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Article Dans Une Revue Clinical Toxicology Année : 2018

Enzalutamide and analytical interferences in digoxin assays

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OBJECTIVE: We report two cases of elevated digoxin plasma levels in patients receiving enzalutamide. Cases reported: The first patient, an 84-year-old male treated with enzalutamide, was hospitalized due to deterioration in his general state. Atrial fibrillation was discovered and treatment with digoxin was initiated. Supratherapeutic digoxin concentrations (4 µg/L and 3.5 µg/L 3 days later) led to treatment being stopped despite the lack of clinical or biological signs of overdose. The second patient, an 84-year-old male treated with digoxin and enzalutamide, was hospitalized for the same reasons. Digoxin concentration upon admission was 2.8 μg/L. Despite stopping treatment, digoxin blood levels were observed to have increased on D3 and D7 following admission (3 and 3.6 μg/L, respectively). However, no clinical or biological findings indicated an overdose. Blood samples were sent to the Pharmacology and Toxicology Laboratory for analysis.

METHODS: The second patient's digoxin plasma level was determined using the chemiluminescent microparticle immunoassay (CMIA®, Abbott, Illinois) method. Enzalutamide levels were determined using HPLC-UV/DAD method. An interference study was performed using different assay methods by adding enzalutamide to control plasma at various concentrations from a Xtandi (40mg) capsule.

RESULTS: Plasma concentration of digoxin at D7 for patient 2 was identical in both laboratories (3.5 vs. 3.6 µg/L). Enzalutamide was found in the patient's plasma (12,5 mg/L). Adding 4, 10, 20, and 40 mg/L of enzalutamide to the untreated plasma showed that the plasma concentration of digoxin was positive (from 0.35 to 3.69 µg/L) using the CMIA method.

CONCLUSIONS: Our results highlight the analytical interferences of enzalutamide with digoxin assays using the CMIA method.

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Dates et versions

hal-02872855 , version 1 (17-06-2020)



Marie Deguigne, Marion Brunet, Chadi Abbara, Alain Turcant, Gaël Le Roux, et al.. Enzalutamide and analytical interferences in digoxin assays. Clinical Toxicology, 2018, 11 (56), pp.1150-1154. ⟨10.1080/15563650.2018.1469758⟩. ⟨hal-02872855⟩


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