Trans-eyelid distribution of epinastine to the conjunctiva following eyelid application in rabbits

Abstract

Purpose: To reveal the penetration of epinastine, an anti-allergic ophthalmic agent, into the eyelid and its distribution to the conjunctiva after administration of a cream formulation on rabbit eyelid skin.

Study design: Experimental study.

Methods: Rabbits were treated with 0.5% epinastine cream on hair-shaved eyelids, followed by preparation of eyelid tissue slices to determine spatial tissue distribution of epinastine by liquid chromatography-tandem mass spectrometry (LC-MS/MS) quantification using laser-microdissected tissues and desorption electrospray ionization mass spectrometry imaging (DESI-MSI). In addition, following either eyelid application of 0.5% epinastine cream or ocular instillation of 0.1% epinastine eye drops, concentration-time profiles of epinastine in the palpebral conjunctiva and bulbar conjunctiva were determined using LC-MS/MS.

Results: Laser microdissection coupled with LC-MS/MS analysis detected high concentrations of epinastine around the outermost layer of the eyelid at 0.5 h post-administration that gradually diffused deeper into the eyelid and was distributed in the conjunctival layer at 8 and 24 h post-administration. Similar time-dependent drug distribution was observed in high-spatial-resolution images obtained using DESI-MSI. Epinastine concentrations in the conjunctival tissues peaked at 4-8 h after administration of 0.5% epinastine cream and then decreased slowly over 72 h post-administration. In contrast, epinastine concentrations peaked quickly and decreased sharply after epinastine eye drop administration.

Conclusion: After the application of epinastine cream to the eyelid skin, epinastine gradually permeated the eyelid. The compound was retained in the conjunctiva for 8-24 h post-administration, indicating that epinastine cream is a promising long-acting formulation for treating allergic conjunctivitis.

Keywords: Allergic conjunctivitis; Epinastine; Eyelid; Imaging; Ocular distribution.

Fig. 1

Determination of epinastine concentrations in rabbit upper eyelid compartments using laser-microdissection (LMD) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) Optical images of rabbit upper eyelid frozen sections before laser-microdissection (LMD) (“Pre LMD”) and after LMD (“Post LMD”), and epinastine concentrations in microdissected fragments (“Epinastine distribution”) at 0.5, 8, and 24 h after eyelid application of 0.5% epinastine cream. Compartments where the epinastine concentrations were below the lower limit of quantification (< 0.1 pg/mm³) are shown in white. #: Approximate area for cream application

Fig. 2

Imaging of epinastine distribution in rabbit upper eyelid section obtained using desorption electrospray ionization mass spectrometry imaging (DESI-MSI) a Whole distribution images of epinastine in rabbit upper eyelid sections determined by DESI-MSI, optical images of hematoxylin-eosin (H&E) staining and merged images (Merged) at 0.5, 8, and 24 h after eyelid application of 0.5% epinastine cream. #: Approximate area for cream application; *: Artifact signals surrounding eyelid tissue. b–d Magnified images of DESI-MSI (upper) and H&E (lower) at 0.5 h (b) and 8 h (c and d) post-dose. d The connective tissues surrounding the meibomian gland indicate the tarsal plate. Epi, epidermis; Orb, orbicularis oculi muscle; HF, hair follicle; Mü, Müller muscle; Cj, conjunctival epithelium; MG, meibomian gland; T, tarsal plate

Fig. 3

Epinastine concentrations in the conjunctiva after topical eyelid application of 0.5% epinastine cream and ocular instillation of 0.1% epinastine eye drops in rabbits Each value represents the mean and standard deviation of four eyes. Palpebral conjunctiva (a) and bulbar conjunctiva (b)