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Chapter 40
Antiviral Drugs
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2. General Principles of Virology
Viral replication
A virus cannot replicate on its own
It must attach to and enter a host cell
It then uses the host cell’s energy to synthesize protein, DNA, and RNA
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4. General Principles of Virology (cont’d)
Viruses are difficult to kill because they live inside the cells
Any drug that kills a virus may also kill cells
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Viral Illnesses
Most viral illnesses are bothersome, but survivable
Effective vaccines have prevented some illnesses
Effective drug therapy is available for a small number of viral infections
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Antiviral Drugs
Antiviral drugs kill or suppress the virus by destroying virions or inhibiting the ability of viruses to replicate; controlled by current antiviral therapy
Immunoglobulins are concentrated antibodies that can attack and destroy viruses
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7. Antiviral Drugs (cont’d)
Viruses controlled by current antiviral therapy
Cytomegalovirus (CMV)
Hepatitis viruses
Herpes viruses
Human immunodeficiency virus (HIV)
Influenza viruses (the “flu”)
Respiratory syncytial virus (RSV)
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8. Antiviral Drugs (cont’d)
Key characteristics of antiviral drugs
Able to enter the cells infected with virus
Interfere with viral nucleic acid synthesis and/or regulation
Some drugs interfere with ability of virus to bind to cells
Some drugs stimulate the body’s immune system
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9. Antiviral Drugs (cont’d)
Best responses to antiviral drugs are in patients with competent immune systems
A healthy immune system works synergistically with the drug to eliminate or suppress viral activity
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10. Classroom Response Question
An 82-year-old woman is unable to take the influenza vaccine due to allergies, but she has been exposed to the virus through a family reunion. She does not yet have symptoms of the flu. Which option would be best for her?
She should receive the flu vaccine as soon as possible.
She should receive zanamivir (Relenza) in the inhalation form.
She should begin oral oseltamivir (Tamiflu) therapy when symptoms begin.
She should begin oral oseltamivir (Tamiflu) therapy as soon as possible.
Correct answer: D
Rationale: Oseltamivir (Tamiflu) is the only one indicated for prophylaxis of influenza infection. Both oseltamivir and zanamivir can be used to treat active influenza illness. Treatment with oseltamivir and zanamivir ideally should begin within 2 days of symptom onset.
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Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

11. Antiviral Drugs (cont’d)
Opportunistic infections
Occur in immunocompromised patients
Would not normally harm an immunocompetent person
Require long-term prophylaxis and antiinfective drug therapy
Can be other viruses, fungi, bacteria, or protozoa
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12. Antiviral Drugs (cont’d)
Used to treat infections caused by viruses other than HIV
Antiretroviral drugs
Used to treat infections caused by HIV, the virus that causes AIDS
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13. Herpes Simplex and Varicella Zoster Virus Infections
Herpes simplex viruses
HSV-1 (oral herpes)
HSV-2 (genital herpes)
Human herpesvirus/VZV
Chickenpox and shingles (HHV-3 or VZV)
Epstein-Barr (HHV-4)
Cytomegalovirus (HHV-5)
Kaposi’s sarcoma (HHV-8)
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14. Antiviral Drugs (non-HIV)
Mechanism of action
Inhibit viral replication
Used to treat non-HIV viral infections
Influenza viruses
HSV, VZV
CMV
Hepatitis A, B, C (HAV, HBV, HCV)
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15. Antiviral Drugs (non-HIV) (cont’d)
Adverse effects
Vary with each drug
Healthy cells are often killed also, resulting in serious toxicities
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16. Antiviral Drugs (non-HIV) (cont’d)
amantadine (Symmetrel)
Narrow antiviral spectrum; active only against influenza A
Most recent guidelines do not recommend use for treatment or prevention of flu
CNS effects: insomnia, nervousness, light-headedness
GI effects: anorexia, nausea, others
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17. Antiviral Drugs (non-HIV) (cont’d)
rimantadine (Flumadine)
Same spectrum of activity, mechanism of action, and indications as amantadine
Fewer CNS adverse effects
Causes GI upset
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18. Antiviral Drugs (non-HIV) (cont’d)
acyclovir (Zovirax)
Synthetic nucleoside analog
Used to suppress replication of HSV-1, HSV-2, VZV
Drug of choice for treatment of initial and recurrent episodes of these infections
Oral, topical, parenteral forms
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19. Antiviral Drugs (non-HIV) (cont’d)
ganciclovir (Cytovene)
Synthetic nucleoside analog
Used to treat infection with cytomegalovirus (CMV)
Oral, parenteral forms
CMV retinitis
Ophthalmic form surgically implanted (Vitrasert)
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20. Antiviral Drugs (non-HIV): Dose-Limiting Toxicities
ganciclovir
Bone marrow toxicity
foscarnet and cidofovir
Renal toxicity
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21. Antiviral Drugs (non-HIV): Neuraminidase Inhibitors
oseltamivir (Tamiflu) and zanamivir (Relenza)
Active against influenza types A and B
Reduce duration of illness
Oseltamivir: causes nausea and vomiting
Zanamivir: causes diarrhea, nausea, sinusitis
Treatment should begin within 2 days of influenza symptom onset
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22. Antiviral Drugs (non-HIV): Ribavirin
Synthetic nucleoside analog
Given orally, or by oral or nasal inhalation
Inhalation form (Virazole) used for hospitalized infants with RSV infections
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HIV and AIDS
Human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome (AIDS)
ELISA (enzyme-linked immunosorbent assay)
Detects HIV exposure based on presence of human antibodies to the virus in the blood
Retrovirus
Transmitted by sexual activity, intravenous drug use, perinatally from mother to child
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26. Four Stages of HIV Infection*
Stage 1: asymptomatic infection
Stage 2: early, general symptoms of disease
Stage 3: moderate symptoms
Stage 4: severe symptoms, often leading to death
*WHO model
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28. Classroom Response Question
A patient with HIV infection is seen in the clinic. The nurse notes the patient is experiencing weight loss, chronic diarrhea, fever, and dropping CD4 counts. The nurse anticipates the patient is in which stage of HIV infection?
Stage 1
Stage 2
Stage 3
Stage 4
Correct answer: C
Rationale: During stage 3, the infection progresses to a moderately symptomatic state. Weight loss, chronic diarrhea, and fever continue, and CD4 counts continue to drop. Opportunistic infections begin, including severe bacterial pneumonias and pulmonary tuberculosis (TB). Pulmonary TB is usually more severe in persons with AIDS and is currently the leading cause of death worldwide for HIV-infected patients.
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29. Opportunistic Infections
Protozoal
Toxoplasmosis of the brain, others
Fungal
Candidiasis of the lungs, esophagus, trachea
Pneumocystis jirovecii pneumonia, others
Viral
CMV disease, HSV infection, others
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30. Opportunistic Infections (cont’d)
Bacterial
Various mycobacterial infections, others
Extrapulmonary TB
Opportunistic neoplasias
Kaposi’s sarcoma, others
HIV wasting syndrome
Major weight loss, chronic diarrhea, chronic fever
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Antiretroviral Drugs
HAART
Highly active antiretroviral therapy
Includes at least three medications
“Cocktails”
These medications work in different ways to reduce the viral load
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32. Antiretroviral Drugs (cont’d)
Reverse transcriptase inhibitors (RTIs)
Block activity of the enzyme reverse transcriptase, preventing production of new viral DNA
Protease inhibitors (PIs)
Inhibit the protease retroviral enzyme, preventing viral replication
Fusion inhibitors
Inhibit viral fusion, preventing viral replication
Entry inhibitor-CCR5 coreceptor antagonists
HIV integrase strand transfer inhibitors
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33. Antiretroviral Drugs (cont’d)
Examples
enfuvirtide (Fuzeon)
indinavir (Crixivan)
maraviroc (Selzentry)
nevirapine (Viramune)
raltegravir (Isentress)
tenofovir (Viread)
zidovudine (Retrovir)
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34. Antiretroviral Drugs: Adverse Effects
Numerous and vary with each drug
Drug therapy may need to be modified because of adverse effects
Goal is to find the regimen that will best control the infection with a tolerable adverse effect profile
Medication regimens change during the course of the illness
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35. Classroom Response Question
A patient with active HIV has been taking zidovudine (Retrovir). Which potential adverse effect may limit the length of time this medication can be taken?
Lactic acidosis
Bone marrow suppression
Hepatomegaly
Fatigue
Correct answer: B
Rationale: The major dose-limiting adverse effect of zidovudine (Retrovir) is bone marrow suppression, and this is often the reason a patient with an HIV infection must be switched to another anti-HIV drug.
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36. Other Viral Infections
Avian flu
West Nile virus (WNV) infection
Severe acute respiratory syndrome (SARS)
H1N1 influenza virus (“swine flu”)
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Nursing Implications
Before beginning therapy, thoroughly assess underlying disease and medical history, including allergies
Assess baseline vital signs and nutritional status
Assess for contraindications, conditions that may indicate cautious use, and potential drug interactions
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38. Nursing Implications (cont’d)
Be sure to teach proper application technique for ointments, aerosol powders, and so on
Emphasize hand washing before and after administration of medications to prevent site contamination and spread of infection
Instruct patients to wear a glove or finger cot when applying ointments or solutions to affected areas
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39. Nursing Implications (cont’d)
Instruct patients to consult their prescriber before taking any other medication, including over-the-counter medications
Emphasize the importance of good hygiene
Inform patients that antiviral drugs are not cures but do help to manage symptoms
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40. Nursing Implications (cont’d)
Instruct patients on the importance of taking these medications exactly as prescribed and for the full course of treatment
Instruct patients to start therapy with antiviral drugs at the earliest sign of recurrent episodes of genital herpes or herpes zoster
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41. Classroom Response Question
The nurse administers maraviroc (Selzentry) to a patient with HIV infection. It is most important for the nurse to monitor which of the following?
CD4 count
Bone marrow suppression
Urinary output
Liver function tests
Correct answer: D
Rationale: The antiretroviral drug maraviroc requires assessment of allergies and liver function as well as review of the list of medications the patient is taking because of the lengthy list of interacting drugs.
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42. Nursing Implications (cont’d)
Monitor for adverse effects
Effects are varied and specific to each drug
Monitor for therapeutic effects
Effects will vary depending on the type of viral infection
Effects range from delayed progression of AIDS and other viruses to decrease in flulike symptoms, decrease in frequency of herpes-like flare-ups, or crusting over of herpetic lesions
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