Streptogramins

Question 1

Synercid intro

Answer 1

Developed in response to the need for antibiotics with activity against resistant gram positive bacteria, namely VRE

Two semi-synthetic pristinamycin derivatives
30:70 ratio Quinupristin/Dalfopritisn

Question 2

MOA

Answer 2

Bactericidal
Quinupristin and dalfopristin act individually on the 50S ribosomal subunit to inhibit early and late stages of bacterial protein synthesis; each agent alone is bacteriostatic, but the combination produces an additive or synergistic effect

Question 3

Mechanism of resistance

Answer 3

1. alteration in ribosomal binding site (erm)
2. Enzymatic inactivation

Question 4

Spectrum of activity

Answer 4

Gram positive organisms
Streptococcus pneumoniae (PRSP)
Enterococcus Faecium - VRE (NO ACTIVITY FOR faecalis)
Staphylococcus aureus and coagulase negative strains (MSSA and MRSA)
Viridans and group streptococcus

Question 5

Pharmacology

Answer 5

Time dependent
Post antibiotic affect for gram positive

Question 6

Absorption

Answer 6

Only parenterally
does not get into the Central nervous system

Question 7

Distribution

Answer 7

Penetrates into extravascular tissue, lung, skin/soft tissue
Does not get into CNS

Question 8

Elimination

Answer 8

both agents are metabolized thru hepatic CYP enzymes

MUST DOSE ADJUST IN HEPATIC insufficiency

Question 9

Clinical use

Answer 9

Not really used much
Very expensive

1. VRE Faecium - 3rd line agent

Question 10

Drug interactions

Answer 10

Cytochrome p450 3A4 inhibitor
Synercid can increase these 3 drugs

HMG-CoA reductase inhibitors - usually older agents but can increase concentration of atorvastatin

Cyclosporine

Carbamazepine

Question 11

Adverse effects

Answer 11

1. Venous irritation/Phlebitis - Recommended to use a central vain when using synercid
2. Myalgias, arthralgias - extremely painful and no full explanation on why it happens