[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Streptogramins](https://durgical.com/en/pharmacology/classes/streptogramins/) › Quinupristin + dalfopristin

# 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.

Updated Nov 1, 2026

Also called: quinupristin/dalfopristin

## Quick facts

**Group**
[Streptogramins](https://durgical.com/en/pharmacology/classes/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.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

◆**Bacterial ribosome, 50S subunit (peptidyl transferase centre and exit tunnel)**Quinupristin + dalfopristin

ⓘ 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.

**Target in 3D:** Bacterial ribosome, 50S subunit (peptidyl transferase centre and exit tunnel). PDB structure 1SM1 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/1SM1) · Drag to rotate · pinch to zoom

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

### Serious (rare, important)

- Severe allergic reactions (hives, angioedema, shortness of breath)
- Clostridioides difficile diarrhoea

## 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.

## Memory aid

«Q and D, the dynamic duo»: alone, two streptogramins that barely slow bacteria; together, a duo that kills E. faecium (not faecalis) and ruins veins.

## 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.

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## Connections

## Related drugs 3

- [Linezolid](https://durgical.com/en/pharmacology/linezolid/)
- [Daptomycin](https://durgical.com/en/pharmacology/daptomycin/)
- [Vancomycin](https://durgical.com/en/pharmacology/vancomycin/)

[← Back to the class: Streptogramins](https://durgical.com/en/pharmacology/classes/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](https://medlineplus.gov/druginfo/meds/a603007.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [COMPLEX OF THE LARGE RIBOSOMAL SUBUNIT FROM DEINOCOCCUS RADIODURANS WITH QUINUPRISTIN AND DALFOPRISTIN](https://www.rcsb.org/structure/1SM1) (RCSB Protein Data Bank, 2026).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/quinupristin-dalfopristin/