1-[(5-chloro-1H-indol-2-yl)carbonyl]-4-methylpiperazine (JNJ 7777120) is the first selective antagonist of the histamine H4 receptor. Johnson & Johnson Pharmaceutical Research and Development is developing JNJ 7777120 for the treatment of inflammatory disorders. JNJ 7777120 demonstrates efficacy as anti-inflammatory agents in vivo. JNJ 7777120 have shown promising activity in down-regulating immune responses in a range of animal disease models including acute inflammation, hapten-mediated colitis, allergic airway inflammation (e.g. allergic rhinitis), colitis, allergic pruritis and atopic dermatitis.

ABT-491 is highly potent, selective and orally active platelet-activating factor (PAF) receptor antagonist, developed by Abbott Laboratories for allergic rhinitis treatment. ABT-491 is a potent antagonist of responses linked to the PAF receptor at the cellular level, especially platelets and neutrophils. ABT-491 was also effective in blocking platelet activation in blood, indicating that the presence of high concentrations of protein and other serum factors slightly alters the ability of ABT-491 to interact with PAF receptor. ABT-491 effectively antagonizes PAF-induced platelet and neutrophil responses at submicromolar concentrations in vitro and exhibits in vivo efficacy in alleviating PAF-mediated inflammatory and pathological processes in various animals, including guinea pigs, mice, and rats, via either i.v., i.p. or p.o. routes.

Pemirolast is a mast cell stabilizer that acts as an antiallergic agent, it is approved in Japan for the treatment of bronchial asthma and of allergic rhinitis. Pemirolast strongly inhibits extracellular Ca2+ influx and the release of intracellular Ca2+, an important factor in the release of chemical mediators, by inhibiting inositol-phospholipid metabolism in mast cells. It also inhibits the release of arachidonic acid. Furthermore contribution of increasing effect on c-AMP based on inhibiting phosphodiesterase is suggested. Main pharmacological effects is an inhibition of release of chemical mediators, e.g. histamine, LTB4, LTC4, LTD4, PGD2, TXB2 and PAF from human lung tissues, abraded fragments of the nasal mucosa, and peripheral leukocytes, rat peritoneal exudate cells, and rat and guniea pig lung tissues.

Rotoxamine ((S)-carbinoxamine) is maleic acid salt of the levorotatory isomer of Carbinoxamine (a first-generation antihistamine of the ethanolamine class). Ethanolamine antihistamines have significant antimuscarinic activity and produce marked sedation in most patients. In addition to the usual allergic symptoms, the drug also treats an irritant cough and nausea, vomiting, and vertigo associated with motion sickness. It also is used commonly to treat drug-induced extrapyramidal symptoms as well as to treat mild cases of Parkinson's disease. Rotoxamine is used to treat runny or stuffy nose, sneezing, itching, watery eyes, hives, skin rash, itching, and other symptoms of allergies and the common cold.

Diphenylpyraline is an antihistamine that prevents but does not reverse, responses mediated by histamine alone. Diphenylpyraline antagonizes most of the pharmacological effects of histamine, including urticaria and pruritus. Also, diphenylpyraline may exhibit anticholinergic actions (as do most of the antihistamines) and may thus provide a drying effect on the nasal mucosa. Antihistamines such as diphenylpyraline used in the treatment of allergy act by competing with histamine for H1-receptor sites on effector cells. This reduces the effects of histamine, leading to a temporary reduction of allergy symptoms.

Menadione, a drug belong to class of Vitamin K, is prescribed for the treatment of hemorrhage, vitamin K deficiency, moderate to severe forms of hypoprothrombinaemia in adults and children. Menadione is a synthetic form of vitamin K, a lipid-soluble vitamin. Vitamin K is a vital cofactor for the biosynthesis of prothrombin, factor VII, IX, X, protein C and protein S. Menadione supports the functions of osteocalcin. Large doses of menadione have been reported to cause adverse outcomes including hemolytic anemia due to glucose-6-phosphate dehydrogenase deficiency, neonatal brain or liver damage, or neonatal death in some rare cases.

Ramatroban is a dual antagonist of thromboxane A2 receptor and PGD2 receptor. The drug was developed by Bayer and tested for the treatment of asthma and allergic rhinitis. In Japan ramatroban reached final approval and is being marketed under the name Baynas. In vitro studies have shown that the drug effectively inhibits smooth muscle cells contraction.

Homochlorcyclizine (INN) is an antihistamine which has been marketed in Japan since 1965. It is used in the treatment of Itching sensation resulting from skin diseases (eczema or dermatitis, pruritus, drug eruption, toxic erythema and infant strophulus), urticaria and allergic rhinitis. Homochlorcyclizine hydrochloride possesses several pharmacological properties: 1) inhibits bradykinin-induced contractions of isolated guinea pig ileum; 2)partially blocks SRS-A (slow-reacting substance of anaphylaxis )- induced contractions in isolated guinea pig il eum. 3) Homochlorcyclizine hydrochloride completely inhibits histamine-induced contractions at a concentration of 0.1μg/mL, while it completely inhibits serotonin or acetylcholine- induced contractions at a concentration of 1μg/mL.

Azelastine (brand names AZEP, ASTEPRO, ASTELIN etc.) a phthalazine derivative, is an antihistamine and mast cell stabilizer available as a nasal spray for hay fever and as eye drops for allergic conjunctivitis. Azelastine is a potent antiallergic compound with histamine H1-receptor antagonist activity and a rapid onset and long duration of action. The major metabolite, desmethylazelastine, also exhibits H1- receptor antagonist activity. AZEP Nasal Spray is administered as a racemic mixture. The racemate, R- and S- enantiomers were equally potent at inhibiting eyelid histamine-induced oedema in rats, however the R-enantiomer was 2-fold less active at inhibiting eyeball histamine-induced oedema.

Azelastine (brand names AZEP, ASTEPRO, ASTELIN etc.) a phthalazine derivative, is an antihistamine and mast cell stabilizer available as a nasal spray for hay fever and as eye drops for allergic conjunctivitis. Azelastine is a potent antiallergic compound with histamine H1-receptor antagonist activity and a rapid onset and long duration of action. The major metabolite, desmethylazelastine, also exhibits H1- receptor antagonist activity. AZEP Nasal Spray is administered as a racemic mixture. The racemate, R- and S- enantiomers were equally potent at inhibiting eyelid histamine-induced oedema in rats, however the R-enantiomer was 2-fold less active at inhibiting eyeball histamine-induced oedema.