Carmustine wafer is a preparation of chemotherapeutic agent used to treat high-grade brain tumor called glioblastoma. This preparation is disc shaped substance which is placed at the site of tumor where it adheres to the malignant cells, thereby, preventing their further division. Side effects such as headache, difficulty in walking, confusion, drowsiness, slow wound healing, and skin rashes are fairly common. Reference: https://www.cancerresearchuk.org/about-cancer/cancer-in-general/treatment/cancer-drugs/drugs/gliadel Image via: https://www.semanticscholar.org/paper/Carmustine-wafer-implantation-for-high-grade-safety-Roux-Caire/8c56184991a7ab97b9da6f1069ac3715fb60b757