Journal of Bioequivalence & Bioavailability

Abstract

Comparison of Two Formulations of Sodium Divalproate Plasma Concentrations after a Single 500 mg Oral Dose in Healthy Subjects, and Stochastic Sub-analysis of the Individual “ Clinical Perceptible ” Levels

Nunez DA, Schiaffino S and Roldán EJA

A new generic formula containing 500 mg of sodium divalproate in enteric releasing coated tablets was compared to the reference product in a pharmacokinetic, randomized, cross-over 2×2 study performed in 24 healthy adult males. After administering a single dose, it was demonstrated that the maximum plasma concentration of valproic acid varies within the 98.4-113.0 range for 90% CI (test/reference); and the area under the curve of plasma levels over the 24 h period following the intake varies within the 91.1-99.5 range; therefore, it can be seen that both parameters are within the range of acceptance for the interchangeability of the products. Individual results show the typical inter- subject and inter -treatment variations of divalproate. Since the latter have an impact on the prescription decision, results are sub-analyzed considering a plasma threshold of valproic acid as effective or stochastically clinical perceptible (Cper).Complete duration of plasma levels above Cper is comparable for both formulations (p<0.81); nevertheless, the test product reaches the Cper value faster than the reference compound (p<0.04). Therefore, we consider that the individual perception of efficacy of the generic product should not be inferior to that of the reference. In conclusion, the tested formula is bioequivalent and the further sub-analysis of individual variations above a plasma level of stochastic clinical perception of effects shows non-relevant differences between both brands.