Ropinirole (INN; trade names Requip, Repreve, Ronirol, Adartrel) is a dopamine agonist of the non-ergoline class of medications, used in the treatment of Parkinson's disease and restless legs syndrome. Although the precise mechanism of action of ropinirole as a treatment for Parkinson's disease is unknown, 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 ropinirole 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. Ropinirole 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 mechanism of ropinirole-induced postural hypotension is presumed to be due to a D2 -mediated blunting of the noradrenergic response to standing and subsequent decrease in peripheral vascular resistance. Ropinirole can cause nausea, dizziness, hallucinations, orthostatic hypotension, and sudden sleep attacks during the daytime. Unusual side effects specific to D3 agonists such as ropinirole and pramipexole can include hypersexuality, punding, and compulsive gambling, even in patients without a history of these behaviors.

Pimozide (Orap) is a diphenylbutylpiperidine that is effective as an antipsychotic agent and as an alternative to haloperidol for the suppression of vocal and motor tics in patients with Tourette syndrome. It is not intended as a treatment of first choice nor is it intended for the treatment of tics that are merely annoying or cosmetically troublesome. It should be reserved for use in Tourette’s Disorder patients whose development and/or daily life function is severely compromised by the presence of motor and phonic tics. Evidence supporting approval of pimozide for use in Tourette’s Disorder was obtained in two controlled clinical investigations, which enrolled patients between the ages of 8 and 53 years. Most subjects in the two trials were 12 or older. Pimozide is an orally active antipsychotic drug product, which shares with other antipsychotics the ability to blockade dopaminergic receptors on neurons in the central nervous system. Although its exact mode of action has not been established, the ability of pimozide to suppress motor and phonic tics in Tourette’s Disorder is thought to be a function of its dopaminergic blocking activity. However, receptor blockade is often accompanied by a series of secondary alterations in central dopamine metabolism and function which may contribute to both pimozide’s therapeutic and untoward effects. In addition, pimozide, in common with other antipsychotic drugs, has various effects on other central nervous system receptor systems which are not fully characterized.

Amoxapine is an antidepressant of the dibenzoxazepine class, chemically distinct from the dibenzazepines, dibenzocycloheptenes, and dibenzoxepines. It is designated chemically as 2-Chloro-11- (1-piperazinyl)dibenz[b,f ][1,4]oxazepine. Amoxapine is an antidepressant with a mild sedative component to its action. The mechanism of its clinical action in man is not well understood. In animals, amoxapine reduced the uptake of norepinephrine and serotonin and blocked the response of dopamine receptors to dopamine. Amoxapine is not a monoamine oxidase inhibitor. Amoxapine is absorbed rapidly and reaches peak blood levels approximately 90 minutes after ingestion. It is almost completely metabolized. The main route of excretion is the kidney. In vitro tests show that amoxapine binding to human serum is approximately 90%. In man, amoxapine serum concentration declines with a half-life of eight hours. However, the major metabolite, 8-hydroxyamoxapine, has a biologic half-life of 30 hours. Metabolites are excreted in the urine in conjugated form as glucuronides. Clinical studies have demonstrated that amoxapine has a more rapid onset of action than either amitriptyline or imipramine. The initial clinical effect may occur within four to seven days and occurs within two weeks in over 80% of responders.

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.

Levodopa (L-DOPA) was first isolated from seedlings of Vicia faba by Marcus Guggenheim in 1913. Levodopa, a dopamine precursor, is an effective and well-tolerated dopamine replacement agent used to treat Parkinson's disease. Oral levodopa has been widely used for over 40 years, often in combination with a dopa-decarboxylase inhibitor carbidopa, which reduces many treatment complications, extending its half-life and increasing levodopa availability to the brain. Entacapone, a catechol-O-methyltransferase inhibitor, can also be used to improve the bioavailability of levodopa, especially when used in conjunction with a carbidopa.

Thiothixene (trade mark Navane) belongs to a class of antipsychotics known as the first-generation antipsychotics, sometimes referred to as conventional or typical antipsychotics. Thiothixene is a thioxanthene antipsychotic which elicits antipsychotic activity by postsynaptic blockade of CNS dopamine receptors resulting in inhibition of dopamine-mediated effects; also has alpha-adrenergic blocking activity. Thiothixene is effective in the management of schizophrenia. Only cis isomer of thiothixene exerts clinical effectivity.

Dicarbine is an orally active drug approved in Russia under the trade name Карбидин, is used for the treatment patients with schizophrenia and alcoholic psychosis. This drug blocks dopamine receptors in various brain parts, which leads to a reduction in the productive symptoms of psychosis: delusions and hallucinations.

LEVOFENFLURAMINE is a levorotatory enantiomer of fenfluramine, a substituted amphetamine which was formerly used to treat obesity. LEVOFENFLURAMINE has dopamine-antagonistic properties and, at high doses, increases dopamine concentrations in rat striatal dialysates. It is essentially inactive to reduce food intake in human subjects.

There is no much available information related to the biological and pharmacological application of imidoline, but this compound has been found to be as potent as chlorpromazine in increasing striatal DOPA accumulation and prolactin secretion in vivo. Imidoline exhibited only weak inhibitory activity towards dopamine-sensitive adenylate cyclase and 3H-spiroperidol binding to striatal membranes in vitro. A proposed active conformation involves intramolecular hydrogen bonding between the protonated dimethylamino group and the oxygen of the imidazolidinone ring. The spatial relationship between the amine nitrogen and phenyl ring in this conformation allows proper fit of imidoline with key dimensions described for the dopamine receptor.

Prosulpride is an aminosulfonylbenzamide derivative with potent neuroleptic activity. Prosulpride selectively blocks the presynaptic dopaminergic receptors and antagonize apomorphine-induced stereotyped behavior, circling behavior, climbing behavior, increased motor activity and some other apomorphine-induced effects related to stimulation of postsynaptic dopaminergic receptors.