What is one proposed mechanism by which valproic acid may cause carnitine deficiency?

• A. Impaired renal handling.
• B. Inhibition of hepatic carnitine synthesis.
• C. Increased intestinal loss.
• D. Inhibition of carnitine transport into cells.

Answer: (A)

Valproic acid can deplete carnitine primarily through renal loss. Carnitine is filtered by the kidneys and normally reabsorbed in the proximal tubule. With valproate exposure, carnitine can be lost in the urine more readily (sometimes via formation of valproylcarnitine or competition for reabsorption), leading to reduced body stores over time. This increased urinary excretion is the most supported mechanism for how valproic acid causes carnitine deficiency. Other proposed ideas, like inhibiting hepatic synthesis, increasing intestinal losses, or blocking cellular uptake, are less consistent with current understanding.