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PHRM 864 > lecture 4 anti-metabolites > Flashcards

lecture 4 anti-metabolites Flashcards

1
Q

what is the role of antimetabolites?

A

dna replication/transcription requires nucleotide building blocks
antimetabolites block these building blocks
block s-phase
myelosuppression is dose-limiting

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2
Q

what antimetabolite is a uridine analog?

A

5-FU

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3
Q

what does 5-FU block?

A

thymidylate synthase

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4
Q

what is the MOA of 5-FU?

A

in pressence of folate, FdUMP binds to thymidylate synthase and traps the enzyme –> inhibits formation of TMP

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5
Q

what is the resistance mechanism of 5- FU?

A

down-regulation of enzyme that convert 5FU to FdUMP
upregulation of thymidylate synthase

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6
Q

what is a polymorphism for 5FU that can effect its efficacy?

A

5% of people have a deficiency in dihydropyridine dehydrogenase (DPD) which breaks down 5-FU
can cause toxicity of 5-FU

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7
Q

what is the use of thymidine for 5FU?

A

rescue drug for patients who overdose

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8
Q

what is the use of leucovorate for 5FU?

A

folate cofactor –> higher folate increases 5FU efficacy

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9
Q

what is the role of cytosine analogs?

A

primary inhibits DNA synthesis

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10
Q

what is cytarabine?

A

pro-drug that converts to ARA-CTP intracellular

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11
Q

what is cytidine deaminase (CDA)?

A

converts cytarabine to non toxic form
not present in brain or spinal cord –> higher risk of toxicity

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12
Q

what is tetrahydrouridine?

A

CDA inhibitor used to increase efficacy of cytarabine

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13
Q

what are purine analogs and what are their functions?

A

6-mercaptopurine
antifolates
inhibits multiple enzymes de novo purine biosynthesis –> blocks synthesis of purine nucleotides

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14
Q

what is thiopurine methyl transferase?

A

inactivates 6MP
10% children in US have polymorphism

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15
Q

what drug can you not take with allopurinol and why?

A

6MP
xanthine oxidase breaks down 6MP
allopurinol is a xanthine oxidase inhibitor

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16
Q

what are antifolates and function?

A

methotrexate
folates are essential Vit B9
essential cofactor for rxn: metabolism of AA + nucleic acid. FH2 converted to FH4

17
Q

what is folic acid?

A

folate
enters the folate pool as FH2
reduction to FH4 by DHFR
DHFR inhibition will reduce the FH4 levels

18
Q

what is methotrexate?

A

binds and inhibits DHFR
reduces FH4 and inhibits TMP

19
Q

what is the use for leucovorin for methotrexate?

A

LV is used to rescue normal tissue from methotrexate toxicity
cofactor that is converted to TH4 intracellularly
increases pressence of TH4 and reverses DHFR inhibition

PHRM 864 (7 decks)

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