2: Aminoglycosides, Streptogramins, and Oxazolidinones Flashcards Preview

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Flashcards in 2: Aminoglycosides, Streptogramins, and Oxazolidinones Deck (52)
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31

what is another way you can get resistance to streptograim that involves gating the exit tunnel

mutation of A2062

32

IV synercid used to treat what

-VRE bacteremia
-MRSA skin infections
-VRE UTIs

33

resistance mechanisms for synercid

-adenine methylation of A2058 = blocks quinupristin, but no effect on dalfopristin (makes it bacteriostatic)
-efflux and enzymatic inactivation (metabolism)

34

what is streptogramin often reserved for

serious life-threatening G(+) infections

35

what will continue to result in more resistant bacterial strains to streptogramins

continued use of virginiamycin in animal feeds

36

in some patients, what has a 14d course of synercid selected for?

resistant forms of E. faecialis, E. faecium, and S. aureus

37

streptogramin side effects

no known significant toxicity
several mild side effects:
-inflammation/pain at injection site
-nausea
-diarrhea
-muscle weakness
-rash

38

why are the PK of streptogramins complicated?

different elimination rates for each component and their metabolites

39

half life of streptogramins

1.5h - linear relationship b/w dose and AUC

40

does synercid cross any barriers?

nope - not BBB or placental barriers

41

what do macrophages do to synercid?

concentrate it up to 50x the extracellular fluid concentrations

42

describe elimination of synercid

75% via biliary excretion (fecal matter)
25% via urine

43

DDI with streptogramins

inhibit CYP3A4
-potential DDI w/ warfarin, diazepam, astemizole, terfenadine, cisapride, non-nucleoside reverse transcriptase inhibitors, and cyclosporine

44

what are two oxazolidinones

linezolid and eperezolid

45

linezolid MOA

interacts with 23S rRNA of 50S with uM affinity - prevents the formation of the 70S initiation complex

46

what is linezolid used to treat

-VRE
-nosocomial pneumonia (MRSA)
-MRSA skin infections

47

why is linezolid a magic bullet

-excellent oral bioavailability
-can be given oral or IV
-half life 4-6h

48

linezolid resistance in what species

initially Enterococcus
now resistant strains of MRSA, E. coli, and others

49

linezolid mechanism of resistance

target site modification
-G2576U in peptidyl transferase center of 23S rRNA: reduced affinity of linezolid to 50S
-other sites of mutation (T2500A) in S. aureus are close to P site

50

linezolid side effects: mild, more severe, and long term

-GI: nausea/vomit/diarrhea
-headache
-tongue discoloration
-oral Candida infection (thrush)

more severe:
-thrombocytopenia
-GI bleeding
-anemia

long-term:
-fully reversible myelosuppression
-neuropathy

51

what should be monitored in linezolid therapy and how often

CBC weekly

52

DDI with linezolid

neither inhibits nor induces cyt p450

reversible, nonselective MAOi -potential to interact w/ adrenergic/serotonergic agents (should not consume large amounts of food/drinks rich in tyramine to avoid significant pressor response)