Levocarnitine-Induced Hypophosphatemia in a Hemodialysis Patient With Acute Valproic Acid Toxicity

L-carnitine acts as a cofactor for VPA metabolism, increasing beta-oxidation of VPA and limiting hepatotoxic metabolites.1 Hypercalcemia is a known metabolic adverse effect with L-carnitine;2 however, a study in hemodialysis patients reported decreased phosphorus levels after its use.3 We present a case in which L-carnitine was administered for acute VPA toxicity and subsequently may have contributed to hypophosphatemia. Hyperphosphatemia decreases production of 1,25-hydroxyvitamin D because of direct and indirect inhibition of the renal enzyme 1[alpha]-hydroxylase.4 Over time, secondary hyperparathyroidism develops, resulting in hypocalcemia, hypophosphatemia, and vitamin D deficiency.5 Our patient's laboratory values were consistent with this.