ANTIVIRAL DRUGS Understanding Viruses Viral replication A

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Antiviral Drugs
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Understanding Viruses

• Viral replication
• A virus cannot replicate on its own
• It must attach to and enter a host cell
• It then uses the host cells energy to synthesize
  protein, DNA, and RNA

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Understanding Viruses

• 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 Infections

• Competent immune system
• Best response to viral infections
• A well-functioning immune system will eliminate
  or effectively destroy virus replication
• Immunocompromised patients have frequent viral
  infections
• Cancer patients, especially leukemia or
  lymphoma
• Transplant patients, due to pharmacologic
  therapy
• AIDS patients, disease attacks immune system

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Antivirals

• 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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Antivirals

• 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 bodys immune system
• 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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Antivirals

• Opportunistic infections
• Occur in immunocompromised patients
• Infections that would not normally harm an
  immunocompetent person
• Require long-term prophylaxis and anti-infective
  drug therapy
• Can be other viruses, fungi, bacteria, or
  protozoa

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Antiviral Medications

• 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
• Herpes-Simplex Viruses
• HSV-1 (oral herpes)
• HSV-2 (genital herpes)
• Varicella Zoster Virus
• Chickenpox
• Shingles

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Antiviral Drugs Nonretroviral

• Mechanism of action
• Inhibit viral replication
• Used to treat non-HIV viral infections
• Influenza viruses
• HSV (herpes simplex virus), VZV (vericella zoster
  virus)
• CMV (cytomegalovirus)
• Hepatitis A, B, C (HAV, HBV, NCV)
• Adverse Effects
• Vary with each drug
• Healthy cells are often killed also, resulting in
  serious toxicities

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Antivirals Drugs-NonretroviralAmantadine
(Symmetrel)

• Narrow antiviral spectrum?active only against
  influenza A
• Used prophylactically when vaccine is not
  available or cannot be given
• Therapeutic use can reduce recovery time
• CNS effects insomnia, nervousness,
  lightheadedness
• GI effects anorexia, nausea, others

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Antivirals Drugs-NonretroviralRimantadine
(Flumadine)

• Same spectrum of activity, mechanism of action,
  and indications as amantadine
• Fewer CNS adverse effects
• Causes GI upset

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Antivirals Drugs-NonretroviralAcyclovir (Zovirax)

• Synthetic nucleoside analog
• Used to suppress replication of
• HSV-1(oral herpes), HSV-2(genital herpes),
• VZV (Varicella chickenpox or shingles)
• Drug of choice for treatment of initial and
  recurrent episodes of these infections
• Oral, topical, parenteral forms

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Antivirals Drugs-NonretroviralGanciclovir
(Cytovene)

• Synthetic nucleoside analog
• Used to treat infection with cytomegalovirus
  (CMV)
• Oral, parenteral forms
• CMV retinitis
• Ophthalmic form surgically implanted
• Ocular injection (fomivirsen)

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Antivirals Drugs-NonretroviralDose-Limiting
Toxicities

• ganciclovir and zidovudine
• Bone marrow toxicity
• foscarnet and cidofovir
• Renal toxicity

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Antivirals Drugs-NonretroviralNeuraminidase
Inhibitors

• oseltamivir (Tamiflu) and zanamivir (Relenza)
• Active against influenza types A B
• Use Reduce duration of illness
• oseltamivir causes nausea vomiting
• zanamivir causes diarrhea, nausea, sinusitis
• Treatment should begin within 2 days of influenza
  symptom onset

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Antivirals Drugs-NonretroviralRibavirin

• Synthetic nucleoside analog
• Given orally, or oral or nasal inhalation
• Inhalation form (Virazole) used for hospitalized
  infants with RSV (respiratory syncytialvirus)
  infections

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HIV

• Human immunodeficiency virus infection
• 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
• Five 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 stages

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Opportunistic Infections

• Protozoal
• Toxoplasmosis of the brain, others
• Fungal
• Candidiasis of the lungs, esophagus, trachea
• Pneumocystis jiroveci pneumonia, others
• Viral
• CMV disease, HSV infection, others
• Bacterial
• Various mycobacterial infections, others
• Extrapulmonary TB
• Opportunistic neoplasias
• Kaposis sarcoma, others

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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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Antiretroviral Drugs

• Reverse transcriptase inhibitors (RTIs)
• Block activity of the enzyme reverse
  transcriptase, preventing production of new viral
  DNA
• Reverse transcriptase inhibitors (RTIs)
• Nucleoside RTIs (NRTIs)
• Nonnucleoside RTIs (NNRTIs)
• Nucleotide RTIs (NTRTIs)
• Examples
• abacavir (Ziagen) delavirdine (Rescriptor)
• didanosine (Videx) lamivudine
  (Epivir)
• stavudine (Zerit) tenofovir (Viread)

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Antiretroviral Drugs

• Protease inhibitors (PIs)
• Inhibit the protease retroviral enzyme,
  preventing viral replication
• Examples
• amprenavir (Agenerase) indinavir (Crixivan)
• nelfinavir (Viracept) ritonavir (Norvir)
• saquinavir (Invirase)

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Antiretroviral Drugs

• Fusion inhibitors
• Inhibit viral fusion, preventing viral
  replication
• Newest class of antiretroviral drugs
• Example enfuvirtide (Fuzeon)

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Antiretroviral Drugs

• Combinations of multiple antiretroviral
  medications are common
• Adverse effects vary with each drug and may be
  severe-monitor for dose-limiting toxicities
• Monitor for signs of opportunistic diseases

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Antiretroviral DrugsAdverse 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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Nursing Implications

• Before therapy, assess underlying disease,
  history, allergies
• Assess baseline VS and nutritional status
• Assess for contraindications, conditions that may
  indicate cautious use, and potential drug
  interactions

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Nursing ImplicationsPatient Education

• Consult their physician before taking other
  medication, including OTCs
• Good hygiene
• Antiviral drugs are not cures but help manage
  symptoms
• Take these medications exactly as prescribed
• Take medications for the full course of treatment

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Nursing ImplicationsPatient Education

• Teach each proper application for ointments,
  aerosol powders
• Hand washing before and after administration of
  medications
• Wear glove or finger cot when applying ointments
• Start therapy with antiviral drugs at the
  earliest sign of recurrent episodes of genital
  herpes or herpes zoster

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Nursing Implications

• 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 flu-like
  symptoms, decrease in frequency of herpes-like
  flare-ups, or crusting over of herpetic lesions
• Monitor for adverse effects
• Effects are varied and specific to each drug