Extrapolation to achieve actual half-life

Hello Everyone, We have done one parallel study to prove Bioequivalence, which failed on the lower side of Cl limits. We want to do crossover study, but in previous study we failed to capture actual half life. The API is having a half life around 4-5 days and we did a parallel study for 2 days. By M&S, we want to extrapolate to get actual half-life. And we want to calculate the sufficient wash-out period so that the carry-over effect will be <5% of Cmax in period 2 of crossover study. We have achieved final model and done with VPC,LLP, please guide me for simulation. Thanks & Regards Anuja ''Legally privileged confidential information and subject to "Disclaimer". http://www.cipla.com/Home/Other/Disclaimer.aspx