Heterogeneity of laboratory test results for antiphospholipid antibodies in patients treated with chlorpromazine and other phenothiazines.

Ninety-seven psychiatric patients who have been treated with the antipsychotic drug chlorpromazine or another phenothiazine have been investigated for the presence of antiphospholipid antibodies. A variety of coagulation studies and specific antiphospholipid immunoassays were performed to define the spectrum of antigen specificity of these antibodies. Coagulation studies showed an increasing sensitivity for the lupus anticoagulant with reagents of differing phospholipid content. Prolonged activated partial thromboplastin times (APTTs) were found in five patients with the use of an insensitive APTT reagent and in 14 patients with a lower phospholipid content reagent. In every case, attempted correction of the clotting time with normal plasma was unsuccessful. Twenty-one patients had abnormal kaolin clotting time profiles. In seven of these patients, test results with both APTT reagents had been normal. Antibody reactivity was tested against three negatively charged phospholipids, phosphatidyl-serine, cardiolipin, and phosphatidylinositol. Only five patients demonstrated reactivity against phosphatidylinositol, whereas high antibody titers were observed in 28 patients against one or both of phosphatidylserine and cardiolipin. Twenty-three of these patients were found to have elevated anticardiolipin-specific IgM antibodies. Overall, 41 of the patients had at least one laboratory abnormality suggestive of antiphospholipid antibody activity. Seven of the 26 patients, taking phenothiazines other than chlorpromazine, had positive test results for antiphospholipid antibodies. No clinical thromboembolic events were recorded in any patient. These findings demonstrate the heterogeneity of antiphospholipid antibody specificity induced in patients treated with various phenothiazine drugs and indicate that none of these patterns of reactivity marks a predisposition for thromboembolism in this population.