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Pharmacology 2. B topics > 24. Pharmacological basics of chemotherapy > Flashcards

24. Pharmacological basics of chemotherapy Flashcards

1
Q

Chemotherapeutic drugs -?

A

Target of this drug does not belong to the body (cancer or infectious agent)

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2
Q

Classification of chemotherapeutics:

A
  1. Antimicrobial
  2. Antineoplastic (anti-cancer)
  3. Antiparasitic
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3
Q

What drugs are included in antimicrobial group of chemotherapeutics?

A
  1. Antibacterial
  2. Antifungal (limited significance in vet med)
  3. Antiviral (limited significance in vet med)
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4
Q

What is the difference between antibacterial and antibiotics?

A

Antibiotics are naturally occuring and antibacterial drugs not neccessary

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5
Q

What drugs are included into antiparasitic group of chemotherapeutics?

A
  1. Antiprotozoal
  2. Endoparasiticidal drugs
  3. Ectoparasiticidal drugs
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6
Q

What is the concept of selective toxicity?

A

The goal is to destroy the target without harming the organism

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7
Q

Types of targets in regard of selective toxicity:

A
  1. Unique targets
  2. Similar targets
  3. Common targets
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8
Q

Unique targets - ?

A

Target that exists in pathogen but is not present in the host (e.g. cell wall - penicillin)

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9
Q

Similar targets - ?

A

Affinity to target is much higher than to the host

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10
Q

Examples of unique targets?

A
  • cell wall
  • ergosterol (fungal cell membrane component)
  • folic acid synthesis (one of the steps)
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11
Q

Examples of drugs having unique target: cell wall

A
  • beta-lactams (penicillins, cephalosporins)
  • glycopeptides (vancomycin)
  • bacitracin
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12
Q

Examples of drugs having unique target: ergosterol

A
  • ergosterol-synthesis inhibitors (azoles: itraconazole, ketoconazole)
  • ergosterol-complex formers (polienes: nystatine, amphothericin B) - form a channel by binding ergosterol -> leakage -> destruction
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13
Q

Examples of drugs having unique target: folic acid synthesis

A

Bacterias are producing folic acid but animals receive it with food -> unique agent

PABA (paraaminobenzoic acid) -> dihydro-folic acid reaction requires enzyme: dihydropteroate-synthetase. This enzyme can be inhibited by sulphonamides (because they are structural analogues of PABA)

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14
Q

Why are sulphonamides very safe? What do they act on?

A

Sulphonamides act on unique target: dihydropteroate synthetase enzyme that participates in conversion of PABA to dihydrofolic acid. Mammals don’t have this reaction in their body, they receive dihydro-folic acid from food

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15
Q

Sulphonamides and ________ often applied together. Why?

A

Trimethoprim. Acts on similar target: dihydrofolate reductase (converting non-active dihydro-folic acid to active tetrahydro-folic acid). So sulphonamides and trimethoprim potentiate each other because act on 2 different steps of the same reaction

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16
Q

What do beta-lactams act on?

A

cell wall

17
Q

What do azoles act on?

A

ergosterol

18
Q

What do glycopeptides act on?

A

cell wall

19
Q

What do polienes act on?

A

ergosterol

20
Q

What do sulphonamides act on?

A

folic acid synthesis that is present only in bacteria

21
Q

What will happen to bacteria if concentration of antibacterial drug is below MIC?

A

Growth of bacteria will not be inhibited

22
Q

What is MIC?

A

minimum inhibitory concentration

23
Q

What is MBC?

A

minimum bactericidal concentration. Minimal concentration that will kill the bacteria

24
Q

What is MPC?

A

mutant prevention concentration. Minimal conc that will inhibit growth even of bacteria that were able to develop resistance

25
Q

What will happen if concentration of the antibacterial drug is between MIC and MPC?

A

“normal” bacteria’s growth will be inhibited but resistant mutant ones will not be affected!! VERY BAD!

26
Q

What are 2 main modes of action of antibacterial drugs?

A
  1. Bactericidal (kills bacteria)
  2. Bacteriostatic (inhibits growth and immune system kills bacteria)
27
Q

What are the conditions when bactericidal drugs should be used?

A
  • life-threatening infections (no time to wait for immune response)
  • immunosuppressed patients (FeLV, FIV)
28
Q

2 possible modes of action of bactericidal drugs

A

Time or concentration dependent. If increase of dosage significantly increases speed of killing bacteria -> concentration-dependent. If only slightly -> time-dependent

29
Q

What bactericidal drugs are time-dependent?

A
  • penicillins
  • cefalosporins
  • potentiated sulphonamides
30
Q

What is postantibiotic effect?

A

Delayed antibacterial effect after the concentration of the drug declined below MIC
(e.g. beta-lactams, aminoglycosides, fluorouinolones)

31
Q

What does synergetic type of action mean?

A

2 drugs potentiate each other. Increase of effectiveness

32
Q

Examples of synergetic action

A
  • penicillin + streptomycin
  • lincomycin (50S inhibitor) + spectinomycin (30S inhibitor) - mainly against mycoplasma
33
Q

What does additive action mean?

A

Don’t potentiate each other, but broad the spectrum of action.

34
Q

Example of additive action

A

gentamicin (aerobic) + metronidazol (anaerobic)

35
Q

What does antagonist action mean?

A

drugs act on the same target -> compete with each other -> decreased effectiveness

36
Q

Example of antagonist action

A

erythromycin + chloramphenicol (both inhibit 50S)

37
Q

2 types of bacterial resistance

A
  1. Chromosomal resistance (spread vertically)
  2. Plasmid encoded (horizontally + vertically)
38
Q

Example of chromosomal resistance

A

MRSA (methicillin resistant S. aureus)

39
Q

Types of transferring of resistance among bacteria

A
  1. conjugation - transferring chromosomal or plasmid encoded resistance genes - THE MOST IMPORTANT ONE
  2. transduction - via bacteriophages
  3. transformation - from dead bacteria (minor significance)

Pharmacology 2. B topics (8 decks)

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