Haematological adverse drug reactions in hospital practice.

A variety of drug-related haematological reactions is regularly encountered in a general hospital. These adverse drug reactions usually manifest as abnormal peripheral blood cell counts, which are usually low, involving one or more cell lines, but which may sometimes be raised as in drug-induced eosinophilia. Antineoplastic cytotoxic therapy, predictably, gives rise to cytopenias, which constitute the bulk of adverse haematological changes encountered in hospital practice. This paper addresses itself primarily to the unpredictable class of drug reactions which keeps the clinician vigilant. Its emphasis is on the clinical aspects and pathogenetic mechanisms of these iatrogenic haematological complications. Differences in tissue pattern of reaction to the same drug and the wide range of unrelated drugs capable of inducing a similar haematological aberration emphasises the role of individual susceptibility as the single most important factor in adverse drug reactions. Clarification of the pathogenetic mechanisms of different adverse drug reactions will ultimately come from the fields of pharmacogenetic and molecular genetics.