[Drug allergy damage to the blood ]

Drug induced blood dyscrasias, leukocytopenia, thrombocytopenia and hemolytic anemia were observed in 7% of 643 adverse drug reactions registered by drug monitoring in Bern, Switzerland, in the period 1970-1973. Life threatening reactions were consistently more frequent in hematological side effects (22%) than in the total of adverse drug reactions (6%). Blood dyscrasias induced by drug allergy are generally believed to belong to the allergic reactions of type II. Antigen-antibody reaction evolves in connection with cells of the blood, either by fixation of the drug itself or a metabolite on the cell surface, or by adsorption of primarily formed antigen-antibody complexes on the cell. In drug induced immune hemolytic anemia three types may be distinguished: 1. the innocent bystander type, caused by quinine, PAS, rifampicin and others, 2. the penicillin-type, caused by penicillins and cephalosporins, and 3. the autoimmune type caused by alpha-methyl-dopa etc. Agranulocytosis in Europe is most frequently due to pyrazolones, while phenothiazines play the leading role in the USA. In pyrazolone agranulocytosis an allergic pathogenesis is very probable, whereas phenothiazines probably induce agranulocytosis by a direct toxic effect on bone marrow cells. The clinical course in pyrazolone agranulocytosis is acute, whereas it is rather insidious in the phenothiazine type. The main drugs causing allergic thrombocytopenia are thiazide diuretics, quinine, quinidine and sulfonamides. Clinical aspects and therapy of drug induced blood dyscrasias are discussed.