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The Public (Y2) > Inhibitors of folate metabolism > Flashcards

Inhibitors of folate metabolism Flashcards

1
Q

Why is folate a dietary supplement rather than tetrahydrofolate?

A

Because folate can enter cells whereas tetrahydrofolate can’t

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2
Q

Tetrahydrofolate is essential for C1 metabolism. True or false?

A

True

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3
Q

Why is the enzyme dihydropteroate synthetase a good antibacterial drug target?

A

Because humans don’t have this enzyme

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4
Q

What is the pka of para-aminobenzoic acid?

A

pKa 5

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5
Q

Prontosil was shown to be a prodrug for which drug?

A

Sulfanilamide

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6
Q

Why is diethylene glycol toxic?

A

Because the liver oxidises the hydroxyl groups to toxic aldehydes

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7
Q

Sulphanilimide mimics PABA, although not very well. True or false?

A

True

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8
Q

What is sulfadiazine used to treat?

A

Toxoplasmosis

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9
Q

Sulfadiazine is 75% ionised at physiological pH and so is 100x more active than sulfanilamide. True or false?

A

True

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10
Q

Folate metabolism is essential for DNA and RNA synthesis and is required for all C1 metabolism. True or false?

A

True

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11
Q

Inhibition of folate synthesis is used to treat bacterial infections, malaria, cancer, rheumatoid arthritis and other diseases. True or false?

A

True

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12
Q

What do bacteria make dihydrofolate from?

A

Pteridine

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13
Q

What do we make dihydrofolate from?

A

Folate

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14
Q

What is trimethoprim used for?

A

Sometimes antimalarial but principally to treat cystitis (UTI)
Typhoid fever
Chronic bronchitis
gonorrhoea in penicillin resistant patients

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15
Q

Why is trimethoprim selectively toxic?

A

Because its affinity for dihydrofolate reductase in bacteria is 50,000x stronger than for human dihydrofolate reductase

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16
Q

Co-trimoxazole is a combination of which two medicines?

A

Trimethoprim

Sulphamethoxazole

17
Q

The chlorophenyl ring in pyrimethamine is more hydrophobic than trimethoprim. True or false?

A

True

18
Q

The pyrimidine ring in pyrimethamine has DHFR activity. True or false?

A

True

19
Q

Methotrexate also targets mammalian DHFR. What is it used for?

A

Anti-cancer agent used against rapidly proliferating tumours

20
Q

Prolonged high doses of methotrexate lead to ______

A

Anaemia

21
Q

In vivo, methotrexate has equal activity against bacterial DHFR and mammalian DHFR but in vivo, it is inactive against bacterial DHFR. True or false?

A

True

22
Q

Why is methotrexate not active in bacteria?

A

Because it is too polar for passive diffusion

23
Q

In very low doses, what is methotrexate used to treat?

A

Rheumatoid arthritis and inflammatory bowel disease

24
Q

Methotrexate, in combination, is also used to terminate pregnancy, especially ectopic pregnancy. True or false?

A

True

25
Q

Very severe reactions take place when methotrexate is taken with penicillin. Why?

A

Penicillin seems to inhibit elimination of methotrexate

The Public (Y2) (35 decks)

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