Evergreening refers to the various strategies whereby owners (innovators/sponsors) of pharmaceutical products use patent laws and minor drug modifications to extend their monopoly privileges on the drug.   An enantiomer patent is another form of evergreening based on a chiral switch strategy. Single-enantiomer drugs represent more than 50% of the top-selling 100 drugs worldwide. There are some studies which go to suggest that drug companies employ chiral switching for life-cycle management/patent protection of the parent racemic drug and also as a marketing strategy. Pharmaceutical companies support evergreening practices. Some chiral switches are performed to re-start the patent clock for a medication without reducing side effects or improving efficacy. A high price can then continue to be charged for a medication. Examples include citalopram and escitalopram, and omeprazole and esomeprazole. In both these medications, proposed theoretical benefits were used to market the enantiopure drugs, without any clinical trials being conducted to provide evidence that the racemic drugs improved patient centered outcomes.