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

H1 receptor:12 nM

Oral administration of Chlorpheniramine (10 mg/kg) can suppress short-term scratching in BALB/c mice experiencing albumin-induced allergic skin irritation and ICR mice injected with histamine subcutaneously. Furthermore, in guinea pigs induced with histamine (ED50=0.17 mg/kg), oral intake of Chlorpheniramine prevents mortality. In rats, a dosage of Chlorpheniramine (20 mg/kg) is capable of blocking the histamine or cholinergic mechanisms that induce rapid eye movement (REM) sleep.

Chlorpheniramine inhibits the binding of [3H] mepyramine to guinea pig cortical histamine H1 receptors (IC50=8.8 nM). It reduces ornithine decarboxylase mRNA translation in MCF-7, MDA-MB 231, and Ehrlich cells at a concentration of 250 μM, subsequently inhibiting cell proliferation. Chlorpheniramine displays antimalarial activity against Chloroquine-Sensitive (CQS) Plasmodium falciparum strain D6 (IC50=61.2uM) and Multidrug-Resistant (MDR) strain Dd2 (IC50=3.9uM). Furthermore, it exhibits cytotoxicity in mouse splenic lymphocytes induced by Concanavalin A (IC50=33.4 μM).

H1-Antihistaminic Activity: The segments (1 cm) of isolated ileum from guinea pigs are suspended in an organ bath containing Tyrode solution (ventilation, 32 °C). The contractile responses to histamine (0.54 μM) are measured with an isotonic transducer. A set concentration of Chlorpheniramine is added in the organ bath 5 minutes before the addition of histamine. IC50 value of Chlorpheniramine is calculated by the probit methond.

Cells are exposed to various concentrations of Chlorpheniramine for 48 hours. Cells are washed, detached, and counted with a Coulter counter for the determination of cell growth.(Only for Reference)