Informing & Supporting Thyroid Patients Since 1985
Informing & Supporting Thyroid Patients Since 1985
Thyroid Research 
Thyroid Research Archive Hyperthyroidism
(July 2003)
The background of the study. The antithyroid drugs carbimazole, methimazole, and propylthiouracil can cause a low white-cell count (neutropenia). In this study, the prevalence and outcome of neutropenia in England and Wales was studied.
How the study was done. The General Practice Research Database, which contains the medical records of patients cared for by many general practitioners in England and Wales, was searched for the years 1988 to 1999 for patients with the diagnostic code for neutropenia (≤500 white blood cells/mm3) in their records. Drug exposure was determined by reviewing prescription information before the diagnosis of neutropenia. Each patient was matched with three control patients of the same age and sex, and from the same practice.
The results of the study. There were 3224 patients with a drug-related neutropenia, of whom 44 had taken an antithyroid drug (probably mainly carbimazole). The estimated overall rate of neutropenia was 120 cases/million people/year. Among 21 classes of drugs, the risk of neutropenia was highest among patients given an antithyroid drug, aminosalicylates (given to patients with inflammatory bowel diseases), drugs given to treat rheumatic disorders, and drugs given to treat seizures.
Among the 44 patients with neutropenia who were treated with an antithyroid drug, 6 had received one prescription (vs. one in the control group), 16 had received two or three prescriptions (vs. one in the control group), and 22 had received four or more prescriptions (vs. two in the control group).
The conclusions of the study. Among commonly administered drugs, the risk of neutropenia is highest in patients treated with an antithyroid drug.
The original article. Van Staa TP, Boulton F, Cooper C, Hagenbeek A, Inskip H, Leufkens HG. Neutropenia and agranulocytosis in England and Wales: incidence and risk factors. Am J Hematol 2003;72:248-54.
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