Ribavirin

Ribavirin is a broad-spectrum antiviral agent classified as a nucleoside analogue. It is a synthetic guanosine analogue whose antiviral activity varies by virus and clinical setting. The drug is available in oral, intravenous, and inhaled forms and is used in different regimens depending on the infection being treated.

The mechanism of action of ribavirin is multifaceted and not fully understood. Its active triphosphate form inhibits inosine monophosphate dehydrogenase, reducing intracellular GTP pools and interfering with viral RNA synthesis. It may also cause lethal mutagenesis by increasing error rates during viral replication and can modulate immune responses, favoring a Th1-type profile in some settings.

Medical uses include historic and current applications in different contexts. Ribavirin has been used in combination with pegylated interferon for chronic hepatitis C, particularly in eras before modern direct-acting antivirals. It is not a first-line agent in most current HCV regimens but may be used in certain treatment protocols. An inhaled form is approved for hospitalized infants and young children with severe respiratory syncytial virus infection. Additionally, ribavirin has been employed, under specific guidelines or outbreak situations, as part of treatment regimens for arenaviruses such as Lassa fever.

Administration, pharmacokinetics, and safety considerations vary by form. Oral ribavirin is well absorbed; inhaled ribavirin achieves high airway concentrations; the drug has a long intracellular half-life and is cleared primarily by the kidneys, requiring dose adjustments in renal impairment. Ribavirin is teratogenic and embryotoxic in animals, and pregnancy should be avoided. Hemolytic anemia is a common adverse effect and monitoring is recommended; interactions with other medications, such as zidovudine, can increase anemia risk.