The prescribing information for Zytiga (abiraterone acetate; Janssen Biotech) has been updated to include new warnings and clinical data.

Zytiga, a CYP17 inhibitor, is indicated in combination with prednisone for the treatment of patients with metastatic castration-resistant prostate cancer (CRPC) and for metastatic high-risk castration-sensitive prostate cancer (CSPC).

The recent update to the labeling describes the risk of QT prolongation and Torsades de Pointes observed in patients who developed hypokalemia in association with treatment. Zytiga may cause hypertension, hypokalemia, and fluid retention as a consequence of increased mineralocorticoid levels resulting from CYP17 inhibition. Clinicians are advised to closely monitor patients with cardiovascular disease and to control hypertension and correct hypokalemia before and during treatment.

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Also, the labeling states that Zytiga plus prednisone/prednisolone is not recommended for use in combination with radium 223 dichloride outside of clinical trials. A phase 3 study investigating the concurrent initiation of Zytiga plus prednisone/prednisolone and radium 233 dichloride found that the combination increased the incidence of fractures and deaths among patients with asymptomatic or mildly symptomatic CRPC with bone metastases when compared with placebo and Zytiga plus prednisone/prednisolone.

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