Nursing Pharmacology: Antiviral Drugs

Nursing Pharmacology: Antiviral Drugs

Antiviral Drugs

Acyclovir and Related Drugs continued:

Acyclovir (Cyclovir, Zovirax etc.) is available in several formulations including intravenous (IV), oral and topical.²
- Acyclovir (Zovirax)⁵
By contrast, valacyclovir (Valtrex, Zelitrex) is an oral formulation.
- Valacyclovir (Valtrex)⁵

IV acyclovir has a number of uses including treatment of mucocutaneous herpes simplex virus (HSV) infections in immunocompromised patients.²

Efficacy assessment of oral acyclovir treatment for mucocutaneous HSV infections in immunocompromised marrow transplant recipients is based in part on results from a randomized, double-blinded, placebo-controlled clinical trial.

**Chronic mucocutaneous Herpes Lesion in HIV-Positive Patient⁶**

"This HIV-positive patient was exhibiting a chronic mucocutaneous herpes lesion for one month in duration. Herpes simplex virus type1 usually is the cause for oral lesions sometimes referred to as “cold sores”, “fever blisters” or more technically known as “recurrent herpes labialis”."⁶

The benefit of using IV acyclovir in these patients include reduced pain duration, reduced time to healing and diminished viral shedding.²
If IV acyclovir is administered prior to drug-induced immunosuppression in the context of chemotherapy or transplantation and if it is administered before lesion development, the drug decreases the likelihood of HSV-associated disease.
- However, following discontinuation of this prophylactic IV acyclovir administration, HSV lesions can recur.²
Varicella-zoster-zoster virus (VZV) disease may afflict about 30% of allogenic hematopoietic cell transplant recipients if they had a history of VZV infection.⁹
- Acyclovir administration reduced VZV infection likelihood at one year following transplantation.
- This result was obtained in a double-blind controlled trial. In the study 77 hemopoietic cell transplant recipients known to be at risk for VZV reactivation were randomized either to acyclovir (800 mg twice daily) or placebo administered for one year following transplantation.
- The principal endpoint was VZV disease at one year.⁹
- Acyclovir administration was found to reduce the likelihood of VZV infections at one year following transplantation (P = 0.006).
  - After one year i.e. following acyclovir discontinuation, VZV-related disease was observed.⁹
IV acyclovir is also central in the treatment of HSV encephalitis, which if untreated is associated with high mortality rates and even with treatment, HSV encephalititis may be associated with significant post-infection morbidity.²

Acyclovir is also used in treating varicella-zoster (VZV) infection and the drug must be administered at higher doses since VZV appears less sensitive to acyclovir compared to herpes simplex virus.²

In immunocompromised patients with herpes zoster, IV acyclovir reduces the likelihood of cutaneous dissemination and visceral complications.

Oral acyclovir may provide some benefit on localized herpes zoster lesions in both immunocompromised and immunocompetent patients.

Furthermore, combining acyclovir with prednisone (tapering regimen) is likely more effective than acyclovir alone, using quality-of-life outcome measures as the metric, in immunocompetent patients over age 50 with herpes zoster.
Using the endpoint of resolution of zoster-associated pain, valacyclovir (Valtrex, Zelitrex) may be more effective compared to acyclovir (Cyclovir, Zovirax) in immunocompetent individuals.

Oral acyclovir was also found to decrease complications in herpes zoster ophthalmicus.²

**Herpes Zoster Ophthalmicus (left)¹⁰; Trigeminal Nerve Distribution (right)¹¹**

"Herpes Zoster Ophthalmicus (HZO), commonly known as shingles, is a viral disease characterized by a painful skin rash in one or more dermatome distributions of the fifth cranial nerve, shared by the eye and orbit."¹⁰	Distribution Scheme of the Trigeminal Nerve¹¹

In chickenpox (varicella-zoster) some clinical benefit has been noted with oral acyclovir when treatment is initiated within a day of rash onset in children (otherwise healthy) or adults.²
- In children who are immunocompromised and suffering chickenpox, IV acyclovir may be an effective therapy.²

References
Acosta EP Flexner C Antiviral Agents (Nonretroviral) Chapter 58 in Goodman & Gilman's The Pharmacological Basis of Therapeutics, 12th edition (Brunton LL Chabner BA Knollmann BC, eds; Brunton LL, ed; Blumenthal DK Murri N Hilal-Dandan R, assoc eds, Knollmann BC, consulting ed, on-line edition) The McGraw-Hill Companies, 2011. Baden LR Dolin R, Chapter 178, Antiviral Chemotherapy, Excluding Antiretroviral Drugs, in Harrison's Online (Dan L. Longo, Anthony S. Fauci, Dennis L. Kasper, Stephen L. Hauser, J. Larry Jameson, Joseph Loscalzo, Eds.), Harrison's Principles of Internal Medicine, 18th edition, The McGraw-Hill Companies, Inc. 2012. Safrin S Antiviral Agents, Chapter 49 in Basic & Clinical Pharmacology, 12 e (Katzung BG Masters SB Trevor AJ) The McGraw-Hill Companies, 2012 (on-line edition) De Clercq E Holy A Acyclic Nucleoside Phosphonates: A Key Class of Antiviral Drugs Nature Reviews: Drug Discovery 4: 928-940, 2005. http://www.nature.com/nrd/journal/v4/n11/fig_tab/nrd1877_F1.html Acyclovir, Drug Monographs, Access Medicine CDC/PHIL (Centers for Disease Control/Public Health Image Library http://phil.cdc.gov/phil/quicksearch.asp (search images for "cold sore"). Shepp DH Newton BA Dandliker PS Flournoy N Meyers JD Oral Acyclovir Therapy for Mucocutaneous Herpes Simplex Virus Infections in Immunocompromised Marrow Transplant Recipients Annals of Internal Medicine 102: 783-785, 1985. Whitley RJ Levin M Barton N Hershey BJ Davis G Keeney RE Welchel J Diethelm AG Kartus P Soong SJ Infections caused by herpes simplex virus in the immunocompromised host: natural history and topical acyclovir therapy. J Infect Dis 150(3) 323-9, 1984 September. Boeckh M Kim HW Flowers MED Meyers JD Bowden RA Long-term acyclovir for prevention of varicella zoster virus disease after allogeneic hematopoietic cell transplantation-a randomized double-blind placebo-controlled study. Blood. 107(5) 1800-1805 March 2006. Cason JB (Feldman BH Cason JB WikiWorks Team) Herpes Zoster Ophthalmicus http://eyewiki.aao.org/Herpes_Zoster_Ophthalmicus Grant JCB Scheme of the Distribution of the Trigeminal Nerve: Source: An atlas of anatomy, by regions, 1962 http://commons.wikimedia.org/wiki/File:Grant_1962_654.png

**Disclaimer**
This Web-based pharmacology and disease-based integrated teaching site is based on reference materials, that are believed reliable and consistent with standards accepted at the time of development. Possibility of human error and on-going research and development in medical sciences do not allow assurance that the information contained herein is in every respect accurate or complete. Users should confirm the information contained herein with other sources. This site should only be considered as a teaching aid for undergraduate and graduate biomedical education and is intended only as a teaching site. Information contained here should not be used for patient management and should not be used as a substitute for consultation with practicing medical professionals. Users of this website should check the product information sheet included in the package of any drug they plan to administer to be certain that the information contained in this site is accurate and that changes have not been made in the recommended dose or in the contraindications for administration. Advertisements that appear on this site are not reviewed for content accuracy and it is the responsibility of users of this website to make individual assessments concerning this information. Medical or other information thus obtained should not be used as a substitute for consultation with practicing medical or scientific or other professionals.