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Clinical study of recovery and half-life of vapor-heated factor VII concentrate
G E Rivard1, I Kovac, M Kunschak
1Hematology Service, Ste-Justine Hospital, Montréal, Quebec, Canada.
Background:
The in vivo recovery and half-life of intermediate-purity, vapor-heated factor VII (FVII) concentrate were determined in patients having a congenital deficiency for FVII according to the 1991 guidelines of the International Society for Thrombosis and Haemostasis.
Study Design And Methods:
A total of 11 patients received a single infusion of the FVII concentrate. Blood was drawn before infusion and 15 and 30 minutes and 1, 2, 4, 8, 12, and 24 hours after. Recoveries were calculated from the highest FVII activity of the first four blood samples drawn after infusion. The two-phase linear regression method was used to estimate the half-life according to the two-compartment model. In addition, a noncompartmental approach was applied.
Results:
The mean recovery value obtained for FVII concentrate, 110.53 percent (SD, +/- 26.37), indicates rapid and efficient incorporation into the blood stream. Equivalent results were obtained with both pharmacokinetics methods and indicate a very short half-life for FVII. A half-life of 6.49 hours (SD, +/- 2.42) was obtained with the compartmental method and a half-life of 5.25 hours (SD, +/- 2.42) with the noncompartmental method.
Conclusion:
The half-life and recovery reported here, along with the specificity of the replacement therapy, the earlier anecdotal cases of clinical efficacy, and the clinical safety of the concentrate with regard to viral infections, recommend vapor-heated FVII concentrate for the treatment of patients with hereditary FVII deficiency.