ABSTRACT The application of polymer based drug delivery devices in dentistry is a relatively new area of research with some exceptions. The present study addresses the development of a novel device based on ethylene-vinyl acetate copolymer (EVA), a thermoplastic and biocompatible material which enables constant drug release of effective concentration over several days to treat oral infections. drugs incorporated in EVA, included tetracycline, doxycyline, chlorhexidine and minocycline (antimicrobial), and diphenhydramine (antihistamine). Nystatin, an antifungal agent, was also included in the study together with its combinations of nystatin-tetracycline (1:1), and nystatin-minocycline (1:1). Polymer casting solutions were prepared by dissolving EVA and the drug in the ratio of 7:1 in 70 ml of dechloromethane of 38°C for 6 hrs. The square films of 3x3 cm and 1 mm thickness were cut from the drug sheet obtained by solvent evaporation. Drug loaded samples were extracted for a minimum of 15 days in 10 ml medium (distilled water for the above antimicrobial and antihistamine agents; water/ethanol (4:1) for nystain and its combinations and 0.9% saline solution to mimic saliva with reference to nystatin). The extracting media were replaced daily. Spectral measurements were made to follow the changes in optical densities (OD) during the kinetics of drug release. λmax values were determined separately for each drug in the appropriate solvent spectrophotometrically. Analysis of the data revealed that among all the drugs studied, tetracycline exhibited the highest release rate and cumulative percent release. The observed significant increase in the values may be attributed to the formation of channels in the copolymer system, drug-drug and drug-polymer interactions. Tetracycline, when combined with nystatin, exhibited a decrease in release pattern. Minocycline showed the least release characteristics compared to others but exhibited an improvement in the release characteristics when combined with nystatin in equal proportion. The “burst” effects due to liberation of surface-bound drug molecules for all the drug-loaded films were also discussed. Drug-loaded EVA (a thermoplastic copolymer), such as tetracycline-nystatin as well as tetracycline alone, may provide a therapeutic material for the development of a novel, local treatment for oral infections.
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