NGD 94-1 is high affinity D4 receptor ligand, shows selective over D1, D2, D3 and D5 receptors. Displays antagonist activity at the human D4.2 receptor (Ki = 3.6 nM in transfected CHO cells) and exhibits agonist activity at the D4.4 receptor in HEK 293 cells.

WAY-100635 is an achiral phenylpiperazine derivative that originally discovered as an antagotist of 5-HT1A receptor. Later WAY-100635 was described as a potent dopamine D4 receptor agonist. WAY-100635 was in preclinical studies for the treatment of Diabetes mellitus, Anxiety and Cognition disorders, howevere the development was discontinued. Isotope labeled WAY-100635 could be used for the study of central 5-HT 1A receptors with potential for application to the study of neuropsychiatric disorders and to the human pharmacology of psychoactive drugs.

Mosapramine (Cremin) is used to treat chronic schizophrenia in Japan. It is a potent dopamine antagonist with high affinity to the dopamine receptor subtypes 2, 3 and 4, and with moderate affinity for the 5-HT2 receptors

Roxindole (EMD-49,980) is a dopaminergic and serotonergic drug which was originally developed for the treatment of schizophrenia. Roxindole has also been investigated as a therapy for the major depressive disorder, Parkinson's disease, and prolactinoma. Roxindole is dopamine autoreceptor-selective agonistic drug with high affinity to D2-like receptors and with much lower affinities to D1-like, % and ol2, muscarinic and 5HT 2 receptors. Additionally, Roxindole exerts 5HT uptake inhibition and 5HT1A agonistic effects. The bioavailability of Roxindole has been estimated at 5% due to a high first-pass metabolization. On the other hand, in 14C distribution studies, Roxindole has crossed the blood-brain barrier readily and the brain concentrations at all intervals have been much higher than corresponding plasma levels. In clinical trials, Roxindole ‘s antipsychotic efficacy was only modest but it was unexpectedly found to produce potent and rapid antidepressant and anxiolytic effects. However, the clinical development of Roxindole was discontinued.