Valproate Interactions

Valproate (valproic acid) depletes carnitine by sequestering it as valproyl-carnitine for mitochondrial transport and by reducing renal reabsorption of free carnitine. Carnitine depletion can impair fatty-acid oxidation and the urea cycle, contributing to raised blood ammonia (hyperammonemia), liver stress, and in some cases encephalopathy.

Aspirin and other salicylates push valproate off its plasma-protein binding sites and slow one of its breakdown pathways, so the active, unbound portion of valproate can rise even when the standard total valproate blood level looks unchanged. This can mask a clinically meaningful increase in active drug and raise the risk of valproate toxicity such as sedation, tremor, confusion, raised ammonia, and liver strain, while aspirin's own anti-clotting effect adds to valproate's tendency to lower platelets.

Taking CBD (including prescription Epidiolex and over-the-counter products) together with valproate raises the chance of liver enzyme elevations well above either drug alone, and the combination has been linked to high blood ammonia that can cause confusion or worsening seizures even when liver tests look only mildly abnormal. This pairing should be managed by the prescribing neurologist with baseline and follow-up liver testing.

Valproate appears to lower biotinidase activity and may impair mitochondrial biotin handling, contributing to subnormal biotin status that has been linked to the drug's characteristic hair thinning and brittle nails. Case reports describe biotin supplementation reversing valproate-related hair loss, though the underlying biotin-status studies are mixed.