Antivirales

Antivirales (antivirals) are medications used to treat viral infections by inhibiting one or more steps of the viral life cycle. They are distinct from antibiotics, which target bacteria, and from vaccines, which aim to prevent infection. Antivirals can reduce disease duration and severity, limit viral spread, and improve outcomes, but they are often virus-specific and must be used with appropriate timing and diagnosis.

Most antivirals work by targeting viral enzymes or processes essential for replication. Mechanisms include entry and fusion inhibitors that block virus attachment or fusion with host cells; uncoating inhibitors that prevent genome release in the cell; nucleoside or nucleotide analogs that terminate viral DNA or RNA synthesis; polymerase inhibitors that block viral replication; protease inhibitors that prevent processing of viral proteins; and integrase inhibitors that stop viral genome integration into the host DNA. Neuraminidase inhibitors prevent release of influenza virions from infected cells. Some agents act broadly against several viruses, while many are specific to one virus family.

Examples span several diseases. Acyclovir and valacyclovir treat herpes simplex and varicella zoster viruses; ganciclovir targets cytomegalovirus. HIV is treated with combinations including nucleoside reverse transcriptase inhibitors, protease inhibitors, integrase inhibitors, and entry inhibitors. Hepatitis C is now commonly treated with direct-acting antivirals such as sofosbuvir and ledipasvir. Influenza is treated with neuraminidase inhibitors like oseltamivir and zanamivir. Remdesivir and nirmatrelvir/ritonavir have been used for SARS-CoV-2. Resistance can arise through viral mutations, emphasizing the importance of combination therapy and stewardship.

Safety and accessibility vary by drug and indication. Side effects, drug interactions, and considerations in pregnancy or immune-compromised individuals must be managed. Ongoing research seeks broader-spectrum agents and improved strategies for emerging viruses.