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Oxazolidinones Flashcards

1
Q

Linezolid structure

A

incorporation of piperazine moiety into basic structure; has 3 rings: hexene with F, 5 membered with N and O inside ring, and 6 membered with N and O inside ring

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2
Q

Linezolid has increased activity due to

A

hydroxyacetyl group to heterocyclic nitrogen on 5 membered ring and fluorine

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3
Q

Linezolid MOA

A

acts as a protein synthesis inhibitor by binding to the V-domain of the 23S RNA component of the 50S ribosomal unit

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4
Q

Linezolid is bactericidal/bacteriostatic

A

bacteriostatic

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5
Q

Linezolid spectrum coverage

A

GRAM + ONLY
dark purple: streptococcus, s. pnuemoniae, viridans, MSSA, MRSA, e, faecalis, e. faecium, VRE
anaerobes: gram +
Misc: mycobacterium tuberculosis, other mycobacterium, nocardia, actinomycetes

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6
Q

Linezolid oral absorption

A

100% IV:PO

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7
Q

Linezolid 1/2 life

A

5 hours so long

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8
Q

Linezolid elimination

A

30-40% renal

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9
Q

Linezolid PK/PD parameters

A

T>MIC, AUC:MIC

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10
Q

Linezolid needs/doesnt need renal adjustment

A

does not

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11
Q

Linezolid CSF penetration

A

good!

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12
Q

Linezolid dosing

A

600mg IV or PO q12 hours

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13
Q

Linezolid adverse effects

A 
hematologic toxicities 
thrombocytopenia (mostly with treatment > 2 weeks)
anemia
weekly CBC
optic neuritis (prolonged use)
peripheral neuropathy (prolonged use)
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14
Q

Linezolid drug interactions

A

does not interact with CYP450s

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15
Q

Linezolid is metabolized by

A

oxidation

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16
Q

Linezolid is a weak, non-selective _____

A

monoamine oxidase inhibitor

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17
Q

What is commonly seen with Linezolid?

A

serotonin syndrome due to excess serotonin in the CNS

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18
Q

signs/symptoms of serotonin syndrome

A 
mental status change
agitation
myoclonus
hyperreflexia
diaphoresis
shivering
tremor
diarrhea
incoordination
fever
19
Q

When does serotonin syndrome develop

A

within 6 hours of initiation of medication of a change in medication that increases serotonin levels

20
Q

There is no _____ SSRI

21
Q

How long does micromedex suggest to wait after discontinuing Effexor or citalopram before taking Linezolid?

A

14 days; 5 weeks with prozac

22
Q

____ outweighs ___ of initiating treatment for infection

A

benefit; risks

23
Q

Linezolid resistance

A

mutation of 23S rRNA
horizontal acquisition of chloramphenicol-florfenicol resistance gene (cfr)
alterations in ribosomal proteins

24
Q

Tedizolid is a

A

novel oxazolidinone prodrug

25
Q

Tedizolid maintains activity against

A

cfr positive strains

26
Q

Tedizolid MOA

A

inhibition of bacterial synthesis by binding to 23S ribosomal RNA of the 50S subunit this prevents the formation of 70S ribosomal initiation complex therefor preventing translation of proteins

27
Q

Tedizolid is bactericidal/bacteriostatic

A

bacteriostatic

28
Q

Tedizolid oral absorption

A

very good 91% IV:PO

29
Q

Tedizolid 1/2 life

A

12 hours very long

30
Q

Tedizolid elimination

A

18% renal, 3% unchanged

31
Q

PK/PD for Tedizolid

32
Q

Tedizolid does/does not need renal adjustment

33
Q

Tedizolid dosing IV

A

QD; 1 hour infusion time x 6d

34
Q

Tedizolid dosing PO

35
Q

Tedizolid spectrum

A

more potent than linezolid against all staphylococci, streptococci, enterococci, MRSA, VISA, VRSA
has activity against linezolid resistant MRSA

36
Q

Tedizolid drug interactions

A

low potential for drug interactions with CYPs

  • weaker reversible inhibition of MAOIs compared to linezolid
  • lower potential to interact with serotonergic agents, MAOIs, and tyramine containing foods
37
Q

How is Tedizolid excreted from the liver?

A

as an inactive, non-circulating sulfate

38
Q

Tedizolid adverse effects

A

peripheral neuropathy and optic nerve disorders

less thrombocytopenia than linezolid

39
Q

Tedizolid resistance

A

mutations in chromosomal genes encoding 23S rRNA or ribosomal proteins

40
Q

Tedizolid retains activity against

A

vancomycin-resistant enterococci and linezolid resistant MRSA that have cfr gene

41
Q

Tedizolid indications

A 
bacteremia
pneumonia
osteomyelitis
skin and soft tissue infections
meningitis
42
Q

Cleavage of which of the following features improves the susceptibility of Tedizolid against resistant bacteria?

a. fluorination in ring B
b. hydroxymethyl group
c. d-ring
d. phosphate group

43
Q

Does Tedizolid have lower risk of serotonin syndrome compared to linezolid?

A

possibly, phase III studies excluded patients on serotonergic agents

44
Q

Which of the following adverse reactions would you be most concerned with a patient taking linezolid 600mg po q12hr for 5 days?

a. thrombocytopenia
b. optic neuritis
c. peripheral neuropathy
d. none

A

d because thrombocytopenia usually after 2 weeks and peripheral neuropathy and optic neuritis usually after 28 days

PC2 (18 decks)

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