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Unit 1: Pharm > Antimetabolites > Flashcards

Antimetabolites Flashcards

1
Q

Name the 3 classes of antimetabolites. Are they cell cycle specific?

A

Folate-analogs, pyrimidine analogs, purine analogs. CCS (S phase)

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2
Q

Name the 2 folate-analogs

A

Methotrexate, pemetrexed

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3
Q

Name the 4 pyrimidine-analogs

A

5-FU (fluorouracil), capecitabine, cytarabine, gemcitabine

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4
Q

Name the purine-analog chemotherapy agent

A

6-MP (mercaptopurine)

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5
Q

Which of the bases A, T, C, G, and U are purines and which are pyrimidines?

A

AG - purines, CTU - pyrimidines

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6
Q

What drug counteracts or “rescues” healthy cells from the otherwise lethally toxic effects of methotrexate?

A

Leucovorin

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7
Q

Name 2 THF-dependent enzymes inhibited by the active/metabolized polyglutamate forms of pemetrexed.

A

DHFR (dihydrofolate reductase) and TS (thymidylate synthase)

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8
Q

What antimetabolite is the most widely used and can be given orally to treat childhood ALL, choriocarcinoma, and many other cancers?

A

Methotrexate

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9
Q

A high dose of methotrexate is needed to treat which kind of cancer?

A

Osteosarcoma

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10
Q

What does it mean to administer methotrexate intrathecally, and for what cancers is this route used?

A

Inject directly into the CNS/CSF for meningeal leukemia or meningeal metastases

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11
Q

Which antimetabolite is used to treat mesothelioma, as well as non-small cell lung cancer, pancreatic cancer, and colon cancer?

A

Pemetrexed

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12
Q

5-FU is enzymatically converted into what 2 active forms, and how do these forms interfere with cell processes?

A

5-FdUMP which competitively inhibits TS (thymidine synthetase), and 5-FdUTP which interferes with RNA function

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13
Q

What is the function of TS (thymidylate synthase)?

A

Makes dUMP into dTMP

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14
Q

What is the newer form of 5-FU, and how does its administration differ from that of the original form?

A

Capecitabine; can be given orally whereas 5-FU is only given intravenously

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15
Q

What antimetabolite is used in a wide variety of combination therapies, but comes at the cost of hand-foot syndrome and severe GI toxicity?

A

5-FU

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16
Q

What cancer is topical 5-FU used to treat?

A

Basal cell carcinoma

17
Q

What cancers is capecitabine approved to treat?

A

Metastatic breast cancer and colorectal cancer

18
Q

What are the longer names for the antimetabolites 5-dFdU, Ara-C, and dFdC?

A

5-dFdU is the active form of capecitabine, Ara-C is cytarabine, dFdC is gemcitabine

19
Q

Describe the 2-step transformation of cytarabine into its active form, and how this form inhibits DNA synthesis

A

Ara-C –> Ara-CMP –> Ara-CTP, which competes with dCTP to be incorporated into DNA

20
Q

How does deoxycytidine kinase act on cytarabine and gemcitabine?

A

adds a phosphate: converts Ara-C to Ara-CMP, and dFdC to dFdCMP

21
Q

Compare cytarabine and gemcitabine in terms of cell cycle specificity and tumor specificity

A

Gemcitabine is more effective against solid tumors and is active throughout the cell cycle, while cytarabine is only active during S phase

22
Q

Cytarabine is the most effective agent for treating what cancer?

A

AML (and it can also treat ALL and blast phase CML)

23
Q

Gemcitabine is the first-line treatment for what cancer?

A

Pancreatic carcinoma

24
Q

How is 6-MP (mercaptopurine) activated and what is this active form?

A

6-MP is metabolized by HGPRT (hypoxanthine-guanine phosphoribosyl transferase) into TIMP (6-thioinosinic acid)

25
Q

List 3 ways the active form of 6-MP (mercaptopurine) inhibits DNA synthesis

A

Inhibits de novo purine base synthesis; inhibits IMP conversion to AMP and XMP; becomes thio-GMP which is incorporated into DNA and RNA

26
Q

What chemotherapy agent is used primarily to maintain remission in ALL patients?

A

6-MP (mercaptopurine)

27
Q

How is 6-MP excreted, and what drug interferes with this process?

A

6-MP is excreted after being metabolized by xanthine oxidase. Allopurinol can inhibit xanthine oxidase and decrease 6-MP excretion.

28
Q

List 3 characteristic side effects of 5-FU chemotherapy.

A

Hand-foot syndrome, cardiac toxicity, and severe GI toxicity

29
Q

What 2 antimetabolites can cause hepatotoxicity as a side effect?

A

Methotrexate and 6-MP

30
Q

What 3 antimetabolites can be used to treat hematologic cancers?

A

Methotrexate, 6-MP, and cytarabine

31
Q

List 3 characteristic side effects of methotrexate chemotherapy.

A

Hepatotoxicity, renal toxicity, and reproductive problems

32
Q

How does leucovorin affect the actions of methotrexate and 5-FU?

A

“Rescues” healthy cells from methotrexate toxicity; potentiates (makes stronger) 5-FU’s effects

33
Q

Why does 5-FU have to be given via IV?

A

It would be degraded too quickly in the gut and liver, and also causes severe GI toxicity

Unit 1: Pharm (10 decks)

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