Anti-viral agents

Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Antiviral AgentsAntiviral Agents


Understanding VirusesUnderstanding Viruses

Viral ReplicationViral Replication

• A virus cannot replicate on its own.A virus cannot replicate on its own.

• It must attach to and enter a host cell.It must attach to and enter a host cell.

• It then uses the host cell’s energy to synthesize It then uses the host cell’s energy to synthesize protein, DNA, and RNA.protein, DNA, and RNA.


Understanding VirusesUnderstanding Viruses

Viruses are difficult to kill because they liveViruses are difficult to kill because they liveinside our cells.inside our cells.

• Any drug that kills a virus may also kill our cells.Any drug that kills a virus may also kill our cells.


Viral InfectionsViral InfectionsCompetent immune system:Competent immune system:• Best response to viral infectionsBest response to viral infections• A well-functioning immune system will eliminate A well-functioning immune system will eliminate

or effectively destroy virus replicationor effectively destroy virus replication

Immunocompromised patients have frequent Immunocompromised patients have frequent viral infectionsviral infections

• Cancer patients, especially leukemia or lymphomaCancer patients, especially leukemia or lymphoma• Transplant patients, due to pharmacological therapyTransplant patients, due to pharmacological therapy• AIDS patients, disease attacks immune systemAIDS patients, disease attacks immune system


AntiviralsAntivirals

Key characteristics of antiviral drugs:Key characteristics of antiviral drugs:• Able to enter the cells infected with virus.Able to enter the cells infected with virus.

• Interfere with viral nucleic acid synthesis and/or Interfere with viral nucleic acid synthesis and/or regulation.regulation.

• Some agents interfere with ability of virus Some agents interfere with ability of virus to bind to cells.to bind to cells.

• Some agents stimulate the body’s immune system.Some agents stimulate the body’s immune system.


AntiviralsAntivirals

Viruses killed by current antiviral therapy:Viruses killed by current antiviral therapy:

• cytomegalovirus (CMV)cytomegalovirus (CMV)

• herpes simplex virus (HSV)herpes simplex virus (HSV)

• human immunodeficiency virus (HIV)human immunodeficiency virus (HIV)

• influenza A (the “flu”)influenza A (the “flu”)

• respiratory syncytial virus (RSV)respiratory syncytial virus (RSV)


Antivirals: Mechanism of ActionAntivirals: Mechanism of Action

Inhibit viral replicationInhibit viral replication

• Inhibit viral attachmentInhibit viral attachment

• Prevent genetic copying of virusPrevent genetic copying of virus

• Prevent viral protein productionPrevent viral protein production


Antivirals Antivirals Synthetic Purine Nucleoside AnaloguesSynthetic Purine Nucleoside Analogues

Two types of nucleosides:Two types of nucleosides:

Purine nucleosidesPurine nucleosides

• guanineguanine

• adenosineadenosine

Pyrimidine nucleosidesPyrimidine nucleosides

• thyminethymine

• cytosinecytosine


Antivirals: Purine NucleosidesAntivirals: Purine Nucleosides

AgentAgent Antiviral ActivityAntiviral Activityguaninesguanines

acycloviracyclovir HSV 1 & 2, VZVHSV 1 & 2, VZVganciclovir (DHPG)ganciclovir (DHPG) CMV retinitis and CMV retinitis and systemicsystemic CMV infectionCMV infectionribavirin (RTCD)ribavirin (RTCD) Influenza types A and B,Influenza types A and B,

RSV, LV, HVRSV, LV, HVadenosinesadenosines

didanosine (ddl)didanosine (ddl) HIVHIVvidarabine (Ara-A)vidarabine (Ara-A) HSV, herpes zosterHSV, herpes zoster


Antivirals: Pyrimidine NucleosidesAntivirals: Pyrimidine Nucleosides

AgentAgent Antiviral ActivityAntiviral Activitycytosinescytosines

lamivudine (3TC)lamivudine (3TC) HIVHIVzalcitabine (ddC)zalcitabine (ddC) HIVHIV

thyminethymineidoxuridine (IDU)idoxuridine (IDU) HSVHSVstavudine (d4T)stavudine (d4T) HIVHIVtrifluridinetrifluridine HSVHSVzidovudine (AZT)zidovudine (AZT) HIVHIV


Other AntiviralsOther Antivirals

amantadine amantadine (Symmetrel) and rimantadine (Flumadine)(Symmetrel) and rimantadine (Flumadine)

• influenza Ainfluenza A

foscarnet (Foscavir)foscarnet (Foscavir)• CMV (retinitis and systemic)CMV (retinitis and systemic)

Neuraminidase Inhibitors: oseltamivir (Tamiflu) Neuraminidase Inhibitors: oseltamivir (Tamiflu) and zanamivir (Relenza)and zanamivir (Relenza)

• influenza types A and Binfluenza types A and B


Antivirals: Side EffectsAntivirals: Side Effects

acycloviracyclovir• Burning when topically applied, nausea, vomiting, Burning when topically applied, nausea, vomiting,

diarrhea, headachediarrhea, headache

amantadine and rimantadineamantadine and rimantadine• Anticholinergic effects, insomnia, lightheadedness, Anticholinergic effects, insomnia, lightheadedness,

anorexia, nauseaanorexia, nausea

didanosine (ddl)didanosine (ddl)• Pancreatitis, peripheral neuropathies, seizuresPancreatitis, peripheral neuropathies, seizures


Antivirals: Side EffectsAntivirals: Side Effects

zidovudine (AZT)zidovudine (AZT)• Bone marrow suppression, nausea, headacheBone marrow suppression, nausea, headache

foscarnet (Foscavir)foscarnet (Foscavir)• Headache, seizures, acute renal failure, nausea, Headache, seizures, acute renal failure, nausea,

vomiting, diarrheavomiting, diarrhea

ganciclovir (Cytovene)ganciclovir (Cytovene)• Bone marrow toxicity, nausea, anorexia, vomitingBone marrow toxicity, nausea, anorexia, vomiting


Antivirals: Nursing ImplicationsAntivirals: Nursing Implications

• Before beginning therapy, thoroughly Before beginning therapy, thoroughly assess underlying disease and medical assess underlying disease and medical history, including allergies.history, including allergies.

• Assess baseline VS and nutritional status.Assess baseline VS and nutritional status.

• Assess for contraindications, conditions Assess for contraindications, conditions that may indicate cautious use, and potential that may indicate cautious use, and potential drug interactions.drug interactions.



• Be sure to teach proper application Be sure to teach proper application technique for ointments, aerosol technique for ointments, aerosol powders, etc.powders, etc.

• Emphasize hand washing before and after Emphasize hand washing before and after administration of medications to prevent site administration of medications to prevent site contamination and spread of infection.contamination and spread of infection.

• Patients should wear a glove or finger cot Patients should wear a glove or finger cot when applying ointments or solutions to when applying ointments or solutions to affected areas.affected areas.



• Instruct patients to consult their physician Instruct patients to consult their physician before taking any other medication, including before taking any other medication, including OTC medications.OTC medications.

• Emphasize the importance of good hygiene.Emphasize the importance of good hygiene.

• Inform patients that antiviral agents are not Inform patients that antiviral agents are not cures, but do help to manage symptoms.cures, but do help to manage symptoms.



• Instruct patients on the importance of taking Instruct patients on the importance of taking these medications exactly as prescribed and these medications exactly as prescribed and for the full course of treatment.for the full course of treatment.

• With zidovudine:With zidovudine:

• Inform patients that hair loss MAY occur so Inform patients that hair loss MAY occur so that they are prepared for this rare adverse that they are prepared for this rare adverse reaction.reaction.

• This medication should be taken on an empty This medication should be taken on an empty stomach.stomach.



Monitor for side effects:Monitor for side effects:

• effects are varied and specific to each agenteffects are varied and specific to each agent



Monitor for therapeutic effects:Monitor for therapeutic effects:

• effects will vary depending on the type of viral effects will vary depending on the type of viral infectioninfection

• Effects range from delayed progression of AIDS Effects range from delayed progression of AIDS and ARC to decrease in flu-like symptoms, and ARC to decrease in flu-like symptoms, decreased frequency of herpes-like flare-ups, decreased frequency of herpes-like flare-ups, or crusting over of herpetic lesions.or crusting over of herpetic lesions.

Education

Anti-viral agents