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Diminished Response to Recombinant Factor VIIa in a Patient with Idiopathic Thrombocytopenic Purpura

Critical Care Resident, Department of Pharmacy Practice, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, Buffalo, NY

Walter S Schroeder, PharmD

Clinical Assistant Professor of Pharmacy and Medicine, Department of Pharmacy Practice, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo

Yijun Cheng, MD

Clinical Fellow in Hematology, Department of Medicine, School of Medicine and Biomedical Sciences, University at Buffalo

Zale P Bernstein, MD

Director of the Adult Hemophilia Center of Western New York, Department of Medicine, School of Medicine and Biomedical Sciences, University at Buffalo

Reprints: Dr. Schroeder, Department of Pharmacy Practice, School of Pharmacy and Pharmaceutical Sciences, Cooke Hall 317, University at Buffalo, Buffalo, NY 14221-1200, fax 716/645-2886, wss2{at}buffalo.edu

OBJECTIVE: To describe the hypotheses that may explain a diminished hemostatic response in a patient receiving multiple doses of recombinant coagulation factor VIIa (rFVIIa) for off-label treatment of bleeding events.

CASE SUMMARY: A 70-year-old female with a significant history of idiopathic thrombocytopenic purpura (ITP) was admitted for coronary artery bypass grafting surgery. The patient developed thrombocytopenia and persistent hemorrhage postoperatively that was refractory to conventional therapy for ITP. She experienced an initial hemostatic response to rFVIIa after receiving 3 doses. During her second trial of rFVIIa a few days later, the duration of hemostatic effect was approximately half that of the first. The patient then received rFVIIa almost daily over the following 9 days to which she remained unresponsive, ultimately resulting in death. All doses in this patient were 9.6 mg (101 µg/kg), except the last, which was 4.8 mg (50.5 µg/kg).

DISCUSSION: Several hypotheses may explain this patient's resistance to rFVIIa therapy. Two involve depletion of platelets or coagulation factors essential for rFVIIa efficacy. Another involves development of an antibody to rFVIIa. The last involves acidemia, which may interfere with the pharmacologic effect of rFVIIa.

CONCLUSIONS: The combination of persistent thrombocytopenia and exhaustion of coagulation factors is the likely cause leading to resistance to rFVIIa therapy in this patient.

Key Words: idiopathic thrombocytopenic purpura, recombinant coagulation factor VIIa

Published Online, October 24, 2006. www.theannals.com, DOI 10.1345/aph.1H331