Abnormal 13 C-Fatty Acid Breath Tests in Patients Treated With Valproic Acid

Breath tests using fatty acids labeled with a stable isotope (carbon 13) were carried out on epileptic patients treated with valproic acid in order to detect abnormal fatty acid metabolism. The patients were given 13 C-octanoic acid or 13 C-palmitic acid orally, and expired air was collected at appropriate intervals for the analysis of 13 CO 2 content by a mass spectrometer. Eight patients were tested in the palmitic acid breath test and nine patients in the octanoic acid breath test. Controls for these tests were patients treated with antiepileptic drugs other than valproic acid and unmedicated cerebral palsy patients. In the valproic acid-treated group, 13 C recovery was reduced by 56% in seven hours on the 13 C-palmitic acid breath test, while the octanoic acid breath test showed a 52% reduction in one hour. This suppression of fatty acid oxidation was significantly correlated with dose of valproic acid in both tests. No influence of other drugs was detected, and the effect of administered carnitine was not conclusive. This study demonstrates the usefulness of 13 C-labeled fatty acid breath tests in clinical practice. ( J Child Neurol 1988;3:250-257).