Other safety alerts
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| Singapore: Xtandi™ (enzalutamide) interference with laboratory test CMIA leading to falsely elevated digoxin plasma levels |
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Health Sciences Authority (HSA) announces that a Dear Healthcare Professional Letter has been issued by Astellas Pharma Singapore Pte. Ltd. to inform healthcare professionals that XtandiTM (enzalutamide) may interfere with the chemiluminescent microparticle immunoassay (CMIA) laboratory test method. This interference can lead to falsely elevated digoxin plasma level results in patients taking enzalutamide, regardless of whether the patient is actually taking digoxin.
Healthcare professionals are advised to confirm the serum digoxin levels using another type of assay before determining the need for discontinuation or dose adjustments of digoxin in patients taking enzalutamide. Enzalutamide may also inhibit the efflux transporter P-glycoprotein (P-gp), leading to increased serum levels of digoxin, a P-gp substrate. Digoxin should therefore be used with caution when administered concomitantly with enzalutamide and may require dose adjustment to maintain optimal plasma concentrations.
Please refer to the following website in HSA for details:
http://www.hsa.gov.sg/announcements/dear-healthcare-professional-letter/xtandi--(enzalutamide)-interference-with-laboratory-test-cmia-leading-to-falsely-elevated-digoxin-plasma-levels
In Hong Kong, there are 4 registered pharmaceutical products containing enzalutamide. They are prescription-only medicines. Enzalutamide is used in the treatment of metastatic castration-resistant prostate cancer. So far, the Department of Health (DH) has received 22 cases of adverse drug reaction reports related to enzalutamide, but these cases were not related to interference with CMIA laboratory test results of digoxin. In light of the above HSA’s announcement, letters to inform local healthcare professionals will be issued, and the matter will be discussed by the Registration Committee of the Pharmacy and Poisons Board of Hong Kong.
Ends/Friday, Jan 16, 2026
Issued at HKT 16:45
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