A chlorpromazine-induced inhibitor of blood coagulation.

An inhibitor of blood coagulation was detected in the plasma of four schizophrenic patients receiving long-term chlorpromazine therapy. The partial thromboplastin time (PTT) was prolonged in all four patients and the prothrombin time (tpt) was prolonged in one. The inhibitor which resembled in many respects that seen in patients with systemic lupus erythematosus (SLE), was shown to be associated with the tigM-rich fractions of the serum. None of the patients manifested a clinical bleeding tendency and in two, discontinuation of the chlorpromazine was followed by a decrease in the activity of the anticoagulant. While three of the patients had a positive antinuclear antibody test (ANA) and the fourth a false positive serology for syphilis, no further evidence for SLE was found.