Any one of a class of cytotoxic drugs that work by blocking the action of topoisomerase enzymes, which promote the uncoiling of the DNA double helix, a necessary preliminary to replication. Topoisomerase I inhibitors include irinotecan (Campto), administered by intravenous infusion for treating advanced colorectal cancer (especially in combination with fluorouracil); and topotecan (Hycamtin), given orally or by intravenous infusion for treating advanced ovarian cancer. Side-effects include delayed but severe diarrhoea and reduction in blood-cell production by the bone marrow. Topoisomerase II inhibitors include etoposide and doxorubicin.
Subjects: Medicine and Health.