Chiral drugs constitute more than 60 % of commercially marketed drugs in which the therapeutic activity resides mainly in one enantiomer while the other form either inactive or exhibits adverse effects. It is known that the enantiomeric forms of drugs have different pharmacological behavior and pharmacokinetics inside human body. Thus, administration of racemic drugs is technically an administration of two different drugs that necessitate careful control of their contents in dosage forms and pharmacokinetic behavior. High performance liquid chromatography with tandem mass spectrometric detection provides very efficient separation and determination of the drug enantiomers in biological matrices with appropriate selectivity and sensitivity. The drug enantiomers are extracted from biological samples using micro-extraction by packed sorbent (MEPS) syringes which can be fully automated and can aid purification and pre-concentration of the analyte. The drug enantiomers are determined in both plasma and saliva samples of human to evaluate the pharmacokinetic parameters of each enantiomer. The pharmacokinetic parameters are compared in plasma and saliva of patients to provide the best and most accurate in-vivo data about the drug enantiomers. The use of saliva as alternative specimen to blood and plasma for establishing exposure to drugs has become a significant direction in clinical and forensic toxicology. The choice of saliva matrix versus blood or plasma should be addressed seriously, given the well-recognized fact that saliva offers a fast and non-invasive sampling. Moreover, screening of potential biomarkers in salivary fluid shall be investigated as the diversity of salivary components and biomarkers whether in healthy or illness conditions facilitates disease surveillance and monitoring.
