indication

For treatment and relief of symptoms of allergies, hay fever, and colds

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. Dexbrompheniramine is a histamine H1 antagonist (or more correctly, an inverse histamine agonist) of the alkylamine class. It provides effective, temporary relief of sneezing, watery and itchy eyes, and runny nose due to hay fever and other upper respiratory allergies.

mechanism of action

Dexbrompheniramine competitively binds to the histamine H₁-receptor. It competes with histamine for the normal H₁-receptor sites on effector cells of the gastrointestinal tract, blood vessels and respiratory tract. This blocks the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms brought on by histamine.

toxicity

Signs of an overdose include fast or irregular heartbeat, mental or mood changes, tightness in the chest, and unusual tiredness or weakness.

biotransformation

Hepatic (cytochrome P-450 system), some renal.

absorption

Antihistamines are well absorbed from the gastrointestinal tract after oral administration.

half life

25 hours

drug interactions

Donepezil: Possible antagonism of action

Galantamine: Possible antagonism of action

Tacrine: The therapeutic effects of the central acetylcholinesterase inhibitor, Tacrine, and/or the anticholinergic, Dexbrompheniramine, may be reduced due to antagonism. The interaction may be beneficial when the anticholinergic action is a side effect. Monitor for decreased efficacy of both agents.

Trimethobenzamide: Trimethobenzamide and Dexbrompheniramine, two anticholinergics, may cause additive anticholinergic effects and enhance their adverse/toxic effects. Monitor for enhanced anticholinergic effects.

Triprolidine: Triprolidine and Dexbrompheniramine, two anticholinergics, may cause additive anticholinergic effects and enhance their adverse/toxic effects. Additive CNS depressant effects may also occur. Monitor for enhanced anticholinergic and CNS depressant effects.

Trospium: Trospium and Dexbrompheniramine, two anticholinergics, may cause additive anticholinergic effects and enhanced adverse/toxic effects. Monitor for enhanced anticholinergic effects.