A new drug delivery system utilizing piggyback contact lenses

We designed and evaluated a new drug delivery system (DDS) in which a drug plate containing levofloxacin was placed between a hydrophilic soft contact lens (SCL) and a non-hydrophilic SCL. The drug plate (diameter 8.0 mm, thickness 0.2 mm) was prepared by coating and freeze-drying a poly(vinyl alcohol) (PVA) disc containing 20, 30 or 40 wt% levofloxacin with a block styrene-(ethylene/butene)-styrene (SEBS) polymer solution. The release rate of the levofloxacin in vitro reduced with an increase in the concentration of SEBS polymer in solution used for coating. The release rate was well controlled and in zero-order kinetics was observed. The drug release from the drug plate consisting of a PVA disc loaded with 30 wt% levofloxacin and coated with 7.5 wt% SEBS polymer solution was 3.07 +/- 0.39 mg during 8 h. This drug plate was placed on an albino rabbit's eye wearing a hydrophilic soft contact lens (SCL), and then covered with a non-hydrophilic SCL. The drug concentrations in the anterior chamber were 156.0 +/- 133.6 micrograms/ml and 193.2 +/- 136.1 micrograms/ml after 4 and 8 h, respectively. The values obtained with frequent instillation of 0.5% levofloxacin every 30 min were 9.9 +/- 4.3 micrograms/ml and 12.5 +/- 10.0 micrograms/ml after 4 and 8 h, respectively. Therefore a significantly higher drug level was achieved with DDS compared to frequent instillation.