Epinastine (Monograph)

Brand name: Elestat
Drug class: Antiallergic Agents
- Histamine H1-receptor Antagonists
Chemical name: 3-Amino-9,13b-dihydro-1H-dibenz[c,f]imidazo[1,5-a]azepine
Molecular formula: C₁₆H₁₅N₃
CAS number: 80012-43-7

Introduction

Relatively selective histamine H₁-receptor antagonist with mast-cell stabilizing properties.

Uses for Epinastine

Allergic Conjunctivitis

Prevention of ocular itching associated with allergic conjunctivitis.

Epinastine Dosage and Administration

Administration

Ophthalmic Administration

Apply topically to the eye as an ophthalmic solution. Not for injection or oral use.

Dosage

Available as epinastine hydrochloride; dosage expressed in terms of the salt.

Pediatric Patients

Allergic Conjunctivitis

Ophthalmic

Children ≥3 years of age: 1 drop of a 0.05% solution in each eye twice daily for up to 8 weeks.

Continue therapy throughout period of exposure (i.e., until pollen season is over or until exposure to offending allergen is terminated), even in absence of symptoms.

Adults

Allergic Conjunctivitis

Ophthalmic

1 drop of a 0.05% solution in each eye twice daily for up to 8 weeks.

Continue therapy throughout period of exposure (i.e., until pollen season is over or until exposure to offending allergen is terminated), even in absence of symptoms.

Related/similar drugs

prednisone, cetirizine ophthalmic, dexamethasone ophthalmic, azelastine ophthalmic, prednisolone ophthalmic, doxylamine

Cautions for Epinastine

Contraindications

• Known hypersensitivity to epinastine or any ingredient in the formulation.

Warnings/Precautions

Specific Populations

Pregnancy

Category C.

Lactation

Distributed into milk in rats; not known whether distributed into human milk. Use with caution.

Pediatric Use

Safety and efficacy not established in children <3 years of age.

Geriatric Use

No overall differences in safety and efficacy relative to younger adults.

Common Adverse Effects

Ocular discomfort (e.g., burning, folliculosis, hyperemia, pruritus), infection (e.g., cold symptoms, upper respiratory infections).

Drug Interactions

No formal drug interaction studies to date.

Epinastine Pharmacokinetics

Absorption

Bioavailability

Limited systemic exposure following topical application to the eye. No increase in systemic absorption following multiple dosing.

Peak plasma concentrations attained approximately 2 hours after ophthalmic administration.

Onset

Rapid onset (within 3–5 minutes).

Duration

8 hours.

Distribution

Extent

Does not penetrate blood-brain barrier.

Distributed into milk in rats; not known whether distributed into human milk.

Plasma Protein Binding

64%.

Elimination

Metabolism

Less than 10% is metabolized.

Elimination Route

55 or 30% of IV dose excreted unchanged in urine or feces, respectively.

Half-life

Approximately 12 hours.

Stability

Storage

Ophthalmic

Solution

Tightly closed bottle at 15–25°C.

Actions

• Inhibits the release of mediators (e.g., histamine) from cells involved in hypersensitivity reactions (e.g., mast cells).

• Exhibits mast-cell stabilizing properties.

• Exhibits some affinity for histamine H₂, α₁- and α₂-adrenergic, and 5-HT₂ receptors.

Advice to Patients

• Importance of learning and adhering to proper administration techniques to avoid contamination of the solution with common bacteria that can cause ocular infections. Serious damage to the eye and subsequent loss of vision may result from using contaminated ophthalmic solutions.

• Importance of delaying insertion of contact lenses for at least 10 minutes after epinastine instillation, since benzalkonium chloride preservative may be absorbed by soft lenses; importance of not wearing contact lenses in the presence of ocular redness.

• Not indicated for contact lens-related ocular irritation.

• Importance of reporting any worsening of symptoms or new-onset ocular pain/discomfort.

• Importance of women informing clinician if they are or plan to become pregnant or plan to breast-feed.

• Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses.

• Importance of informing patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

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