Non-structural protein 5B (NS5B) inhibitors are a class of direct-acting antivirals widely used in the treatment of chronic hepatitis C. Depending on site of action and chemical composition, NS5B inhibitors may be categorized into three classes—nucleoside active site inhibitors (NIs), non-nucleoside allosteric inhibitors, and pyrophosphate analogues. Subsequently, all three classes are then subclassified. All inhibit RNA synthesis by NS5B but at different stages/sites resulting in inability of viral RNA replication. Expression of direct-acting NS5B inhibitors does not take place in cells that are not infected by hepatitis C virus, which seems to be beneficial for this class of drugs. Low efficacy, serious side effects, development of resistance of previously available hepatitis C treatments were the greatest concerns prior to the development of direct-acting antivirals, and remained a problem at the beginning of their development. Therefore, combinational direct-acting antiviral therapies were preferable. Research has demonstrated that specific anti-hepatitis C virus agents such as NS5B inhibitors lead to improved efficacy and tolerability. Medical uses Hepatitis C is one of the most significant diseases to affect humans but despite its global impact, there are no vaccines or effective therapies without major side effects. The hepatitis C virus non-structural protein 5B (NS5B) has become a target of choice for the development of anti-hepatitis C virus drugs, as it is not expressed in cells that are not infected by hepatitis C virus. The treatment for patients with chronic hepatitis C that was used prior to the development of direct-acting antivirals was ribavirin plus pegylated interferon alfa-2a. This treatment was dissatisfactory in many cases, both for the lack of efficacy and because of side effects. Sofosbuvir, a highly potent inhibitor of the NS5B polymerase, is active across all genotype of hepatitis C virus. It has high efficacy in combination with several other drugs, like ledipasvir, either with or without peginterferon-alfa. It has many advantages due to its tolerability, high potency, high resistance barrier, low side effects and oral administration. Another advantage of sofosbuvir is the low rates of interactions with other drugs, as its metabolism does not go through the CYP3A4 pathway. However, its cost can be a challenge, as all the new direct-acting antiviral drugs can be very expensive. Adverse effects Comparing the virological response of NS5B inhibitors to previous therapy of chronic hepatitis C with the combination of interferon and ribavirin, it was possible to observe a significant difference in efficacy and safety. The