ABSTRACT
Drug repurposing process aims to identify new uses for the existing drugs to overcome traditional de novo drug discovery and development challenges. At the same time, as viral infections became a serious threat to humans and the viral organism itself has a high ability to mutate genetically, and due to serious adverse effects that result from antiviral drugs, there are crucial needs for the discovery of new antiviral drugs, and to identify new antiviral effects for the exciting approved drugs towards different types of viral infections depending on the observed antiviral activity in preclinical studies or clinical findings is one of the approaches to counter the viral infections problems. This narrative review article summarized mainly the published preclinical studies that evaluated the antiviral activity of drugs that are approved and used mainly as antibacterial, antifungal, antiprotozoal, and anthelmintic drugs, and the preclinical studies included the in silico, in vitro, and in vivo findings, additionally some clinical observations were also included while trying to relate them to the preclinical findings. Finally, the structure used for writing about the antiviral activity of the drugs was according to the families of the viruses used in the studies to form a better image for the target of antiviral activity of different drugs in the different kinds of viruses and to relate between the antiviral activity of the drugs against different strains of viruses within the same viral family.
