Drug discovery and development involve a number of stages to develop a novel drug, therefore a reduction in time frame new approach is developed which is repurposing of existing drugs. Till to date, the importance of drug repurposing is significantly increased to identify new use of the pre-existing drug. Repurposed of the drug can be achieved by two methods, one is unintentionally and another by systemically (Parvathaneni, Kulkarni, Muth and Gupta, 2019). Drug repurposing is one type of drug recycling, to treat except the original one. For the new drug approximately 15 years can be taken place to bring it in the market as compared to repurposed drug takes only 3 to 12 years (Dey, 2019). This literature review is about drug repurposing with its development, opportunities and challenges. There are a number of methods are developed to identify and validate target of drug repurposing such as, computational and experimental. Both methods are different in lots of way except proteomics and genomics because these two entities make cells and tissues. These Omics are good biomarkers for the accurate treatment of disease. (Talev
i, 2018). There are a number of the opportunities of drug repurposing such as, when economic conditions are not good, unclear pathophysiology of rare disease, repurposing method is quick way to identify genetic variation, responsible factors of the disease and identified protein target (Pushpakom et al., 2018). There is low risk of adverse drug reaction and toxicity. Drug repurposing has high success rate i.e. 1/10 as compared to novel drug discovery i.e.1/10000. In the drawback, impairment in patenting new use of existing medicine, sometimes chances of the rejection because of previous toxic, adverse reaction and safety history. There are some strategies to accelerate drug repurposing such as, in silico models, target docking, artificial intelligence (AI). For the promotion of drug repurposing collaboration for bringing new ideas and approaches, corporate social responsibility, social media is also helpful to promote the awareness of drug repurposing (Dey, 2019). The main aim and objective of this literature review is, to review repurposed drugs with their potential as repurposed use including advances and challenges.