Metoclopramide (5-Chloro-2-methoxyprocainamide) is a dopamine D2 antagonist which has been used for treatment of a variety of gastrointestinal symptoms over the last thirty years. In various countries, metoclopramide is the antiemetic drug of choice in pregnant women. Findings provide reassurance regarding the safety of metoclopramide for the fetus when the drug is given to women to relieve nausea and vomiting during pregnancy. Evidence also supports its use for gastroparesis (poor stomach emptying) and gastroesophageal reflux disease. It appears to bind to dopamine D2 receptors where it is a receptor antagonist, and is also a mixed 5-HT3 receptor antagonist/ 5-HT4 receptor agonist.

PG 01037 dihydrochloride (PG-01037 2HCl) is a potent and selective dopamine D3 receptor antagonist with a Ki of 0.7 nM.

Cariprazine hydrochloride (RGH188 hydrochloride) is an antipsychotic drug, is a D3 and D2 receptor partial agonist((Ki of 0.085 nM and 0.49 nM, respectively)

Hexamethonium Bromide (Hexamethonium Dibromide), a specific antagonist of neuronal-type nicotinic AChR in ganglia, is poorly absorbed from the gastrointestinal tract and does not cross the blood-brain barrier.

N-Desmethylclozapine (Desmethylclozapine) is an antagonist of serotonin (5-HT) receptor subtype 5-HT2C (IC50: 7.1 nM). It also is an antagonist at dopamine D4 receptors, an agonist at δ-opioid receptors.