Influence of food on the pharmacokinetics of a new multiple unit sustained release sodium valproate formulation.

The influence of concomitant food intake on the pharmacokinetics of sodium valproate (CAS 1039-66-5) was studied in 16 healthy male volunteers. A single dose of a new sustained release formulation containing 300 mg sodium valproate (Orfiril long) was administered on two occasions either after a 12-h over-night fast or immediately after a standardised high energy high fat breakfast. A wash-out period of at least 1 week elapsed between the administrations. Valproate serum concentrations were measured by gas chromatography at intervals suitable for obtaining concentration-time curves for both regimens up to 72 h. The mean maximum serum concentration after fasting (17.0 micrograms/ml) was virtually the same as after a meal (16.8 micrograms/ml). Maximum concentrations were reached after 8 h for both nutritional states. The rate of elimination was not affected (terminal half-life approximately 15 h). The mean AUC0-infinity values were 468 micrograms/ml x h in fasting subjects and 458 micrograms/ml x h in postprandial subjects. The 90% confidence intervals for all pharmacokinetic target parameters were entirely confined in the bioequivalence range of 80 to 125%. The confidence intervals were even tighter, thus demonstrating homogeneity of drug release from the newly developed sodium valproate sustained release preparation. Bioequivalence with respect to extent and rate of absorption is therefore concluded for the comparison of fasting and non-fasting administration. The bioavailability of the sustained release sodium valproate preparation is not altered by the concomitant ingestion of food.