ATC Group: D04A Antipruritics, incl. antihistamines, anesthetics, etc.

Benzocaine is a local anaesthetic of the ester type, acting to produce reversible loss of sensation by preventing or diminishing the generation and transmission of sensory nerve impulses near the site of application. Depolarisation of the neuronal membrane and ion exchange are reversibly inhibited.

Cinchocaine is a local anaesthetic agent and is suitable for surface or spinal anaesthesia and for relaxing sphincteric spasms. It is an anaesthetic of the amide type. It is more toxic than cocaine by local application but its local anaesthetic action is greater so it can be used in lower concentrations. Its action is more prolonged than lignocaine.

Clemastine is an H₁-receptor antagonist. It inhibits selectively the histamine receptors of the H₁ type and reduces capillary permeability. It exerts a potent antihistaminic and antipruritic effect with a fast onset and long duration of action.

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.

Diphenhydramine is an ethanolamine-derivative antihistamine. It is an antihistamine with anticholinergic and marked sedative effects. It acts by inhibiting the effects on H₁-receptors. Diphenhydramine is effective in reducing sleep onset (i.e., time to fall asleep) and increasing the depth and quality of sleep.

Doxepin is not a central nervous system stimulant nor a monoamine oxidase inhibitor. The current hypothesis is that the clinical effects are due, at least in part, to influences on the adrenergic activity at the synapses so that deactivation of noradrenaline by reuptake into the nerve terminals is prevented.

Lidocaine, like other local anaesthetics, causes a reversible blockade of impulse propagation along nerve fibres by preventing the inward movement of sodium ions through the nerve membrane. Local anaesthetics of the amide-type are thought to act within the sodium channels of the nerve membrane.

Mepyramine is a first generation antihistamine, targeting the H1 receptor. However, it rapidly permeates the brain and so often causes drowsiness as a side effect. Mepyramine is a histamine H1 receptor inverse agonist. It binds to a G protein-coupled form of the receptor and promotes a G protein-coupled inactive state of the H1 receptor that interferes with the Gq/11-mediated signaling. Mepyramine competes with histamine for binding at H1-receptor sites on the effector cell surface, resulting in suppression of histaminic edema, flare, and pruritus. The sedative properties of mepyramine occur at the subcortical level of the CNS. It has mild hypnotic properties and some local anesthetic action and is used for allergies (including skin eruptions) both parenterally and locally. It is a common ingredient of cold remedies.

Promethazine is a potent, long acting, antihistamine with additional anti-emetic central sedative and anti-cholinergic properties.

Tetracaine is a local anaesthetic and is believed to act by blocking nerve conduction mainly by inhibiting sodium ion flux across the axon membrane.