• CHANDRAKALA V Department of Pharmaceutics, East Point College of Pharmacy, Avalahalli, Bengaluru, Karnataka, India.
  • UTPAL KUMAR SANKI Department of Biostatistics, ICON Plc, Bengaluru, Karnataka, India.


Objective: New technique was adopted and validated to estimate pivotal sample size from the pilot study data and to establish bioequivalence (BE) of highly variable drugs (HVD), paroxetine, a novel controlled release (CR) matrix tablets utilized ghatti Gum as a rate controlling membrane, in human subject under fed conditions by reference scale design.

Methods: Bootstrapping technique was adopted to calculate the pivotal sample size from pilot study data for HVD paroxetine. The reliability and validation of the method were tested in a semi replicate three sequence (RRT, RTR, and TRR where T stand for test drug and R stand for reference drug) cross-over BE study in 24 healthy subjects under fed conditions.

Results: The ratio of the pharmacokinetic (PK) metric obtained from the bootstrapping technique after log transformation was 1.04 for Cmax, 1.23 for AUCT, and 1.21 for AUCI with corresponding power of the study which was greater than 80% from pilot study data simulation. The ratio of the PK metric obtained from the reference scaling design in the present study was 1.00 for Cmax, 1.21 for AUCT, and 1.17 for AUCI. The upper limit of the Cmax, AUCT, and AUCI at 95% confidence limit was −0.143, −0.136, and −0.17, respectively.

Conclusion: The test paroxetine CR formulation was bioequivalent with reference drug under fed conditions. The technique used for estimation of the sample size in the pivotal study was found reliable, and bootstrapping technique plays an important role in calculating sample size where intrasubject variability was immaterial.

Keywords: Reference Scaling, Bootstrapping Techniques, Sample Size, Bioequivalence, Controlled Release


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