Most current anti-nausea medications fall into 6 different pharmacologic classes:

1.  Muscarinic receptor antagonists including atropine and hyoscine derived from nightshades and may affect the area post rami directly

2.  Histamine Receptor Antagonists such as dimenhydrinate and diphenhydramine tested on US Troops in 1948 and which often contain stimulating medication to offset sedating effect.

3.  Dopamine Receptor Antagonists including Phenothiazines such as Promethazine in 1947 and chlorpromazine in 1950.  

4.  Benzodiazepines such as lorazepam which does not directly affect the area post rami but enhances GABA which reduces anxiety, produce sedative effect with potential for anterograde amnesia.

5.  Selective 5-hydroxytryptamine, (5HT3) receptor antagonists such as metoclopramide originally developed to offset emetic effect from cisplatin at those receptors and leading to selective agents such as granisetron.

6.  Neurokinin Receptor Antagonists which offset the effect of substance P but have been found to reduce chemotherapy induced emesis.