Domperidone is a peripherally selective D2 receptor antagonist. It acts as an antiemetic and a prokinetic agent through its effects on the chemoreceptor trigger zone and motor function of the stomach and small intestine. Domperidone was not approved in USA due to risks of cardiac arrhythmias, cardiac arrest, and sudden death, but is available in other countries. However, FDA allows access to Domperidone through an expanded access investigational new drug application (IND) to patients with gastroesophageal reflux disease with upper GI symptoms, gastroparesis, and chronic constipation. As an “off-label” use, domperidone is prescribed to breastfeeding women to enhance their milk production.

2,4-Dichlorophenoxyacetic acid (2,4-D) was the first synthetic herbicide to be commercially developed and has commonly been used as a broadleaf herbicide for over 60 years. It is a selective herbicide that kills dicots without affecting monocots and mimics natural auxin at the molecular level. 2,4-D was developed during World War II as one of many so-called phenoxy herbicides by aiming to increase crop yields for a nation at war. It was commercially released in 1946 becoming the first successful selective herbicide and allowed for greatly enhanced weed control in wheat, maize, rice, and other similar cereal crops because it specifically targets dicots. This herbicide family is said to have “initiated an agricultural revolution and laid the corner stone of present-day weed science” when it was first marketed in the 1940s.

Blonanserin is an antagonist of dopamine and serotonin receptors developed for the treatment of schizophrenia. Blonanserin was approved in Japan and Korea, but was never marketed in the USA.

Tiapride is a drug that selectively blocks D2 and D3 dopamine receptors in the brain. It is used to treat a variety of neurological and psychiatric disorders including dyskinesia, alcohol withdrawal syndrome, negative symptoms of psychosis, and agitation and aggression in the elderly. A derivative of benzamide, tiapride is chemically and functionally similar to other benzamide antipsychotics such as sulpiride and amisulpride known for their dopamine antagonist effects. Tiapride is marketed under various trade names and is widely available outside of the United States. The most common trade name for tiapride is Tiapridal, which is used throughout Europe, Russia, as well as parts of South America, the Middle East, and North Africa. It is also sold under different names in Italy (Italprid, Sereprile), Japan (Tialaread, Tiaryl, Tiaprim, Tiaprizal), Chile (Sereprid), Germany (Tiaprid, Tiapridex), and China (Tiapride).

Etoperidone is an atypical antidepressant introduced in Europe in 1977. The activity of etoperidone is made mainly by its major metabolite 1-(3'-chlorophenyl)piperazine (mCPP). mCPP binds with different affinity to most of the serotonergic receptors and adrenergic receptors. This metabolite is an agonist of 5-HT2c and an antagonist of 5-HT2a. Part of etoperidone structure contributes to the activity in the α-adrenergic receptors. Etoperidone has been studied for the treatment of depression, tremors in Parkinson, extrapyramidal symptoms and male impotence. It is not certain if it was ever approved and marketed but its current status is withdrawn.

Sertindole (brand names: "Serdolect" and "Serlect") is an antipsychotic medication. Sertindole was developed by the Danish pharmaceutical company Lundbeck and marketed under license by Abbott Labs. Like other atypical antipsychotics, it has activity at dopamine and serotonin receptors in the brain. It is used in the treatment of schizophrenia. Sertindole is not approved for use in the United States and was discontinued in Australia in January 2014. In Europe, sertindole was approved and marketed in 19 countries from 1996, but its marketing authorization was suspended by the European Medicines Agency in 1998 and the drug was withdrawn from the market. In 2002, based on new data, the EMA's CHMP suggested that Sertindole could be reintroduced for restricted use in clinical trials, with strong safeguards including extensive contraindications and warnings for patients at risk of cardiac dysrhythmias, a recommended reduction in maximum dose from 24 mg to 20 mg in all but exceptional cases, and extensive ECG monitoring requirement before and during treatment.

Pipotiazine (Piportil), also known as Pipothiazine, is a typical antipsychotic of the phenothiazine class used in the United Kingdom and other countries for the treatment of schizophrenia. Its properties are similar to those of chlorpromazine. Piportil® L4 (pipotiazine palmitate) is the palmitic ester of pipotiazine, a piperidine phenothiazine with antipsychotic properties and weak sedative activity. The esterification of pipotiazine is responsible for its prolonged duration of action. The onset of action appears usually within the first 2 to 3 days after injection and the effects of the drug on psychotic symptoms are significant within one week. Improvement in symptomatology lasts from 3 to 6 weeks, but adequate control may frequently be maintained with one injection every 4 weeks. However, in view of the variations in individual response, careful supervision is required throughout treatment. Piportil L4 has actions similar to those of other phenothiazines. Among the different phenothiazine derivatives, Piportil L4 appears to be less sedating and to have a weak propensity for causing hypotension or potentiating the effects of CNS depressants and anesthetics. However, it produces a high incidence of extrapyramidal reactions.

Trifluperidol is an antipsychotic butyrophenone derivative. It is a high-affinity sigma receptor blocker and it was strongly selective for NR1a/2B receptors. It exhibit pharmacological effects and a mechanism of action very similar to that of phenothiazines and thioxanthenes in that it blocks dopaminergic receptors. It is more selective with respect to D2 receptors. Trifluperidol is indicated for the treatment of acute and chronic schizophrenia, mania and hypomania, organic psychoses, childhood behavioral disorders, agitation in psychotic illness and motor tics. Trifluperidol has been suspected as a cause of cataract in Japan. Patients receiving trifluperidol treatment may develop a parkinsonian-like syndrome which responds to withdrawal of the drug or concurrent administration of an anti-parkinsonian drug. Acute dystonias and akathisia are other acute extrapyramidal effects; tardive dyskinesia may supervene after longer periods of treatment.

Talipexole is a D2 receptor agonist which was marketed in June 1996 in Japan for the treatment of Parkinson's disease. Clinical trials with talipexole in patients with Parkinson's disease demonstrated statistically significant improvements from baseline for parkinsonian symptoms including akinesia, rigidity, tremor and gait disturbances.

Raclopride is a salicylamide neuroleptic, that acts as a selective antagonist of D2 dopamine receptors both in vitro and in vivo. Tritium-labelled raclopride has properties that demonstrate its usefulness as a radioligand for the labelling of dopamine-D2 receptors : 3H-Raclopride has a high affinity for the rat and human dopamine-D2 receptors, the non-specific binding of 3H-raclopride is very low, not exceeding 5% of the total binding and the distribution of the 3H-raclopride binding sites in the brain closely correlates with the dopaminergic innervation. The binding of 3H-raclopride is blocked by dopamine-D2 agonists and antagonists, while the D1 agonist SKF 38393 and the Dl antagonist SCH 23390 have much less potency. The interaction of dopamine with 3H-raclopride binding results in a shallow competition curve, which suggests that 3H-raclopride, similar to other dopamine-D2 radioligands, labels both high and low agonist affinity states of the dopamine-D2 receptor. The in vivo receptor binding studies performed with 3H-raclopride also demonstrate its favorable properties as a dopamine-D2 receptor marker in vivo In contrast to some other compounds used as radioligands, raclopride enters the brain readily and binds with a low component of non-specific binding in all dopamine-rich brain areas. A saturation curve may be achieved in vivo binding studies since injections of increasing concentrations of 3H-raclopride appears to be saturated at concentrations above 25 mkCi (corresponding to approximately 5 nmol/kg). Raclopride antagonizes apomorphine-induced hyperactivity in the rat at low doses (ED50 = 130 nM/kg i.p.) but induces catalepsy only at much higher doses (ED50 = 27 mkM/kg i.p.). Radiolabelled raclopride has been used as a ligand for in vitro and in vivo autoradiography in rat and primate brains. Raclopride C 11 is used with positron emission tomography (PET) as a clinical research tool to determine dopamine type 2 (D 2) receptor density in the human brain under normal and pathological conditions. For example, raclopride C 11 used in PET studies has served to confirm the age-related decrease in striatal dopamine D2 receptor density, which may be associated with a decline in the motor as well as cognitive functions. In patients with Alzheimer's disease, raclopride C 11 may be used to examine neuroreceptor distribution and quantities, which may help in the analysis of degenerative alterations of neuron populations and neuroreceptor systems in patients with this disease. In Huntington's disease, in which degeneration of neostriatal interneurons occurs (postsynaptic to the dopaminergic input), specific binding of raclopride C 11 to D 2 receptors may serve as one of the parameters in predicting performance in cognitive tasks.