Background Imatinib, a tyrosine kinase inhibitor (TKI), is a substrate and inhibitor of cytochrome P450, therefore imatinib can be affected by concomitant drugs or a change in the concentration of other drugs. The absorption of imatinib can also be modified due to interactions. Haouala et al. (2011) reviewed available evidence about it.

Purpose To investigate the incidence of, and potential interactions between, imatinib and other drugs the patients were on.

Materials and methods This cross-sectional study was done in June 2013. Patients diagnosed with chronic myeloid leukaemia (CML) and treated with imatinib were selected. A database of drug interactions was made. The information was obtained from Micromedex and Lexicomp databases and from several scientific papers. Patients’ other medicines were obtained from the digital treatment histories. Interactions were analysed according to the drug, effects on concentrations, mechanism and severity.

Results 41 patients were selected, 56% female. The median age was 59 years (range: 24–91). A total of 73 potential interactions were detected in 33 patients: median of 1.8 interactions per patient (0–7). 45% of the interactions affected the concentration of imatinib: 77% of them could increase its concentration and 23% decrease it. 70% of the interactions affected the metabolism of the TKI and 30% modified its absorption. 55% of the interactions could change the concentration of the other drug (88% in terms of increasing it and 12% decreasing it). Interacting drugs were omeprazole (13%), simvastatin (10%) and ibuprofen (8%). Regarding the severity, 95% were classified as ‘moderate’, 5% as ‘mild’ and none as ‘major’.

Conclusions We found a high incidence of potential interactions between imatinib and other medicines. Almost half of the interactions affected imatinib. These findings led us to establish regular communication with physicians to avoid possible adverse effects or lack of efficacy.

No conflict of interest.