Detection of drug‐dependent antibodies by the 51cr platelet lysis test: Documentation of immune thrombocytopenia induced by diphenylhydantoin, diazepam, and sulfisoxazole

Abstract

Sudden, severe thrombocytopenia developed in each of three patients receiving diphenylhydantoin, diazepam, and sulfisoxazole, respectively. Recovery followed discontinuance of the drugs. An antiplatelet antibody requiring the presence of an appropriate drug for interaction with platelets was demonstrated in each case by the ⁵¹Cr platelet lysis test using normal, paroxysmal nocturnal hemoglobinuric, or enzyme‐treated normal platelets as target cells. These antibodies could not be detected by techniques that depend on clot retraction inhibition, complement fixation, or platelet factor‐3 activation. Quinine‐ and quinidine‐dependent antiplatelet antibodies in the serum of 16 patients who developed acute thrombocytopenia while taking either quinine or quinidine could be demonstrated readily with the ⁵¹Cr platelet lysis test and could also be detected by other methods employed.