Ribavirin-¹³C₅is intended for use as an internal standard for the quantification of ribavirin by GC- or LC-MS. Ribavirin is an antiviral guanosine nucleoside analog.^1,2Upon entry into cells, ribavirin is metabolized to an active triphosphate form that induces viral RNA chain termination and inhibits viral polymerases. It reduces replication in a panel of seven RNA and four DNA viruses in Vero cells (EC₅₀s = 2-95 µg/ml).³Ribavirin also reduces replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Vero cells (EC₅₀= 109.5 µM).⁴Aerosol administration of ribavirin (30 mg/kg) reduces mortality in a mouse model of influenza A infection.⁵Formulations containing ribavirin have been used in the treatment of respiratory syncytial virus (RSV), hepatitis C virus (HCV), and viral hemorrhagic fevers.

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