Streptogramin and Oxazolidinone Flashcards
Which antibiotics are in streptogramin?
- quinupristin
- dalfopristin
What drug is this?
quinpristin
What drug is this?
dalfopristin
Which structures of quinpristin and dalfopristin (Synercid) allow for salt formation and enhance water solubility?
- amino side chains
Explain how Synercid, quinpristin, and dalfopristin compare with regards to bacteriostatic vs bacteriocidal.
- quinpristin and dalfopristina re both bacteriostatic alone
- syndercid is bacteriostatic against enterococcus faecium and bactericidal against strains of methicillin-susceptible and methicillin-resistant staphylococci.
What is the route of administration of Synercid?
parenterally
What is the mechanism of action of dalfopristin?
- Interferes with the peptidyl transferase-catalyzed step of peptide synthesis
- prevents the formation of a peptide bond
What is the mechanism of action of quinpristin?
- Quinpristin binds in the ribosomal tunnel and causes blockage of the tunnel
- inhibits protein synthesis
What are the therapeutic uses for Synercid?
- VRE bacteremia
- MRSA
- VRE UTI
What are the different resistance mechanisms to quinpristin?
- adenine methylation of A2058 in the 23 S rRNA
- efflux and enzymatic inactivation by resistant bacteria
- tx of VRE (overuse)
- use in animal feeds
What are the side effects of synercid?
- inflammation
- injection site pain
- GI
What are the characteristics of Synercid pharmacokinetics?
- different elimination rates for each component
- linear relationship between the dose and the AUC
- BBB not penetrated
- clearance is 75% through biliary excretion
What drug interactions is synercid involved in?
- streptogramins inhibit CYP 3A4
- a lot of potential interactions
What drug is this?
linezolid
oxazolidinones
What is the mechanism of action of oxazolidinones?
linezolid
- Linezolid binds to 50S ribosomal subunit.
- This interaction prevents formation of the 70S initiation complex –> which then prevents translation and bacterial protein synthesis
What are the therapeutic uses for linezolid?
- VRE
- nosocomial pneumonia caused by methicillin-resistant strains of staphylococcus aureus
- skin infections caused by methicillin-resistant strains of staphylococcus aureus
- VRE = vancomycin resistant enterococcus faecium
Why should linezolid be used only to treat or prevent infections that are proven or strongly suspected to be caused by multiple drug-resistant gram-positive bacteria?
- to reduce development of drug-resistant bacteria
- to maintain the effectiveness
What is the resistance mechanism for linezolid?
- target site modification
- G to U subsitution in the peptidyl transferase center of 23S rRNA at position 2576
- leads to reduced affinity of linezolid for 50S subunit
What are the side effects of linezolid?
- GI side effects
- headache
- tongue discoloration
- thrush
- anemia
- linezolid induced neuropathy
What is the main metabolic pathway of linezolid?
- linezolid is metabolized via morpholine ring oxidation
What are the pharacokinetics for linezolid?
- 100% bioavailable after oral administration
- half-life: 4-6 hours
can be administered IV or PO
Is linezolid involved with CYP450 interactions?
No :)
What potential drug interactions is linezolid involved with?
Linezolid inhibits monoamine oxidase (MAO) which means it can potentially interact with adrenergic and serotonergic agents
What are counseling points for linezolid?
- avoid consuming large quantities of foods with tyramine in order to avoid pressor response
- use in caution in patients who are sensitive to increases in BP due to preexisting conditions
How does tedizolid phosphate compare to linezolid?
- tedizolid is more potent than linezolid vs MRSA
- the mechanism of action is the same
2nd gen oxazolidinone, prodrug
