Histamine H2-receptor antagonists are widely used in the treatment of gastrointestinal diseases related to gastric acid hypersecretion. Cimetidine was introduced into medical practice in 1976 and ranitidine, famotidine and nizatidine in 1981, 1985 and 1987, respectively. Haematological adverse effects are relatively uncommon and most have been reported in cases of cimetidine administration. These adverse effects are reviewed under 4 main headings: (a) blood cytopenias and leucocytosis; (b) coagulation disorders related to drug interactions with oral anticoagulants; (c) reduction of dietary iron absorption; and (d) reduction of dietary cobalamin absorption. 85 reported cases of blood cytopenias attributed to these drugs are reviewed, of which 75 (88%) were associated with cimetidine therapy. In postmarketing surveillance studies, the incidence of cimetidine-associated blood cytopenia has been evaluated at about 2.3 per 100,000 patients. Neutropenia and agranulocytosis are by far the most frequently encountered. Whatever the drug or the type of cytopenia, this adverse effect is almost always rapidly reversible when treatment is stopped. Moreover, in several cases other factors such as underlying diseases or additional drugs could have been responsible, at least partly, for the cytopenia. The pathophysiological basis of these adverse effects remains poorly explained. Various mechanisms have been proposed, which in some cases are probably associated: (a) direct toxicity for haemopoietic stem cells; (b) drug-induced immune reactions leading to blood or bone marrow cell damage, and (c) drug interactions, with increased and prolonged action of potentially haematotoxic drugs. Mechanisms (a) and (c) appear to be of particular clinical importance in cases of impaired renal elimination of H2-receptor antagonists. Cimetidine and probably to a lesser extent ranitidine potentiate the action of oral anticoagulants of both coumarin and indanedione structure. This may result in haemorrhagic complications. Such action is a consequence of the reduced hepatic metabolism of oral anticoagulants through a dose-dependent, reversible inhibition of cytochrome P450. Malabsorption of dietary iron and cobalamin appears to result from inhibition of gastric secretion by the H2-receptor antagonists. This is of no clinical importance in short term treatment, but long term use of H2-receptor antagonists may theoretically contribute to the occurrence of iron or cobalamin deficiency anaemia.
A 34‐year‐old woman with typical chronic myelogenous leukemia was treated with daily busulfan (total dose, 1600 mg approximately) from July 1978 to June 1981. In February 1981, she noticed a progressive deterioration of her clinical status, characterized by increasing dyspnea and productive cough. In July 1981, an open lung biopsy revealed pulmonary alveolar proteinosis. The patient died of progressive respiratory failure in August 1981. The association between chronic myelogenous leukemia and pulmonary alveolar proteinosis is briefly reviewed. The report discusses the possible etiologic role of busulfan therapy in the development of pulmonary alveolar proteinosis.
Therapy-related leukemias are generally preceded by a preleukemic phase of several months duration, characterized by pancytopenia, abnormal bone marrow findings, and nonrandom chromosomal abnormalities in almost all cases. No specific therapeutic guidelines are recommended in this preleukemic phase or any other type of preleukemia; aggressive combination chemotherapy is usually withheld until the full expression of leukemia. A 22-yr-old man with therapy-related preleukemia following treatment of Hodgkin's disease received as primary treatment ablative chemotherapy followed by marrow transplantation from his histocompatible sister. At day 316, the patient is still in complete bone marrow recovery with a normal donor karyotype. In the light of the very poor results obtained with conventional chemotherapy regimens once the leukemic phase is established, we suggest that bone marrow transplantation, if undertaken before leukemic conversion, may be the treatment of choice in young adults with therapy-related preleukemia.
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