Methiothepin mesylate (Metitepine mesylate) is a potent and non-selective 5-HT2 receptor antagonist, used as an antipsychotic.

A-77636 is a potent, selective, and long-acting oral dopamine D1 receptor agonist with an effective concentration (EC50) of 1.1 nM and a corresponding pEC50 value of 8.13. It demonstrates the highest affinity for the dopamine D1 receptor with a dissociation constant (Ki) of 39.8 nM and a pKi of 7.40 ± 0.09. Notably, A-77636 exhibits antiparkinsonian activity [1].

Metoclopramide hydrochloride hydrate (Metoclopramide monohydrochloride monohydrate) is a dopamine D2 antagonist that is a drug used for digestive dysfunction. It acts as an anti-emetic

L-DOPA (Levodopa) is an amino acid precursor of dopamine with antiparkinsonian properties. Levodopa is a prodrug that is converted to dopamine by DOPA decarboxylase and can cross the blood-brain barrier. When in the brain, levodopa is decarboxylated to dopamine and stimulates the dopaminergic receptors, thereby compensating for the depleted supply of endogenous dopamine seen in Parkinson's disease. To assure that adequate concentrations of levodopa reach the central nervous system, it is administered with carbidopa, a decarboxylase inhibitor that does not cross the blood-brain barrier, thereby diminishing the decarboxylation and inactivation of levodopa in peripheral tissues and increasing the delivery of dopamine to the CNS.

JNJ-37822681 is a novel, highly selective dopamine D₂ receptor antagonist characterized by a rapid dissociation rate from the dopamine D₂ receptor.