Quantification of intraoperative administration of mitomycin-C in filtering surgery with surgical sponge material.

PURPOSE

To determine the absorption and release of mitomycin-C 0.4 and 0.2 mg/mL from sponge-like specimens of Spongostan film (Ferrosan, Copenhagen, Denmark) and the scleral and conjunctival impregnation in an experimental model of filtering surgery.

METHODS

The maximum amount of mitomycin per volume unit that Spongostan is able to absorb was determined physically as the difference between dry weight and soaked weight. Mitomycin-C activity in known volumes of Spongostan after mitomycin-C release in vitro also was determined at 0, 1, 10, and 30 seconds and 1, 3, 5, 10, 15, and 30 minutes. Antibiotic activity of the specimens was evaluated by means of bioassay. Millimeters of inhibition of bacterial growth were related to microg of mitomycin activity according to a reference curve obtained from known amounts of mitomycin-C. Finally, 10 eyes of 10 rabbits underwent filtering surgery with intraoperative application of mitomycin by means of the Spongostan film. The Spongostan implants then were removed and tested for mitomycin activity. Scleral and conjunctival specimens were obtained for bioassay.

RESULTS

The maximum capacity of 25 mm2 x 0.5 mm thick Spongostan films saturated in 0.4 and 0.2 mg/mL solutions of mitomycin-C were 8.49 microg and 4.23 microg, respectively. Biologic activity (bioassay determination) was 8.24 microg and 4.19 microg of mitomycin-C, respectively. In vitro release of mitomycin was gradual until 30 minutes. In vivo mitomycin release from Spongostan after 5 minutes was 6.91 microg. Impregnation with the antimitotic was better in conjunctiva than sclera.

CONCLUSION

Bioassay permits quantification of mitomycin-C activity. The release from sponge specimens is gradual, and impregnation was better in conjunctiva than sclera.