Transcript Pharmacology and the Nursing Process, 4th ed. Lilley/Harrington

Chapter 40
Antiviral Drugs
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General Principles of Virology

Viral replication
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

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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General Principles of Virology
(cont’d)
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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


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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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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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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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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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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?
A. She should receive the flu vaccine as soon as possible.
B. She should receive zanamivir (Relenza) in the
inhalation form.
C. She should begin oral oseltamivir (Tamiflu) therapy
when symptoms begin.
D. She should begin oral oseltamivir (Tamiflu) therapy as
soon as possible.
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Antiviral Drugs (cont’d)

Opportunistic infections
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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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Antiviral Drugs (cont’d)

Antiviral drugs
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
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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Herpes Simplex and Varicella
Zoster Virus Infections
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Herpes simplex viruses
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
HSV-1 (oral herpes)
HSV-2 (genital herpes)
Human herpesvirus/VZV
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Chickenpox and shingles (HHV-3 or VZV)
Epstein-Barr (HHV-4)
Cytomegalovirus (HHV-5)
Kaposi’s sarcoma (HHV-8)
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Antiviral Drugs (non-HIV)
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Mechanism of action
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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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Antiviral Drugs (non-HIV) (cont’d)

Adverse effects
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
Vary with each drug
Healthy cells are often killed also, resulting in serious
toxicities
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Antiviral Drugs (non-HIV) (cont’d)

amantadine (Symmetrel)
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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, lightheadedness
GI effects: anorexia, nausea, others
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Antiviral Drugs (non-HIV) (cont’d)

rimantadine (Flumadine)
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Same spectrum of activity, mechanism of action, and
indications as amantadine
 Fewer CNS adverse effects
 Causes GI upset
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Antiviral Drugs (non-HIV) (cont’d)

acyclovir (Zovirax)
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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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Antiviral Drugs (non-HIV) (cont’d)

ganciclovir (Cytovene)
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Synthetic nucleoside analog
 Used to treat infection with cytomegalovirus (CMV)
 Oral, parenteral forms
 CMV retinitis
• Ophthalmic form surgically implanted (Vitrasert)
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Antiviral Drugs (non-HIV):
Dose-Limiting Toxicities

ganciclovir
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
Bone marrow toxicity
foscarnet and cidofovir

Renal toxicity
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Antiviral Drugs (non-HIV):
Neuraminidase Inhibitors
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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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Antiviral Drugs (non-HIV):
Ribavirin
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

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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Four Stages of HIV Infection*
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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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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?
A. Stage 1
B. Stage 2
C. Stage 3
D. Stage 4
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Opportunistic Infections
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Protozoal
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Toxoplasmosis of the brain, others
Fungal

Candidiasis of the lungs, esophagus, trachea
 Pneumocystis jirovecii pneumonia, others

Viral
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CMV disease, HSV infection, others
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Opportunistic Infections (cont’d)
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Bacterial
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Opportunistic neoplasias
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Various mycobacterial infections, others
Extrapulmonary TB
Kaposi’s sarcoma, others
HIV wasting syndrome
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Major weight loss, chronic diarrhea, chronic fever
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Antiretroviral Drugs
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HAART
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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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Antiretroviral Drugs (cont’d)
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Reverse transcriptase inhibitors (RTIs)
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
Protease inhibitors (PIs)
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Inhibit the protease retroviral enzyme, preventing viral
replication
Fusion inhibitors
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
Block activity of the enzyme reverse transcriptase,
preventing production of new viral DNA
Inhibit viral fusion, preventing viral replication
Entry inhibitor-CCR5 coreceptor antagonists
HIV integrase strand transfer inhibitors
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Antiretroviral Drugs (cont’d)
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Examples

enfuvirtide (Fuzeon)
 indinavir (Crixivan)
 maraviroc (Selzentry)
 nevirapine (Viramune)
 raltegravir (Isentress)
 tenofovir (Viread)
 zidovudine (Retrovir)
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Antiretroviral Drugs:
Adverse Effects
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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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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?
A. Lactic acidosis
B. Bone marrow suppression
C. Hepatomegaly
D. Fatigue
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Other Viral Infections
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Avian flu
West Nile virus (WNV) infection
Severe acute respiratory syndrome (SARS)
H1N1 influenza virus (“swine flu”)
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Nursing Implications
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
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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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Nursing Implications (cont’d)
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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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Nursing Implications (cont’d)
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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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Nursing Implications (cont’d)
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
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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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?
A. CD4 count
B. Bone marrow suppression
C. Urinary output
D. Liver function tests
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Nursing Implications (cont’d)
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Monitor for adverse effects
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
Effects are varied and specific to each drug
Monitor for therapeutic effects
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
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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