Antiviral Drugs
ANTIVIRAL DRUGS
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Introduction
· Antiviral drugs are
medications designed to treat viral infections by inhibiting the development
and replication of viruses.
· Unlike antibiotics,
which target bacteria, antiviral drugs are specific to viruses.
· They are essential in
managing diseases caused by viruses such as HIV, herpes, hepatitis, and
influenza.
Definition
· Antiviral drugs are
agents that inhibit the ability of viruses to multiply, thus reducing the
severity and duration of viral infections.
Classification
· Antiviral drugs can
be classified based on the type of virus they target or their mechanism of
action.
Based on Virus Type
1.
Anti-Herpesvirus Agents
o
Acyclovir: Used for herpes simplex virus (HSV)
and varicella-zoster virus (VZV).
o
Valacyclovir: A prodrug of acyclovir with better
bioavailability.
2.
Anti-HIV Agents
o
Zidovudine (AZT): A nucleoside reverse transcriptase
inhibitor.
o
Efavirenz: A non-nucleoside reverse
transcriptase inhibitor.
o
Lopinavir/Ritonavir: Protease
inhibitors.
3.
Anti-Hepatitis Agents
o
Interferon alpha: Used for hepatitis B and C.
o
Sofosbuvir: Used for hepatitis C.
4.
Anti-Influenza Agents
o
Oseltamivir (Tamiflu): A neuraminidase
inhibitor.
o
Amantadine: Inhibits the uncoating of the
influenza A virus.
Based on Mechanism of Action
1.
Viral Uncoating Inhibitors
o
Amantadine: Blocks the M2 proton channel of
influenza A virus.
2.
Nucleoside and Nucleotide Analogs
o
Acyclovir: Mimics nucleotides and gets
incorporated into viral DNA, leading to chain termination.
o
Tenofovir: Used for HIV and hepatitis B.
3.
Protease Inhibitors
o
Ritonavir: Inhibits HIV protease, preventing
viral protein processing.
4.
Neuraminidase Inhibitors
o
Oseltamivir: Inhibits influenza virus
neuraminidase, preventing viral release.
5.
Reverse Transcriptase Inhibitors
o
Zidovudine: Inhibits HIV reverse transcriptase,
preventing viral DNA synthesis.
Pharmacokinetics
The pharmacokinetics of antiviral drugs
can vary widely, but typically involve absorption, distribution, metabolism,
and excretion processes.
·
Absorption: Some antivirals are well absorbed
orally (e.g., oseltamivir), while others may require intravenous administration
(e.g., acyclovir).
·
Distribution: Antivirals must penetrate cells and
reach intracellular sites where viruses replicate. Some drugs, like acyclovir,
have good tissue penetration.
·
Metabolism: Many antiviral drugs are metabolized
in the liver. For example, valacyclovir is converted to acyclovir.
·
Excretion: Antivirals are often excreted by the
kidneys. Monitoring kidney function is important in drugs like tenofovir.
Mechanism of Action
Antiviral drugs work by targeting
specific stages of the viral life cycle:
1.
Attachment and Entry Inhibitors: Prevent viruses
from binding to host cells.
2.
Uncoating Inhibitors: Prevent the release
of viral genetic material into host cells.
3.
Nucleoside/Nucleotide Analogs: Mimic natural
nucleotides and disrupt viral DNA/RNA synthesis.
4.
Reverse Transcriptase Inhibitors: Block the
transcription of viral RNA into DNA.
5.
Protease Inhibitors: Prevent the
cleavage of viral polyproteins into functional proteins.
6.
Neuraminidase Inhibitors: Prevent the release
of new viral particles from infected cells.
Uses
Antiviral drugs are used to:
·
Treat acute viral infections (e.g., influenza, herpes simplex).
·
Manage chronic viral infections (e.g., HIV, hepatitis B and C).
·
Prevent viral infections in high-risk populations (e.g., prophylaxis in
HIV, influenza).
Adverse Effects
Common adverse effects of antiviral
drugs include:
·
Gastrointestinal Distress: Nausea, vomiting,
diarrhea.
·
Hematologic Toxicity: Anemia, leukopenia
(common with zidovudine).
·
Neurotoxicity: Headache, dizziness (seen with
amantadine).
·
Nephrotoxicity: Kidney damage (noted with acyclovir
and tenofovir).
·
Hepatotoxicity: Liver damage (associated with
protease inhibitors).
Contraindications
Contraindications vary by drug but may
include:
·
Hypersensitivity: Known allergy to the drug.
·
Renal Impairment: Drugs like acyclovir and tenofovir
require dose adjustments.
·
Liver Disease: Protease inhibitors can exacerbate
hepatic conditions.
·
Pregnancy and Lactation: Some antivirals are
contraindicated due to potential teratogenic effects.
Role of Nurses
Nurses play a crucial role in the
management of antiviral therapy:
1.
Assessment: Monitor patient history, allergies,
and current medications to prevent interactions.
2.
Administration: Ensure correct dosages and routes of
administration, educate patients on proper use.
3.
Monitoring: Observe for therapeutic effects and
adverse reactions, monitor lab results (e.g., kidney and liver function tests).
4.
Patient Education: Inform patients about the importance
of adherence to therapy, potential side effects, and signs of toxicity.
5.
Support: Provide emotional support and
counseling, especially for patients with chronic conditions like HIV or
hepatitis.
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