Antiviral Drugs (Non-retroviral)

Introduction

• Antiviral drugs act on viruses — obligate intracellular parasites that hijack host machinery. Selective toxicity is possible because virus-directed enzymes (distinct from host enzymes) can be targeted, sparing the host cell.
• Most agents are virustatic — active only against replicating virus, not latent virus; they block a defined step of the replication cycle.
• Because viral replication often peaks before symptoms appear, antivirals are most effective when started early (prophylactic / pre-emptive) — a key clinical limitation.
• Acyclovir (Elion) is the prototype that launched the field; this topic covers non-retroviral agents only — anti-herpes, anti-influenza and anti-hepatitis (HIV/retroviruses are covered separately).