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Antivirals for herpesviruses: Nursing Pharmacology


acyclovir (Sitavig, Zovirax); valacyclovir (Valtrex); ganciclovir (Zirgan); valganciclovir (Valcyte); famciclovir (Famvir)
Guanosine analogs
Interfere with DNA synthesis → decrease viral replication
  • Mucocutaneous herpes simplex virus: herpes genitalis and herpes labialis (cold sores) 
  • Herpes simplex encephalitis (IV) 
  • Varicella (chickenpox) 
  • Herpes zoster (shingles) 
  • Cytomegalovirus infection
Acyclovir, Ganciclovir: IV, TOP
Valacyclovir, Vanganciclovir, Famciclovir: PO
  • Headaches
  • Agitation
  • Tremors
  • Confusion
  • Myoclonus
  • Hallucinations
  • Encephalopathy
  • Seizures 
  • Nausea
  • Vomiting
  • Diarrhea
  • Constipation
  • Abdominal pain 

  • Famciclovir: menstrual changes, hepatotoxicity 
  • Acyclovir IV use: pain or phlebitis at the injection site 
  • Acyclovir, valacyclovir: thrombotic thrombocytopenic purpura, and hemolytic uremic syndrome 
  • Valganciclovir: hematologic toxicity, carcinogenesis, impaired fertility, fetal toxicity (boxed warnings) 
  • Pregnancy, breastfeeding 
  • Neurologic, renal, or hepatic disease 
  • Acyclovir, valacyclovir: electrolyte imbalance, dehydration 

Drug interactions: 
  • Acyclovir: zidovudine increases risk of CNS side effects, aminoglycosides increase nephrotoxicity 
Assessment and monitoring: acyclovir for herpes simplex virus infection 
  • Current symptoms: lesion location; presence of pain, itching, or drainage 
  • Laboratory test results: renal and hepatic function, CBC, PCR, herpes culture test 

  • Side effects 
  • Therapeutic response: absence of lesions and symptoms

Client education 
  • Purpose of medication: to help to decrease symptoms associated with the herpes simplex virus; does not eliminate the infection; does not prevent spread to others 
    • Refrain from sexual activity when sores or other signs of herpes are present 
    • Always use latex or polyurethane condoms during sex 
  • Take their medication with plenty of water, with or without food, on a regular schedule 
  • Stay hydrated during treatment 
  • Side effects 
    • Headaches, fatigue, nausea, and vomiting 
    • Contact healthcare provider if symptoms do not resolve or get worse

Herpesviruses are a family of DNA viruses that include herpes simplex virus or HSV types 1 and 2, varicella-zoster virus or VZV, cytomegalovirus or CMV for short, Epstein-Barr virus or EBV, and human herpesvirus or HHV 6, 7, and 8.

Certain herpesvirus infections can be treated with a class of antiviral medications called guanosine analogs, which include medications that end in the suffix -clovir.

The main drugs used to treat herpes infections include valacyclovir, valganciclovir, and famciclovir, which are given orally, as well as acyclovir and ganciclovir, which can also be administered topically or intravenously in addition to orally.

Once administered, guanosine analogs act by inserting into the replicating viral DNA. As a result, viral DNA synthesis is halted, ultimately stopping viral replication.

Now, clients taking guanosine analogs may experience headache and nausea. These medications can also cause a skin rash, pruritus, nephrotoxicity, and hypersensitivity reactions like Stevens-Johnson syndrome and angioedema.

Acyclovir and valacyclovir can cause neurological side effects, including agitation, tremors, confusion, and myoclonus; more rarely, clients can develop hallucinations, and even encephalopathy or seizures.

Acyclovir and valacyclovir can also lead to thrombotic thrombocytopenic purpura, and hemolytic uremic syndrome. Acyclovir can also cause pain or phlebitis at the injection site when given intravenously.

On the other hand, famciclovir can cause menstrual changes and hepatotoxicity. Finally, valganciclovir has boxed warnings for hematologic toxicity, carcinogenesis, impaired fertility, and fetal toxicity.

Now, regarding contraindications, guanosine analogs should be used with caution during pregnancy and breastfeeding, and in clients with neurologic, hepatic, or renal disease.

Acyclovir and valacyclovir should also be used cautiously when there’s an electrolyte imbalance or dehydration.

In addition, acyclovir should not be used in combination with zidovudine, as it increases the level of zidovudine and the risk of neurologic side effects; aminoglycosides combined with acyclovir increase the risk of nephrotoxicity.

Okay, now, when your client with a genital herpes simplex virus infection is prescribed an antiviral medication like acyclovir, first perform a baseline assessment, noting their current symptoms, including lesion location, as well as the presence of pain, itching, or drainage.

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  2. "Pharmacology" Elsevier Health Sciences (2014)
  3. "Mosby's 2021 Nursing Drug Reference" Mosby (2020)
  4. "Saunders Comprehensive Review for the NCLEX-RN Examination" Saunders (2016)
  5. "Lehne's Pharmacology for Nursing Care" Elsevier Health Sciences (2014)
  6. "Overview of Herpesvirus Infections" Merck Manual Professional Version (2019)
  7. "Valacyclovir-Induced Thrombotic Thrombocytopenic Purpura" Cureus (2020)