The application of drug delivery systems in oral environment is relatively a new area of research with the exception of release of
fluoride ions from
polyalkenoate cements and their predecessor
silicate cements. The present study addresses development of a novel device based on
ethylene vinyl acetate copolymer (EVA), a
biocompatible material which enables constant drug release over several days to treat oral
infections. Drugs incorporated in EVA included
tetracycline,
minocycline and
nystatin together with combinations (C) of nytatin-
tetracycline (1 : 1) and
nystatin-
minocycline (1 : 1).
Polymer casting solutions were prepared by dissolving EVA and the drugs in the ratio of 10 : 1 in 70 ml of
dichloromethane at 38 degrees C for 6 h. Thin square films of 3x3 cm and 1 mm thickness were cut from the dry sheet obtained by
solvent evaporation.
Drug loaded samples were extracted for a minimum of 15 days in 10 ml medium (water or water/
ethanol (1 : 2) or
0.9% saline solution) which is replaced daily. Spectral measurements were made to follow changes in optical densities (OD) during release kinetics. Analysis of the data revealed that among all the drugs tested
tetracycline exhibited the highest release rate (56.15microg/cm2/day) and % cumulative release (27.92). The observed enhanced values may be interpreted as due to the channels formed due to changes in free volume (microvoids). In case of
nystatin-
minocycline combination, the observed increased values of release rates and percent cumulative release, may be attributed to the swelling component or channels or relative hydrophobic interactions. Initial "burst" effects due to liberation of surface-bound
drug molecules were observed with reference to all the three drugs and the combinations of drugs studied. Among all the drugs,
minocycline exhibited the least "burst" effect suggesting that the
drug is more homogeneously distributed in the copolymer.
Drug loaded EVA thermoplastic copolymer may provide a favorable therapeutic material for the development of a novel, local treatment for oral, mucosal and periodontal
infections.