How Does Pemetrexed Work?Pemetrexed belongs to a group of drugs known as folate antimetabolites, folate antagonists, or antifolates. It works by preventing the conversion of folic acid into its active form. Cells need that active form of folic acid to make DNA and RNA -- important molecules essential for cell division.
Pemetrexed is somewhat selective for cancer cells, meaning that it is more likely to affect cancer cells instead of healthy cells. However, as with most forms of chemotherapy, some healthy cells will be affected, and this process is likely responsible for many of the side effects of chemotherapy.
When and How to Take ItSome general considerations to keep in mind when taking pemetrexed include the following:
- Pemetrexed comes as an injection. It is injected slowly (infused) into a vein. Each infusion takes about 10 minutes. In most cases, you will receive one infusion every 21 days.
- You must take 400 to 1000 mcg of folic acid (as recommended by your healthcare provider) for seven days before your pemetrexed infusion and continue until at least 21 days after your last dose.
- You must also receive an intramuscular vitamin B12 injection while taking this medication. You should get your first vitamin B12 injection one week before your first pemetrexed infusion and then once after every three dosages of pemetrexed (usually about once every nine weeks for most people).
- Your healthcare provider may recommend a vitamin B12 injection the same day as each additional pemetrexed treatment.
- You must take the corticosteroid medication dexamethasone 4 mg to help prevent skin rashes due to pemetrexed. In most cases, the steroid is taken the day before, the day of, and the day after the infusion.