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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 ;
PubChem CID	23724510;
ChemSpider	21106373 ;
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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.

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.

Administration

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.

Mechanism of action

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]

Pharmacokinetics

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).

Side effects

^[2]

Serious:

Common:

Joint aches (arthralgia) or muscle aches (myalgia)
Nausea, diarrhea (C. diff associated) or vomiting
Rash or itching
Headache
Hyperbilirubinemia
Anemia
Thrombophlebitis

Drug interactions

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

References

^ ^a ^b ^c ^d Denyer SP, Hodges N, Gorman SP, eds. (2004). Hugo and Russell's Pharmaceutical microbiology (7th ed.). Blackwell Science. p. 212. ISBN 978-0-632-06467-0.
^ Epocrates v 19.5

Allington DR, Rivey MP (January 2001). "Quinupristin/dalfopristin: a therapeutic review". Clinical Therapeutics. 23 (1): 24–44. doi:10.1016/S0149-2918(01)80028-X. PMID 11219478.
Lamb HM, Figgitt DP, Faulds D (December 1999). "Quinupristin/dalfopristin: a review of its use in the management of serious gram-positive infections". Drugs. 58 (6): 1061–97. doi:10.2165/00003495-199958060-00008. PMID 10651391. S2CID 209144323.
Manzella JP (December 2001). "Quinupristin-dalfopristin: a new antibiotic for severe gram-positive infections". American Family Physician. 64 (11): 1863–6. PMID 11764864..
Paradisi F, Corti G, Messeri D (January 2001). "Antistaphylococcal (MSSA, MRSA, MSSE, MRSE) antibiotics" (PDF). The Medical Clinics of North America. 85 (1): 1–17. doi:10.1016/s0025-7125(05)70302-3. hdl:2158/329747. PMID 11190346.
"Synercid". U.S. Food and Drug Administration. Archived from the original on 2007-06-18.

[hugo-1] Denyer SP, Hodges N, Gorman SP, eds. (2004). Hugo and Russell's Pharmaceutical microbiology (7th ed.). Blackwell Science. p. 212. ISBN 978-0-632-06467-0.

[2] Epocrates v 19.5

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