An antiviral drug used in the management of herpes simplex and herpes zoster.
A prodrug, being converted in vivo to acyclovir.
Trade name Valtrex.
A prodrug esterified version of acyclovir that has greater oral bioavailability than acyclovir.
Converted by esterases to the active drug acyclovir, as well as the amino acid valine, via hepatic first-pass metabolism.
Acyclovir, the active metabolite of valacyclovir, is active against most species in the herpesvirus family. In descending order of activity: Herpes simplex virus type I (HSV-1), Herpes simplex virus type II (HSV-2), Varicella zoster virus (VZV), Epstein-Barr virus (EBV), and Cytomegalovirus (CMV).
Activity is predominantly active against HSV, and to a lesser extent VZV, with limited efficacy against EBV and CMV.
Shown to lower or eliminate the presence of the Epstein-Barr virus in patients with acute mononucleosis, leading to a significant decrease in the severity of symptoms.
It is inactive against latent viruses in nerve ganglia.
Resistance has not been clinically significant.
Used for Herpes B virus post-exposure prophylaxis.
Used as a preventative agent of CMV disease following organ transplantation, and as prophylaxis against herpesvirus’ in immunocompromised patients.
Common adverse drug reactions include: nausea, vomiting, diarrhea and headache.
Infrequent adverse effects include: agitation, vertigo, confusion, dizziness, edema, arthralgia, sore throat, constipation, abdominal pain, rash, weakness and/or renal impairment.
The recommended dosage for treatment of cold sores is 2 grams twice daily for 1 day taken 12 hours apart.
Therapy for cold sores should be initiated at the earliest symptoms.
The recommended dose for treatment of initial genital herpes is 1 gram twice daily for 10 days, and is most effective when administered within 48 hours of the onset of signs and symptoms.
Recommended dosage for treatment of recurrent genital herpes is 500 mg twice daily for 3 days, with Initiation of treatment at the first sign or symptom of an episode.
Recommended dosage for chronic suppressive therapy of recurrent genital herpes is 1 gram once daily in patients with normal immune function.
In patients with a history of 9 or fewer recurrences of recurrent genital herpes per year, an alternative dose is 500 mg once daily.
In HIV-infected patients with a CD4+ cell count ≥ 100 cells/mm³, the recommended dosage for chronic suppressive therapy of recurrent genital herpes is 500 mg twice daily.
Recommended dosage for reduction of transmission of genital herpes in patients with a history of 9 or fewer recurrences per year is 500 mg once daily for the partner.
The recommended dosage for treatment of herpes zoster is 1 gram 3 times daily for 7 days.
Treatment for herpes zoster should be initiated at the earliest point of diagnosis, and is most effective when started within 48 hours of the onset of rash.
Recommended dosage for the treatment of cold sores in pediatric patients ≥ 12 years of age is 2 grams twice daily for 1 day taken 12 hours apart.
Recommended dosage for treatment of chickenpox in immunocompetent pediatric patients 2 to < 18 years of age is 20 mg/kg administered 3 times daily for 5 days.
Available in 500 mg and 1 gram tablets.