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Chemotherapeutic Agents > Nucleic Synthesis > Flashcards

Nucleic Synthesis Flashcards

1
Q

What are 5 ways to interfere with nucleic acid synthesis?

A
  1. Alteration of base-pairing properties of the template
  2. Inhibition of either DNA or RNA polymerase
    3.Direct effects on DNA itself
  3. Inhibition of DNA gyrase
  4. Inhibition of nucleotide synthesis
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2
Q

How do Acridines work?

A

Intercalating agents - Produce frameshift mutations by sandwiching themselves between adjacent bases in DNA
Prevents bacterial reproduction

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3
Q

What are they used against?

A

Topical against gram +ve bacteria
Surface disinfectant & superficial wounds

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4
Q

What is an example of an acridine?

A

Proflavine - very toxic

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5
Q

How does Actinomycin work?

A

Intercalates in minor groove of double helix between guanine cytosine base pairs
Interferes with RNA polymerase
Causes hairpin loops

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6
Q

How is Actinomycin D administered?

A

I.V.

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7
Q

How is actinomycin D distributed?

A

Widely bar BBB

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8
Q

Where is actinomycin D absorbed?

A

poorly absorbed from GIT
Limited plasma binding
crosses placenta

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9
Q

How is actinomycin D metabloised?

A

Minimally by the liver

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10
Q

How is actinomycin excreted?

A

Via the biliary routes and urine

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11
Q

What does actinomycin D inhibit?

A

Gram +ves/-ves and some fungi

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12
Q

What are actinomycin D’s clinical uses?

A

Treatment of Wilm’s tumour
Combination chemotherapy
High antibacterial activity

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13
Q

What are the adverse effects of Actinomycin D?

A

Hepatotoxicity, carcinogenicity, hematological toxicity, GIT distress and motility, hypersensitivity

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14
Q

What is metronidazole?

A

Alkylating agent - forms covalent bonds with bases in DNA
Prevents replication and has cytotoxic effects

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15
Q

What is an example of a metronidazole?

A

Falgyl (prodrug)

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16
Q

What is metronidazole’s mode of action?

A

Reductive activation by intracellular trasnport proteins
Forms reduced cytotoxic compounds which binds to DNA
Loss of helical DNA structure and strand breakage - prevents nucleic acid synthesis

17
Q

What does metronidazole act against?

A

Anaerobic infections
Antiprotozoal infections

18
Q

What are metronidazole’s clinical uses?

A

Combination therapy against Helicobacter pylori
Oral infections
Amoebic dysentery

19
Q

How is metronidazole administered?

A

Oral
I.V.

20
Q

How is metronidazole absorbed?

A

Rapidly absorbed after oral admin.

21
Q

How is it distributed?

A

Bioavailability of almost 100%

22
Q

How is metronidazole metabolised?

A

Hepatic metabolism

23
Q

How is metronidazole excreted?

A

Kidneys in urine
some faecal elimination

24
Q

What are the side effects of metronidazole?

A

GIT distress and motility
Dermatological effects
Neurotoxicity
Stevens-Johnson syndrome

25
Q

What are the mechanisms of resistance proposed?

A

Specific resistance genes
Reduced drug uptake
Efflux systems
Decreased activation

26
Q

What are Fluoroquinilones?

A

Bacterial enzyme (topoisomerases)

27
Q

What are fluoroquinolone’s mechanism of action?

A

Catalyses ATP-dependent negative supercoiling of double stranded closed-circular DNA
G-ve - inhibits DNA gyrase
G+ve - inhibits topoisomerase IV
Induce synthesis of exonucleases - breakdown of DNA

28
Q

What is an example of a fluoroquinolone?

A

Ciprofloxacin

29
Q

What does V act fluoroquinolone act against?

A

G-ve/+ organisms

30
Q

How are fluoroquinolones administered?

A

Oral
I.V.
Topical

31
Q

How are fluoroquinolones absorbed?

A

Well absorbed from GIT in oral admin

32
Q

How are fluoroquinolones distributed?

A

All tissues and body fluids
Ofloxacin crosses BBB

33
Q

How are fluoroquinolones metabolised?

A

Hepatic metabolism - can inhibit cytochrome p450 enzymes

34
Q

How are fluoroquinolones excreted?

A

Renal excretion
Some biliary elimination

35
Q

What are fluoroquinolones clinical uses?

A

Ciprofloxacin - G-ve organisms, UTIs, chlamydia
Morfloxacin - UTIs

36
Q

What are common fluoroquinolones side effects?

A

GIT upset
Alleregic reactions
CNS effects
Renal impairment

37
Q

What resistance mechanisms are used against fluoroquinolones?

A

Altered target - chromosomal mutations in bacterial genes
Efflux pumps and porin channels cause decreased accumulation

Chemotherapeutic Agents (14 decks)

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