Antimetabolites
Mimicking DNA building blocks or their cofactors to block DNA synthesis.
Class card
- Drugs
- Methotrexate and Fluorouracil
- Used for
- Leukemias, such as acute lymphoblastic leukemia
- Non-Hodgkin lymphoma
- Breast cancer
- Colorectal cancer
- Known for
- Bone marrow suppression
- Mouth ulcers and mucositis
- Name stems
- -uracil, -trexate
3 cards: the class, and each drug in it.
Mechanism of action
How do antimetabolites work?
Antimetabolites resemble natural molecules that cells use to build DNA and RNA, such as folate or the pyrimidine bases, closely enough to enter the same pathways. There they block a key enzyme or are built into the nucleic acid, so DNA synthesis fails. Actively dividing tissues feel it most: the tumor, bone marrow, the mouth and gut lining, and a developing fetus.
The drugs
Antimetabolites with a card
Uses
What are antimetabolites used for?
- Leukemias, such as acute lymphoblastic leukemia
- Non-Hodgkin lymphoma
- Breast cancer
- Colorectal cancer
- Head and neck cancer
- Rheumatoid arthritis and psoriasis (methotrexate)
Side effects
Side effects of antimetabolites
- Bone marrow suppressionKnown forSerious
- Mouth ulcers and mucositisKnown forSerious
- DiarrheaSerious
- Nausea and vomiting
- Serious infectionsSerious
- Hair loss
- Photosensitivity
- Harm to an unborn babySerious
- Impaired fertility
What the class has in common. Each drug's card has its own, and Known for marks what an exam expects you to know.
Watch for
Cautions
- Check blood counts often: marrow suppression can be severe and fatal.
- They can harm a fetus: confirm pregnancy status and use contraception during and after treatment.
- Slow clearance raises toxicity sharply: kidney impairment for methotrexate, DPD deficiency for fluorouracil.
Remember them
A way to remember them
Antimetabolites are counterfeit parts on the DNA production line.
Methotrexate imitates folate and blocks DHFR; fluorouracil imitates uracil and blocks thymidylate synthase. Either way, dividing cells cannot make DNA.
Written for biofideX
Name stems
-uracil means uracil derivative (anticancer or antithyroid)
Fluorouracil, an anticancer antimetabolite, and propylthiouracil, an antithyroid drug, share the ending. WHO splits them into -racil and -thiouracil.
-trexate means folic acid analogue (methotrexate type)
Methotrexate blocks dihydrofolate reductase, so cells lack the reduced folate they need to make DNA. Pemetrexed and raltitrexed end in -trexed, the stem for thymidylate synthase inhibitors.
- Every drug name stem
Don't mix them up
Classes easily confused with these
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Antimetabolite (NCI Thesaurus)
- Methotrexate injection: label (DailyMed)
- Fluorouracil injection: label (DailyMed)
- Fluorouracil Injection (NCI)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Cancer chemotherapy
Practice antimetabolites with the other classes in this group: what each drug is, how it works, what it treats and what it's known for.
Start Practicing