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
