ATC Group: R06AB Substituted alkylamines

Chlorphenamine is a potent antihistamine (H₁-antagonist). Antihistamines diminish or abolish the actions of histamine in the body by competitive reversible blockade of histamine H₁-receptor sites on tissues. Chlorphenamine also has anticholinergic activity.

Dexchlorpheniramine, the d-isomer of the racemic compound chlorpheniramine, is two times more active than chlorpheniramine. Dexchlorpheniramine does not prevent the release of histamine, but rather, competes with free histamine for binding at the H₁-receptor sites, and competitively antagonizes the effects of histamine on H₁-receptors in the GI tract, uterus, large blood vessels, and bronchial muscle. Blockade of H₁-receptors also suppresses the formation of oedema, flare, and pruritus that result from histaminic activity. Since dexchlorpheniramine binds to central and peripheral H₁-receptors, sedative effects are likely to occur. Dexchlorpheniramine has high antihistaminic activity, moderate anticholinergic effects and minimal sedative effects.

Dimetindene is an antihistaminic of the alkylamine group. Its action is the result of the capture of histamine Η₁ subunits. It has mild anticholinergic and sedative action.