Table 1.

Total sample size required for 90% co-primary power^a for symmetric and asymmetric equivalence margins

GMR	Equivalence margins (%)	CV (%)	Attrition rateb (%)	Total sample sizec (n)	Total enrolled sample size (n)
95%	80–125	50	25	326	436
	80–140	50	25	326	436
100%	80–125	50	25	234	312
	80–140	50	25	194	260
105%	80–125	50	25	318	424
	80–140	50	25	150	200

AUCτ area under the concentration versus time curve in the dosing period, CI confidence interval, C_max maximum (or peak) concentration, CV coefficient of variation common to AUCτ and C_max, GMR geometric mean ratio common to AUCτ and C_max

^aCo-primary power is the probability that the 90% CI for the GMR lies within the equivalence margins for both AUCτ and C_max. For illustration purposes, AUCτ and C_max are treated as uncorrelated; the required sample size will be slightly smaller if these parameters are positively correlated

^bAttrition rate is the expected attrition from the analyses of AUCτ and C_max

^cTotal sample size is the evaluable sample size required in the analysis, assuming 1:1 randomization; total enrolled sample size: required enrolled sample size taking into account attrition from the analysis