Antiviral Agents and Mechanisms

Antiviral Agents and Mechanisms

• Oseltamivir can cause nausea, diarrhea, and abdominal discomfort.
• Important nursing responsibilities include monitoring for seizures at treatment onset, allergies, and abnormal behavior.
• Administer Oseltamivir with food to mitigate gastrointestinal disturbances.
• Zanamivir administration requires assessment for breathing problems and bronchospasm signs.

Adamantine Derivatives

• Amantadine and Rimantadine are effective against Influenza A, both for treatment and prevention.
• Initiating treatment before or immediately after exposure prevents infection in 70-90% of cases.
• Amantadine can also treat Parkinsonism, while contraindications include epilepsy, gastric ulcer, and pregnancy.
• Mechanism involves blocking the M2 protein, crucial for viral uncoating.
• Resistance develops via mutations in the M2 protein.

Structure of Viruses

• Viruses lack cell walls/membranes and rely on the host for metabolic processes.
• They contain either DNA or RNA inside a protein coat and may have a lipid envelope.
• Viral replication involves stages from attachment to the host cell to release of new virions.

Antiviral Action Mechanisms

• Antivirals may block viral entry, exit, or act inside host cells.
• Few selective agents prevent viral replication without harming host cells.
• Effective antivirals target specific viral proteins, often viral nucleic acid synthesis enzymes.

Treatment of Respiratory Infections

• Key respiratory infections include Influenza A/B and RSV.
• Antiviral agents are used when patients are allergic to vaccines or when high-risk outbreaks occur.

Neuraminidase Inhibitors

• Neuraminidase is essential for the viral life cycle and facilitates the release of virions from infected cells.
• Oseltamivir (Tamiflu) and Zanamivir (Relenza) inhibit this enzyme, effective against influenza A, B, and avian strains.
• They should be administered within 24-48 hours for symptom relief and prevention.

Pharmacokinetics and Adverse Effects

• Oseltamivir is an orally administered prodrug processed in the liver, with a half-life of 6-10 hours.
• Zanamivir has low oral bioavailability and is inhaled; it has a shorter half-life of 2-5 hours.
• Both can cause effects like bronchospasm, cough, delirium, and hallucinations.

Amantadine Pharmacokinetics

• Amantadine is well absorbed orally, penetrates the CNS, and has a long half-life (16 hours).
• Rimantadine has extensive liver metabolism with a longer half-life (30 hours) but less CNS penetration.

Ribavirin

• Ribavirin is a synthetic guanosine analog with broad-spectrum activity against various viruses, including RSV and Hepatitis C.
• Mechanism involves conversion to ribavirin-triphosphate, inhibiting viral RNA synthesis.
• Adverse effects include anemia, CNS, and GI symptoms, with aerosol use may cause mucosa irritation and bronchospasm in infants.