Chapter 10: Antiviral Agents

The body’s natural defense includes interferons, tissue hormones that block viral replication, and some antivirals are genetically engineered versions of these. The chapter classifies antivirals into several groups based on their viral targets and mechanisms of action. Agents for Influenza A and respiratory viruses, such as amantadine and oseltamivir, work by preventing the virus from shedding its protein coat and entering the host cell, thereby halting replication. Drugs targeting DNA viruses like herpes simplex, herpes zoster, and cytomegalovirus (CMV), including acyclovir and ganciclovir, inhibit viral DNA replication by creating non-effective, shorter DNA chains. A major focus is dedicated to antiretroviral agents used for Human Immunodeficiency Virus (HIV), which attacks helper T cells (CD4 cells) leading to Acquired Immunodeficiency Syndrome (AIDS) or AIDS-related complex (ARC). Due to the virus's ability to mutate and remain dormant, HIV treatment necessitates combination therapy using multiple drugs to attack the virus at various points in its complex life cycle. These classes include the Nucleoside Reverse Transcriptase Inhibitors (NRTIs) and Nonnucleoside Reverse Transcriptase Inhibitors (NNRTIs), which block the synthesis of viral DNA; Protease Inhibitors (PIs), which prevent the formation of infectious, mature virus particles; Fusion Inhibitors (e.g., enfuvirtide), which stop the virus from fusing with the cellular membrane to enter the cell; CCR5 Coreceptor Antagonists (e.g., maraviroc), which block the necessary receptor site for viral entry; and Integrase Inhibitors (e.g., raltegravir), which prevent the essential enzyme integrase from inserting the viral DNA into the host chromosome. The use of fixed-combination drugs helps improve patient adherence to these complex, multi-pill regimens. Additionally, specialized agents treat serious liver infections: Anti-Hepatitis B agents (adefovir, entecavir, telbivudine) inhibit reverse transcriptase and block viral replication, and abrupt cessation can cause viral exacerbation. New Anti-Hepatitis C drugs, often highly effective protease inhibitors (e.g., simeprevir, sofosbuvir), are used in combination therapies; however, their high cost has sparked widespread debate in the healthcare system. Nursing care considerations across all classes emphasize monitoring for common adverse effects such as gastrointestinal distress, CNS changes (dizziness, insomnia), and potentially severe renal and hepatic toxicity. Patients must be educated that antivirals do not cure the diseases and that adherence to the full regimen is critical to prevent resistance. Finally, locally active antivirals, such as docosanol, are available for treating localized viral infections like warts or eye infections and generally cause only local irritation.