[Brimonidine absorption and release from 1. Day acuvue disposable contact lenses]

We studied absorption and release of brimonidine tartrate while wearing 1 Day Acuvue contact lenses.

A regression chart was obtained from 320 nm ultraviolet absorption (UV) for different dilutions of brimonidine tartrate in ophthalmic solutions (Alphagan(R)). 40 microliter of opthalmic solution was placed in the concavity of the contact lens; after a series of time intervals, lens was drained and introduced in a test-tube containing 2 ml of saline and underwent a quick cleansing. Next, lens was withdrawn from this tube and introduced into another test tube containing 2 ml of saline. Test tube was changed at intervals of 5 minutes. UV absorption is measured on each resulting tube until reading is 0. Contents of tubes in microgram of product were calculated according to regression chart. Total absorption will show substance penetration in lens. Release of substance is appreciated when lens is loaded during 1 minute and then placed in a tube containing 2 ml of saline introduced in the spectrophotometer which measures UV absorption minute by minute.

Within the first minute, 51.54 microgram of product are absorbed (64.42% of a total of 80 microgram contained in a drop of ophthalmic solution), 20% found in lens surface and 44% penetrated the lens. If soaked during 3 minutes, lens takes 71% of fluid, 20% on surface and 50% into the lens itself. Release in 2 ml of saline is 19.33 microgram (37.5% of 51.54 microgram) in 1 hour, 25.57 microgram (49.6%) in 2 hours and 29.7 microgram (57.6%) after 3 hours. If saline is changed every 5 minutes, 100% of product is released in 35 minutes.

Disposable contact lenses 1. DAY ACUVUE(R) are able to take and release brimonidine tartrate in vitro.