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PR3151 > Protein Synthesis Inhibitors > Flashcards

Protein Synthesis Inhibitors Flashcards

1
Q

What do the protein synthesis inhibitors act on?

A

30S, 50S Ribosomal subunits

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2
Q

What class of drugs are used against 30S?

A

Tetracyclines, glycylcycline, aminoglcosides

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3
Q

How does tetracycline work?

A

Tetracyclines concentrate intracellularly and bind irreversibly to 30S subunit of bacteria ribosome, prevent binding of tRNA to the A site of the mRNA-ribosome complex, thus inhibiting protein synthesis

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4
Q

What to avoid when taking tetracyclines?

A

Food(best on empty stomach)
Dairy products containing calcium –> decrease absorption and F

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5
Q

Can pregnant women take tetracyclines?

A

No.

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6
Q

What does tetracyclines bind to during distribution?

A

Tissues undergoing calcification
(Bones/teeth)

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7
Q

How is CSF penetration for tetracyclines?

A

Moderate
(More for mino and doxycycline)

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8
Q

Can tetracyclines be taken with beta-lactams?

A

No. Avoid administering both

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9
Q

Is tetracyclines effectuve against Pseudomonas?

A

No

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10
Q

Which tetracyclines be used against MRSA?

A

Doxycycline

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11
Q

How are tetracyclines administered?

A

Orally

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12
Q

What does tetracycline cover?

A

Gram negative and positive(MRSA)
- Rickettsia
- Chlamydia
- Mycoplasma
- Vibrio cholerae
- Yersinia Pestis

  • S pneumoniae
  • Bacillus anthracis
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13
Q

What can treat acne too?

A

Doxycycline,minocycline

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14
Q

How are the tetracyclines excreted?

A

Tetracycline: R
Doxycycline: unchanged in bile n urine
Minocycline: Liver

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15
Q

Name a glycylcycline

A

Tigecycline

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16
Q

Why are glycylcycline developed?

A

Overcome resistance from efflux pumps and/or ribosomal protection with a stringer affinity to active site of 30S, blocking entry of transfer RNA

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17
Q

How is tigecycline administered?

A

IV, poor oral F

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18
Q

Is it good for bloodstream infections?

A

No

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19
Q

How is tigecycline excreted

A

Bile/fecal

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20
Q

When is dose adjustment for tigecycline needed?

A

Hepatic impairment, no need for renal impairment

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21
Q

What is tigecycline used for?

A
  1. MRSA
  2. multi-drug resistant streptococci
  3. Vancomycin-resistant enterococci (VRE)
  4. Extended spectrum beta-lactamase(ESBL) gram negative bacteria, resistant to carbepenem
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22
Q

Can tigecycline be used against Pseudomonas?

A

No.

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23
Q

ADR of tigecycline

A
  1. GI discomfort (take on empty stomach)
  2. Discolouration of teeth stunt growth
  3. Hepatotoxicity
  4. Phototoxicity (use sunscreen)
  5. Vestibular dysfunction: dizzyness, vertigo, tinnitus more for minocycline.
  6. Renal SE
  7. Superinfection for prolonged use (CDAD >2m)
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24
Q

CI of tetracyclines/tigecycline

A

Pregnant women, children <8yo
Oral Sulfonylurea

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25
Q

How does aminoglycosides work?

A

Aminoglycoside diffuse through aqueous porin channels for gram-negative bacteria and transport across inner membrane via active transport(can be inhibited by anaerobic conditions, drop in pH and hyperosmolarit)

Aminoglycosides distorts ribosome structure by binding to them and 1. blocking formation of initiation complex
2. Causing misreading of codons as wrong amino acyl tRNA are able to bind to A site without matching codon present in mRNA in that position
3. Inhibit translocation

26
Q

Aminoglycosides has a synergistic effect with _____________ against ___________ though they work primarily against ______

A

Cell wall synthesis inhibitors

Gram positive bacteria

Aerobic gram negative bacteria and mycobacteria

27
Q

Aminoglycosides has a _______-dependent killing

A

Concentration

28
Q

Administration of aminoglycosides

A

Mainly Parenteral (except neomycin), poor oral F due to polar

29
Q

Can Aminoglycosides be used for CSF infections?

A

No

30
Q

Excretion of aminoglycosides

A

Renal

31
Q

Name 5 aminoglycosides

A
  1. Gentamicin
  2. Tobramycin
  3. Amikacin
  4. Streptomycin
  5. Neomycin
32
Q

What does aminoglycosides cover?

A

Gram negatives
- Klebsiella
- Escherichia coli
- Pseudomonas
- Acinetobacter
- 2nd line for tuberculosis

33
Q

What has the widest range among aminoglycosides?

A

Amikacin IM/IV/IT

34
Q

______ is used with _____ to treat enterobacteriaceae (Klebsiella, Proteus) + enterococcal endocarditis

A

Gentamicin/streptomycin

Penicillin/ceftriaxone

35
Q

What aminoglycoside can be used against Pseudomonas?

A

Tobramycin, Amikacin

36
Q

Which aminoglycosides is most toxic?

A

Neomycin (oral and topical)

37
Q

What is applied topically for bowel prep for surgery?

A

Neomycin

38
Q

CI for neomycin

A

Intestinal obstruction, gastric/ intestinal ulcer, hx of Aminoglycoside hypersensitivity

39
Q

Excretion for aminoglycosides

A

Renal except neomycin(faeces)

40
Q

What is amikacin ineffective against?

A

Anaerobic gram positive strains

41
Q

What is streptomycin ineffective against?

A

Aerobic GNR

42
Q

ADR of Aminoglycosides

A
  1. Ototoxicity
  2. Nephrotoxicity
  3. Neuromuscular paralysis
  4. Hypersensitivity rxns: rash, contact Dermatitis
  5. CI: Pregnancy, <8yo
43
Q

Monitoring for aminoglycosides

A

Renal, hearing, myasthenia gravis
- avoid use with other nephrotoxic drugs (Amphotericin B, Vancomycin, NSAIDs and neuromuscular blocking agents)
- TDM, RFT (Urea, creatinine, electrolytes)

44
Q

6 amiNOglycosides

A

NO protein synthesis
mainly aerobic gram Negative Organisms
NO use in pregnancy
NO oral administration
NO CSF pentration
Nephro and Ototoxicity

45
Q

Factors tt predispose to Nephro/ototoxicity

A
  1. Dose
  2. Duration >5d
  3. Concomitant nephrotoxic drugs
  4. Age (renal function)
  5. Genetic
46
Q

Mechanisms of resistance against aminoglycosides

A
  1. Increased efflux pumps
  2. Aminoglycoside inactivating enzyme production
  3. Altered 30S
  4. Inhibition of Aminoglycoside uptake
47
Q

What classes of drugs are used for protein synthesis inhibition of 50S?

A

Macrolides
Lincosamide - Clindamycin
Oxazolidinones - Linezolid

48
Q

Macrolides MOA

A

inhibit 50S ribosomal subunit, inhibiting translocation step such that peptide chain is unable to move to P site

49
Q

Name 3 macrolides

A
  1. Erythromycin
  2. Clarithromycin
  3. Azithromycin
50
Q

Cns penetration of macrolides?

A

Poor

51
Q

Macrolides are effective against?

A

Atypicals,
Substitute for penicillin allergy

52
Q

Mocrolide clearance

A

Ec - hepatic
A - biliary,excretion, unchanged in faeces

53
Q

ADR of macrolides

A
  1. GI
  2. Hepatotoxicity
  3. Ototoxicity
  4. QTc prolongation
  5. ddi - cyp450 inhibitor
54
Q

Clindamycin MOA

A

Binds to 50s subunit, inhibit p synthesis,

Antagonistic effect with macrolides (cross resistance)

55
Q

Clindamycin is effective against?

A

MRSA
Streptococcus
PR anaerobic bacteria (bacteroides, clostridioides perfringen)

56
Q

Entry into CNS for clindamycin

A

Poor

57
Q

ADR clindamycin

A
  1. Esophageal irritation - take with a glass of water
  2. GI DV
  3. CDAD
58
Q

Resistance to clindamycin

A

Altered 50s by aa substitution
Alterations in 23s by methylation and nucleotidylation of hydroxyl grp of clindamycin

59
Q

Linezolid covers?

A

Gram positive bacteria

60
Q

Moa of linezolid

A

Binds to 23s ribosomal rna of 50s and prevents 70s initiation complex

61
Q

Cautions in linezolid

A

DNU within 2w of MAOI
Avoid tyrosine containing food and serotonergic drugs –> hypertensive crisis

PR3151 (12 decks)

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