[Retrospective Investigation of the Risk Factors for Severity in Panitumumab-Induced Hypomagnesemia]

Hypomagnesemia caused by panitumumab can often lead to severe adverse effects, such as arrhythmia. However, the risk factors are still controversial. To clarify the risk factors and time to onset of panitumumab-induced hypomagnesemia, we retrospectively investigated the records of 30 patients who had received panitumumab. They were divided into Grade B2 hypomagnesemia and non-Grade B2 hypomagnesemia groups, according to their serum magnesium levels, and we compared patients' backgrounds, laboratory values, and concomitant drugs between the 2 groups. Univariate analysis revealed that hypocalcemia and non-administration of an oral magnesium preparation were significantly associated with Grade B2 hypomagnesemia induced by panitumumab. Incipient grade 1 hypocalcemia was observed after incipient Grade 1 hypomagnesemia in both groups. The occurrence of these complications was significant in the Grade B2 hypomagnesemia group. Thereafter, in all patients of the Grade B2 hypomagnesemia group that exhibited both complications, hypomagnesemia developed to Grade 2 or higher. The development of Grade 3 and Grade 4 hypomagnesemia without the development of Grade 2 hypomagnesemia was observed in 2 patients each. Thus, aggravation of hypomagnesemia can be expected upon the administration of panitumumab, and therefore, not only serum magnesium levels, but also serum calcium levels need to be monitored.