Drug Groups

approved

Description

Methdilazine is a phenothiazine compound with antihistaminic activity. It is used in the treatment of various dermatoses to relieve pruritus.

Indication

Used for the symptomatic relief of hypersensitivity reactions and particularly for the control of pruritic skin disorders

Pharmacology

In allergic reactions an allergen interacts with and cross-links surface IgE antibodies on mast cells and basophils. Once the mast cell-antibody-antigen complex is formed, a complex series of events occurs that eventually leads to cell-degranulation and the release of histamine (and other chemical mediators) from the mast cell or basophil. Once released, histamine can react with local or widespread tissues through histamine receptors. Histamine, acting on H₁-receptors, produces pruritis, vasodilatation, hypotension, flushing, headache, tachycardia, and bronchoconstriction. Histamine also increases vascular permeability and potentiates pain. Methdilazine is a histamine H₁ antagonist. It competes with histamine for the normal H₁-receptor sites on effector cells of the gastrointestinal tract, blood vessels and respiratory tract. It provides effective, temporary relief of sneezing, watery and itchy eyes, and runny nose due to hay fever and other upper respiratory allergies.

Toxicity

Symptoms of overdose include clumsiness or unsteadiness, convulsions, drowsiness, dryness of mouth, nose, or throat, feeling faint, flushing or redness of face, hallucinations, muscle spasms (especially of neck and back), restlessness, shortness of breath or troubled breathing, shuffling walk, tic-like movements of head and face, trembling and shaking of hands, and trouble in sleeping.

Affected Organisms

Absorption

Well absorbed in the digestive tract.

References

External Links