Idiosyncratic drug-induced haematological abnormalities. Incidence, pathogenesis, management and avoidance.

Haematological dyscrasias remain important because they are potentially fatal. Their accurate reporting is required to confirm the cause-effect relationship of suspected adverse drug reactions (ADRs); to estimate their incidence; and, by risk-benefit analysis of such events, to introduce preventive measures to reduce their impact. Limitations within the available data on haematological ADRs are reviewed and some suggestions made for improvement. The drugs most commonly associated with haematological dyscrasias are listed. An understanding of the pathogenesis of haematological dyscrasias is essential for their effective management and these are briefly reviewed. Features common to the management of the different types of haematological dyscrasia include the early involvement of a haematologist and drug information pharmacist and the accurate identification and early withdrawal of any likely offending agent. Guidelines for the management of drug-induced aplastic anaemia, agranulocytosis, thrombocytopenia and haemolytic anaemia are presented and the potential value of granulocyte and granulocyte-macrophage colony-stimulating factors (G-CSF; GM-CSF) in the management of agranulocytosis is specifically mentioned. Finally, general principles are discussed whereby serious haematological ADRs might be prevented. These include: the importance of continuing education for drug prescribers; policies on the restricted prescribing of likely offending agents; the use of written instructions for patients; and, the use of haematological monitoring. The guidelines presented in this article should be adapted to meet local circumstances and would prove suitable subjects for audit of their effectiveness.