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PHRM 865 > Streptogramin and Oxazolidinone > Flashcards

Streptogramin and Oxazolidinone Flashcards

1
Q

What two antibiotics are found in synercid?

A

quinuprisitin and dalfopristin

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2
Q

What part of the structure of quinupristin and dalfopristin allow salt formation and enhance water solubility?

A
  • amino side chains
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3
Q

Is quinupristin bactericidal or bacteriostatic

A

bacteriostatic

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4
Q

Is dalfopristin bactericidal or bacteriostatic

A

bacteriostatic

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5
Q

are quinupristin and dalfopristin used together bactericidal or bacteriostatic

A

bactericidal!

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6
Q

How are streptogramins administered?

A

parenterally

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7
Q

What is the mechanism of action of dalfopristin?

A
  • dalfopristin directly interferes with the peptidyl transferase-catalyzed step of peptide synthesis
  • inhibits amino acids from linking with each other (A –> P site)
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8
Q

What is the mechanism of action of quinupristin

A

binds the ribosomal tunnel and blocks causes blockage of the tunnel

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9
Q

What are the therapeutic uses of synercid?

A
  • VRE (enteroccus faecium)
  • skin infections caused by MRSA
  • vancomycin resistant enteroccus faecium urinary track infections
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10
Q

What part of the ribosome does synercid bind to

A

23S rNA

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11
Q

What is the quinupristin resistance mechanisms?

A
  • adenine methylation of A2058 in the 23S rNA
  • efflux and enzymatic inactivation
  • this makes synercid bacteriostatic
  • does not affect dalfopristin
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12
Q

How to overcome quinupristin resistance

A

extension of the dosing of synercid to TID allows for more sustained tissue drug levels

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13
Q

What are the side effects of synercid

A
  • non known signficant toxicity presented by synercid
  • inflammation and pain at site of injection
  • nausea
  • diarrhea
  • muscle weakness
  • rash
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14
Q

What is the PK of synercid

A
  • complicated because of different elimination rates for each drug
  • gram + infections achieve up to 85% of the serum concentrations
  • blood/brain or placental barriers are not penetrated
  • clearance is 75% biliary excretion
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15
Q

What are the potential drug interactions associated with synercid

A
  • inhibit cyp 3A4
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16
Q

What is the mechanism of action of the oxazolidinones

A

inhibit bacterial protein synthesis at the peptide chain elongation stage by potent interaction with the 50s ribosomal subunit

17
Q

What is the main therapeutic use of linezolid

A
  • vancomycin resistant enterococcus faecium
  • nosocomial pneumonia caused by MRSA
  • skin infections caused by MRSA
18
Q

Why should linezolid used only to treat or prevent infections that are proven or strongly suspected to be caused by multiple drug resistance gram positive bacteria

A

to reduced the development of drug resistant bacteria and maintain the effectiveness of linezolid (the emergence of linezolid resistance has been reported)

19
Q

What is the resistance mechanism of linezolid

A
  • target site modification with G to U substitution in the peptidyl transferase center of the 23S rRNA at position 2576
  • reduces affinity of linezolid to the 50s subunit
  • mutations that lie in proximity of the P sigte which confirms the MOA of oxazolidinones
20
Q

What are the main side effects of linezolid?

A
  • GIeffects
  • headache
  • tongue discoloration
  • thrush
  • thrombocytopenia
  • anemia
  • GI bleeding
  • fully reversible myelosuppression
  • linezolid induced neuropathy
21
Q

What is the main metabolic pathway of linezolid

A

morpholine ring oxidation

22
Q

What is the PK of linezolid

A
  • 100% bioavailable after oral adminiistration
  • has half life of 4-6 hours
  • orally or iv admin
23
Q

What are the drug interactions associated with linezolid

A
  • potent, reversible, nonselective inhibitor of MOAi
  • potential interactions with adrenergic and serotenergic
  • reversible potentiation of pressor response to pseudoephedrine
  • should be used in caution in patients who are sensitive to increases in BP due to preexisting conditions
  • tyramine
24
Q

Compare the potency of tedizolid and linezolid

A

more potent than linezolid vs mrsa

25
Q

compare the MOA of tedizolid and linezolid

A

same mechanism of action (tedizolid phosphate is tedizolid prodrug)

26
Q
A

PHRM 865 (9 decks)

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