ISOCROMIL, a chromone, is an antiallergic agent. It is a mediator release inhibitor used for the treatment of passive cutaneous anaphylaxis and as an anti-asthmatic.

Carabestine is the active first-pass metabolite of Ebastine and acts as a histamine H1 receptor antagonist which has been investigated as a potential allergy medication. Ebastine is marketed under a number of brand names.

Linetastine has anti-inflammatory and anticarcinogenic effects. It is a potent inhibitor of 5-lipoxygenase. It also inhibits histamine release and epidermal cyclooxygenase activity. It also markedly inhibited TPA-stimulated leukotriene B4 formation, but inhibited formation of prostaglandin E2, a cyclooxygenase product, only slightly. This suggested that neither cyclooxygenase inhibition nor antihistaminic activity were essential to the anti-inflammatory action of linetastine. The anti-inflammatory effect of oral linetastine is probably due to 5-lipoxygenase inhibition. Oral administration of linetastine almost completely suppressed Cyp1a1 mRNA levels in mouse epidermis induced by a topical application of 3-methylcholanthrene or benzo[a]pyrene to mouse skin. Oral administration of linetastine inhibited DMBA-caused skin tumor initiation at least in part by inhibiting Cyp1a1 mRNA induction and epidermal aryl hydrocarbon hydroxylase activity. Linetastine had been in phase II clinical trial for the treatment of allergic rhinitis. However, this study was discontinued.

Octasine is an antihistamine agent that has never been marketed.

Dimetholizine has antihypertensive activity. It is an antihistaminic agent too. Histamine H1 receptor was predicted as a primary target for dimetholizine. Moreover, it was found to bind the Dopamine D2 and 5-HT1A receptors. Dimetholizine was predicted to be alpha1D-Adrenergic blocker.

Efletirizine is histamine H1 receptor antagonist. Restricted to topical use. It was under investigation in Phase III (in Europe) clinical studies for the treatment of allergic rhinitis and chronic idiopathic urticarial. Research was discontinued in 2005 due to limited clinical efficacy and safety data. Efletirizine also reduced ocular itching.

Tibenelast is an orally active phosphodiesterase inhibitor that was undergoing phase II clinical trials in the USA as a bronchodilator. In preclinical studies Tibenelast is moderately active against the lung and stomach enzyme while being a very weak inhibitor of the heart enzyme and it does not inhibit enzymes involved in arachidonic acid metabolism. Tibenelast shows potent anti-anaphylactic activity in guinea pigs without cardiovascular effects at the bronchodilatory doses.

Levomequitazine is the L-enantiomer of mequitazine. The antihistaminergic activity mainly resides in the S-enantiomer, L-mequitazine, whereas the anticholinergic activity mainly resides in the D-enantiomer. It was shown, that L-enantiomer of mequitazine is less potent antagonist of human M3 muscarinic acetylcholine receptors than D-enantiomer. In vitro binding studies have shown that the affinity of L-mequitazine for H1 receptors is approximately ten times higher and to muscarinic receptors ten times lower, compared to d-mequitazine. Memory impairment was observed after administration of L-mequitazine 10 mg alone on delayed recall. This could be due to indirect effects of H1 receptor blockade. L-mequitazine 10 mg produced mild driving impairment, whereas L-mequitazine 2.5 and 5.0 mg show no effects on driving. Levomequitazine had been in phase III clinical trials by Pierre Fabre for the treatment of perennial allergic rhinitis and seasonal allergic rhinitis.

Clocinizine is an antihistamine derivative of diphenylmethylpiperazine. Clocinizine is a competitive and reversible H1 receptor antagonist. The drug is marketed in Spain under tradename Senioral in combination with phenylpropanolamine for temporary relief of nasal congestion in colds, rhinitis, and sinusitis.

Mapinastine (E 4716) is a selective antagonist of histamine H1 receptors. In animal models, mapinastine exerts antiallergic and anti-asthmatic properties. It demonstrated a lack of central effects. Mapinastine development has been discontinued.