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Neuraminidase inhibitors

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Oseltamivir CVVH

 

Pascale Gruber & Charles Gomersall

Currently available agents

  • oseltamivir
  • zanamivir

Mode of action

  • specifically target one of two surface structures of influenza virus, the neuraminidase protein
  • neuraminidase enables the virus to emerge from the host cell and form new viruses. By inhibiting neuraminidase, these agents prevent the virus from spreading to other cells.

Oseltamivir

Pharmacokinetics

  • orally administered prodrug
  • high bioavailability (90%)
  • undergoes hepatic metabolism to the active carboxylate
  • oseltamivir carboxylate
    • 3% protein bound
    • renally excreted with an elimination half life of 6-10 hours. The dose should be halved in patients with creatinine clearance <30 ml/min
      • in vitro data suggest that a daily maintenance dose (mg) of 0.52-1.27 times the ultrafiltration rate (ml/min) should be adequate.
  • An oseltamivir-resistant influenza A/H5N1variant has recently been isolated
  • Current guidelines for influenza A/H5N1 recommend that oseltamivir should be administered within 48 hours at a dose of 75mg twice daily for five days in adults, with weight adjusted doses for children (table). In more severe cases higher doses and a longer course of therapy has been recommended. The efficacy of neuramidase inhibitors diminishes substantially if administered after 60 hours of infection and efficacy suboptimal when instituted later in the course of illness.
Weight (kg) Twice daily dose (mg)
≤15 30
15-23 45
23-40 60
>40 75
Weight adjusted doses for children

Zanamivir

  • less likely to be of use in the critically ill as it is only available as a dry powder for inhalation.
  • bioavailability by this route is only 20% and may be reduced in severe pneumonia
  • drug delivery may be problematic in children, the elderly and intubated patients

First posted March 2006

© Pascale Gruber & Charles Gomersall March 2006

©Charles Gomersall, October, 2009 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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