Lack of kinetic interaction between valproic acid and citrus pectin

To determine the influence of ingestion of dietary fiber (citrus pectin) in the kinetic disposition of valproic acid, two studies were conducted in adult volunteers. Twelve healthy subjects took single oral doses of 500 mg valproic acid in a form of sodium valproate as coated tablets, on two occasions: under fasting conditions (treatment A) or immediately after ingestion of 14 g citrus pectin (treatment B). In each study, a randomized, single-dose, two-way crossover design was used, and 8 days elapsed between the two trials. Assays were carried out for valproic acid in plasma samples, which were collected from zero to 48 hours after drug administration. The peak plasma concentration (60.52 vs. 55.74 micrograms x ml-1), the time to peak concentration (3.47 vs. 3.91 h), the absorption rate constant (0.12 vs. 0.12 h-1), and the area under the plasma concentration-time curve (1324.0 vs. 1268.5 micrograms x h x ml-1) did not differ significantly between treatments A and B (median, Wilcoxon test). These results suggest that the administration of citrus pectin does not alter the rate and extent of absorption of valproic acid administered as a single dose to healthy volunteers.