A potent, selective and orally active receptor antagonist of leukotriene D4, verlukast (MK-571), was discovered and developed from a styrylquinoline lead structure based on a hypothetical model of the leukotriene D4 receptor. MK-571 blocks the action of LTD4 in animals and man, and is effective in a number of animal models of antigen-induced bronchoconstriction at plasma concentration at or below 2 ug/mL. MK-571 also blocks antigen-induced asthmatic responses in man. MK-571 is a potent and selective leukotriene D4 (LTD4) antagonist and ABCC multidrug resistance protein 1(MRP1) inhibitor. The cysteinyl leukotrienes (CysLTs), LTC4, LTD4, and LTE4, mediate their actions through two distinct G-protein coupled receptors. LTD4 is the preferred ligand for the CysLT1 receptor, whereas LTC4 and LTD4 bind with approximately equal affinity to the CysLT2 receptor. MK-571 is a selective, orally active CysLT1 receptor antagonist. It blocks the binding of LTD4, but not LTC4, to human and guinea pig lung membranes with Ki values of 0.22 nM and 2.1 nM, respectively. MK-571 effectively blocks LTD4 activation of recombinant human and mouse CysLT1 receptors but is ineffective at blocking LTC4 or LTD4 activation of the recombinant human or murine CysLT2 receptors.

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).

Pitofenone is a spasmolytic agent. It exerts anticholinesterase and antimuscarinic activities. Pitofenone is used to relieve pain and spasms of smooth muscles. Pitofenone is also used for the treatment of back pain, sprains, and strains. Pitofenone is used in combination along with fenpiverinium bromide, and metamizole sodium. The drug is currently sold in Eastern Europe and India under various trade names. The combined preparation possesses strong analgesic, spasmolytic, cholinolytic and anti-inflammatory effects on the smooth muscles predominantly of the gastrointestinal and urogenital tract. Indications are strong pain in gastric or intestinal colic, kidney and gallstones, and for painful menstruation. Pitofenone hydrochloride present in the combination exerts papaverin-like spasmolytic effect on the vascular and extra-vascular smooth muscles of the stomach, intestines, urinary tract, biliary tract, and uterus.

Itopride is a dopamine D2 receptor antagonist and inhibitor of acetylcholinesterase. It is indicated in the for the treatment of gastrointestinal symptoms caused by reduced gastrointestinal motility, such as functional non-ulcer dyspepsia (chronic gastritis), gastric fullness, rapid satiation, pain or discomfort in the upper abdomen, anorexia, heartburn, nausea, and vomiting. The drug is not approved in the USA or UK but is available in Japan and Western European countries.

Tiemonium (often used in a form of iodide or methylsulphate salt) is a muscarinic acetylcholine receptor antagonist, which is available in Asia (mainly Bangladesh) for the alleviation of muscle spasms of the intestine, biliary system, uterus and urinary bladder in gastrointestinal, biliary, urinary and gynecological diseases.

Proroxan is a non-selective а-adrenoblocker. Proroxan was found to prevent the development of hypertensive crises and improve cerebral bioelectrical parameters in most of hypertensive patients. Proroxan has been used as an antihypertensive and in the treatment of Ménière’s disease, motion sickness, and allergic dermatitis.

Minaprine, a psychotropic drug, which was effective in the treatment of various depressive states. This drug was withdrawn because of the serious side effect. It was found, that minaprine inhibited the following enzymes, acetylcholinesterase and monoamine oxidase (MOA) A. It also binds to dopamine D1 and D2 receptors. Experiments on rodents also have revealed that minaprine suppressed the inhibitory effect of hydroxytryptamine (5-HT) on dopamine (DA) release via the inhibition of 5-HT binding at the 5-HT2 receptor on the nerve terminal.

The anticholinergic agent Flutropium is a classic competitive antagonist of acetylcholine. In in vitro experiments it is more effective than atropine. A poor enteral absorption is to be expected; this can be concluded from the low relative effectiveness after oral administration. After local administration as an aerosol it is superior to atropine with regard to both effectiveness and duration of action. It is used in Japan to treat asthma and chronic obstructive pulmonary disease. Flutropium can be described as a preparation which is free of side effects.

Vapiprost is a potent dicyclopentadiene thromboxane receptor antagonist that was being developed by Glaxo Wellcome in Japan. Vapiprost has been shown to be a potent and specific thromboxane (Tx)A2 receptor blocking drug in vitro using platelets and both vascular and airways smooth muscle preparations from different species. The drug is active in various experimental models of thrombosis. The potential clinical applications for a thromboxane receptor blocking drug include the treatment of thrombotic events and occlusive vascular disease. Phase III trials were underway in Japan for the treatment of deep vein thrombosis, which later were discontinued.

Aptiganel (CNS 1102, Cerestat), a selective ligand with antagonized properties for the ion-channel site of the N-methyl-D-aspartate receptor-channel complex, was developed as a neuroprotective agent for focal brain ischemia. However, in the clinical trials in patients with acute ischemic stroke aptiganel was not efficacious at either of the tested doses and may be harmful. That is why its further study was discontinued.