A pharmacokinetic comparison of three pharmaceutical formulations of nimesulide in healthy volunteers.

Background/aim: Switching the patient from one pharmaceutical formulation of the same drug to another, may lead to therapeutic inadequancy in some cases. To minimize the risk, careful pharmacokinetic studies are desired in the pre-registration period and afterwards.

Methods: A randomized, crossover design with one-week wash-out period between each dose was applied. Serum samples, obtained before dosing and at various appropriate time points up to 15 hours, were analyzed for nimesulide content by a high-performance liquid chromatographic method with ultraviolet (LU) detection. The pharmacokinetics and relative bioavailability of three different pharmaceutical formulations containing nimesulide, manufactured by the same pharmaceutical factory, were studied prospectively in 12 healthy subjects of both sexes. A single 100-mg oral dose of nimesulide was given to the volunteers in the form of conventional tablets, mouth dissolving tablets or as a suspension. Analysis of variance, power analysis, 90% confidence intervals, and two one-sided tests were used for the statistical analysis of pharmacokinetic parameters.

Results: The tolerability of all preparations was excellent. The respective confidence intervals of the ratios of geometric means of C(max) and AUC(0-infinity) of nimesulide were out of acceptable limits either for conventional tablets in comparison with suspension or for mouth dissolving tablets when compared with conventional tablets. A comparison of mouth dissolving tablets with suspension showed a statistically significant difference between C(max) values (suprabioavailability of mouth dissolving tablets), while the point estimate of the ratio of geometric means of AUC(0-infinity) was 0.945 with the corresponding 90% confidence interval of 0.902-0.991. At the 5% level of significance, there were no differences between the formulations under the study in times elapsed to peak serum concentrations, as revealed by the non-parametric Wilcoxon signed ranks test.

Conclusion: Only a 90% confidence interval for the relative differences of log-transformed AUC(0-infinity) values of nimesulide absorbed from mouth dissolving tablets vs. suspension was included in the 80% to 125% interval proposed by the Food and Drug Administration (FDA). On that basis, mouth dissolving tablets (Nimulid-MD) were considered bioequivalent to Nimulid suspension according to the extent of drug absorption. Concerning the comparable amounts of nimesulide available in the systemic circulation after application of these formulations the one might not expect therapeutic failure after switching the patient from one to another.