Background Several patients treated with Glivec for chronic myeloid leukaemia were switched to the equivalent drug imatinib, after the expiry of the patent. However, the switch in some patients has revealed a suspected adverse reaction, which led to the re-use of the originator drug.
Purpose The aim of the study was to analyse the incidence and type of reports of adverse reactions before and after the switch by comparing them with national data.
Material and methods At our hospital, the use of equivalent imatinib began massively in October 2017. For the analysis of 7 months, two periods were compared: October 2016 to May 2017 (period 1: pre-switch) and October 2017 to May 2018 (period 2: post-switch). The source of the reports is the pharmacovigilance’s database of the Italian drug agency. The formulations in the market were also analysed in terms of composition.
Results In period 1, 77 patients were treated with Glivec and one adverse drug reaction was reported (1.3% eczema). During period 2, 69 patients were treated and there were five reports (two epigastric pain, diarrhoea, pruritus, one vomiting, one stomatitis, oedema, dyspnea, one skin rash), all with the equivalent drug (7.2%). None of these were serious. Because of the intolerance, three patients were switched back to Glivec. The increase in the number of reports was also reflected in the national data. From the authorisation of the marketing to the expiration of the patent (192 months) 330 reports of adverse reactions to Glivec were sent (1.7 ADR/month), while from the patent expiry to May 2018, 174 adverse reactions were reported and at least 123 were from an imatinib equivalent (10 ADR/month). The increase in reports post-switch was 83%. Regarding the formulation, there are differences in terms of pharmaceutical form (capsules/tablets), excipients and type of coating.
Conclusion Results suggest a possible correlation between the switch and the increase in the number of reports. However, as pointed out by AIFA, whenever a new equivalent drug comes on the market, the attention to reports may increase. It would be interesting to understand which components have caused adverse reactions and to identify patients at risk.
References and/or acknowledgements No conflict of interest.
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