Quinelorane is an octahydropyrimido[4,5-g]quinolone derivative patented by American pharmaceutical company Eli Lilly and Co. as for the treatment anxiety, Parkinson's syndrome, depression, and hypertension. Quinelorane acts as an agonist of dopamine agonist for the D2 and D3 receptors. In preclinical studies Quinelorane (IM) treatment produced dose-dependent effects on male sexual responding. Penile erections and masturbation were markedly facilitated following treatment with either 2.5 or 5 micrograms/kg quinelorane. Higher doses of quinelorane (10 and 25 micrograms/kg) generally did not further augment sexual responding but rather resulted in a return in sexual responding to control vehicle levels. Quinelorane had a biphasic effect on yawning behavior of the monkeys with low doses (2.5 and 5 micrograms/kg) facilitating yawning and high doses (25 micrograms/kg) inhibiting yawning.

Ecopipam (SCH-39166) is a selective D1 dopamine receptor antagonist both in vitro and in vivo. Additionally, it exhibits saturable, high-affinity binding to D5 receptors. Ecopipam was studied clinically for a variety of indications, including schizophrenia, drug abuse, and obesity, but in each case undesirable effects were observed. Currently, ecopipam is in clinical trials for the treatment of Lesch-Nyhan and Gilles de la Tourette's syndromes.

Adrogolide is a chemically stable prodrug of the dopamine D1 receptor agonist A-86929. Adrogolide is rapidly converted in plasma to A-86929. A-86929 has high affinity and functional selectivity for the dopamine D1 receptor. Adrogolide has been in phase II clinical trials for the treatment of Parkinson's disease and cocaine abuse. However, this research has been discontinued. The adverse events associated with its use of adrogolide were of mild-to-moderate severity and included injection site reaction, asthenia, headache, nausea, vomiting, postural hypotension, vasodilitation, and dizziness.

Carmoxirole is a dopamine D2 receptor agonist with limited central activity that modulates sympathetic activation and subsequently reduces pre-load and afterload in animals. It was shown, that carmoxirole induced beneficial effects on hemodynamic and neurohumoral parameters in heart failure. In addition, experimental evidence showed that carmoxirole lowered blood pressure in various models of hypertension mainly or exclusively through inhibition of noradrenaline release from sympathetic nerve endings. That effect of carmoxirole was mediated by presynaptic dopamine receptors with the characteristic that release inhibition was restricted to low rates of sympathetic nerve discharge.

Adrogolide is a chemically stable prodrug of the dopamine D1 receptor agonist A-86929. Adrogolide is rapidly converted in plasma to A-86929. A-86929 has high affinity and functional selectivity for the dopamine D1 receptor. Adrogolide has been in phase II clinical trials for the treatment of Parkinson's disease and cocaine abuse. However, this research has been discontinued. The adverse events associated with its use of adrogolide were of mild-to-moderate severity and included injection site reaction, asthenia, headache, nausea, vomiting, postural hypotension, vasodilitation, and dizziness.

Sonepiprazole exhibits highly specific binding to the D4 dopamine receptor with more than 100-fold selectivity for the D4 receptor over other receptors, including dopamine, serotonin, and adrenergic receptors. It is a neutral antagonist at the D4 dopamine receptor and is devoid of dopamine agonist activity. Sonepiprazole selectively induces c-fos expression in the prefrontal cortex and blocks behavioral, biochemical, and genomic effects of repeated amphetamine administration in rats. Sonepiprazole was investigated as an antipsychotic for the treatment of schizophrenia in a placebo-controlled clinical trial, but in contrast to its comparator olanzapine no benefits were found and it was not researched further for this indication.

Aplindore (DAB-452) is a small molecule that displays potent dopamine D2 receptor partial agonist activity in in vitro and in vivo assays and is predicted to have antipsychotic efficacy without motor side effects. Aplindore had been in phase II clinical trials for the treatment of Parkinson's disease and restless legs syndrome. Aplindore was generally well tolerated and there were no withdrawals due to adverse events and no serious adverse events.

AstraZeneca R&D Charnwood (formerly Astra Charnwood, a subsidiary of AstraZeneca) was developing sibenadet (Viozan, AR-C68397AA) for the potential treatment of chronic obstructive pulmonary disease and asthma. Sibenadet is a dual D2 dopamine receptor, beta2-adrenoceptor agonist that combines bronchodilator activity with the sensory afferent modulating effects associated with D2-receptor agonism. Development of sibenadet has been discontinued due to disappointing efficacy findings.

Epinine or deoxyepinephrine is an active form of Ibopamine, which is used as a cardiovascular agent in congestive heart failure. Epinine is a stimulant of alpha-adrenoceptor activities: alpha-1 and alpha-2. Experiments on pig’s eyes have shown that epinine can be a promising candidate substance for intraoperative (e.g., cataract surgery) intracameral use in humans.

Quinpirole (LY 171,555) is a psychoactive drug and research chemical which acts as a selective D2 and D3 receptor agonist. Quinpirole is the most widely used D2 agonist in in vivo and in vitro studies. Specific quinpirole binding in rat brain was saturable, and dependent on temperature, membrane concentration, sodium concentration and guanine nucleotides. Saturation analysis revealed high affinity binding characteristics (KD = 2.3 nM) which were confirmed by association-dissociation kinetics. The regional distribution of [3H]quinpirole binding sites roughly paralleled the distribution of [3H]spiperone binding sites, with greatest densities present in the striatum, nucleus accumbens and olfactory tubercles. A variety of drugs, most notably monoamine oxidase inhibitors (MAOls), inhibit the binding of [3H]quinpirole, but not [3H]spiperone or [3H](-)N-n-Propylnorapomorphine, in rat striatal membranes by a mechanism that does not appear to involve the enzymatic activity of MAO. Clinically antidepressant MAOIs exhibited selectivity between sites labeled by [3H]quinpirole and [3H]spiperone as did a number of structurally related propargylamines and N-acylethylenediamine derivatives and other drugs such as debrisoquin and phenylbiguanide. Quinpirole has been shown to increase locomotion and sniffing behavior in mice and induces compulsive behavior symptomatic of obsessive compulsive disorder in rats.