Drug promiscuity and polypharmacology are much discussed topics in pharmaceutical research. Drug repositioning applies established drugs to new disease indications with increasing success. As polypharmacology, defined a drug's ability to bind to several targets but due to possible side effects, this feature is not taken into consideration. Thus, the pharmaceutical industry focused on the development of highly selective single-target drugs. Nowadays after lot of researches, it is clear that polypharmacology is important for the efficacy of drugs. There are side effects but on the other hand, this gives the opportunity to uncover new uses for already known drugs and especially for complex diseases. Thus, it is clear that there are two sides of the same coin. There are several approaches to discover new drugs targets, as analysis of genome wide association, gene expression data and networks, structural approaches with alignment methods etc. Computational drug discovery and design has experienced a rapid increase in development which is mainly due to the increasing cost for discovering new compounds. Since drug development is a very costly venture, the pharmaceutical industry puts effort in the repositioning of withdrawn or already approved drugs. The costs for bringing such a drug to market are 60% lower than the development of a novel drug, which costs roughly one billion US dollars. Thus, target prediction, drug repositioning approaches, protein-ligand docking and scoring algorithms, virtual screening and other computational techniques have gained the interest of researchers and pharmaceutical companies.