Epinastine HCl Ophthalmic Solution

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Contamination of Tip and Solution

Patients should be instructed to avoid allowing the tip of the dispensing container to contact the eye, surrounding structures, fingers, or any other surface in order to avoid contamination of the solution by common bacteria known to cause ocular infections. Serious damage to the eye and subsequent loss of vision may result from using contaminated solutions.

Bottle should be kept tightly closed when not in use.

Use with Contact Lenses

Patients should be advised not to wear a contact lens if their eye is red. Epinastine HCl Ophthalmic Solution 0.05% should not be used to treat contact lens-related irritation.

The preservative in Epinastine HCl Ophthalmic Solution 0.05%, benzalkonium chloride, may be absorbed by soft contact lenses. Contact lenses should be removed prior to instillation of Epinastine HCl Ophthalmic Solution 0.05% and may be reinserted after 10 minutes following its administration.

Topical Ophthalmic Use Only

Epinastine HCl Ophthalmic Solution 0.05% is for topical ophthalmic use only and not for injection or oral use.

Mechanism of Action

Epinastine is a topically active, direct H1-receptor antagonist and an inhibitor of the release of histamine from the mast cell. Epinastine is selective for the histamine H1-receptor and has affinity for the histamine H2­ receptor. Epinastine also possesses affinity for the α1, α2-, and 5-HT2–receptors.

Pharmacokinetics

Fourteen subjects, with allergic conjunctivitis, received one drop of Epinastine HCl Ophthalmic Solution 0.05% in each eye twice daily for 7 days. On day 7, average maximum epinastine plasma concentrations of 0.04±0.014 ng/ml were reached after about two hours indicating low systemic exposure. While these concentrations represented an increase over those seen following a single dose, the day 1 and day 7 Area Under the Curve (AUC) values were unchanged indicating that there is no increase in systemic absorption with multiple dosing. Epinastine is 64% bound to plasma proteins. The total systemic clearance is approximately 56 L/hr and the terminal plasma elimination half-life is about 12 hours. Epinastine is mainly excreted unchanged. About 55% of an intravenous dose is recovered unchanged in the urine with about 30% in feces. Less than 10% is metabolized. The renal elimination is mainly via active tubular secretion.

Epinastine HCl 0.05% has been shown to be significantly superior to vehicle for improving ocular itching in patients with allergic conjunctivitis in clinical studies using two different models: (1) conjunctival antigen challenge (CAC) where patients were dosed and then received antigen instilled into the inferior conjunctival fornix; and (2) environmental field studies where patients were dosed and evaluated during allergy season in their natural habitat. Results demonstrated a rapid onset of action for epinastine HCl 0.05% within 3 to 5 minutes after conjunctival antigen challenge. Duration of effect was shown to be 8 hours, making a twice daily regimen suitable. This dosing regimen was shown to be safe and effective for up to 8 weeks, without evidence of tachyphylaxis.