Famotidine (MK-208) is a propanimidamide and histamine H2-receptor antagonist with antacid activity. As a competitive inhibitor of histamine H2-receptors located on the basolateral membrane of the parietal cell, famotidine reduces basal and nocturnal gastric acid secretion, resulting in a reduction in gastric volume, acidity, and amount of gastric acid released in response to various stimuli.

Zotepine, an antipsychotic agent, is a potent antagonist of 5-HT2A, 5-HT2C, Histamine H1, α1-adrenergic, and Dopamine D2 receptors, with Kds of 2.6 nM, 3.2 nM, 3.3 nM, 7.3 nM, and 8 nM, respectively. Zotepine is a second-generation antipsychotic with a primary use as a treatment for schizophrenia, although clinical trials have been conducted into its efficacy as an antimanic agent in patients with acute bipolar mania.

Chlorpheniramine maleate (NCI-C55265) is a histamine H1 antagonist used in allergic reactions, hay fever, rhinitis, urticaria, and asthma.

Niaprazine is a histamine H1-receptor antagonist with marked sedative properties. Niaprazine has antihistamine and antiserotonin activities and can be used for sleep disorder research[1][2]. Niaprazine exhibits a low affinity for the vesicular monoamine transporter and for D2, α2, β, H1 and mAch receptors. Niaprazine, particularly the (+)stereoisomer, has a higher affinity for α1 (Ki = 77 nM) and 5-HT2 (Ki = 25 nM) binding sites, but is poorly recognized by 5-HT1A and 5-HT1B binding sites[2]. Niaprazine (60 mg/kg; i.p.; once) treatment increases rat brain 5-hydroxyindole acetic acid (5-HIAA) concentrations 30 min after treatment, and reduced them at 3-8 hr after treatment. Niaprazine also produces a short-lasting depletion of rat brain noradrenaline (NA) and dopamine (DA)[3]. Animal Model: Male Sprague-Dawley rats (150-200 g)[3] [1]. D Scherman, et al. Molecular pharmacology of niaprazine. Prog Neuropsychopharmacol Biol Psychiatry. 1988;12(6):989-1001. [2]. P G Rossi, et al. Niaprazine in the treatment of autistic disorder. J Child Neurol. 1999 Aug;14(8):547-50. [3]. P E Keane, et al. The effect of niaprazine on the turnover of 5-hydroxytryptamine in the rat brain. Neuropharmacology. 1982 Feb;21(2):163-9.

Pimethixene (Calmixen) is a highly potent 5-HT1A, 5-HT2A, 5-HT2B, 5-HT2C, histamine H1, dopamine D2 and D4.4 as well as muscarinic M1 and M2 receptors antagonist(pKis of 7.63, 10.22, 10.44, 8.42, 10.14, 8.19, 7.54, 8.61 and 9.38, respectively).