In this book a variety of techniques for the extraction of drugs from the plasma matrix have been investigated, the data was subjected to different statistical evaluation procedures, to properly evaluate the measured analytical outcomes. After evaluating the concentration–time profiles of pooled samples, previously harvested from dosed human volunteers, the effect of different extraction procedures on the calculated pharmacokinetic parameters was compared. Two types of drugs, classified as Non-Insulin-Dependent Diabetes Mellitus (NIDDM) active ingredients were selected in this study. Glibenclamide was chosen to represent a highly protein bound drug, whereas Metformin was chosen to represent a low protein bound drug. The primary bioanalytical methods validation parameters such as recovery, selectivity, specificity, sensitivity, limit of quantitation and limit of detection, in addition to uncertainty in the analytical measurement have been extensively reviewed. Rigorous approaches using different statistical weights for evaluating calibration data were also derived for each drug using various experimental conditions.