indication

For the temporary relief of the signs and symptoms of allergic conjunctivitis.

pharmacology

Emedastine is a relatively selective H₁-receptor antagonist.

mechanism of action

Emedastine is a relatively selective, histamine H₁ antagonist. In vitro examinations of emedastine's affinity for histamine receptors demonstrate relative selectivity for the H₁ histamine receptor. In vivo studies have shown concentration-dependent inhibition of histamine-stimulated vascular permeability in the conjunctiva following topical ocular administration. Emedastine appears to be devoid of effects on adrenergic, dopaminergic and serotonin receptors.

toxicity

Somnolence and malaise have been reported following daily oral administration.

biotransformation

Two primary metabolites, 5-hydroxyemedastine and 6-hydroxyemedastine, are excreted in the urine as both free and conjugated forms. The 5'-oxoanalogs of 5-hydroxyemedastine and 6-hydroxy-emedastine and the N-oxide are also formed as minor metabolites.

absorption

Ophthalmic use of emedastine usually does not produce measurable plasma concentrations.

half life

The elimination half-life of oral emedastine in plasma is 3-4 hours.

route of elimination

Approximately 44% of the oral dose is recovered in the urine over 24 hours with only 3.6% of the dose excreted as parent drug. Two primary metabolites, 5- and 6-hydroxyemedastine, are excreted in the urine as both free and conjugated forms.