Quinupristin

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Quinupristin is a streptogramin antibiotic used in combination with dalfopristin to form the drug quinupristin/dalfopristin, marketed under the brand name Synercid. This combination is used to treat infections caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VRE).

Mechanism of Action

Quinupristin belongs to the streptogramin class of antibiotics, which are divided into two groups: streptogramin A and streptogramin B. Quinupristin is a streptogramin B antibiotic. It works by binding to the 50S ribosomal subunit of the bacterial ribosome, inhibiting protein synthesis. When used in combination with dalfopristin, a streptogramin A antibiotic, the two drugs exhibit a synergistic effect, enhancing their antibacterial activity.

Clinical Uses

Quinupristin/dalfopristin is primarily used to treat severe infections caused by Gram-positive bacteria, particularly those resistant to other antibiotics. It is effective against:

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

Administration and Dosage

Quinupristin/dalfopristin is administered intravenously. The typical dosage is 7.5 mg/kg every 8 to 12 hours, depending on the severity of the infection and the patient's renal function.

Side Effects

Common side effects of quinupristin/dalfopristin include:

• Nausea
• Vomiting
• Diarrhea
• Myalgia
• Arthralgia
• Rash

Serious side effects may include hepatotoxicity and thrombophlebitis.

Resistance

Bacterial resistance to quinupristin can occur through various mechanisms, including:

• Modification of the target site on the 50S ribosomal subunit
• Enzymatic inactivation of the antibiotic
• Efflux pumps that expel the antibiotic from the bacterial cell

History

Quinupristin was developed as part of the effort to find new antibiotics effective against resistant strains of bacteria. It was approved for medical use in combination with dalfopristin in the late 1990s.

See Also

• Streptogramin
• Dalfopristin
• Antibiotic resistance
• Gram-positive bacteria