Release of Corticosteroids from EVA Copolymer for Oral Lichen Planus

Corticosteroids are the mainstay of therapy for vesiculoerosive disorders such as oral lichen planus.  Problems with mucoadhesion, salivary dilution and consistent dosage of topical medications such as HCS limit their effectiveness. Systemic corticosteroids such as PDS have undesirable side effects when delivered in high doses or over extended periods of time. Objective:  The main objective of this in vitro study is to develop a device for local delivery of corticosteroids at therapeutic levels to treat oral lichen planus.  Methods:  Ethylene vinyl acetate (EVA) copolymer films containing 2.5 weight % drugs were prepared from film casting solutions in dichloromethane solvent.  The drugs used in the study include PDS and HCS.  Different concentrations of the drugs: 2.5, 5.0, 7.5, 10% were used to study the effect of drug loading on the drug release rate at 37°C into double distilled water as an extracting medium.  Thin square films of 3x3cm with a thickness of 0.8mm were cut from the dry sheet obtained by solvent evaporation.  Drug release rates were determined using UV-spectrophotometric measurements showing close agreement among the triplicate film samples.  Results:  Time-release profiles exhibited an “initial burst” during the first 48 hours followed by a near constant release at longer intervals of time for about 14 days.  The mean rate of steady-state PDS release (16.5 µg/cm²·day) was calculated from the slope of the curve between cumulative drug release and time.  Conclusions:  Studies showed that there was a sustained release of drug for an extended period of time, thus providing a basis for therapeutic intervention for lichen planus and other oral diseases.  Supported by NIH-NIDCR grant R01 DEE 15267.