chapter 40 antiviral drugs copyright © 2014 by mosby, an imprint of elsevier inc
TRANSCRIPT
Chapter 40
Antiviral Drugs
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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
General Principles of Virology
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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
General Principles of Virology (cont’d)
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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
Viral Illnesses
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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
Antiviral Drugs
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Viruses controlled by current antiviral therapyCytomegalovirus (CMV)Hepatitis virusesHerpes virusesHuman immunodeficiency virus (HIV)Influenza viruses (the “flu”)Respiratory syncytial virus (RSV)
Antiviral Drugs (cont’d)
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Key characteristics of antiviral drugsAble to enter the cells infected with virusInterfere with viral nucleic acid synthesis and/or regulationSome drugs interfere with ability of virus to bind to cellsSome drugs stimulate the body’s immune system
Antiviral Drugs (cont’d)
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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
Antiviral Drugs (cont’d)
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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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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
Antiviral Drugs (cont’d)
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Antiviral drugs Used to treat infections caused by viruses other than
HIV Antiretroviral drugs
Used to treat infections caused by HIV, the virus that causes AIDS
Antiviral Drugs (cont’d)
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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)
Herpes Simplex and Varicella Zoster Virus Infections
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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)
Antiviral Drugs (non-HIV)
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Adverse effects Vary with each drug Healthy cells are often killed also, resulting in serious
toxicities
Antiviral Drugs (non-HIV) (cont’d)
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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
Antiviral Drugs (non-HIV) (cont’d)
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rimantadine (Flumadine) Same spectrum of activity, mechanism of action, and
indications as amantadine Fewer CNS adverse effects Causes GI upset
Antiviral Drugs (non-HIV) (cont’d)
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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
Antiviral Drugs (non-HIV) (cont’d)
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ganciclovir (Cytovene) Synthetic nucleoside analog Used to treat infection with cytomegalovirus (CMV) Oral, parenteral forms CMV retinitis
• Ophthalmic form surgically implanted (Vitrasert)
Antiviral Drugs (non-HIV) (cont’d)
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ganciclovir Bone marrow toxicity
foscarnet and cidofovir Renal toxicity
Antiviral Drugs (non-HIV): Dose-Limiting Toxicities
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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
Antiviral Drugs (non-HIV): Neuraminidase Inhibitors
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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
Antiviral Drugs (non-HIV): Ribavirin
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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
HIV and AIDS
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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
Four Stages of HIV Infection*
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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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Protozoal Toxoplasmosis of the brain, others
Fungal Candidiasis of the lungs, esophagus, trachea Pneumocystis jirovecii pneumonia, others
Viral CMV disease, HSV infection, others
Opportunistic Infections
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Bacterial Various mycobacterial infections, others Extrapulmonary TB
Opportunistic neoplasias Kaposi’s sarcoma, others
HIV wasting syndrome Major weight loss, chronic diarrhea, chronic fever
Opportunistic Infections (cont’d)
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HAART Highly active antiretroviral therapy Includes at least three medications
• “Cocktails”
These medications work in different ways to reduce the viral load
Antiretroviral Drugs
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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
Antiretroviral Drugs (cont’d)
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Examples enfuvirtide (Fuzeon) indinavir (Crixivan) maraviroc (Selzentry) nevirapine (Viramune) raltegravir (Isentress) tenofovir (Viread) zidovudine (Retrovir)
Antiretroviral Drugs (cont’d)
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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
Antiretroviral Drugs: Adverse Effects
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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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Avian flu West Nile virus (WNV) infection Severe acute respiratory syndrome (SARS) H1N1 influenza virus (“swine flu”)
Other Viral Infections
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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
Nursing Implications
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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
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
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
Nursing Implications (cont’d)
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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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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
Nursing Implications (cont’d)
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