Time-dependent changes in serum magnesium levels in patients receiving cetuximab with low baseline serum sodium levels.

Cetuximab causes electrolyte abnormalities, such as hypomagnesemia, hypokalemia, and hypocalcemia. However, little is known about the relationships between the onset of hypomagnesemia, patient background before administration, and time-dependent changes in serum magnesium levels. Therefore, we examined the patient backgrounds that influenced the onset of hypomagnesemia and the time-dependent changes in serum magnesium levels in patients receiving cetuximab. A retrospective study was performed to investigate patients with advanced or recurrent colorectal cancer or head and neck cancer, treated with a cetuximab regimen from 2012 to 2020 at Kindai University Nara Hospital. In total, 52 patients who met the inclusion criteria were enrolled in this study. The serum magnesium level was significantly lower in the hyponatremia before the administration group than in the non-hyponatremia group (p < 0.001). Univariate logistic regression analysis revealed that the baseline serum sodium levels (odds ratio [OR]: 0.741, 95% confidence interval [CI]: 0.588-0.934) and the combination of magnesium oxide tablet (OR: 0.997, 95% CI: 0.995-0.999) were one of the independent factors for hypomagnesemia. These results indicated that hyponatremia before administration may be an indicator of serum magnesium levels after administration of cetuximab. Cetuximab-induced hypomagnesemia may be predicted using baseline serum sodium levels, and hypomagnesemia may be prevented by administration of magnesium oxide tablets. Our findings provided new evidence for the management of serum magnesium levels in patients receiving cetuximab.