Kinetics of drug delivery from methylcellulose sponges

Purpose. To quantitatively evaluate the kinetics of fluid transfer from microsurgical sponges in a laboratory model, in order to understand the kinetics of mitomycin C delivery using these sponges. Methods. The amount of fluid transferred from soaked methylcellulose (Weck-cel) sponges to small pieces of filter paper used to simulate episcleral tissue and tenon's fascia was measured as a function of time, sponge size, baseline hydration status of the filter paper, and technique of sponge application. Results. The time course of fluid delivery from methylcellulose sponges to filter paper was nonlinear, and was characterized by a rapid delivery phase over the first 15 to 30 seconds, followed by a slow phase extending to at least 5 minutes. Sponge size and baseline hydration of the paper significantly influenced the rate and amount of fluid delivered. Fluid delivery was significantly increased by replacing the sponge every minute with a new sponge. Conclusion. The transfer of fluid from a microsurgical sponge displays nonlinear kinetics, with the majority of delivery occurring in the firstl5-30 seconds. Sponge size, hydration status of the recipient tissue, and technique of sponge application are significant variables influencing the amount of fluid, and therefore mitomycin C, delivered.