Activation of kinin-prekallikrein system after infusion of factor VIII concentrates in hemophilic patients.

Possible changes in the kinin-prekallikrein system after infusion of factor VIII concentrate were studied in seven patients with severe hemophilia. The functional and immunological activities of factors XI and XII, prekallikrein, high molecular weight kininogen, and C-1-esterase inhibitor were measured before and at 0.5, 2, 6, and 12 hours after infusion of 50 U/kg of factor VIII concentrate. A significant decrease (P less than 0.05) in the functional and immunological activities of prekallikrein was observed at 0.5 and 2 hours after factor VIII administration. The other proteins did not change. The results suggest that the kinin system is activated after infusion of high doses of factor VIII concentrate, although clinical evidence of such activation by these changes was not detected.