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

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

5. 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

6. 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)

7. 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

8. 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

9. 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

10. 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

11. Antivirals Drugs-Nonretroviral Amantadine (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

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

13. Antivirals Drugs-Nonretroviral Acyclovir (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

14. Antivirals Drugs-Nonretroviral Ganciclovir (Cytovene)
Synthetic nucleoside analog
Used to treat infection with cytomegalovirus (CMV)
Oral, parenteral forms
CMV retinitis
Ophthalmic form surgically implanted
Ocular injection (fomivirsen)

15. Antivirals Drugs-Nonretroviral Dose-Limiting Toxicities
ganciclovir and zidovudine
Bone marrow toxicity
foscarnet and cidofovir
Renal toxicity

16. Antivirals Drugs-Nonretroviral Neuraminidase 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

17. Antivirals Drugs-Nonretroviral Ribavirin
Synthetic nucleoside analog
Given orally, or oral or nasal inhalation
Inhalation form (Virazole) used for hospitalized infants with RSV (respiratory syncytialvirus) infections

19. 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

20. 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

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

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

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

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

25. 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

26. 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

27. 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

28. Nursing Implications Patient 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

29. Nursing Implications Patient 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

30. 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