Drugs

, Volume 58, Issue 6, pp 1061–1097

Quinupristin/Dalfopristin

A Review of its Use in the Management of Serious Gram-Positive Infections
  • Harriet M. Lamb
  • David P. Figgitt
  • Diana Faulds
Adis Drug Evaluation

DOI: 10.2165/00003495-199958060-00008

Cite this article as:
Lamb, H.M., Figgitt, D.P. & Faulds, D. Drugs (1999) 58: 1061. doi:10.2165/00003495-199958060-00008

Abstract

Quimipristin/dalfopristin is the first parenteral streptogramin antibacterial agent, and is a 30: 70 (w/w) ratio of 2 semisynthetic pristinamycin derivatives. The combination has inhibitory activity against a broad range of Gram-positive bacteria including methicillin-resistant staphylococci, vancomycin-resistant Enterococcus faecium (VREF), drug-resistant Streptococcus pneumoniae, other streptococci, Clostridium perfringens and Peptostreptococcus spp. The combination also has good activity against selected Gram-negative respiratory tract pathogens including Moraxella catarrhalis, Legionella pneumophila and Mycoplasma pneumoniae. Quinupristin/dalfopristin has poor activity against E. faecalis. The combination is bactericidal against staphylococci and streptococci, although constitutive erythromycin resistance can affect its activity. As for many other agents, quinupristin/dalfopristin is generally bacteriostatic against E. faecium.

In patients with methicillin-resistant S. aureus (MRSA) or VREF infections participating in prospective emergency-use trials, quinupristin/dalfopristin 7.5 mg/kg every 8 or 12 hours achieved clinical or bacteriological success in ≥64% of patients. Emergence of resistance to quinupristin/dalfopristin was uncommon (4% of patients) in those with VREF infections. Quinupristin/dalfopristin 7.5 mg/kg 8- or 12-hourly also achieved similar clinical success rates to comparator agents in patients with presumed Gram-positive complicated skin and skin structure infections or nosocomial pneumonia (administered in combination with aztreonam) in 3 large multicentre randomised trials.

Systemic adverse events associated with quinupristin/dalfopristin include gastrointestinal events (nausea, vomiting and diarrhoea), rash and pruritus. Myalgias and arthralgias also occur at an overall incidence of 1.3%, although higher rates (2.5 to 31%) have been reported in patients with multiple comorbidities. Venous events are common if the drug is administered via a peripheral line; however, several management options (e.g. use of central venous access, increased infusion volume) may help to minimise their occurrence. Hyperbilirubinaemia has been documented in 3.1% of quinupristin/dalfopristin recipients versus 1.3% of recipients of comparator agents. Quinupristin/dalfopristin inhibits cytochrome P450 3A4 and therefore has the potential to increase the plasma concentrations of substrates of this enzyme.

Conclusions: Quinupristin/dalfopristin, the first parenteral streptogramin, offers a unique spectrum of activity against multidrug-resistant Gram-positive bacteria. In serious Gram-positive infections for which there are other treatment options available, the spectrum of activity and efficacy of quinupristin/dalfopristin should be weighed against its tolerability and drug interaction profile. However, in VREF or unresponsive MRSA infections, where few proven treatment options exist, quinupristin/dalfopristin should be considered as a treatment of choice for these seriously ill patients.

Antibacterial Activity

Quinupristin/dalfopristin (30: 70 ratio) is a parenteral streptogramin agent. Both quinupristin and dalfopristin possess inhibitory antibacterial activity; however, as a combination, they demonstrate markedly increased or synergistic activity. Varying the ratio of quinupristin to dalfopristin or replacing dalfopristin with its active metabolite (RP 12536) does not appear to affect the in vitro inhibitory activity of the combination.

An overview of published in vitro data reveals that quinupristin/dalfopristin has inhibitory activity against a broad range of Gram-positive bacteria including: staphylococci (regardless of methicillin susceptibility), Enterococcus faecium (regardless of vancomycin susceptibility), Streptococcus pneumoniae (regardless of penicillin or erythromycin susceptibility), S. pyogenes, S. agalactiae, viridans streptococci, Clostridium perfringens and Peptostreptococcus spp. Quinupristin/dalfopristin has more variable activity against Corynebacterium jeikeium, Listeria monocytogenes, Leuconostoc spp. and other Gram-positive anaerobes. The combination also has good activity against selected Gram-negative pathogens including Moraxella catarrhalis, Legionella pneumophila, Neisseria meningitidis and Mycoplasma pneumoniae. It possesses little or no activity against E. faecalis or Haemophilus influenzae.

Although resistance to the macrolide, lincosamide and streptogramin (MLS) family of antibiotics is common, resistance to quinupristin/dalfopristin is unusual. When characterised in staphylococci, quinupristin/dalfopristin resistance was always associated with 2 to 4 resistance genes (i.e. vga, vgb, vatB and/or erm). Rare clinical isolates of E. faecium. are resistant (minimum inhibitory concentration of ≥8 mg/L) to quinupristin/dalfopristin; characterised strains possessed the satA gene. In enterococci and streptococci, but not staphylococci, quinupristin acts as an inducer of MLSB resistance.

Quinupristin/dalfopristin is rapidly bactericidal against some strains of staphylococci and streptococci, but generally has bacteriostatic activity against E. faecium. Quinupristin/dalfopristin is not consistently bactericidal against staphylococcal strains with constitutive MLSB resistance. Compared with vancomycin, quinupristin/dalfopristin demonstrated greater bactericidal activity against some staphylococcal strains (p < 0.05 in 1 study), but similar or less activity against others. Quinupristin/dalfopristin has a postantibiotic effect (PAE) against Gram-positive bacteria.

Against methicillin-resistant Staphylococcus aureus (MRSA), rifampicin is synergistic with quinupristin/dalfopristin. Against VREF, doxycycline showed synergism with quinupristin/dalfopristin and also prevented or delayed the emergence of resistance in vitro. Amoxicillin, ampicillin/sulbactam and vancomycin may also have some synergistic activity with quinupristin/dalfopristin against VREF.

Pharmacokinetic Profile

After a single infusion of quinupristin/dalfopristin 7.5 mg/kg, peak plasma concentrations (Cmax) for quinupristin and dalfopristin ranged from 2.6 to 2.8 mg/L and 7.1 to 7.2 mg/L, respectively, in healthy volunteers. After administration of multiple doses, clearance of the drug appeared to decrease by approximately 20%.

Dalfopristin has 1 and quinupristin 2 active metabolites, the Cmax values of which range from 0.29 to 1.1 mg/L. Penetration of quinupristin/dalfopristin and metabolites into human blister fluid is approximately 40% of that achieved in plasma.

Elimination half-lives (t½β) for quinupristin and dalfopristin in healthy volunteers after a single 7.5 mg/kg dose ranged from 0.91 to 1.14 hours and 0.45 to 0.71 hours, respectively. Plasma clearance was high and ranged from 0.82 to 0.87 L/h · kg. 75 and 77% of a [14C]-radiolabelled dose of quinupristin and dalfopristin, respectively, was excreted in the faeces, and 15 and 19% excreted in the urine.

In patients with cirrhosis, the mean area under the concentration-time curve of quinupristin and dalfopristin (and their respective metabolites), increased by approximately 2.8- and 1.5-fold, respectively, compared with healthy volunteers. Clearance of quinupristin/dalfopristin may be slightly reduced in patients with severe chronic renal failure. Age, gender and obesity appear to have no clinically significant effects on the pharmacokinetics of quinupristin/dalfopristin.

Quinupristin/dalfopristin inhibits the biotransformation rate of cytochrome P450 3A4 (CYP3A4) substrates in vitro and clinical studies confirm that quinupristin/dalfopristin decreases the plasma clearance of cyclosporin, nifedipine and midazolam.

Therapeutic Use in Gram-Positive Infections Infections

Caused by Multidrug-Resistant Pathogens: As part of the emergency-use programme, intravenous quinupristin/dalfopristin 7.5 mg/kg 8-hourly achieved clinical success in 64 and 76% of patients according to intention-to-treat analysis in 2 trials of patients with MRSA infections. Intravenous quinupristin/dalfopristin 5 or 7.5 mg/kg every 8 hours achieved similar response rates to vancomycin 1g every 12 hours in 39 patients with uncomplicated catheter-related staphylococcal bacteraemia in a single-blind randomised trial.

In prospective emergency-use trials, quinupristin/dalfopristin 7.5 mg/kg every 8 or 12 hours achieved per-protocol bacteriological success rates (eradication or presumed eradication) of 68 and 71% of patients with VREF infections. About two-thirds of patients had intra-abdominal infection or bacteraemia of unknown origin and many patients had underlying conditions. Emergence of resistance to quinupristin/dalfopristin was documented in 4% of patients, although higher incidences (14%) were reported at 2 US centres. Therapy with quinupristin/0 dalfopristin may be associated with E.faecalis superinfection.

Skin and Skin Structure Infections: Intravenous quinupristin/dalfopristin 7.5 mg/kg 12-hourly achieved a similar clinical success rate (68.2%) to comparator agents (70.7%) in patients with presumed Gram-positive complicated skin and skin structure infections in 2 large multicentre randomised trials; comparator agents were vancomycin 1g 12-hourly, cefazolin 1g 8-hourly or oxacillin 2g 6-hourly either alone or in combination. Overall bacteriological success rates were similar in both treatment groups, although quinupristin/dalfopristin was associated with lower eradication rates against methicillin-susceptible S. aureus and Gram-positive cocci and Gram-negative rods according to a by-pathogen analysis.

Nosocomial Pneumonia: Similar rates of clinical success were achieved with quinupristin/dalfopristin 7.5 mg/kg 8-hourly (56%) and vancomycin lg 12-hourly (58%) in patients with Gram-positive nosocomial pneumonia in a randomised trial. Both agents were administered in combination with aztreonam 2g 8-hourly. The most common pathogens were S. aureus (40% of isolates), S. pneumoniae (8%), P. aeruginosa (7%) and H. influenzae (7%). Quinupristin/dalfopristin and vancomycin were also equally effective (54% clinical success rate) in a subset of intubated patients.

Tolerability

Adverse events associated with quinupristin/dalfopristin are mild to moderate in severity in over 80% of cases. Treatment discontinuation because of adverse events was necessary in 15.3 to 19.1% of patients (vs 4.7 to 9.5% with comparator agents) in clinical trials.

If administered via a peripheral line, quinupristin/dalfopristin can be associated with venous-related events (usually pain and/or inflammation) in 34.9 to 74.0% of patients. Appropriate management (use of a central line, peripherally inserted central venous catheter or a larger infusion volume) may help to minimise these events.

Quinupristin/dalfopristin was associated with myalgias and/or arthralgias in 1.3% of patients (n = 1099) versus an incidence of 1.1% (n = 1094) in patients receiving comparator agents. However, the incidence seems to increase in the more severely ill (2.5 to 30.7% in 4 trials). Symptoms are generally mild to moderate in severity and reverse on cessation of therapy.

Other events associated with quinupristin/dalfopristin include gastrointestinal events (nausea, vomiting and diarrhoea), rash and pruritus. According to an overview of all clinical trial data in patients and healthy volunteers (n = 2429), nausea occurred in 4.6% of recipients, vomiting and diarrhoea in 2.7% each and rash in 2.5%.

Increased conjugated bilirubin levels were documented in 3.1% of quinupristin/dalfopristin recipients versus 1.3% of recipients of comparator agents; an increase in total bilirubin to ≥5 times the upper normal limit was documented in 0.9 versus 0.2% of patients. The incidence of hepatic dysfunction was similar in both treatment groups.

Dosage and Administration

Quinupristin/dalfopristin is indicated for the treatment of clinically significant infections due to VREF, skin and soft tissue infections and nosocomial pneumonia in the UK, and serious or life-threatening infections associated with VREF bacteraemia and complicated skin and skin structure infections (caused by methicillin-susceptible S. aureus or S. pyogenes) in the US. The recommended dosage is 7.5 mg/kg administered as a 1-hour intravenous infusion every 8 or 12 hours for ≥7 days for complicated skin and skin structure infections, every 8 hours for 10 days for nosocomial pneumonia (UK only), and every 8 hours for serious or life-threatening infections associated with VREF bacteraemia.

Dosage adjustment should not be necessary in elderly or obese patients, in those undergoing peritoneal dialysis or in patients with renal impairment, although UK labelling states that quinupristin/dalfopristin should be used with caution in patients with impaired renal function. Dosage reduction may be necessary in patients with hepatic insufficiency, although recommendations have not yet been validated.

Coadministration with any agent that is metabolised mainly by the CYP3A4 enzyme system should be avoided. In particular, drugs metabolised by CYP3A4 and that can prolong the corrected QT interval should not be coadministered with quinupristin/dalfopristin. Where quinupristin/dalfopristin and cyclosporin must be used concomitantly, monitoring of cyclosporin whole blood concentrations is recommended.

Copyright information

© Adis International Limited 1999

Authors and Affiliations

  • Harriet M. Lamb
    • 1
  • David P. Figgitt
    • 1
  • Diana Faulds
    • 1
  1. 1.Adis International LimitedMairangi Bay, Auckland 10New Zealand

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