•There is an emerging need for new therapies for rare diseases in a shorter time frame.•Drug repurposing could arise from serendipitous observations or exploiting side effects.•Today, researchers have addressed drug repurposing in a systematic manner but there are challenges to be overcome for successful repurposing in the future. Traditional drug discovery and development involves several stages for the discovery of a new drug and to obtain marketing approval. It is necessary to discover new strategies for reducing the drug discovery time frame. Today, drug repurposing has gained importance in identifying new therapeutic uses for already-available drugs. Typically, repurposing can be achieved serendipitously (unintentional fortunate observations) or through systematic approaches. Numerous strategies to discover new indications for FDA-approved drugs are discussed in this article. Drug repurposing has therefore become a productive approach for drug discovery because it provides a novel way to explore old drugs for new use but encounters several challenges. Some examples of different approaches are reviewed here.