Antiviral drugs work by interfering with viral replication inside infected host cells. They are used to treat infections caused by viruses like HIV, hepatitis, herpes, influenza, and cytomegalovirus. Antiviral drugs must be able to enter infected cells and interfere with viral nucleic acid synthesis or the virus's ability to bind to cells. The immune system also works synergistically with antiviral drugs to eliminate the virus. While antiviral drugs can control viral infections, they have side effects since they may also kill healthy cells. It is important that patients take antiviral medications exactly as prescribed and for the full course of treatment.

1. Antiviral Drugs
RAY ARBIND

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)
•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)

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. 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. 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. 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. 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