Quinupristin and dalfopristin are streptogramin antibiotics Overview of Antibacterial Drugs Antibacterial drugs are derived from bacteria or molds or are synthesized de novo. Technically, “antibiotic” refers only to antimicrobials derived from bacteria or molds but is often (including... read more , which, like macrolides Macrolides Macrolides (see table Macrolides) are antibiotics that are primarily bacteriostatic; by binding to the 50S subunit of the ribosome, they inhibit bacterial protein synthesis. Macrolides are relatively... read more and lincosamides Lincosamides, Oxazolidinones, and Streptogramins Lincosamides (clindamycin), oxazolidinones (linezolid, tedizolid), and streptogramins (dalfopristin [streptogramin A] and quinupristin [streptogramin B]) are structurally different but are grouped... read more , 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 Streptococcal Infections Streptococci are gram-positive aerobic organisms that cause many disorders, including pharyngitis, pneumonia, wound and skin infections, sepsis, and endocarditis. Symptoms vary with the organ... read more
and staphylococci Staphylococcal Infections Staphylococci are gram-positive aerobic organisms. Staphylococcus aureus is the most pathogenic; it typically causes skin infections and sometimes pneumonia, endocarditis, and osteomyelitis... read more 
, including strains resistant to other antibiotic classesAtypical respiratory pathogens (Mycoplasma pneumoniae Mycoplasmas Mycoplasmas are ubiquitous bacteria that differ from other prokaryotes in that they lack a cell wall. Mycoplasma pneumoniae is a common cause of pneumonia, particularly community-acquired pneumonia... read more , Chlamydophila pneumoniae, Legionella pneumophila Legionella Infections Legionella pneumophila is a gram-negative bacillus that most often causes pneumonia with extrapulmonary features. Diagnosis requires specific growth media, serologic or urine antigen testing... read more
)
Q/D inhibits Enterococcus faecium Enterococcal Infections Enterococci are gram-positive, facultative anaerobic organisms. Enterococcus faecalis and E. faecium cause a variety of infections, including endocarditis, urinary tract infections, prostatitis... read more , including vancomycin-resistant strains. Enterococcus 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.
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.
