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Quinupristin (top) and dalfopristin (bottom)
Combination of
Quinupristin Streptogramin antibiotic
Dalfopristin Streptogramin antibiotic
Clinical data
Routes of
Legal status
Legal status
  • ℞-only (U.S.)
CAS Number 126602-89-9 N
ATC code J01FG02 (WHO)
PubChem CID 23724510
ChemSpider 21106373 YesY
 NYesY (what is this?)  (verify)

Quinupristin/dalfopristin (pronunciation: kwi NYOO pris tin / dal FOE pris tin) (trade name Synercid) is a combination of two antibiotics used to treat infections by staphylococci and by vancomycin-resistant Enterococcus faecium.

Quinupristin and dalfopristin are both streptogramin antibiotics, derived from pristinamycin. Quinupristin is derived from pristinamycin IA; dalfopristin from pristinamycin IIA. They are combined in a weight-to-weight ratio of 30% quinupristin to 70% dalfopristin.


Intravenous, usually 7.5 mg/kg every 8–12 hours

Mechanism of action[edit]

Quinupristin and dalfopristin are protein synthesis inhibitors in a synergistic manner. While each of the two is only a bacteriostatic agent, the combination shows bactericidal activity.

  • Dalfopristin binds to the 23S portion of the 50S ribosomal subunit, and changes the conformation of it, enhancing the binding of quinupristin[1] by a factor of about 100. In addition, it inhibits peptidyl transfer.[1]
  • Quinupristin binds to a nearby site on the 50S ribosomal subunit and prevents elongation of the polypeptide,[1] as well as causing incomplete chains to be released.[1]


Clearance by the liver, half-life 1–3 hours (with persistence of effects for 9–10 hours).

Side effects[edit]

  1. Joint aches (arthralgia) or muscle aches (myalgia)
  2. Nausea, diarrhea or vomiting
  3. Rash or itching
  4. Headache
  5. Phlebitis
  6. Hyperbilirubinemia

Drug interactions[edit]

The drug inhibits P450 and enhances the effects of terfenadine, astemizole, indinavir, midazolam, calcium channel blockers, warfarin, cisapride and ciclosporin.


  1. ^ a b c d Page 212 in: Title: Hugo and Russell's pharmaceutical microbiology Authors: William Barry Hugo, Stephen P. Denyer, Norman A. Hodges, Sean P. Gorman Edition: 7, illustrated Publisher: Wiley-Blackwell, 2004 ISBN 0-632-06467-6, ISBN 978-0-632-06467-0 Length: 481 pages

Further reading[edit]