While manufacturing generic drugs, the drug companies use the same active ingredients and, they have the same risks and benefits as their brand name likeness. Also, generic drugs have the same quality, strength, purity and stability as brand name drugs. The generic drugs are less expensive as compared to branded drugs as generic manufacturers do not have the investment costs of the developer of a new drug. New drugs are generally developed under patent protection. Bioequivalence is based on rate and extent, but rate and extent is depending on the absorption. Absorption is depending on drug dissolution, permeability and solubility. Firstly permeability and solubility related to biopharmaceutical classification system discovered by Gordon Amidon et al. in 1995. Bio analysis carried out with help of LC/MS and use of Solid phase extraction, Liquid/Liquid extraction, Protein precipitation.