Lurasidone is a novel antipsychotic agent approved for the treatment of schizophrenia in a number of countries including the UK and is also approved in the USA and Canada for the treatment of bipolar depression as either a monotherapy or adjunctive therapy with lithium or valproate. In addition, lurasidone is in phase III of a clinical trial for the treatment patient with major depressive disorder and for the treatment of irritability associated with autistic disorder. The mechanism of action of lurasidone, as with other drugs having efficacy in schizophrenia, is unknown but is known, that lurasidone has a high affinity for dopamine D2, serotonin 5-HT2A and serotonin 5-HT7 receptors where it has antagonist effects. In addition, lurasidone is a partial agonist at the serotonin 5-HT1A receptor and has no appreciable affinity for histamine or muscarinic receptors.

Paliperidone (9-OH-risperidone) is the primary active metabolite of the older antipsychotic risperidone. While its specific mechanism of action is unknown, it is believed that paliperidone and risperidone act via similar if not the same pathways. It has been proposed that the drug's therapeutic activity in schizophrenia is mediated through a combination of central dopamine Type 2 (D2) and serotonin Type 2 (5HT2A) receptor antagonism. Paliperidone is also active as an antagonist at alpha 1 and alpha 2 adrenergic receptors and H1 histaminergic receptors, which may explain some of the other effects of the drug. Paliperidone was approved by the FDA for treatment of schizophrenia on December 20, 2006. Very common adverse effects are: headache, tachycardia, somnolence and insomnia.

Pramipexole is a nonergot dopamine agonist with high relative in vitro specificity and full intrinsic activity at the D2 subfamily of dopamine receptors, binding with higher affinity to D3 than to D2 or D4 receptor subtypes. The relevance of D3 receptor binding in Parkinson's disease is unknown. The precise mechanism of action of Pramipexole as a treatment for Parkinson's disease is unknown, although it is believed to be related to its ability to stimulate dopamine receptors in the striatum. This conclusion is supported by electrophysiologic studies in animals that have demonstrated that Pramipexole influences striatal neuronal firing rates via activation of dopamine receptors in the striatum and the substantia nigra, the site of neurons that send projections to the striatum. Pramipexole is used for the treatment of signs and symptoms of idiopathic Parkinson's disease.

Bupropion, an antidepressant of the aminoketone class and a non-nicotine aid to smoking cessation, is chemically unrelated to tricyclic, tetracyclic, selective serotonin re-uptake inhibitor, or other known antidepressant agents. Compared to classical tricyclic antidepressants, Bupropion is a relatively weak inhibitor of the neuronal uptake of norepinephrine, serotonin, and dopamine. In addition, Bupropion does not inhibit monoamine oxidase. Bupropion produces dose-related central nervous system (CNS) stimulant effects in animals, as evidenced by increased locomotor activity, increased rates of responding in various schedule-controlled operant behavior tasks, and, at high doses, induction of mild stereotyped behavior. Bupropion is marketed as Wellbutrin, Zyban, and generics. Bupropion is indicated for the treatment of major depressive disorder (MDD). WELLBUTRIN, WELLBUTRIN SR, and WELLBUTRIN XL are not approved for smoking cessation treatment, but bupropion under the name ZYBAN is approved for this use.

Metoclopramide is a dopamine D2 antagonist that is used as an antiemetic. Metoclopramide inhibits gastric smooth muscle relaxation produced by dopamine, therefore increasing cholinergic response of the gastrointestinal smooth muscle. It accelerates intestinal transit and gastric emptying by preventing relaxation of gastric body and increasing the phasic activity of antrum. Simultaneously, this action is accompanied by relaxation of the upper small intestine, resulting in an improved coordination between the body and antrum of the stomach and the upper small intestine. Metoclopramide also decreases reflux into the esophagus by increasing the resting pressure of the lower esophageal sphincter and improves acid clearance from the esophagus by increasing amplitude of esophageal peristaltic contractions. Metoclopramide's dopamine antagonist action raises the threshold of activity in the chemoreceptor trigger zone and decreases the input from afferent visceral nerves. Studies have also shown that high doses of metoclopramide can antagonize 5-hydroxytryptamine (5-HT) receptors in the peripheral nervous system in animals. Metoclopramide is used for the treatment of gastroesophageal reflux disease (GERD). It is also used in treating nausea and vomiting, and to increase gastric emptying.

Bromocriptine is an ergot derivative with potent dopamine receptor agonist activity, which activates post-synaptic dopamine receptors. Bromocriptine is indicated for the treatment of dysfunctions associated with hyperprolactinemia. Bromocriptine therapy is indicated in the treatment of acromegaly and in the treatment of the signs and symptoms of idiopathic or postencephalitic Parkinson’s disease. It is approved as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. Some commonly reported adverse reactions include nausea, fatigue, dizziness, vomiting and headache. Bromocriptine may interact with dopamine antagonists, butyrophenones and certain other agents.

Loxapine is a dibenzoxazepine tricyclic antipsychotic agent, available for oral and inhalatory administration, classified as a typical antipsychotic. Loxapine acts as an antagonist at central serotonin and dopamine receptors. Adasuve (loxapine inhalation powder) is a prescription medicine that is used to treat acute agitation in adults with schizophrenia or bipolar I disorder.

Carbidopa is a competitive inhibitor of aromatic L-amino acid decarboxylase that does not cross the blood-brain barrier, is routinely administered with levodopa (LD) for the treatment of the symptoms of idiopathic Parkinson’s disease (paralysis agitans), postencephalitic parkinsonism, and symptomatic parkinsonism, which may follow injury to the nervous system by carbon monoxide intoxication and/or manganese intoxication. Current evidence indicates that symptoms of Parkinson’s disease are related to depletion of dopamine in the corpus striatum. Administration of dopamine is ineffective in the treatment of Parkinson’s disease apparently because it does not cross the blood-brain barrier. However, levodopa, the metabolic precursor of dopamine, does cross the blood- brain barrier, and presumably is converted to dopamine in the brain. When levodopa is administered orally it is rapidly decarboxylated to dopamine in extracerebral tissues so that only a small portion of a given dose is transported unchanged to the central nervous system. For this reason, large doses of levodopa are required for adequate therapeutic effect and these may often be accompanied by nausea and other adverse reactions, some of which are attributable to dopamine formed in extracerebral tissues. Carbidopa inhibits decarboxylation of peripheral levodopa. Carbidopa has not been demonstrated to have any overt pharmacodynamic actions in the recommended doses.

Dopamine, a sympathomimetic amine vasopressor, is the naturally occurring immediate precursor of norepinephrine. G protein-coupled dopamine receptors (D1, D2, D3, D4, and D5) mediate all of the physiological functions of the catecholaminergic neurotransmitter dopamine, ranging from voluntary movement and reward to hormonal regulation and hypertension. Dopamine HCl is indicated for the correction of hemodynamic imbalances present in the shock syndrome due to myocardial infarction, trauma, endotoxic septicemia, open-heart surgery, renal failure, and chronic cardiac decompensation as in congestive failure.