Thrombocytopenia due to digitoxin: Demonstration of antibody and mechanisms of action

Abstract

A case of digitoxin-induced thrombocytopenia is reported. Clot retraction inhibition studies using patient's platelet-rich plasma and digitoxin yielded positive results. Platelet factor 3 assay established the sensitivity of the patient to digitoxin. The sensitivity was specific for digitoxin; negative results were obtained with digoxin, ouabain, Cedilanid and digitoxigenin. Amino acid nitrogen generation was observed when platelets were incubated with the patient's serum and digitoxin. Studies using tritiated digitoxin demonstrated concentration of the drug on the surface of the platelet in the presence of the patient's serum. Negative results were obtained with red blood cells, latex particles and platelets treated with sodium cyanide. Starch gel electrophoresis demonstrated increased binding of digitoxin to the gamma globulin fraction of the patient's serum. The interaction of drug, antibody and platelets in druginduced thrombocytopenia is discussed.