Quinupristin/dalfopristin, or 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.

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Quinupristin/dalfopristin

Quinupristin (top) and dalfopristin (bottom)
Combination of
Quinupristin	Streptogramin antibiotic
Dalfopristin	Streptogramin antibiotic
Clinical data
Pregnancy category	AU: B3 B (U.S.)
Routes of administration	IV
ATC code	J01FG02 (WHO)
Legal status
Legal status	US: ℞-only
Identifiers
CAS Number	126602-89-9 N
PubChem CID	23724510
ChemSpider	21106373 Y
NY (what is this?)  (verify)

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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 hours (infections/life threatening VRSA); every 12 hours (skin infections). No renal dosing adjustments, hepatic dosing adjustments are not defined, consider reducing dose.

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 CYP450:3A4 inhibitor, half-life quinupristin 0.8 hours, dalfopristin 0.7 hours (with persistence of effects for 9–10 hours).

[2]

Serious:

1. C.diff-associated diarrhea
2. superinfection
3. anaphylactoid reactions
4. angioedema

Common:

1. Joint aches (arthralgia) or muscle aches (myalgia)
2. Nausea, diarrhea (C. diff associated) or vomiting
3. Rash or itching
4. Headache
5. Hyperbilirubinemia
6. Anemia
7. Thrombophlebitis

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