonist activity. Note that some drugs act on the level of the CNS, others on the level of the GI tract, and yet others on both the CNS and GI tract. More information about these agents is depicted in the following graphics.
A patient receives a prophylactic dose of droperidol near the end of surgery. In the recovery room, the patient becomes nauseated and vomits. What do you recommend?
Extra info: Close A rescue anti-emetic is likely to be more efficacious if its mechanism is different than the failing agent. Therefore, ondansetron (a 5-HT3 antagonist) is likely to be more efficacious than the other anti-emetics. Domperidone, alizapride, and metoclopramide all are primarily D2 antagonists like droperidol.