Many drugs have been reported to have caused anaemia. The most serious form involves marrow aplasia, but the way in which this is produced is not understood. A number of drugs lead to megaloblastic anaemia and where this is caused by interference with dihydrofolate reductase the explanation is obvious. However, some substances, notably anticonvulsants, cause megaloblastic anaemia by some other mechanism. A number of drugs cause intestinal bleeding with anaemia as a result. Sideroblastic anaemia is a relatively rare condition, sometimes caused by drugs, particularly those used in the treatment of tuberculosis. Leukaemia very occasionally supervenes in patients with drug-induced aplastic anaemia.
PIP: Several forms of drug-induced anemia are discussed. Anemia resulting from toxic effects on the marrow may occur after large doses or long treatment courses of alkylating agents, the plant alkaloids vinblastine and vincristine, and antibiotics used in cancer chemotherapy. A lesion of the stem cells in bone marrow is thought to be caused. Aplastic anemia has been produced by chloramphenicol in a small percentage of cases. This has led to its disuse except when no suitable alternative is available or where the mortality of the disease being treated is high. Some nonnarcotic analgesics, e.g., amidopyrine, have caused agranulocytosis. Gold injections have also been implicated. Insecticides or an inhaled agent such as benzine or a glue solvent may cause hypoplastic anemia. A list is given of drugs that have been reported as having caused aplastic anemia. Chromosomal changes have rarely been reported. An alleric mechanism is sometimes responsible for drug-induced aplastic anemia. There may be individual variations in ability to metabolize a drug. Treatment of drug-induced aplastic anemia requires transfusions. Bone marrow transplants have also been used. Antibiotic therapy is needed. Oral contraceptives may be of value if there is menorrhagia. Megaoloblastic anemia may be due to defective metabolism of folate. Anticonvulsant drugs may also cause megaloblastic anemia, especially primidone. Giving folic acid with these drugs may prevent this development. Oral contraceptives have been reported to cause folate depletion but megaloblastic anemia has not been shown to follow. Alimentary bleeding with peptic ulcer or following drug use may cause anemia. Sideroblastic anemia may be a congenital abnormality of iron metabolism or an acquired form induced by drugs or lead poisoning. Pyridoxine therapy is used. Drug-induced leukemia may follow use of radioactive compounds or may develop in patients with a drug-induced aplastic anemia.