Hypermagnesemia in a Cat Secondary to Suspected Intoxication

To describe the management of a unique case of hypermagnesemia in a cat.

An 8-year-old spayed female domestic shorthair cat was presented for acute-onset stupor, hypothermia, and bradycardia. Overtly elevated ionized (>1.5 mmol/L [>3.6 mg/dL]; reference interval: 0.4-0.8 mmol/L [0.9-1.9 mg/dL]) and total magnesium (3.0 mmol/L [7.3 mg/dL]; reference interval: 0.74-1.0 mmol/L [1.8-2.5 mg/dL]) concentrations were identified. A thorough history uncovered the long-term at-home administration of an anxiolytic supplement containing magnesium stearate as an inactive ingredient. No other sources of nondietary magnesium were identified. A diagnosis of magnesium toxicosis was reached. Secondarily, an acute kidney injury developed. After 10 days of hospitalization, the cat was successfully discharged with normalized kidney and electrolyte values.

Few case reports regarding magnesium toxicosis and its management exist in the veterinary literature. A rare case of hypermagnesemia is presented in this report, highlighting the importance of a complete laboratory workup that includes an evaluation of magnesium levels in previously healthy animals that present with otherwise unexplained clinical signs.