Antiviral Agents Introduction

Antiviral Agents Overview

Introduction to Antiviral Agents

• Antiviral agents are used to treat diseases caused by viruses, such as warts and common colds. Viruses consist of either DNA or RNA encased in a protein coat and must enter host cells to replicate.

Types of Viruses Treated with Antivirals

• Common viruses that respond to antiviral therapy include:

• Influenza A and other respiratory viruses.

• Herpes viruses, including cytomegalovirus (CMV).

• Human Immunodeficiency Virus (HIV), which causes AIDS.

• Hepatitis B and C viruses.

Management of Viral Infections

• Treatment for viral infections often involves symptomatic management, especially for influenza A and respiratory viruses. Vaccines have been developed for some strains, but drug therapy is preferred once an infection manifests. The therapeutic action of antivirals is believed to prevent viral replication and cell entry.

Specific Antiviral Agents

Agents for Influenza A and Respiratory Viruses

• Key antiviral agents include:

• Amantadine: Used primarily for influenza A.

• Oseltamivir (Tamiflu): Commonly used in hospitals; effective against H1N1.

• Ribavirin: Noted as teratogenic (Category X) during pregnancy.

• Rimantadine: Another option for treating influenza.

Adverse Effects and Precautions

• Common adverse effects include CNS effects like dizziness, lightheadedness, insomnia, cardiovascular issues like orthostatic hypertension, and urinary retention. Patients should be educated on these risks before starting antiviral treatment. Safety precautions include avoiding driving or hazardous tasks due to potential side effects.

Agents for Herpes and Cytomegaloviruses

Mechanism of Action

• These agents inhibit viral DNA replication by competing with viral substrates, leading to the formation of shorter non-effective DNA chains. This mechanism is crucial in treating infections caused by herpes simplex virus types I & II, varicella-zoster virus, and CMV infections affecting immunocompromised individuals.

Drug Choices and Contraindications

• Acyclovir is the drug of choice for children with herpes or CMV infections but has contraindications such as renal impairment and severe CNS disorders due to potential side effects like dizziness or lightheadedness during treatment. Special caution is advised when prescribing this medication during pregnancy due to its potential carcinogenic effects on bone development in children.

Adverse Effects