Panitumumab-Related Hypomagnesemia in Patients With Colorectal Cancer

PurposeHypomagnesemia is an adverse reaction associated with epidermal growth factor receptor (EGFR)-targeting monoclonal antibodies. Of the 2 EGFR antibodies approved by the US Food and Drug Administration—cetuximab and panitumumab—cetuximab-induced hypomagnesemia has been extensively characterized but panitumumab-induced hypomagnesemia has not.MethodsIn this retrospective study, the clinical course of hypomagnesemia is described in three 64- to 68-year-old men who received panitumumab monotherapy or panitumumab-plus-irinotecan therapy for colorectal cancer for 8 to 21 weeks.ResultsThe onset of hypomagnesemia was variable, ranging from 1 week to 10 weeks following the initiation of panitumumab. Magnesium levels did not normalize until 4 to 8 weeks after discontinuation of the agent. Of the patients in the study, 2 had new onset of grade 3 hypomagnesemia 1 to 3 weeks after panitumumab was discontinued. Management was magnesium sulfate 2 g infusion weekly and magnesium oxide 1,200 mg oral repletion daily. ...