Antiviral Drugs: Nursing Pharmacology Study Guide

Antiviral Drugs: Generic and Brand Names

Commonly encountered antivirals by generic and brand name:

• Influenza A and Respiratory Viruses Drugs
• amantadine (Symmetrel)
• oseltamivir (Tamiflu)
• ribavirin (Rebetron, Virazole)
• rimantadine (Flumadine)
• zanamivir (Relenza)
• Herpes and Cytomegaloviruses (CMV) Drugs
• acyclovir (Zovirax)
• cidofovir (Vistide)
• famciclovir (Famvir)
• foscarnet (Foscavir)
• ganciclovir (Cytovene)
• valacyclovir (Valtrex)
• valganciclovir (Valcyte)
• Agents for HIV and AIDS
• Non-nucleoside Reverse Transcriptase Inhibitors
• delavirdine (Rescriptor)
• efavirenz (Sustiva)
• etravirine (Intelence)
• nevirapine (Viramune)
• rilpivirine (Edurant)
• Nucleoside Reverse Transcriptase Inhibitors (NRTI)
• abacavir (Ziagen)
• didanosine (Videx)
• emtricitabine (Emtriva)
• lamivudine (Epivir)
• stavudine (Zerit XR)
• tenofovir (Viread)
• zidovudine (AZT) (Retrovir, Aztec)
• Protease Inhibitors
• atazanavir (Reyataz)
• darunavir (Prezista)
• fosamprenavir (Lexiva)
• indinavir (Crixivan)
• lopinavir (Kaletra)
• nelfinavir (Viracept)
• ritonavir (Norvir)
• saquinavir (Fortovase)
• tipranavir (Aptivus)
• Fusion Inhibitors
• enfurvirtide (Fuzeon)
• CCR5 Coreceptor Antagonists
• maraviroc (Selzentry)
• Integrase Inhibitors
• raltegravir (Isentress)
• Anti Hepatitis B Agents
• adefovir (Hepsera)
• entecavir (Baraclude)
• telbivudine (Tyzeka)
• Anti Hepatitis C Agents
• boceprevir (Victrelis)
• telaprevir (Incivek)
• Locally Active Antiviral Agents
• docosanol (Abreva)
• ganciclovir (Vitrasert)
• imiquimod (Aldara)
• penciclovir (Denavir)
• trifluridine (Viroptic)

Disease Spotlight: Viral Diseases

A virus is a single strand of DNA or RNA inside a protein coat. It cannot run its own metabolism, so it must enter a host cell, inject its DNA or RNA, and reprogram the cell to make the components the virus needs to replicate. Because the virus lives inside host cells, vaccines are hard to develop and drugs that hit the virus often hit the cell too. Still, several viruses respond to antiviral therapy: influenza A, herpes viruses, CMV, HIV, hepatitis B and C, and some viruses that cause warts and eye infections.

Agents for Influenza A and Respiratory Viruses

These treat respiratory flu from influenza A and B and respiratory syncytial virus (RSV). Vaccines are the first line, but drug therapy is the option once a patient is symptomatic and the infection is not resolving on its own.

Therapeutic Action

The exact mechanism is unknown. The working belief is that these agents prevent shedding of the viral protein coat and block the virus from entering the cell, which stops replication and kills the virus.

Indications

Respiratory flu, especially in health care workers and high-risk individuals. The CDC currently recommends four FDA-approved influenza antivirals: oseltamivir (Tamiflu), zanamivir (Relenza), peramivir (Rapivab), and baloxavir marboxil (Xofluza), all active against influenza A and B, with treatment most effective when started within 48 hours of symptom onset (CDC). Oral oseltamivir is the preferred agent for hospitalized patients and for suspected novel influenza A infection, including avian (H5N1) flu, because it can be taken by patients of any age and is the most studied option for severe disease. Zidovudine has been used safely in pregnant women.

Across age groups: children are very sensitive to most antivirals, so expect more severe reactions, give smaller doses, and remember that many antivirals lack proven safety and efficacy in this group. Adults need teaching that antibiotics do not treat viral disease, and HIV patients need to understand antivirals control but do not cure. Pregnant women are generally not given antivirals unless benefits clearly outweigh risk to the fetus or neonate; women of childbearing age on these drugs should use barrier contraceptives, and the CDC advises women with HIV not to breast-feed. Older adults, especially those with hepatic or renal dysfunction, are more prone to adverse effects.

Pharmacokinetics

Here are the characteristic interactions of agents for respiratory viruses and the body in terms of absorption, distribution, metabolism, and excretion:

Contraindications and Cautions

Renal impairment alters metabolism and excretion, particularly of amantadine, zanamivir, and oseltamivir. In pregnancy and lactation, amantadine, rimantadine, and oseltamivir are used for treatment only when benefits outweigh risks.

Adverse Effects

CNS effects (light-headedness, dizziness, insomnia) may relate to dopamine levels in the brain. CV: orthostatic hypotension. GU: urinary retention.

Interactions

Anticholinergics increase atropine-like effects with amantadine or rimantadine. Rimantadine reduces the effectiveness of acetaminophen and aspirin. Antacids and NRTIs reduce the effectiveness of ribavirin. Isoniazid increases the incidence of rifampin-related hepatitis. Rifampin decreases the effectiveness of antiarrhythmics, hormonal contraceptives, corticosteroids, antifungals, and CNS depressants. St. John's wort decreases serum levels of protease inhibitors and increases metabolism of antivirals cleared through the cytochrome P450 system.

Agents for Herpes and Cytomegaloviruses

These treat herpes infections (cold sores, encephalitis, shingles, genital infection) and CMV (eye, respiratory tract, and liver infection).

Therapeutic Action

They inhibit viral DNA replication by competing with viral substrates to form shorter, noneffective DNA chains.

Indications

Infections caused by the DNA viruses herpes simplex, herpes zoster, and CMV, including in immunocompromised patients such as those with AIDS and multiple infections. Acyclovir is the drug of choice for children with herpes virus or CMV infection.

Pharmacokinetics

Here are the characteristic interactions of agents for herpes virus and CMV and the body in terms of absorption, distribution, metabolism, and excretion:

Contraindications and Cautions

Known drug allergy (hypersensitivity) and renal impairment (altered excretion) are cautions, as are pregnancy and lactation. Severe CNS disorders matter because these drugs can cause headache, neuropathy, paresthesias, confusion, and hallucinations. In children with AIDS, cidofovir carries potential carcinogenic and fertility effects, so use caution. Foscarnet, ganciclovir, and valganciclovir can affect bone development and growth, and the safety of famciclovir in children younger than 18 years is not established.

Adverse Effects

CNS: headache, depression, paresthesias, neuropathy. GI: nausea, vomiting. GU: renal dysfunction and failure. IV and topical site: rash, inflammation, burning. Cidofovir is associated with severe renal toxicity and granulocytopenia. Ganciclovir and valganciclovir cause bone marrow suppression. Foscarnet has been linked to seizures, especially with electrolyte imbalance.

Interactions

Aminoglycosides increase renal toxicity. Zidovudine increases the risk of drowsiness.

Agents for HIV and AIDS (Antiretroviral Drugs)

HIV is treated with combination antiretroviral therapy (ART), and adherence is the single biggest driver of success. The HHS panel notes that once-daily and single-tablet regimens improve adherence over more complex schedules, which is why simplified combinations are favored (HHS). Missed doses let resistant virus emerge, so patients need a regimen they can actually keep.

Nonnucleoside Reverse Transcriptase Inhibitors

These act directly on HIV activity inside the cell.

Therapeutic Action

They bind directly to HIV reverse transcriptase and block both RNA- and DNA-dependent DNA polymerase activity, cutting off the information transfer the virus needs to build viral DNA, so replication becomes impossible.

Indications

Treatment of documented AIDS or ARC with decreased helper T cells and increased opportunistic infection, in combination with other antiviral drugs.

Pharmacokinetics

Here are the characteristic interactions of nonnucleoside reverse transcriptase inhibitors and the body in terms of absorption, distribution, metabolism, and excretion:

Contraindications and Cautions

In pregnancy, no adequate studies exist, so use only when benefits clearly outweigh risk. Safety of delavirdine in children is not established.

Adverse Effects

CNS: dizziness, blurred vision, headache. GI: dry mouth, constipation or diarrhea, nausea, abdominal pain, dyspepsia. A flu-like syndrome may occur, though it can also reflect the underlying disease.

Interactions

Do not combine delavirdine with antiarrhythmics, clarithromycin, dapsone, antituberculosis drugs, calcium-channel blockers, warfarin, quinidine, indinavir, or saquinavir. Do not combine efavirenz with midazolam, rifabutin, triazolam, or ergot derivatives. Hormonal contraceptives and protease inhibitors cause loss of nevirapine effectiveness. St. John's wort decreases antiviral effect.

Nucleoside Reverse Transcriptase Inhibitors (NRTIs)

This was the first drug class developed for HIV. It competes with the naturally occurring nucleosides the virus needs to build its DNA chain. Those substitute nucleosides lack the substance needed to extend the chain, so the chain cannot lengthen or insert into the host DNA.

Therapeutic Action

Competing with naturally occurring nucleosides so the viral DNA chain cannot lengthen or insert into host DNA.

Indications

Combination therapy for adults and children with HIV. Lamivudine oral solution can treat chronic hepatitis B. Zidovudine is used to prevent maternal transmission of HIV.

Pharmacokinetics

Here are the characteristic interactions of nonnucleoside NRTIs and the body in terms of absorption, distribution, metabolism, and excretion:

Contraindications and Cautions

In pregnancy, no adequate studies exist except for zidovudine, which is proven safe. Use caution with tenofovir, zidovudine, and emtricitabine in hepatic dysfunction or severe renal impairment. Zidovudine can aggravate bone marrow suppression.

Adverse Effects

Abacavir can cause serious-to-fatal hypersensitivity reactions (fever, chills, rash, fatigue, GI upset, flu-like symptoms); discontinue immediately and list the patient with the Abacavir Hypersensitivity Registry. Didanosine causes serious pancreatitis, hepatomegaly, and neurological problems. Emtricitabine and tenofovir cause severe and fatal hepatomegaly with steatosis. Zidovudine causes severe bone marrow suppression. Tenofovir shifts body fat distribution, with loss from arms, legs, and face and deposition on the trunk, neck, and face.

Interactions

Tenofovir raises the serum level of didanosine; in combination therapy, give it 2 hours before or 1 hour after didanosine. Alcohol causes severe toxicity with abacavir. Antibiotics and antifungals lose effectiveness when combined with didanosine. Cyclosporine causes severe drowsiness and lethargy with zidovudine. Lamivudine and zalcitabine inhibit each other.

Protease Inhibitors

Protease inhibitors block protease activity within the HIV virus.

Therapeutic Action

By blocking protease, which is essential for viral maturation, they leave the virus immature and noninfective, unable to fuse with and inject itself into a cell.

Indications

Combination therapy for the treatment of HIV infection.

Pharmacokinetics

Here are the characteristic interactions of nonnucleoside NRTIs and the body in terms of absorption, distribution, metabolism, and excretion:

Contraindications and Cautions

In pregnancy and lactation, only saquinavir is not teratogenic, though it crosses into breast milk. Hepatic dysfunction increases toxicity, especially with fosamprenavir and darunavir. Darunavir can cause diabetes mellitus and hyperglycemia, so patients on antidiabetic drugs need dose adjustment, and darunavir is associated with mild to severe dermatologic reactions including Stevens-Johnson syndrome. Safety of indinavir in children younger than 12 years is not established, and darunavir should not be used in children younger than 3 years because of potential toxicity.

Adverse Effects

GI: nausea, vomiting, diarrhea, anorexia, and changes in liver function with elevated cholesterol and triglyceride. Skin: rashes, pruritus, Stevens-Johnson syndrome.

Interactions

Pimozide, rifampin, triazolam, and midazolam cause severe toxic effects with nelfinavir. Nonsedating antihistamines, sedatives and hypnotics, and antiarrhythmics cause many potentially serious toxic effects with ritonavir.

Fusion Inhibitor

Introduced in 2003, this drug acts at a different site than the other HIV antivirals.

Therapeutic Action

It prevents the virus from fusing with the human cell membrane, blocking entry of the HIV-1 virus into the cell.

Indications

Combination therapy for adults and children older than 6 years with HIV-1 replication despite ongoing antiretroviral therapy.

Pharmacokinetics

Here are the characteristic interactions of fusion inhibitors and the body in terms of absorption, distribution, metabolism, and excretion:

Contraindications and Cautions

Pregnancy and lactation (potential harm to fetus and neonate) and known hypersensitivity to the drug.

Adverse Effects

CNS: insomnia, depression, peripheral neuropathy. GI: nausea, diarrhea. Respiratory: pneumonia. Local: injection-site reactions.

Interactions

No reported drug interactions, but use caution when combining with any drug.

CCR5 Coreceptor Antagonist

Introduced in 2007.

Therapeutic Action

It blocks the receptor site on the cell membrane that the HIV virus must interact with to enter the cell.

Indications

Combination therapy with other antivirals.

Pharmacokinetics

Here are the characteristic interactions of CCR5 coreceptor antagonists and the body in terms of absorption, distribution, metabolism, and excretion:

Contraindications and Cautions

Pregnancy, lactation, and known hypersensitivity. Renal impairment raises the risk of toxicity. Safety in children is not established.

Adverse Effects

CNS: dizziness, changes in consciousness. Severe hepatotoxicity has been reported with maraviroc, often preceded by a systemic allergic reaction with eosinophilia and rash.

Interactions

Cytochrome P450 CYP3A inhibitors (ketoconazole, lopinavir/ritonavir, saquinavir, ritonavir, atazanavir, delavirdine) raise serum levels and toxicity of maraviroc. CYP3A inducers (nevirapine, rifampin, efavirenz) lower serum levels and effectiveness of maraviroc. St. John's wort causes loss of maraviroc's antiviral effect.

Integrase Inhibitors

Released in late 2007.

Therapeutic Action

They inhibit integrase, the virus-specific encoded enzyme needed for replication. Blocking integrase prevents formation of HIV-1 provirus, lowering viral load and raising active CD4 cells.

Indications

Reserved for patients previously treated with other antivirals who show a return to viral replication.

Pharmacokinetics

Here are the characteristic interactions of integrase inhibitors and the body in terms of absorption, distribution, metabolism, and excretion:

Contraindications and Cautions

Contraindicated with known hypersensitivity to any component, as initial treatment for adults, for use in children, and for nursing mothers. Use caution if the patient is at risk for rhabdomyolysis or myopathy and during pregnancy.

Adverse Effects

CNS: headache, dizziness. Musculoskeletal: rhabdomyolysis, myopathy.

Interactions

Rifampin lowers serum levels of raltegravir. St. John's wort reduces antiviral effectiveness.

Anti-Hepatitis B and C Agents

Hepatitis B is a serious-to-potentially-fatal viral infection of the liver, spread by blood or blood products, sexual contact, or contaminated needles and instruments; affected patients may become chronic or carriers. Hepatitis C is the leading cause of most liver transplants because of progressive liver disease. After initial HCV infection most people develop chronic hepatitis C, and some progress to cirrhosis; transmission is similar to HBV.

Therapeutic Action

Anti-hepatitis B agents inhibit reverse transcriptase in the hepatitis B virus and cause DNA chain termination, blocking viral replication and lowering viral load.

Indications

Treatment of adults with chronic hepatitis B and C who show active viral replication plus either persistent elevations in serum aminotransferase or histologically active disease.

Pharmacokinetics

Here are the characteristic interactions of anti-hepatitis agents and the body in terms of absorption, distribution, metabolism, and excretion:

Contraindications and Cautions

For anti-hepatitis B: known drug allergy (hypersensitivity), lactation (potential toxicity to the infant), and renal or liver impairment (increased toxicity risk). For anti-hepatitis C: pregnancy, hepatitis B, and HIV infection, where safety is not established.

Adverse Effects

Anti-hepatitis B should not be stopped abruptly because of the risk of hepatitis B exacerbation. CNS: headache, dizziness, nausea. GI: diarrhea, elevated liver enzymes, severe hepatomegaly with steatosis. GU: lactic acidosis and renal impairment. Anti-hepatitis C causes CNS effects (headache, fatigue), GI effects (nausea, diarrhea), and immunological effects (bone marrow suppression, severe skin reactions).

Interactions

Nephrotoxic drugs increase the risk of renal toxicity.

Nursing Considerations

These apply across antiviral classes, with the class-specific points noted above.

Nursing Assessment

Screen for the listed cautions and contraindications (drug allergies, hepatorenal impairment, pregnancy and lactation, severe CNS disorders) to prevent complications. Do a full physical (other medications, orientation and reflexes, vital signs, skin color, temperature, lesions) for baseline data and to catch adverse effects. Check hepatic and renal function tests for baseline kidney and liver function. For antiretrovirals, check CBC with differential and helper T cell counts to gauge bone marrow activity, disease severity, and drug effectiveness.

Nursing Diagnoses

Acute pain related to GI, CNS, GU, or dermatological effects of the drug. Disturbed sensory perception (kinesthetics) related to CNS effects. Imbalanced nutrition, less than body requirements, related to GI effects.

Implementation with Rationale

Start the drug as soon after viral exposure as possible to maximize effectiveness and cut complications. Give influenza A vaccine before flu season when possible. Ensure good hydration to reduce kidney toxicity, and monitor renal and hepatic function before and during therapy for dose adjustments. Make sure the patient takes the complete course and every drug in a combination to keep the regimen effective and limit resistant strains; dose around the clock when indicated to hold the critical concentration. Stop the drug for severe rash, especially with blisters or fever, to avert serious reactions. Wear protective gloves when applying topical agents to avoid inadvertent absorption. Provide safety precautions (side rails, lighting, orientation, assistance) if CNS effects occur. Teach patients to avoid sexual intercourse when treating genital herpes since the drug does not cure it, to avoid driving and hazardous tasks if dizzy or drowsy, and that anti-hepatitis drugs must be taken continuously because stopping can trigger acute hepatitis B exacerbation. Anti-hepatitis patients should keep regular blood tests and medical followup and report severe weakness, muscle pain, palpitations, yellowing of the eyes or skin, and trouble breathing.

Evaluation

Monitor response to therapy: relief of respiratory or herpes/CMV symptoms, reduction of AIDS or ARC signs with maintained helper T cell levels, or decreased viral load with anti-hepatitis agents. Monitor for adverse effects (orientation and affect, blood pressure, urinary output, GI upset, renal and hepatic function, skin, blood counts). Confirm understanding by having the patient name the drug, its indication, and the adverse effects to watch for, and monitor compliance.

Frequently Asked Questions

Do antivirals cure viral infections?

Most do not. They slow viral replication so the immune system can clear or control the infection, which is why early treatment and a full course matter. HIV antiretrovirals, for example, suppress the virus and protect immune function but do not eliminate it.

When should an influenza antiviral be started?

As soon as possible. The CDC notes antiviral treatment works best when started within 48 hours of symptom onset, though it is still recommended beyond that window for hospitalized patients and those with severe or progressive illness.

Which flu antivirals does the CDC recommend?

Four FDA-approved drugs: oseltamivir (Tamiflu), zanamivir (Relenza), peramivir (Rapivab), and baloxavir marboxil (Xofluza). Oral oseltamivir is preferred for hospitalized patients and for suspected novel influenza A, including avian flu.

Why is adherence so important with HIV antiretroviral therapy?

Skipped doses let the virus replicate and select for resistant strains, which can render a regimen useless. Combination therapy and consistent dosing are what keep viral load suppressed, so once-daily and single-tablet regimens are favored to make adherence easier.

What does the nurse monitor during antiviral therapy?

Renal and hepatic function before and during treatment, since most of these agents are cleared by the kidneys and many are nephrotoxic or hepatotoxic. For antiretrovirals, also follow CBC with differential and helper T cell counts to gauge marrow activity and drug effectiveness.

Are antivirals safe in pregnancy?

Generally they are reserved for pregnancy only when the benefit clearly outweighs fetal risk. Zidovudine is the notable exception, used safely to prevent maternal-to-infant HIV transmission. Women of childbearing age on antivirals should use reliable contraception, and the CDC advises women with HIV not to breastfeed.