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Anti-microbes > Protein synthesis inhibitors > Flashcards

Protein synthesis inhibitors Flashcards

1
Q

What are the 3 tetracyclines?

A
  1. Tetracycline
  2. Doxycycline
  3. Minocycline
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2
Q

What is the mechanism of action of the tetracyclines?

A

Tetracyclines concentrate intracellularly in susceptible organisms and bind reversibly to the 30S subunit of the bacterial ribosome.

This action prevents binding of the tRNA to the A site of the mRNA-ribosome complex, inhibiting bacterial ribosome synthesis

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3
Q

What products should tetracyclines be avoided with?

A

Dairy products or other substances that contain divalent and trivalent cations (Mg, Al, Fe) as it decreases absorption

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4
Q

How well do tetracyclines penetrate the CSF?

A

Moderate CSF penetration

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5
Q

What class of antibiotics should not be given with tetracyclines?

A

Beta lactams

Tetracyclines will arrest the growth of bacteria while beta lactams rely on bacterial growth to be effective

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6
Q

Are tetracyclines safe to be given during pregnancy?

A

No. All are Cat D as they cross the placental barrier and concentrate in fetal bones and dentition

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7
Q

What is tetracyclines spectrum of coverage?

A

Broad spectrum of gram-positive, gram-negative, atypical & spirochete bacteria + MRSA

Ineffective against P. aeruginosa & Proteus spp.

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8
Q

What are the 2 bacteria that tetracyclines lack activity against?

A

P. aeruginosa & Proteus spp.

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9
Q

What is the route of administration of tetracycline?

A

PO

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10
Q

What is the route of administration of doxycycline?

A

PO (good oral bioavailability), IV

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11
Q

Which tetracycline has good oral bioavailability?

A

Doxycycline; almost completely absorbed from the GI tract

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12
Q

What is the route of administration of Minocycline?

A

PO

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13
Q

How are the 3 tetracyclines excreted?

A
  1. Tetracycline is primarily eliminated in the kidney
  2. Doxycycline is eliminated in bile & urine
  3. Minocycline is metabolised in the liver before excretion
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14
Q

What 2 mechanisms of tetracycline resistance do glycylcyclines overcome?

A
  1. Efflux pumps
  2. Ribosomal protection
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15
Q

What is the mechanism of action of tigecycline?

A

Binds reversibly to the 30S ribosomal subunit, preventing the binding of tRNA to the A site of the mRNA-ribosome complex thereby inhibiting protein synthesis

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16
Q

What is the route of administration of tigecycline?

A

IV; poor oral bioavailability

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17
Q

Does tigecycline have good oral bioavailability?

A

No

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18
Q

Is tigecycline safe for pregnancies?

A

No, Cat D

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19
Q

Should tigecycline be given for bacteraemia?

A

No, tigecycline has low plasma conc.

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20
Q

How is tigecycline excreted?

A

Biliary/fecal

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21
Q

What is the spectrum of activity of tigecycline?

A

Broad spectrum against gram-positives & gram-negatives

Covers MRSA, VRE, ESBL gram-negs & multidrug-resistant streps

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22
Q

What spp. is tigecycline not active against?

A

Pseudomonas & Proteus spp.

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23
Q

Tetracyclines & tigecyclines are contraindicated in what patients?

A
  1. Pregnant women
  2. Breast-feeding women
  3. Children under 8
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24
Q

What is the mechanism of action of aminoglycosides?

A

Aminoglycosides distort the structure of ribosomes by binding to them and:
1. Block the formation of the initiation complex
2. Cause misreading of the codons
3. Inhibit translocation

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25
Q

What other class of antibiotics exhibits synergism with aminoglycosides?

A

Beta lactams enhance entry of aminoglycosides

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26
Q

The uptake of aminoglycosides into the inner membrane is mediated by active transport and they are hence unable to be used to treat what kind of bacteria?

A

Anaerobes since their energy-dependent phase can be inhibited by anaerobic conditions

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27
Q

Are aminoglycosides bactericidal or bacteriostatic?

A

Bactericidal

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28
Q

How is CSF penetration of the aminoglycosides?

A

Inadequate CSF penetration

29
Q

How are aminoglycosides eliminated?

A

Renal clearance

30
Q

What is the route of administration of aminoglycosides?

A

Parental; poor oral bioavailability

31
Q

What is the spectrum of coverage of aminoglycosides?

A

Mainly aerobic gram-negative bacteria

32
Q

What is the most frequent use of aminoglycosides?

A

Empirical therapy for serious infections such as septicemia, UTI & nosocomial RTI

33
Q

Which aminoglycoside is highly nephrotoxic if given parentally?

A

Neomycin

34
Q

What are the 4 adverse effects of aminoglycosides?

A

PONS

  1. Paralysis
  2. Ototoxicity
  3. Nephrotoxicity
  4. Skin rash (hypersensitivity)
35
Q

Are aminoglycosides safe to use in pregnancies?

A

No. Cat D in pregnancy

36
Q

Which aminoglycoside should be given synergistically with beta-lactams to treat gram-positive cocci?

A

Gentamicin

37
Q

What are the 5 aminoglycosides?

A
  1. Gentamicin
  2. Tobramycin
  3. Amikacin
  4. Streptomycin
  5. Neomycin
38
Q

What is the preferred aminoglycoside against P. aeruginosa?

A

Tobramycin

39
Q

What other nephrotoxic drugs should not be given with aminoglycosides?

A
  1. Vancomycin
  2. Amphotericin B
  3. NSAIDs
  4. NMBAs
40
Q

What groups of patients are aminoglycosides contraindicated in?

A
  1. Pregnant patients
  2. Myasthenia Gravis
  3. Patients with renal dysfunction
41
Q

What is the mechanism of action of macrolides?

A

They bind reversibly with the 50S ribosomal, inhibiting protein synthesis

42
Q

What are some infections that macrolides can be used for?

A
  1. RTI due to S. pneumoniae, H. influenzae, Moracella catarrhalis & atypical pneumonia
  2. STDs due to N. gonorrhae & Chlamydia
  3. H. pylori infection
43
Q

What is the spectrum of coverage of macrolides?

A

Broad spectrum coverage of gram-negative & gram-positives. Covers atypicals

44
Q

What is the route of administation of macrolides?

A

Good oral bioavailability; oral/IV

45
Q

Are macrolide CSF penetration good?

A

No

46
Q

What are the adverse effects when taking macrolides?

A

QT HOG

  1. Prolong QT interval
  2. Hepatotoxicity
  3. Ototoxicity
  4. Gastric distress
47
Q

What are the adverse effects when taking tetracyclines/glycylcyclines?

A

PCGS

  1. Phototoxicity
  2. Calcium deposition
  3. Gastric discomfort
  4. Superinfection - thrush
48
Q

Macrolides induce CYP450 enzymes.

True/False?

A

False

Macrolides inhibity CYP450 enzymes

48
Q

What are the 3 macrolides?

A
  1. Erythromycin
  2. Clarithromycin
  3. Azithromycin
49
Q

How are macrolides excreted?

A

Erythromycin & Clarithromycin metabolised hepatically and excreted in bile

Azithromycin eliminated largely unchanged in faeces

49
Q

What are the 2 protein synthesis inhibitors that are safe for use in pregnancy?

A
  1. Macrolides
  2. Clindamycin
50
Q

What antibiotic has cross-resistance with macrolides?

A

Clindamycin

51
Q

What is the spectrum of coverage of clindamycin?

A

Mostly gram-positive organisms & anaerobic infections

52
Q

What is the main indication of clindamycin?

A

Serious/severe anaerobic infections

53
Q

What is the route of administration of clindamycin?

A

Oral/IV/topically

54
Q

How is clindamycin eliminated?

A

Hepatically

55
Q

How is CSF penetration of clindamycin?

A

Poor

56
Q

What is the mechanism of action of clindamycin?

A

Binds to the 50S subunit of the bacterial ribosome, inhibiting protein synthesis

57
Q

Why do clindamycin & macrolides exhibit cross-resistance?

A

They both act at sites of proximity

58
Q

What are the 2 main methods of resistance towards macrolides?

A
  1. ERM gene expression
  2. Efflux pumps
59
Q

What are the adverse effects when taking clindamycin?

A
  1. CDAD
  2. GI effects
60
Q

What is the mechanism of action of linezolid?

A

Binds to the bacteria 23S ribosomal RNA of the 50S subunit, preventing the formation of the initiation complex and hence inhibiting protein synthesis

61
Q

What is the spectrum of coverage of linezolid?

A

Only gram-positive organisms

62
Q

What is linezolid route of administration?

A

Oral/IV

63
Q

How is the CSF penetration of linezolid?

A

Good

64
Q

What is linezolid effective against?

A

Gram-positive strains that are resistant to other agents (MRSA, VRE, VRSA, MDR streps)

65
Q

What are the adverse effects when taking linezolid?

A
  1. GI symptoms
  2. Bone marrow suppression
  3. Seratonin syndrome - due to MAO inhibition
  4. Irreversible peripheral neuropathies & optic neuritis
66
Q

What kinds of food and medications should be avoided with linezolids?

A
  1. Tyramine-containing foods
  2. Serotonergic drugs
67
Q

Is linezolid indicated in treatment of catheter-related bloodstream infections?

A

No

Anti-microbes (9 decks)

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