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.

Pyrovalerone is a psychostimulant. It has a central action. Pyrovalerone inhibits the dopamine transporter and the norepinephrine transporter, and is a weak inhibitor of the serotonin transporter. Pyrovalerone was demonstrated to reduce symptoms of chronic fatigue in humans. It stimulated locomotor activity in mice. Though pyrovalerone is still occasionally prescribed, it is used infrequently due to problems with abuse and dependence. Side effects of pyrovalerone include anxiety, fragmented sleep or insomnia and trembling, shaking or muscle tremors.

Zuclopenthixol is indicated the management of the manifestations of schizophrenia and other mental illnesses with disturbances in thinking, emotional reactions and behaviour. It is also used to treat the manic phase of manic depressive illness. Zuclopenthixol, a thioxanthene derivative, has high affinity for both dopamine D1 receptors and dopamine D2 receptors. Zuclopenthixol also has high affinity for α1-adrenergic and 5-HT2 receptors. Zuclopenthixol (CLOPIXOL®) is avavilable in the form of tablets and solution for intramuscular injections.

Cinnarizine is a piperazine derivative with antihistaminic, antiserotonergic, antidopaminergic, and calcium channel-blocking activities. It inhibits calcium translocation across the vestibular sensory cells in the ampullae and maintains endolymph flow by preventing constriction of the stria vascularis. It is currently used for the treatment of nausea, vomiting, and vertigo caused by Meniere’s disease and other vestibular disorders. Cinnarizine is also used for prevention and treatment of motion sickness. Chronic use of cinnarizine may induce extrapyramidal symptoms.

Laquinimod is a new orally available carboxamide derivative, which is currently developed for relapsing remitting (RR) and chronic progressive (CP) forms of multiple sclerosis (MS; RRMS or CPMS) as well as neurodegenerative diseases. The mechanism of action of laquinimod is not fully elucidated because the molecular target is not known. Treatment with laquinimod led to a significant and persistent increase in brain-derived neuroprotective factor (BDNF) serum levels compared to placebo treatment. In human studies, a decrease of pro-inflammatory and an increase of anti-inflammatory cytokines have been measured. After commercial launch the unexpected severe cardiac adverse events (AEs) such as serositis, pericarditis, and myocardial infarction were detected.

Clebopride is a dopamine antagonist drug. It is used to treat functional gastrointestinal disorder such as nausea or vomiting. Unchanged parent drug was the most abundant compound in human urine. Major metabolites included the hydroxylation at benzyl group to yield carbinolamine and its further N-dealkylation product, and the piperidine ring hydroxylation/oxidation metabolite (a lactam).

Dimebon (latrepirdine) is an orally available, small molecule, gamma carboline derivative that was developed and used in Russia as an over-the-counter oral antihistamine for allergy treatment since 1980s. In 1990s it was shown that Dimebon has promising potential in treating neurodegenerative diseases. In 2003, Medivation Inc acquired the rights to Dimebon. Medivation went public in December 2004, with Dimebon as the only drug in its pipeline. The product was being developed by Medivation and Pfizer as a treatment for early-stage Alzheimer's disease and Huntington's disease. However, development was discontinued by Medivation and Pfizer in early 2012. Dimebon inhibits alpha-Adrenergic receptors (alpha1A, alpha1B, alpha1D, and alpha2A), Histamine H1 and H2 receptors and Serotonin 5-HT2c, 5-HT5A, 5-HT6 receptors with high affinity. Dimebon may act by blocking NMDA receptors or voltage-gated Ca2+ channels and by preventing mitochondrial permeability pore transition.

Budipine is an antiparkinsonian drug, which was developed by Byk Gulden (now Takeda) for the treatment of Parkinson's disease. The drug has multiple mechanisms of action: it was found to interfere with dopamine biosynthesis, mainly by inhibiting MAO-B enzyme and stimulating aromatic L-amino acid decarboxylase. Also the drug inhibits the dopamine re-uptake and has weak affinity to NMDA and muscarinic receptors. Budipine passes the blood-brain barrier, is metabolized by hydroxylation, and is excreted by both in urine and feces within 24 h.

Bencyclane, a cycloheptane, is a vasodilator, antiplasmodic and a platelet aggregation inhibitor found to be effective in a variety of peripheral circulation disorders. Bencyclane has various other potentially useful pharmacological effects such as smooth muscle relaxation. Under the trade name Halidor it is used in several European countries to treat the symptoms of atherosclerosis, occlusive arterial disease. Its mechanism may involve block of calcium channels. However as was shown in vitro it does not act by a direct influence on the Ca2+ pumps of vascular smooth muscle cells. In in vitro biochemical assays related to smooth muscle excitation-contraction coupling, binding to beta 1-, beta 2-, and alpha-adrenergic receptors, inhibition of phosphodiesterase activity, and antagonism of calcium accumulation bencyclane bound to alpha- and beta-receptors. Bencyclane appeared to be a promising anti-sickling agent that can be used orally in sickle cell anaemia (SCD).

Remoxipride is a substituted benzamide. It is a weak, but relatively selective, central dopamine D2-receptor antagonist and appears to have preferential affinity for extrastriatal dopamine D2-receptors. It also has marked affinity for central sigma receptors. It was introduced by Astra (Roxiam) at the end of the eighties and was prescribed as an atypical antipsychotic. Remoxipride was withdrawn from the market worldwide by Astra because of several cases of aplastic anaemia associated with the drug.