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PROTEIN SYNTHESIS INHIBITORS Flashcards

1
Q

Commonly used antibiotics can be classified into 7 major antibiotic classes. What are they?

A

Fluoroquinolones
Tetracyclines
Glycopeptides
Beta Lactams
Aminoglycosides
Macrolides
Metronidazole

(FTG BAMM)

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2
Q

Which antibiotics inhibit 30S ribosomal units?

A

Aminoglycosides
Tetracycline

(AT)

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3
Q

Which antibiotics inhibit 50S ribosomal units?

A

Clindamycin
Amphenicols
Macrolides

(CAM)

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4
Q

Aminoglycosides are generally effective against aerobic Gram negative bacteria. T or F

A

True

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5
Q

What are the routes of administration of AGs

A

IM or IV except oral neomycin given before surgery which is not absorbed

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6
Q

What are AGs co-administered with?

A

Cell-wall synthesis inhibitors

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7
Q

Do AGs work reversibly or irreversibly?

A

Irreversibly

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8
Q

AGs are used to treat what?

A

Pneumonia, MRSA, Endocarditis, some +G bacteria (Upper Respiratory Tract Procedures), Bacteremia, Sepsis, Topical skin infections, UTIs

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9
Q

What are the side effects of AGs?

A
  1. Ototoxicity (rev. vestibular, irrev. auditory)
  2. Nephrotoxicity (rev)
  3. Neuromuscular junction blockade
  4. Pregnancy Cat C (8th nerve)
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10
Q

Are aminoglycosides bacteriostatic or bacteriocidal?

A

Bacteriocidal

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11
Q

Are AGs O2 dependent or not?

A

They are O2 dependent

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12
Q

AGs is gotten from which organism?

A

Actinomycetes – Streptomyces griseus

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13
Q

What was the first AG?

A

Streptomycin – 1944

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14
Q

List the naturally occuring aminoglycosides

A

Streptomycin
Neomycin
Kanamycin
Tobramycin
Gentamicin

(So Noah Killed The Goat?)

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15
Q

What AGs are semisynthetic derivatives?

A

Semisynthetic derivatives:
Amikacin (from Kanamycin)
Netilmicin (from Sisomicin)

(Amy, Can Neti See Sio?)

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16
Q

Name the characteristics of AGs

A

All are sulfate salts which are highly water soluble;
Solutions are stable for months
They ionize in solution are not absorbed orally,
Distribute only extracellularly,
Do not penetrate brain or csf.
More active in alkaline ph.

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17
Q

In the structure of AGs, ___ are joined to ___ by ____?

A

Two amino sugars joined to a non sugar aminocyclitol by –o- glycosidic bond.

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18
Q

In majority of aminoglycosides the aminocyclitol or non sugar moeity is _____.
However in streptomycin, the aminocyclitol is _____ which is not placed centrally as in other aminoglycosides.

A

2-deoxystrepamine, streptidine

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19
Q

In the streptomycin structure, the combination of streptose amino sugar and N-Methyl-L glucosamine amino sugar is called?

A

Streptobiosamine

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20
Q

List the systemic AGs

A

Streptomycin
Gentamicin
Kanamycin
Amikacin
Sisomicin
Tobramicin
Netilimicin

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21
Q

What are the topical AGs?

A

Neomycin
Framycetin

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22
Q

What are the 3 ways by with AGs inhibit protein synthesis is 30S ribosomes?

A
  1. Blocks protein synthesis at the initiation complex stage
  2. Mis-coding of RNA occurs, with production of nonfunctional or toxic proteins
  3. Break up of polysomes into nonfunctional monosomes.
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23
Q

What -G aerobes are AGs active against?

A

Enterobacteriaceae;
Proteus sp., Pseudomonas aeruginosa
E. coli, Enterobacter sp.
Klebsiella
Shigella

(SP²E²K)

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24
Q

What +G aerobes are AGs active against?

A

(Usually in combination with ß-lactams)

  1. S. aureus and coagulase-negative staphylococci
  2. Viridans streptococci
  3. Enterococcus sp. (gentamicin)
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25
Q

AGs are slightly polar basic drugs. T or F

A

F. They are highly polar basic drugs

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26
Q

AGs are mostly administered as injections because?

A

They have poor oral bioavailability

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27
Q

AGs are poorly distributed and poorly protein bound. T or F.

A

True

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28
Q

Why can the unchanged drug (AGs) be seen in urine?

A

AGs do not undergo any significant metabolism.

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29
Q

Nearly all oral dose is excreted unchanged in urine. T or F

A

F. Nearly all IV dose is excreted unchanged in urine

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30
Q

How do you measure AG dose for people with renal insufficiency.

A

Renal dose = Normal therapeutic dose / Sr creatinine value (mg/dl)

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31
Q

What is the Cockroft-Gault equation?

A

Cockroft gault formula: CrCl (Creatinine Clearance) = (140-age) x weight (kg) / (sCr x 72)

– For females multiply above value by 0.85

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32
Q

What is the formula for a corrected dose for a case of renal insufficiency?

A

Corrected dose = Normal dose x pt CrCl / Normal CrCl

https://medicalguidelines.msf.org/en/viewport/TUB/english/appendix-12-dose-adjustments-in-renal-insufficiency-20324400.html - for solved examples

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33
Q

How do AGs cause nephrotoxicity?

A

By direct proximal tubular damage - reversible if caught early

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34
Q

What are the risk factors for nephrotoxicity due to AGs?

A

Risk factors: High troughs, prolonged duration of therapy, underlying renal dysfunction, concomitant nephrotoxins

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35
Q

How do AGs cause ototoxicity?

A

8th cranial nerve damage – irreversible vestibular and auditory toxicity

Vestibular: dizziness, vertigo, ataxia
Auditory: tinnitus, decreased hearing

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36
Q

When do AGs cause neuromuscular paralysis?

A

Can occur after rapid IV infusion especially with;
Myasthenia gravis or
Concurrent use of succinylcholine during anaesthesia

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37
Q

When steps should be taken to avoid AG toxicity?

A
  1. Levels need to be monitored to prevent toxicity due to high serum levels
  2. To be avoided where risk factors for renal damage exist e.g Dehydration, Renal toxic drugs
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38
Q

What is the most important mechanism of resistance to AGs?

A

Inactivation by Aminoglycoside modifying enzymes

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39
Q

What are the 3 mechanisms of resistance to AGs?

A
  1. Enzymatic modification (phosphorylation, acetylation & adenylation of aminoglycosides); plasmid mediated
  2. Decreased drug uptake (efflux pumps)
  3. Target site modification (16S rRNA methylation decreases binding affinity)
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39
Q

Aminoglycosides should be given as a large single dose for a successful therapeutic outcome. T or F

A

True

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40
Q

Multiple small doses will lead to treatment failure and likely to lead to renal toxicity. T or F

A

True

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41
Q

Avoid use in liver failure but safe in renal failure. T or F

A

False.

Avoid use in renal failure but safe in liver failure

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41
Q

With Streptomycin, ribosomal resistance develops slow. T or F

A

False.

Ribosomal resistance develops fast

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42
Q

Streptomycin has limited usefulness as single agent. T or F

A

True

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43
Q

Streptomycin is used to treat ___, ___, ____, in combination with _____

A

Plague, tularemia and brucellosis – In combination with tetracycline

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44
Q

Streptomycin is used to treat ____, caused by S. viridans and S. faecalis with ____, but ____ is preferred.

A

SABE (Sub acute Bacterial endocarditis): due to Streptococcus Viridans & faecalis – With penicillin but gentamicin preferred

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45
Q

Streptomycin is comes in what dosage form?

A

Sterile dry powder or in sterile solution, 400 or 500mg/ml. i/m injection

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46
Q

Streptomycin injection may result in?

A

Usually painful, hot tender masses.

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47
Q

What is the standard dosage of streptomycin?

A

1g to 2g (15 to 25mg/kg)/day in 2 divided doses 7 to 10/7.

Up to 6 months in TB

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48
Q

Gentamicin is obtained from?

A

Micromonospora purpurea

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49
Q

Gentamicin is the least used aminoglycoside. T or F

A

F. Most commonly used aminoglycoside

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50
Q

Gentamicin is less potent than Streptomycin. T or F

A

F. More potent than Streptomycin

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51
Q

Gentamicin has a broader spectrum which includes what organisms?

A

Pseudomonas, proteus, E.coli, klebsiella, enterobacter, serratia

SP²E²K

52
Q

Gentamicin has low cost, reliability of use, short experience. T or F

A

F. Low cost, reliability of use, long experience

53
Q

Gentamycin acts synergistically with what antibiotics?

A

Acts synergistically with ampicillin, penicillin G, Ticarcillin, ceftriaxone, Vancomycin

PAT the VC

54
Q

Gentamycin is ineffective against M.tuberculosis. T or F

55
Q

Gentamycin is relatively less nephrotoxic. T or F

A

F. Relatively more nephrotoxic

56
Q

Gentamycin use restricted to serious Gm -ve bacillary infections. T or F

57
Q

Gentamycin is used with ____ to treat septicaemia, sepsis, fever in immunocompromised patients

A

Used with penicillins

58
Q

Gentamycin is used with metronidazole to treat ___

A

Pelvic infections

59
Q

Gentamycin is used to treat SABE with ___

A

Penicillin G, ampicillin or vancomycin

60
Q

Gentamycin is used to treat Coliform infection with _____

A

ampicillin or ceftriaxone

61
Q

Gentamycin is used to treat pseudomonal infections with ______

A

Ticarcillin

62
Q

Gentamycin is used to treat meningitis by Gm -ve bacilli with _____

A

Third generation cephalosporin alone or with gentamicin

63
Q

Gentamycin SO4 vials & prefilled syringes come in what concentrations?

A

40mg/ml, 10mg/ml 240 or 280mg/2ml.

64
Q

Gentamycin comes in what dosage forms?

A

Ointment, cream, ophthalmic preparations.

65
Q

What is the appropriate dose of gentamycin for neonates?

A

6mg/kg dly ÷2 equally spaced injections for neonates with severe infections.

66
Q

State the guideline for adjustment of dose in renal insufficiency.

A

If Creatinine clearance (ml/min): 25<x<100, %maximal daily dosing: 25<x<100, Frequency of dosing = Every 24 hours

If Creatinine clearance (ml/min): 10-20, %maximal daily dosing: 40, 60, 80, Frequency of dosing = Every 48 hours

67
Q

Tobramycin is identical to gentamicin and used interchangeably. T or F

68
Q

Why can tobramycin be used in the treatment of bacteremia, osteomyelitis & pneumonia.

A

Tobramycin is superior against pseudomonas and proteus infections

69
Q

Tobramycin is less potent on pseudomonas and hemolytic streptococci. T or F

A

False. Tobramycin is more potent on pseudomonas and -hemolytic streptococci

70
Q

Tobramycin’s ototoxicty and nephrotoxicity is probably lower than Sisomicin. T or F

71
Q

Which aminoglycoside has the highest nephrotoxicity?

A

neomycin > gentamicin ≥ tobramycin ≥ amikacin ≥ netilmicin > streptomycin

72
Q

Amikacin is the ____ toxic semisynthetic derivative of _____

A

more, kanamycin

73
Q

Which aminoglycoside has the broadest antimicrobial activity?

74
Q

Which AG is used in hospitals where gentamicin and tobramycin resistant microorganisms are prevalent.

75
Q

Why can amikacin be used when there is resistance to aminoglycoside

A

It makes use of inactivating enzymes.

The 1-N-AHBA group of amikacin has been reported to prevent inactivation in remote susceptible groups.

76
Q

What is the dose of amikacin?

A

15mg/kg/day in 1-3 doses

77
Q

Which AG has the same uses as gentamycin, is the reserved drug for hospital acquired Gm -ve bacillary infections and is used to treat multidrug resistant TB along with other drugs

78
Q

Netilimicin is the semisynthetic derivative of ______

79
Q

Netilimicin is very resistant to aminoglycoside inactivating enzymes. T or F

A

False. Relatively resistant to aminoglycoside inactivating enzymes

80
Q

Netilimicin is more active against klebsiella, enterobacter, staphylococci and pseudomonas aeruginosa. T or F

A

False.

More active against klebsiella, enterobacter & staphylococci

Less active against pseudomonas aeruginosa

81
Q

Why can Netilimicin be used in place of gentamicin?

A

It is not metabolized by majority of the aminoglycoside – metabolizing enzymes and may be active against bacteria that are resistant to gentamicin.

82
Q

Neomycin has a wide spectrum against Gm -ve cocci and some gm +ve bacilli. T or F

A

False. Neomycin has a wide spectrum against Gm -ve bacilli and some gm +ve cocci

83
Q

Pseudomonas and strep. pyogenes not sensitive to neomycin. T or F

84
Q

Which AG is limited to topical use?

85
Q

Neomycin is topically used in skin, eye and external ear infections combined with ______ or ______ to widen antibacterial spectrum and to prevent emergence of resistant strains

A

bacitracin or polymyxin-B

86
Q

Neomycin is used for bladder irrigation along with _____

A

polymyxin B

87
Q

What is the dose for oral neomycin?

A

Preparation of bowel before surgery 1 gm TDS

88
Q

How does neomycin help in hepatic coma?

A

Suppresses ammonia forming coliforms and prevents encephalopathy (Lactulose more preferred)

89
Q

Kanamycin is used in TB. T or F

90
Q

Kanamycin is used in combination when microorganisms are resistant to the more commonly used agents. T or F

91
Q

Kanamycin involves administration of large doses with risk of ototoxicity & nephrotoxicity. T or F

92
Q

Why is Framycetin very similar to neomycin?

A

It is too toxic for systemic administration. So, it is used topically on skin, eye and ear.

93
Q

Tetracycline is obtained from?

A

Soil actinimycetes.

94
Q

Tetracyclines is broad spectrum antibiotic having four cyclic ring nucleus. T or F

95
Q

Tetracycliines have a hydronaphthacene nucleus containing four fused rings. T or F

96
Q

All tetracyclines are slightly sweet solids, weakly water soluble, their hydrochlorides are less soluble. T or F

A

False. All tetracyclines are slightly bitter solids, weakly water soluble, their hydrochlorides are more soluble.

97
Q

________ is an example of a long acting tetracycline

A

Doxycycline

98
Q

________ is an example of a short acting tetracycline

A

Tetracycline

99
Q

Give 3 examples of tetracyclines available for clinical use

A

Oxytetracycline

Demeclocycline

Minocycline.

100
Q

The MOA of tetracycline is primarily _____

A

BACTERIOSTATIC

101
Q

State the 3 MOAs of tetracycline

A
  1. Inhibit protein synthesis by binding to 30s ribosome in susceptible organism.
  2. Inhibit binding of aminoacyl tRNA to the acceptor site of mRNA peptide chain fails to grow.
  3. Prevents polypeptide synthesis
102
Q

What is the mechanism of resistance of tetracycline

A
  1. Concentrating mechanism become less effective.
  2. Bacteria acquire capacity to pump tetracyclines out.
  3. Plasmid mediated synthesis of a “Protection” protein which protects the ribosomal binding site from tetracyclines.
103
Q

What is the spectrum of activity of tetracyclines?

A
  1. Gram positives: aerobic cocci (Staphylococci, Streptococci) and rods
  2. Gram negative aerobic bacteria
  3. Atypical organisms like
    Mycoplasmas, Chlamydiae, Rickettsiae, Protozoa
104
Q

Tetracyclines can be used to treat?

A

Atypical pneumonia
Cholera
Brucellosis
Plague
Rickettsial infection

105
Q

Tetracyclines is completely absorbed by g.i.t. T or F

A

False. Incompletely absorbed by g.i.t.

106
Q

Absorption of tetracyclines is better if taken in empty stomach. T or F

107
Q

Doxycycline & Minocycline are completely absorbed irrespective of food. T or F

108
Q

Tetracyclines have chelating property with potassium and other metals forms insoluble and unabsorbable complexes. T or F

A

False. Tetracyclines have chelating property with calcium and other metals forms insoluble and unabsorbable complexes.

109
Q

Milk, iron preparation, non-systemic antacids and sucralfate reduces tetracycline absorption. T or F

110
Q

Tetracyclines are concentrated in liver and spleen and bind to the connective tissue in bone and teeth. T or F

111
Q

State the degrees of protein binding in tetracyclines

A

High (Demeclocycline, Doxycycline, & Minocycline)

Moderate (Tetracycline)

Low (Oxytetracycline)

112
Q

Tetracyclines are primarily excreted in urine by?

A

Glomerular filtration

113
Q

Can breastfeeding mothers take tetracyclines?

A

No. They are secreted in milk and affect the infant.

114
Q

Give advice for use of tetracyclines.

A
  1. The capsule should be taken 1/2hr before or 2hr after food.
  2. Tetracyclines are not recommended by i.m. route. (painful & poor absorption).
  3. Topical preparation are available but should not be used because of high risk of sensitization.
115
Q

What are the adverse effects of tetracyclines?

A

Epigastric pain, nausea, vomiting and diarrhoea by their irritant property.

Oesophageal ulceration

Photosensitivity reaction

Liver damage and jaundice occurs occasionally.

Tetracyclines have chelating property and affect the teeth and bones.

116
Q

All Tetracyclines except Doxycycline accumulate and enhance renal failure. T or F

117
Q

State 5 precautions when using tetracyclines

A

Should not be used during pregnancy, lactation and in children

Should be avoided in patients on diuretics increases blood urea.

Do not mix injectable Tetracyclines with Penicillin causes inactivation.

Do not inject Tetracyclines intrathecally.

Tooth discoloration when used in pregnancy, lactation or childhood

118
Q

Tetracyclines have very good tissue penetration and their usually limited to; Skin and soft tissue infections, Chlamydia. T or F

119
Q

Name 4 macrolides you know

A

Erythromycin

Clarithromycin

Azithromycin

Telithromycin

120
Q

Macrolides are bacteriostatic. T or F

121
Q

What are the MOAs of macrolides?

A
  1. Inhibit bacterial RNA-dependent protein synthesis
  2. Bind reversibly to the 23S ribosomal RNA of the 50S ribosomal subunits
  3. Block translocation reaction of the polypeptide chain elongation
122
Q

State the spectrum of activity of macrolieds

A
  1. Gram-Positive Aerobes: Activity: Clarithromycin>Erythromycin>Azithromycin
    MSSA
    S. pneumoniae
    Beta haemolytic streptococci and viridans streptococci

Gram-Negative Aerobes:
Activity: Azithromycin>Clarithromycin>Erythromycin
H. influenzae, M. catarrhalis, Neisseria sp.

NO activity against Enterobacteriaceae

Anaerobes: upper airway anaerobes

Atypical Bacteria

123
Q

What are the mechanisms of resistance to macrolides?

A
  1. Altered target sites
    Methylation of ribosomes preventing antibiotic binding
  2. Cross-resistance occurs between all macrolides
124
Q

What can macrolides be used to treat?

A

Cellulitis/Skin and soft tissue
Beta haemolytic streptococci
Staphylococcus aureus

Intra-cellular organisms
Chlamydia
Gonococcus

125
Q

Macrolides are best used in atypical pneumonia. T or F?

126
Q

Macrolides have poor tissue and cellular penetration and are not useful in susceptible intracellular infections. T or F

A

False. Excellent tissue and cellular penetration
Very useful in susceptible intracellular infections

127
Q

Macrolides have gastrointestinal side effects (up to 33 %) especially which macrolide?

A

Erythromycin

128
Q

The macrolides are inactivated in the liver, and the major route of elimination is in the bile. T or F

PHA 411 (3 decks)

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