Dose determination of fondaparinux in healthy cats

Am J Vet Res. 2012 Apr;73(4):556-61. doi: 10.2460/ajvr.73.4.556.


Objective: To establish practical doses and administration frequencies of fondaparinux for cats that would approximate human therapeutic peak and trough plasma anti-factor Xa activities for thromboprophylaxis (TP) and thrombosis treatment (TT) protocols.

Animals: 6 healthy adult purpose-bred cats.

Procedures: Dosage protocols for TP and TT were selected on the basis of a single compartment pharmacokinetic model incorporating data from humans but modified to account for the higher body weight-normalized cardiac output of cats. Fondaparinux was administered at 0.06 mg/kg, SC, every 12 hours (TP) for 7 days in one session, and 0.20 mg/kg, SC, every 12 hours (TT) for 7 days in another, with a minimum of 1 week separating the sessions. Plasma anti-factor Xa activity was measured before fondaparinux administration (day 1) and at 2 (peak) and 12 (trough) hours after drug administration on days 1 and 7. Platelet aggregation and thromobelastographic (TEG) parameters were also measured 2 hours after drug administration on day 7.

Results: Peak plasma anti-factor Xa activities on day 7 for TP (median, 0.59 mg/L; range, 0.36 to 0.77 mg/L) and TT (median, 1.66 mg/L; range, 1.52 to 2.00 mg/L) protocols were within therapeutic ranges for humans. However, only the TP protocol achieved trough anti-factor Xa activity considered therapeutic in humans (median, 0.19 mg/L; range, 0.00 to 0.37 mg/L) on day 7. There were significant changes in the TEG parameters at peak for the TT protocol, suggesting a hypocoagulable state. No significant changes in platelet aggregation were evident for either protocol.

Conclusions and clinical relevance: A fondaparinux dosage of 0.06 or 0.20 mg/kg, SC, every 12 hours, was sufficient to achieve a peak plasma anti-factor Xa activity in cats that has been deemed therapeutic in humans. This study provided preliminary data necessary to perform fondaparinux dose-determination and clinical efficacy studies.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anticoagulants / administration & dosage
  • Anticoagulants / blood
  • Anticoagulants / pharmacokinetics*
  • Blood Platelets / drug effects
  • Cats*
  • Dose-Response Relationship, Drug
  • Drug Administration Schedule
  • Factor Xa / drug effects
  • Factor Xa / metabolism
  • Female
  • Fondaparinux
  • Male
  • Polysaccharides / administration & dosage
  • Polysaccharides / blood
  • Polysaccharides / pharmacokinetics*
  • Thrombelastography / veterinary


  • Anticoagulants
  • Polysaccharides
  • Factor Xa
  • Fondaparinux