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Frcr Oncology > Antimetabolites > Flashcards

Antimetabolites Flashcards

1
Q

What is 5FU

A

Antimetabolite
Fluropyrimidine analog

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2
Q

Cell cycle in which sfu acts

A

S phase

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3
Q

Moa of 5Fu

A

Inhibition of thymidylate synthase by metabolite FdUMP which leads to accumulation of dUMP , which is incorporated into DNA as dUTP, which results in DNA Synthesis and function as well as alterations in RNA processing and m RNA translation

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4
Q

Absorption of 5 fu

A

I’ve Route only

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5
Q

Distribution of 5FU

A

Highest concentrations in GI mucosa , bone marrow liver, also in third space fluid collections and csf and brain

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6
Q

Excretion of 5FU

A

Urine

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7
Q

Half life of 5 fu

A

10 to 20 ins

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8
Q

What is MTX

A

Anti metabolite
Anti folate
Folic acid analogue

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9
Q

Mechanism of action of MTX

A

Inhibits the di hydro folic acid reductase that converts DHFA to THFA

Inhibits the de novo synthesis of purines thereby inhibits the DNA synthesis and function

Active on the S phase

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10
Q

What is folinic acid rescue

A

Folinic acid is given 1 day after high dose MTX to rescue the normal cells, from the toxic effect of MTX

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11
Q

Mechanism of folinic acid rescue

A

Selective uptake in normal cells due to the low levels of MTX poly Glutamates

It can be converted to Formyl THFA without the action of DHFA reductase enzyme

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12
Q

Routes of administration MTX

A

Oral and Iv

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13
Q

Uses of oral MTX

A

Given once a week

Inflammatory bowel, crowns , Rheumatoid arthritis

Along with folks acid

MTX on mondays and folic acid on fridays

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14
Q

Dose limiting side effects of MTX and how would u treat it

A

Mucositis and stomatitis

Oral cryotherapy
Benzydamine mouth wash

Grade 4- parenteral treatment

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15
Q

Emetogenic potential of MTX

A

Minimal MTX less than 50 mg/m2

Low MTX 50 to 250

Moderate MTX more than 250

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16
Q

Does MTX cross Bbb

A

At high doses

17
Q

Metabolism of MTX

A

Liver

18
Q

Excretion of MTX

A

Urine

19
Q

Indications of MTX

A

Breast
HNC
All
Hl
Primary CNS lymphoma
Bladder
Gtc

20
Q

Dose of MTX

A

Low dose :
Weekly - 25 mg/m2 IV
Monthly - 10 TO 50 mg/m2

Moderate dose
100 to 500 mg/m2 every 2-3 weekly

High dose
1 to 12 gram per m2 over 3 to 24 hours Q 1-3 weeks

21
Q

Others routes of MTX

A

Intra thecal : 10 to 15 mg twice weekly till CSF is clear
Followed by weekly for 4 weeks
Followed by monthly dose

IM :
25 mg per m2 every 3 weeks

22
Q

Dose reduction in MTX

A

Renal impairment

23
Q

Other dose limiting toxicity of MTX

A

Myelosuppression

24
Q

MOA of pemetrexed

A

Inhibits - thymidalate synthase - resulting in decreased thymidine available for DNA synthesis

inhibits DHFR and GARFT which are required for synthesis of purine de novo

25
Q

Cell cycle of pemetrexed

A

G1/S

26
Q

Excretion of pemetrexed

A

Urine 80%

27
Q

Indications and doses of pemetrexed

A

NSCLC - non squamous locally advanced / metastatic along with cisplatin or second line agent

Mesothelioma

Dose 500 mg/ m2 every 3 weeks

28
Q

Caution before pemetrexed

A

Folic acid 400 microgram per oral 7 days before starting pemetrexed and 21 days after the completion of pemetrexed

Vitamin B12 1000 microgram IM 7 days prior to the first dose then every 9 weeks until 3 cycles are completed

29
Q

Toxicity of pemetrexed

A

Myelosuppression dose limiting

Skin toxicity : rashes Dexa 4mg PO 4 mg

30
Q

What is capecitabine

A

Fluropyrimidine analogue
Antimetabolite
Active is S phase

31
Q

Dose limiting of capecitabine

A

Diarrhoea
Withhold if grade 2/3
Start loperamide

32
Q

Other toxicities and how do you prevent

A

Hand foot syndrome ( palmar plantar erythrodesesthesia )
VIT b6 50 to 150 mg orally to prevent
Followed by dose reduction

33
Q

Dose and indications

A

1250 mg/ m2 Po bd with food
In breast cancer and colorectal ca

Dose reduction to 825 mg/ m2 in case of toxicity

34
Q

Metabolism of capecitabine

A

Liver

Converted to 5FU with thymidine phosphorylase followed by 5FdUMP to inhibit DNA synthesis and FUTP to inhibit RNA synthesis and FBAL INACTIVE METABOLITE by DPD

Frcr Oncology (7 decks)

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