Quinupristin + dalfopristin
Streptogramins
Streptogramins
IV combination of two streptogramins that, bound to the 50S ribosome, kill resistant gram-positives such as vancomycin-resistant E. faecium.
Also called: quinupristin/dalfopristin
Quick facts
- Group
- Streptogramins
- Target
- Bacterial ribosome, 50S subunit (peptidyl transferase centre and exit tunnel)
- Used for
- Complicated skin
- Key effects
- Pain · Arthralgia and myalgia · Nausea
- Monitor
- Infusion site · Muscle and joint pain · Liver function
- ATC
- J01FG02
No doses: the clinician sets them by the current guideline.
Mechanism of action
The figure shows the 50S ribosomal subunit of Deinococcus radiodurans, a model bacterium, with both molecules bound; the highlighted ligand (DOL) is dalfopristin, and quinupristin sits next to it in the exit tunnel.
Dalfopristin (streptogramin A) binds the 50S peptidyl transferase centre and changes its shape; this raises the affinity of quinupristin (streptogramin B), which lodges in the macrolide site and causes release of incomplete chains. Together they are bactericidal against streptococci and many staphylococci, and bacteriostatic against E. faecium.
- Dalfopristin binds the 50S and changes its shape
- Quinupristin binds more tightly in the tunnel
- Elongation halts and short chains are released
- The joint action is bactericidal
Indications
- Complicated skin and soft-tissue infections by methicillin-susceptible S. aureus or S. pyogenes
- Serious vancomycin-resistant Enterococcus faecium infections, when no better tolerated option exists
Adverse effects
Common
- Pain, inflammation and phlebitis in the infusion vein
- Arthralgia and myalgia, worse in liver failure
- Nausea, diarrhoea, vomiting, rash and headache
Contraindications
- Allergy to quinupristin, dalfopristin or other streptogramins
Key interactions
- Narrow-margin CYP3A4 substrates (ciclosporin, tacrolimus)
- Levels rise; they are monitored and their dose may need lowering.
- Warfarin, diazepam, simvastatin and other CYP3A4 substrates
- Higher levels and risk of toxicity.
- QTc-prolonging drugs that are CYP3A4 substrates
- Used with caution and monitoring.
What is monitored
- Infusion site (phlebitis)
- Muscle and joint pain
- Ciclosporin or tacrolimus levels if combined
- Liver function: liver failure raises its levels
Administration and safety
- Slow IV infusion; a central venous line reduces phlebitis and pain
- Discontinued in the US; where it is used, the local product label is followed
Nursing care
- Check the infusion site and change it if phlebitis appears
- Ask about muscle or joint pain during treatment
- Review other drugs for CYP3A4 substrates
- Watch for watery or bloody diarrhoea
Pharmacokinetics
- Absorption
- IV only.
- Metabolism
- Hepatic, by conjugation; it inhibits CYP3A4.
- Elimination
- Mainly via bile and faeces; no adjustment in kidney failure or dialysis.
- Half-life
- Very short, under one hour for each component.
Test yourself
Think of the answer, then tap the question to see it.
Which component of quinupristin-dalfopristin helps the other bind?
Dalfopristin: it changes the 50S conformation and increases quinupristin binding.
Which toxicities limit the use of quinupristin-dalfopristin?
Phlebitis at the infusion site and the arthralgia-myalgia syndrome.
A kidney transplant recipient on tacrolimus receives quinupristin-dalfopristin. What is monitored?
Tacrolimus levels: the combination inhibits CYP3A4 and can raise them to toxic levels.
Connections
← Back to the class: Streptogramins
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Quinupristin and Dalfopristin Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); COMPLEX OF THE LARGE RIBOSOMAL SUBUNIT FROM DEINOCOCCUS RADIODURANS WITH QUINUPRISTIN AND DALFOPRISTIN (RCSB Protein Data Bank, 2026).
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Representative model, for educational purposes only.