- If the patient has the uridine diphosphate (UDP) glucuronosyltransferase 1 family, polypeptide A1 (UGT1A1) polymorphism (7/7), they do not metabolize the irinotecan normally, so these patients will start out at a two dose level reduction; For patients on an EIAED, the starting dose will be 275 mg/M2, and for patients not on an EIAED, the starting dose will be 75 mg/M2;