Pharmacology of Quinupristin-dalfopristin

Quinupristin-dalfopristin is a combination antibiotic medication used to treat certain types of severe bacterial infections. It belongs to a class of drugs known as streptogramins. Below is a comprehensive overview of its pharmacology:

Mechanism of Action

Quinupristin and dalfopristin work synergistically to inhibit bacterial protein synthesis. Quinupristin binds to the 50S ribosomal subunit and changes the shape of the ribosome, which enhances the binding of dalfopristin. Dalfopristin also binds to the 50S ribosomal subunit and inhibits the early stages of protein synthesis. Together, they create a bactericidal effect against susceptible bacteria.

Spectrum of Activity

Quinupristin-dalfopristin is active against a variety of gram-positive bacteria, including:

  • Methicillin-resistant Staphylococcus aureus (MRSA)
  • Vancomycin-resistant Enterococcus faecium (VREF)
  • Streptococcus pneumoniae
  • Streptococcus pyogenes

It is not effective against gram-negative bacteria or Enterococcus faecalis.


  • Absorption: Quinupristin-dalfopristin is not absorbed orally and must be administered intravenously.
  • Distribution: It is widely distributed throughout the body, including in skin and soft tissues.
  • Metabolism: Both quinupristin and dalfopristin are metabolized in the liver.
  • Excretion: The metabolites are excreted primarily through the bile and feces.


Quinupristin-dalfopristin is used to treat:

  • Severe skin and skin structure infections
  • Bloodstream infections
  • Infections associated with intravenous catheters

Contraindications and Precautions

  • It should not be used in patients with known hypersensitivity to quinupristin, dalfopristin, or any other component of the formulation.
  • Caution is advised in patients with hepatic impairment as the drug is metabolized in the liver.

Adverse Effects

Common adverse effects include:

  • Infusion site reactions
  • Nausea and vomiting
  • Diarrhea
  • Rash

Drug Interactions

Quinupristin-dalfopristin can interact with other medications metabolized by the cytochrome P450 system, potentially leading to increased or decreased levels of these medications.

Dosage and Administration

The drug is administered intravenously, and the dosage depends on the severity of the infection and the patient’s body weight.

Clinical Trials and Efficacy

Several clinical trials have demonstrated the efficacy of quinupristin-dalfopristin in treating severe bacterial infections, particularly those caused by MRSA and VREF.


Quinupristin-dalfopristin is a valuable antibiotic for the treatment of severe gram-positive bacterial infections, especially those resistant to other antibiotics. However, its use should be reserved for specific cases due to the potential for adverse effects and drug interactions. Proper patient selection and monitoring are essential to optimize therapeutic outcomes.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always seek the advice of a healthcare provider with any questions regarding a medical condition.

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