- Day 1: Intravenous (through a vein) infusions of pemetrexed. Small groups (3 to 6) of patients are given pemetrexed at a certain dose level. If the first group experiences no significant side effects, the next group receives a higher dose. This continues in succeeding groups for up to five dose levels until the maximum tolerated study dose (highest dose that patients can be given safely) is determined.