Quinupristin and dalfopristin are streptogramin antibiotics, which, like macrolides and lincosamides, inhibit the synthesis of bacterial proteins.
Quinupristin/dalfopristin (Q/D) is given together in a fixed 30/70 combination; this combination has synergistic bactericidal activity against the following:
Streptococci and staphylococci, including strains resistant to other antibiotic classes
Some gram-negative anaerobic bacilli
Peptostreptococcus species
Atypical respiratory pathogens (Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila)
Q/D inhibits Enterococcus faeciumEnterococcus faecalis is resistant.
Q/D is given via a central IV catheter because phlebitis frequently occurs when Q/D is given via a peripheral vein. Up to 30% of patients develop significant myalgias. Q/D may cause hyperbilirubinemia.
Dosage reduction is required for severe hepatic insufficiency but not for renal insufficiency.
Safety Warning
Q/D may inhibit the metabolism of drugs that are metabolized by the cytochrome P-450 (CYP450) 3A4 isoenzyme system.