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Antiviral Drugs

Antiviral Drugs. 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 cell’s energy to synthesize protein, DNA, and RNA. Understanding Viruses.

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Antiviral Drugs

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  1. Antiviral Drugs

  2. 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 cell’s energy to synthesize protein, DNA, and RNA

  3. Understanding Viruses Viruses are difficult to kill because they live inside the cells • Any drug that kills a virus may also kill cells

  4. 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

  5. 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)

  6. 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 body’s 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. Antivirals Drugs-NonretroviralRimantadine (Flumadine) • Same spectrum of activity, mechanism of action, and indications as amantadine • Fewer CNS adverse effects • Causes GI upset

  12. 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

  13. 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)

  14. Antivirals Drugs-NonretroviralDose-Limiting Toxicities • ganciclovir and zidovudine • Bone marrow toxicity • foscarnet and cidofovir • Renal toxicity

  15. 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

  16. 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

  17. 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

  18. 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 • Kaposi’s sarcoma, others

  19. Antiretroviral Drugs HAART - Highly active antiretroviral therapy • Includes at least three medications • “cocktails” • These medications work in different ways to reduce the viral load

  20. 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)

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

  22. Antiretroviral Drugs • Fusion inhibitors • Inhibit viral fusion, preventing viral replication • Newest class of antiretroviral drugs • Example: enfuvirtide (Fuzeon)

  23. 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

  24. 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

  25. 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

  26. 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

  27. 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

  28. 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

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