IgM Inhibitors of the Contact Activation Phase of Coagulation in Chlorpromazine- Treated Patients

S ummary . In this report we have described three patients with chronic schizophrenia on long-term chlorpromazine therapy who developed asymptomatic IgM inhibitors of the intrinsic phase of blood coagulation. The anticoagulant resulted in decreased measurements of all of the plasma clotting factors in the intrinsic pathway (factors VIII, IX, XI, XII, Fletcher factor and Fitzgerald factor). Using crude coagulation reagents, the serum of these patients interfered with the clot promoting activity of contact product. To determine the relationship between drug therapy and these IgM inhibitors, we have studied nine additional schizophrenic patients on long-term chlorpromazine therapy. All nine chlorpromazine-treated patients had significantly increased levels of serum IgM and asymptomatic inhibitors of coagulation. We conclude that long-term high-dose chlorpromazine treatment of schizophrenic patients results in an increased concentration of IgM which has inhibitory activity in the contact phase of blood coagulation.