Chapter 11 (Antivirals)

Antiviral Drugs Overview

Chapter 11

This chapter discusses antiviral drugs, which are specifically designed to combat viral infections. More than 200 viruses cause disease in humans, highlighting the importance of developing effective antiviral therapies.

Mechanism of Viral Infection

  1. Invasion of Cells: Viral cells invade a living cell.

  2. Replication: The virus injects its genetic material, which hijacks the host cell's machinery to replicate itself.

  3. Release: Newly formed viral cells exit the host cell and seek to infect new cells.

Categories of Antiviral Drugs

  • Antivirals: General treatment for various viral infections.

  • Antiretrovirals: Specific treatment for HIV/AIDS infection.

Actions of Antivirals

  • Antiviral drugs combat viral infections by preventing reproduction within the host cell.

  • They can be toxic to human cells and are more challenging to develop than antibiotics, which are used to prevent or treat secondary bacterial infections.

Labeled Uses of Antivirals

Antivirals are administered for various infections, including:

  • Cytomegalovirus (CMV): Particularly important in transplant patients.

  • Hepatitis B and C: Infections affecting the liver.

  • Herpes Simplex Virus: Both types (HSV-1 and HSV-2) responsible for cold sores and genital herpes, respectively.

  • Herpes Zoster (Shingles): A manifestation of the varicella (chickenpox) virus.

  • Influenza A and B: Antivirals are approved for treating these strains.

Unlabeled Uses

Some antiviral medications may also be used for unapproved indications, including:

  • CMV and HSV infections following transplant procedures.

  • Varicella pneumonia.

Adverse Reactions to Antivirals

Common adverse reactions include:

  • Nausea, vomiting, diarrhea (N/V/D)

  • Headaches

  • Rashes

  • Fever

  • Insomnia

General Contraindications

  • Contraindicated in patients with a history of allergies.

  • Pregnancy and lactation must be approached with caution, weighing risks and benefits.

Drug Interactions

Here are some common drug interactions that can increase serum levels of antivirals:

  • Probenecid (for gout)

  • Cimetidine (for gastric upset)

  • Ibuprofen (for pain relief)

  • Imipenem-cilastatin (an anti-infective agent)

  • Anticholinergic agents (for bladder spasms)

  • Theophylline (for respiratory issues)

Specific Antiviral Drugs

Amantadine (Symmetrel)

  • Uses: Effective against Influenza A.

  • Adverse reactions: Includes nausea, diarrhea, dizziness, and hypotension.

  • Interactions: Increases side effects of anticholinergics which can lead to dry mouth and confusion.

Ribavirin (Virazole)

  • Uses: Treats Respiratory Syncytial Virus (RSV) and chronic Hepatitis C.

  • Adverse Reactions: Worsening pulmonary status, bacterial pneumonia, hypotension.

  • Special Considerations: Inhalation form requires solution replacement every 24 hours and is classified as pregnancy category X.

Zanamivir (Relenza)

  • Uses: For prevention and treatment of Influenza A and B.

  • Adverse Reactions: Nausea, headache, rhinitis, and mucous membrane irritation.

  • Teaching: Administered by inhalation using a Diskhaler, every 12 hours for 5 days.

Antiretroviral Drugs

Uses and Mechanisms

  • Applications: Effective against Hepatitis B and HIV/AIDS.

  • HAART (Highly Active Antiretroviral Therapy): Combination of several drugs targeting different life cycle stages of the virus.

    • Protease inhibitors: Block the maturation of viral particles.

    • Reverse transcriptase inhibitors: Prevent HIV material from converting to DNA in the host cell.

    • Entry inhibitors: Stop HIV from entering cells.

    • Integrase inhibitors: Prevent integration of HIV genetic material into the host DNA.

General Adverse Reactions to Antiretrovirals

  • Nausea, vomiting, diarrhea, altered taste, headache, chills, rash, and numbness.

Contraindications

  • History of allergies, during lactation, or when taking specific medications like cisapride or pimozide.

Special Considerations for Antiretrovirals

  • Must monitor for complications associated with infection or treatment, particularly in immunocompromised patients. Regular assessments of blood counts are critical.

Monitoring and Managing Patient Needs

Nutritional Imbalance

  • Manage nausea through dietary modifications, such as small frequent meals and good oral hygiene.

Risk for Injury

  • Monitor patients carefully, especially for peripheral neuropathy, ensuring safety measures are in place.

Risk for Infection in Immunosuppressed Clients

  • Maintain strict hygiene practices to prevent infections, particularly among those receiving antiviral treatment.

Clinical Applications of Antivirals

  • Influenza Treatment: Utilize Oselttamivir (Tamiflu) for patients diagnosed with Influenza A or B, supported by microbiological results.