Oral absorption of the drug is a very important issue especially when the drug is poorly bioavailable, given for long periods and expensive. Poorly bioavailable drugs remain sub-therapeutic because a major portion of a dose never reaches the plasma or exerts its pharmacological effect unless and until very large doses are given which may also lead to serious side effects. Any significant improvement in bioavailability will result in lowering the dose or the dose frequency of that particular drug. Bioenhancers are chemical entities which promote and augment the bioavailability of the drugs which are mixed with them and do not exhibit a synergistic effect with the drug. The various bio enhancers available are piperine, garlic, Carum carvi, Cuminum cyminum, lysergol, naringin, quercetin, aziridine, glycyrrhizin, stevia, cow urine distillate ginger.