Abstract
Purpose. Imatinib treatment causes muscle cramps in up to
40% of patients, but their pathogenesis is unknown. We present
a case series illustrating an association between imatinib,
relative hypocalcaemia, and the development of cramps.
Patients. The index patient developed muscle spasms and
cramps after receiving imatinib for gastrointestinal stromal tumour
(GIST) for 5 months. The adjusted serum calcium had dropped to the
lower limit of normal. The low serum calcium and muscle cramps
improved on stopping imatinib and recurred on rechallenge. We
reviewed the medical records of 16 further patients.
Results. Two patients reported muscle cramps (12%).
There was a rapid and sustained reduction in adjusted serum
calcium in the first 6 months from 2.45 ± 0.11 mmol/L
(mean ± SD) to 2.30 ± 0.08 mmol/L (