Transcript AntibioticsAntiviral..

ANTIVIRAL DRUGS
Understanding Viruses
Viral replication
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A virus cannot replicate on its own
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It must attach to and enter a host cell
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It then uses the host cell’s energy to synthesize protein, DNA,
and RNA
Understanding Viruses
Viruses are difficult to kill because they live
inside the cells
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Any drug that kills a virus may also kill cells
Viral Infections
Competent immune system:
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Best response to viral infections
A well-functioning immune system will eliminate or effectively destroy virus
replication
Immunocompromised patients have frequent viral infections
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Cancer patients, especially leukemia or lymphoma
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Transplant patients, due to pharmacologic therapy
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AIDS patients, disease attacks immune system
Antivirals
Viruses controlled by current antiviral therapy
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Cytomegalovirus (CMV)
Hepatitis viruses
Herpes viruses
Human immunodeficiency virus (HIV)
Influenza viruses (the “flu”)
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Respiratory syncytial virus (RSV)
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Antivirals
Key characteristics of antiviral drugs
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Able to enter the cells infected with virus
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Interfere with viral nucleic acid synthesis and/or regulation
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Some drugs interfere with ability of virus to bind to cells
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Some drugs stimulate the body’s immune system
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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
Antivirals
Opportunistic infections
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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
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
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Herpes-Simplex Viruses
 HSV-1
(oral herpes)
 HSV-2 (genital herpes)

Varicella Zoster Virus
 Chickenpox
 Shingles
Antiviral Drugs: Nonretroviral
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Mechanism of action

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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)
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Adverse Effects
Vary with each drug
 Healthy cells are often killed also, resulting in serious
toxicities

Antivirals Drugs-Nonretroviral
Amantadine (Symmetrel)
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Narrow antiviral spectrumactive only against influenza A
Used prophylactically when vaccine is not available or cannot be
given
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Therapeutic use can reduce recovery time
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CNS effects: insomnia, nervousness, lightheadedness
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GI effects: anorexia, nausea, others
Antivirals Drugs-Nonretroviral
Rimantadine (Flumadine)
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Same spectrum of activity, mechanism of action, and
indications as amantadine
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Fewer CNS adverse effects
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Causes GI upset
Antivirals Drugs-Nonretroviral
Acyclovir (Zovirax)
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Synthetic nucleoside analog
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Used to suppress replication of:
 HSV-1(oral
herpes), HSV-2(genital herpes),
VZV (Varicella – chickenpox or shingles)
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Drug of choice for treatment of initial and recurrent
episodes of these infections
Oral, topical, parenteral forms
Antivirals Drugs-Nonretroviral
Ganciclovir (Cytovene)
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Synthetic nucleoside analog
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Used to treat infection with cytomegalovirus (CMV)
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Oral, parenteral forms
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CMV retinitis
 Ophthalmic
form surgically implanted
 Ocular injection (fomivirsen)
Antivirals Drugs-Nonretroviral
Dose-Limiting Toxicities
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ganciclovir and zidovudine
 Bone
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marrow toxicity
foscarnet and cidofovir
 Renal
toxicity
Antivirals Drugs-Nonretroviral
Neuraminidase Inhibitors
oseltamivir (Tamiflu) and zanamivir (Relenza)
 Active against influenza types A & B
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Use: Reduce duration of illness
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oseltamivir: causes nausea & vomiting
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zanamivir: causes diarrhea, nausea, sinusitis
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Treatment should begin within 2 days of influenza symptom
onset
Antivirals Drugs-Nonretroviral
Ribavirin
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Synthetic nucleoside analog
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Given orally, or oral or nasal inhalation
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Inhalation form (Virazole) used for hospitalized infants
with RSV (respiratory syncytialvirus) infections
HIV
Human immunodeficiency virus infection
 ELISA (enzyme-linked immunosorbent assay)
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Detects HIV exposure based on presence of human antibodies to the virus in the blood
Retrovirus
Transmitted by:
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Sexual activity, intravenous drug use, perinatally from mother to child
Five Stages of HIV Infection
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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 stages
Opportunistic Infections
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Protozoal
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Toxoplasmosis of the brain, others
Fungal
Candidiasis of the lungs, esophagus, trachea
 Pneumocystis jiroveci pneumonia, others
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Viral
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CMV disease, HSV infection, others
Bacterial
Various mycobacterial infections, others
 Extrapulmonary TB
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Opportunistic neoplasias
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Kaposi’s sarcoma, others
Antiretroviral Drugs
HAART - Highly active antiretroviral therapy
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Includes at least three medications
 “cocktails”
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These medications work in different ways to reduce
the viral load
Antiretroviral Drugs
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Reverse transcriptase inhibitors (RTIs)
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Reverse transcriptase inhibitors (RTIs)
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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)
didanosine (Videx)
stavudine (Zerit)
delavirdine (Rescriptor)
lamivudine (Epivir)
tenofovir (Viread)
Antiretroviral Drugs
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Protease inhibitors (PIs)
 Inhibit
the protease retroviral enzyme, preventing viral
replication
 Examples:
amprenavir (Agenerase)
indinavir (Crixivan)
nelfinavir (Viracept)
ritonavir (Norvir)
saquinavir (Invirase)
Antiretroviral Drugs
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Fusion inhibitors
 Inhibit
viral fusion, preventing viral replication
 Newest
class of antiretroviral drugs
 Example:
enfuvirtide (Fuzeon)
Antiretroviral Drugs
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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
Antiretroviral Drugs:
Adverse Effects
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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
Nursing Implications
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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
Nursing Implications
Patient Education
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Consult their physician before taking other medication,
including OTCs
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Good hygiene
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Antiviral drugs are not cures but help manage symptoms
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Take these medications exactly as prescribed
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Take medications for the full course of treatment
Nursing Implications
Patient Education
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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
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
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Effects are varied and specific to each drug