Albumin Levels in Tear Film Modulate the Bioavailability of Medically-Relevant Topical Drugs

Area of Science:

• Ophthalmology
• Pharmacology
• Biochemistry

Background:

• Ocular pathology can cause albumin to leak into tear fluid, potentially hindering ophthalmic drug absorption.
• Albumin binding to drugs may restrict their transport across ocular barriers, affecting therapeutic efficacy.

Purpose of the Study:

• To investigate the impact of tear albumin levels on the bioavailability of tropicamide and latanoprost.
• To assess how albumin affects drug absorption and pharmacological effects in the eye.

Main Methods:

• A randomized, vehicle-controlled crossover trial was conducted in eight beagle dogs.
• Tears were treated with artificial tears (control) or canine albumin (0.4% or 1.5%).
• Ophthalmic drugs (tropicamide or latanoprost) were administered, and pupil diameter and intraocular pressure were measured.

Main Results:

• Tear albumin significantly impacted pupil diameter for both tropicamide and latanoprost.
• Tropicamide's maximal effect and overall exposure were reduced by 6.2-8.5% in the presence of albumin.
• Albumin did not significantly affect intraocular pressure when administered with latanoprost.

Conclusions:

• Albumin in the tear film can bind to topically applied drugs, reducing their bioavailability and intraocular penetration.
• Further clinical studies are needed to confirm these findings with other ophthalmic medications.