Ocular sustained delivery of prednisolone using hyaluronic acid benzyl ester films

Abstract Hyaluronic acid benzyl ester films were studied for ocular delivery of prednisolone. The four polymers used were HYAFF 11 p25 (25% benzyl ester, 75% sodium salt), HYAFF 11 p50 (50% benzyl ester, 50% sodium salt), HYAFF 11 p75 (75% benzyl ester, 25% sodium salt) and HYAFF 11 (100% benzyl ester). The polymer with the lowest degree of esterification, HYAFF 11 p25, was the most hydrophilic and released drug faster than those with higher degrees of esterification, HYAFF 11 and HYAFF 11 p75, which are generally less hydrophilic. Tear fluid prednisolone concentrations were measured in rabbits after administration of the test films. Areas under the tear fluid concentration vs time curves (AUC 0–8 h ) were calculated for all the dosage forms, from the time of dosing to 8 h post-dosing. The HYAFF 11 p25 films provided higher initial concentrations which rapidly declined below 30 μg/ml, 2 h post-dosing. Concentrations for the HYAFF 11 p75 film dropped below 30 μg/ml, 3 h post-dosing. The HYAFF 11 films provided the best results with sustained concentrations between 45 and 72 μg/ml for the 8 h study period. The results show that sustained delivery of prednisolone to the eye may be achieved with the use of hyaluronic acid esters.