Daclatasvir, sold under the brand name Daklinza, is an antiviral medication used in combination with other medications to treat hepatitis C (HCV). The other medications used in combination include sofosbuvir, ribavirin, and interferon, vary depending on the virus type and whether the person has cirrhosis. It is taken by mouth. Common side effects when used with sofusbivir and daclatasvir include headache, feeling tired, and nausea. With daclatasvir, sofosbuvir, and ribavirin the most common side effects are headache, feeling tired, nausea, and red blood cell breakdown. It should not be used with St. John's wort, rifampin, or carbamazepine. It works by inhibiting the HCV protein NS5A. Daclatasvir was approved for use in the European Union in 2014, and the United States and India in 2015. It is on the World Health Organization's List of Essential Medicines. The brand Daklinza is being withdrawn by Bristol Myers Squibb in countries where the drug is not typically prescribed, and Bristol Myers Squibb says it will not enforce its patents in those countries. Medical use Daclatasvir is used only in combination therapy for the treatment of hepatitis C genotype 1, 3, or 4 infections; the agents used in combination, which include sofosbuvir, ribavirin, and interferon, vary based on the virus genotype, whether the person has cirrhosis and if a liver transplantation took place. It is not known whether daclatasvir passes into breastmilk or has any effect on infants. Adverse effects There is a serious risk of bradycardia when daclatasvir is used with sofosbuvir and amiodarone. Because it has not been extensively studied as a single agent, it is unknown what specific side effects are linked to this medication alone. Adverse events on daclatasvir have only been reported on combination therapy with sofosbuvir or triple therapy with sofosbuvir/ribavirin. Common adverse events occurring in >5% of people on combination therapy (sofosbuvir + daclatasvir) include headache and fatigue; in triple therapy (daclatasvir + sofosbuvir + ribavirin) the most common adverse events (>10%) include headache, fatigue, nausea and hemolytic anemia. Daclatasvir could cause hepatitis B re-activation in people co-infected with hepatitis B and C viruses. The European Medicines Agency (EMA) has recommended screening all people for hepatitis B before starting daclatasvir for hepatitis C in order to minimize the risk of hepatitis B reactivation. Interactions Concomitant use of drugs that are strong inducers of the cytochrome P450 CYP3A is contraindicated due to decreased therapeutic effect and resistance of drug.