Classification of antiviral agents

Viral nucleic acid synthesis inhibitors

This extensive category includes drugs that block key enzymes responsible for copying the virus's genetic material.

• Viral DNA polymerase inhibitors. This is the main group of medicinal agents that disrupt viral DNA synthesis using a DNA template. A classic representative is acyclovir, a structural analogue of guanosine that incorporates directly into herpes virus DNA, halting its elongation. Another important drug, foscarnet, is capable of inhibiting DNA polymerase not only in herpes viruses but also in HIV.
• Reverse transcriptase inhibitors. Reverse transcriptase is essentially an RNA-dependent DNA polymerase. Drugs in this group block a unique process: DNA synthesis on a viral RNA template. This property makes them the foundation of therapy for HIV infection. Within the group, a distinction is made between nucleoside inhibitors (including zidovudine and lamivudine) and non-nucleoside inhibitors (e.g., efavirenz).

Note: although reverse transcriptase is biologically a type of DNA polymerase, in educational classification these two groups are often considered adjacently as independent classes.

Drugs acting on other replication stages

If searching for a drug requires selecting an agent fundamentally unrelated to polymerase inhibitors, it is logical to consider medications that block viral entry or the assembly of its particles.

• HIV protease inhibitors. This is a different group of drugs that does not affect DNA synthesis. They act at a later stage—the post-translational processing phase. By blocking the protease, drugs (such as ritonavir) disrupt the proper maturation of viral proteins.
• Fusion inhibitors. These act on the earliest stage of infection. A representative of this group, enfuvirtide, specifically blocks HIV entry into the target cell. It is important to remember that such drugs are highly specific and do not act at all against other pathogens, such as the influenza virus.

Spectrum of activity of drugs in type A influenza treatment

For competent therapy selection, it is crucial to perform a differential diagnosis and distinguish drugs with specific anti-influenza activity from agents of other groups (e.g., antiretrovirals, which are ineffective against influenza).

Among drugs with proven clinical efficacy against the influenza virus, the following groups are distinguished:

1. Neuraminidase inhibitors. The main representative is oseltamivir. Its mechanism of action consists in disrupting the release of newly formed virions from the infected cell.
2. M2 channel blockers. This group includes rimantadine. It works inside the cell by disrupting the virus "uncoating" process. The drug is exclusively specific to the influenza A virus, though high resistance to it is noted in modern practice.
3. Interferon inducers. Agents such as kagocel stimulate the production of the patient's own (endogenous) interferons in the body. They are successfully used for both treatment and prevention.
4. Broad-spectrum drugs. A vivid example is ribavirin. It is capable of inhibiting the synthesis of both viral RNA and viral DNA. It exhibits high activity against the influenza virus, but its use is limited due to pronounced toxicity.

Class and exam questions

What else to study on this topic

• Mechanism of acyclovir incorporation into herpes virus DNA
• Differences between nucleoside and non-nucleoside reverse transcriptase inhibitors
• Causes of high influenza A virus resistance to M2 channel blockers
• Post-translational processing of viral proteins as a pharmacological target
• Mechanism of endogenous interferon production stimulation by kagocel

Other topics in the "Antivirals" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.