Sponge delivery variables and tissue levels of 5-fluorouracil

Abstract

Aim - To study how the delivery of 5-fluorouracil (5-FU) to ocular tissues is affected by altering delivery variables. Method - Sponge(s) soaked in radiolabelled 5-FU were placed between the conjunctiva and sclera of pig eyes. Application time, sponge size, sponge make (Altomed, Weck, Merocel), and 5-FU concentration were varied. Conjunctival and scleral tissue levels were determined in samples taken from the application site. Results - Dose-response curves for scleral and conjunctival 5-FU levels against application time showed increasing tissue levels that reached a plateau after 2-3 minutes. Application beyond 3 minutes did not increase tissue levels. There was no difference in tissue levels between 7 x 4 and 3.5 x 2 mm sponges. Altomed sponges produced 5-FU tissue levels that were twice as high as those obtained with Weck-cell (p < 0.01) or Merocel (p < 0.02) sponges. Changing the 5-FU concentration from 25 mg/ml to 6.25 mg/ml reduced the conjunctival concentration by a factor of 3.5 (p < 0.003). Conclusion - Application time up to 3 minutes, sponge make, and 5-FU concentration can have a large effect on the tissue delivery of 5-FU. Application time beyond 3 minutes, using 3.5 x 2 mm or 7 x 4 mm sponges, and replacing sponges every minute did not have a significant effect on tissue levels. This study models the effect that different variables can have on the ocular tissue levels of an antimetabolite applied intraoperatively.