Evaluation of a subcutaneously implanted biodegradable matrix with and without cisplatin in horses

Summary Objective The aim of this study was to determine the biodegradability and platinum release profile of a calcium sulphate matrix (Matrix III) implanted subcutaneously in horses. Study design Matrix III with and without cisplatin was implanted subcutaneously in the cervical region of five horses with normal cervical skin. Methods Five 3‐mm beads of Matrix III alone and ten 3‐mm beads containing 7% cisplatin were implanted subcutaneously in the cervical region. Tissues were harvested every 7 days for 35 days. Biodegradability and histologic tissue reaction were determined. Inductively coupled plasma mass spectrometry was used to determine platinum concentration 3, 6, 9, 12 and 15 mm from each implantation site. Plasma and distant skin biopsies were harvested every 7 days. Repeated measures ANOVA was performed to determine differences between the 5 weeks and the five distances from the implant. Results Matrix III alone caused local inflammation that resolved early, and the implant had absorbed completely by 28 days leaving only focal fibrosis. Matrix III containing 7% cisplatin incited persistent histologically evident inflammation that appeared to be clinically insignificant. The implants had not been completely absorbed by 35 days. Platinum tissue concentration decreased with time after implantation and as distance from the implant increased. Therapeutic concentrations remained in the tissue at Day 35. Conclusions Matrix III with 7% cisplatin resulted in chemotherapeutic platinum concentrations sustained for 35 days.