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Y2 Pharmaco > Macrolides, Clindamycin & Linezolids > Flashcards

Macrolides, Clindamycin & Linezolids Flashcards

1
Q

Name the 3 Macrolides.

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

Name the ABs that can potentially cause Ototoxicity.

A
  1. Aminoglycosides
  2. Vancomycins
  3. Macrolides
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3
Q

[T/F] Macrolides are bacteriocidal.

A

F.
- bacteriostatic, arrests growth of bacteria only
- does not kill/dip the population

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4
Q

How are Macrolides administered?

A

Oral & Parentral administration avail.

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5
Q

What are Macrolides often indicated for.

A

Atypical microbes.
- legionella, chlamydia, mycoplasma

Also indicated for: RTIs, CAP

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6
Q

How are Macrolides cleared & excreted?

A

Metabolised hepatically, excreted primarily via bile

  • pxs w hepatic dysfunction => treat cautiously
  • like most 50S ribosomal subunit targeting ABs (macrolides & clindamycins)
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7
Q

[T/F] Clarithromycin & Azithromycin have a higher activity against atypical bacteria than Erythromycin.

A

True.

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8
Q

[T/F] Macrolides are a good alternative to B lactams & Vancomycins

A

Yes. In cases of px w renal impairment esp

  • cuz b lactams & vancomycins are cleared renally + vancomycins are nephrotoxic
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9
Q

Main issue in Macrolides (Adverse effects)

A

GI distress & motility
- may lead to poor px compliance
- most severe in Erythromycin
- thus, Clarithromycin & Azithromycin modified to cause less GI distress

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10
Q

Briefly list the Adverse effects of Macrolides.

A
  1. GI distress & motility
  2. Hepatotoxicity
  3. Ototoxicity (deafness)
  4. Prolongation of QT interval => caution in pxs w pro-arrhythmic conditions
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11
Q

Can Macrolides be used in pregnancy?

A
  • on par w beta lactams, aka can be given as alternative to penicillin in indivs w b-lactam allergy
  • crosses placenta
  • clearance rate in pregnancy is faster in late pregancy

Erythromycin & Azithromycin => cat B
Clarithromycin => cat C

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12
Q

Clindamycin is primarily used to treat..

A

Anaerobic infections

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13
Q

Why do Clindamycins have cross-resistance w Macrolides?

A
  • likely due to ‘erm genes’ + that the 2 act at sites of proximity
  • clindamycin n erythromycin not structurally related but act at sites of proximity
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14
Q

Clindamycins and Macrolides not given together. Why?

A
  • they act at sites of proximity => can antagonise each others action
  • note: they are not structurally related despite acting on sites of proximity
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15
Q

Which drug has the highest risk of causing CDAD?

A

Clindamycin.
- cuz clostridium is a gram pos anaerobe that is not covered by clindamycin (always)
- despite clindamycin having large gram +ve & anaerobe coverage

** thus, clindamycin contraindicated in pxs w pseudomembranous colitis or ulcerative colitis

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16
Q

Clindamycin has good coverage against..

A
  1. Gram +ves
  2. Anaerobes e.g. bacteroides, clostridiodes perfringen

Primarily: 1. MRSA 2. Streptococcus 3. Anaerobes 4. Penicillin resistant anaerobic bacteria

17
Q

What is resistant against Clindamycin?

A

Almost all aerobic Gram neg bacteria are resistant

  • rmb clindamycin got larger gram pos & anaerobic coverage!
18
Q

[T/F] Clindamycins have good spectrum of activity against oral pathogens

A

True.

  • excellent alt to penicillin for tx of dental abscesses cuz of bacterial susceptibility to the drug
  • great oral absorption + low emergence of bacterial resistance & good AB levels in bone
  • oral infections often due to anaerobes
19
Q

[T/F] Clindamycins often used for prophylaxis against endocarditis.

A

True.
- endocarditis prophylaxis prior to dental procedures
- in pxs w acquired valvular damage, congenital heart disease, valve replacements & cardiomyopathy
- but not for wisdom tooth surgery or joint replacement pxs

20
Q

Name the ABs that have MRSA coverage.

A
  1. Clindamycins
  2. 5th gen cephalosporin: Ceftaroline (only B lactam w MRSA converage)
  3. Vancomycins
  4. Tetracyclines
  5. Cotrimoxazole (fluoroquinolones no longer used against staphs due to resistance)
  6. Linezolid
21
Q

Distribution of Clindamycin:

A
  • excellent bone & salivary gland penetration
  • well distribution into body fluids & bone
  • poor entry to CSF
22
Q

Can Clindamycin be used during pregnancy?

A

Yes. Cat B

23
Q

Brief adverse effects of clindamycin?

A
  1. Take w full glass of water to reduce esophageal irritation
  2. Skin rashes
  3. CDAD
    - most likely AB to cause CDAD
    - C. Difficile always resistant to clindamycin
    - contraindicated in pxs w pseudomembranous colitis or ulcerative colitis
24
Q

Why is Clindamycin a substitute for Macrolide resistant strains?

A

Clindamycin is not a substrate for macrolide efflux pumps

25
Q

What are some ABs that only cover gram +ve bac?

A
  1. Linezolid
  2. Vancomycin
  3. P2: penicillinase-resistant penicillins
26
Q

Use of Linezolid is restricted as it has coverage over strains that are resistant to other agents. Which are these specific strains?

A
  1. Penicillin-resistant strains of S. Pneumoniae
  2. Methicillin-resistant staph (MRSA)
  3. Vancomycin intermediate staph
  4. Vancomycin-resistant strains of staph (VRSA)
  5. Vancomycin-resistant strains of enterococci (VRE)

(MRSA, VRE, VRSA)

27
Q

Coverage/Antimicrobial activity of Linezolid?

A

Gram +ve organisms
- staphylococci
- streptococci
- enterococci
- listeria monocytogenes

+ including all the super resistant strains (MRSA, VRE, VRSA)

28
Q

What bacteria are intrinsically resistant to Linezolid?

A

Gram-negative infections
- gram -ve pathogenic bacteria => intrinsically resistant due to efflux pumps that force linezolid out of the cell faster than it can accumulate

29
Q

Administration of Linezolid?

A

Oral or IV
- excellent oral bioavailibility

30
Q

Distribution of Linezolid.

A
  • well distributed through body
  • good penetration into CSF
31
Q

Clearance and excreted of Linezolid?

A
  • broken down by nonenzymatic oxidation to two inactive metabolites
  • approx 80% of dose appears in urine
  • no dose adjustments req in renal or hepatic dysfunction
32
Q

Brief adverse effects of Linezolid

A
  1. Bone marrow suppression
    - need to monitor blood counts
    - as thrombocytopenia has been reported in patients taking the drug for longer than 10 days
  2. GI effects
  3. Serotonin syndrome
    - due to monoamine oxidase inhibitor
  4. Irreversible peripheral neuropathies & optic neuritis
  5. Tongue & teeth discolouration (reversible on finishing therapy)
33
Q

Contraindications of Linezolid

A
  1. Catheter-related bloodstream infections
  2. Do not use within 2 weeks of MAO inhibitors e.g. phenelzine
  3. Avoid theramine-containing foods & serotonergic drugs -> may precipitate hypertensive crisis
    - e.g. aged cheese, cured/smoked meats, draft beer
34
Q

Why cant Linezolids be used w catheter related bloodstream infections?

A
  • such pxs treated w linezolid => higher chance of death
  • catheter related infections often caused by gram neg bacteria
  • pxs w gram neg infections or mixed(+ve & -ve) infections have higher mortality when treated w linezolid
35
Q

Name the ABs that target the 50S ribosomal subunit, inhibiting protein synthesis.

A
  1. Macrolides
    - penicillin substitute, effective against atypical microbes
  2. Clindamycins
    - mostly +ves, anaerobes, MRSA, streptococcus
  3. Linezolids
    - unique mech: binds specifically to 23S ribosomal RNA of 50S subunit
    - reserved class like carbapenems
36
Q

CNS penetration of Macrolides?

A

Poor

37
Q

Resistance of Macrolides occurs due to

A
  • acquisition of erm genes => results in reduced binding of macrolides to 50S ribosomal subunit
  • not used as first line drugs in odontogenic infections due to resistance (higher prevalence of resistance to macrolides in anaerobic streptococci, viridans grp streptococci
38
Q

Clindamycin is metabolised and excreted via?

A

Hepatic, extensive oxidative metabolism at the liver to inactive products

  • excreted as bioinactive metabolites

Y2 Pharmaco (22 decks)

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