Recombinant factor VIIa (rFVIIa; NovoSeven(R)) is a recent addition to
the hemostatic alternatives for the treatment of hemophiliacs with in
hibitors. A drawback in the use of rFVIIa has been its half-life of on
ly about 2 h, which necessitates very frequent and punctual injections
. We evaluated the stability of reconstituted, but not further diluted
, rFVIIa in 3 infusion systems (WalkMed(TM) 350 and CADD(R)-Plus minip
umps and Meddex 2001 syringe pump). The factor VII (F VII) activity wa
s maintained for at least 3 days at room temperature with only a minor
and clinically insignificant increase in oxidized forms of rFVIIa and
minimal leaching of the plastic softeners dibutylphthalate and di-oct
ylphthalate after 24-48 h. Addition of heparin, 5-10 U/ml, to reconsti
tuted rFVIIa caused a loss of about 50% of the activity within 4 h of
storage in the infusion system, whereas low molecular weight heparin h
ad no such effect. Repeated samples showed that the infusion systems m
aintained sterility. Reconstituted rFVIIa did not support bacterial gr
owth when inoculated with Staphylococcus aureus or Escherichia coli to
any greater extent than did reconstituted factor VIII, lidocaine in s
aline or heparin in saline. Two patients were treated with continuous
infusion of rFVIIa on 4 occasions (total knee arthroplasty, wound revi
sion, and twice straightening of a 90 degrees contracture of the knee
under general anaesthesia). A preoperative pharmacokinetic evaluation
was performed, and the clearance was used to calculate the maintenance
,dose, aiming at a FVII level of 10 U/ml, which proved to be a hemosta
tic level. The first patient had no change in the clearance during the
two treatment episodes. He suffered from repeated thrombophlebitis at
the infusion site. The second patient had a progressive decrease of t
he clearance from 86.4 to 24.7 ml/h/kg. He received during the first t
reatment a parallel infusion with heparin (approximate to 250 U/24 h)
to the same venous access and did not develop thrombophlebitis during
3.5 days of therapy. For the second episode low molecular weight hepar
in was added directly to the infusion bag, and no adverse effects were
observed. Continuous infusion with rFVIIa is thus feasible with the m
inipumps used by us, eliminates the need for 2 h injections and reduce
s the total dose of rFVIIa by 50-75%, depending on the behaviour of th
e clearance.