DEMOGRAPHIC CONSIDERATIONS IN BIOEQUIVALENCE STUDIES. S. Lamouche, Ph.D., K. Boulanger, M.Sc., E. Shink, Ph.D., F. Trabelsi, Ph.D., M. Tanguay, Ph.D. SFBC Anapharm PURPOSE: The objective of bioequivalence (BE) studies is to evaluate whether two products are equivalent in rate and extent of absorption. Attempts are made to diminish or tightly control any confounding variables in order to achieve this objective. It is sometimes argued that enrolling a more homogeneous population would reduce the intra-subject coefficients of variability (ISCV) of pharmacokinetics parameters, thus requiring fewer subjects. The purpose of this study was to conduct a retrospective analysis on BE studies conducted at SFBC Anapharm to examine the impact of demographic factors on the ISCV. METHODS: 75 two-way cross-over BE studies involving anti-hypertensives and anti-depressants were included in this analysis. These therapeutic areas were chosen as they offered the largest pool of study with the least restrictive inclusion criteria for the initial study population. For each individual study, the ISCV was recalculated considering a more homogenous population where subjects satisfied stringent inclusion criteria for the factor being investigated: Factor Included Excluded Gender Men only Women Age 18 to 55 years 56 years and older Ethnicity Caucasian only All but Caucasians Body mass index (BMI) ≥ 19 and 24.9 kg/m2 ≤ < 19 and > 25 kg/m2 Smoking Non-smokers Smokers The ISCV with and without the subset of the original population being investigated were compared by parametric (Student Paired T-Test) and non-parametric (Signed Rank test) tests. RESULTS: Overall, the majority of studies showed a reduced ISCV when including a more homogeneous population in terms of Gender (p = 0.0009), Age (p = 0.0273), and Smoking (p = 0.0164). For anti-hypertensives, only Gender (p = 0.0004) and Age (p = 0.038) had an impact whilst for anti-depressants, Smoking was the only significant factor (p = 0.0310). CONCLUSIONS: Restricting study population in terms of Gender, Age, and Smoking could be associated with a decrease in ISCV, although this was not observed for all drugs investigated. However, being more stringent for BMI and Ethnicity did not result in changes in ISCV. These results may be useful in designing future BE studies with special emphasis on demographic factors.