VHE is generally characterized by an acute onset of impaired consciousness, focal
neurologic symptoms, and increased seizure frequency. The exact mechanism of VHE is unclear but relates to the accumulation of toxic
valproic acid metabolites and elevated
ammonia levels.
Carnitine is an essential cofactor in the proper metabolism of
valproic acid and
ammonia elimination. A lack of
carnitine is thought to contribute to
hyperammonemia.
Valproic acid is thought to increase renal metabolism of
glutamate and may contribute to
ammonia production.
Levocarnitine, the active isomer of
carnitine, has been used to treat VHE resulting from
valproic acid overdose as well as usual dosages of
valproic acid. A literature search of PubMed was conducted for all English-language articles published from 1948 to May 2011 regarding the use of
levocarnitine for VHE. Search terms included
levocarnitine,
l-carnitine,
valproic acid, and
hyperammonemia encephalopathy. Although large, randomized controlled trials of
levocarnitine treatment in VHE are lacking,
levocarnitine has been shown to be generally safe and effective in retrospective trials and case reports. Overall, there is more literature supporting the use of
levocarnitine in VHE associated with acute overdose than with short- or long-term treatment with usual dosages of
valproic acid. No adverse events related to
levocarnitine therapy were reported in any of the literature reviewed. Prospective trials are needed to further support the efficacy and safety of
levocarnitine in the treatment of VHE.
CONCLUSION: