Acyclovir facts
Valtrex facts

Valtrex (Valacyclovir)

Generic Name: Valacyclovir Hydrochloride

Brand Name: Valtrex, Zelitrex

Dosage forms and strength: 500 mg, 1000 mg caplets

Valtrex Uses
Valtrex (Valacyclovir hydrochloride) is an antiviral agent. It is indicated for the treatment of herpes zoster (shingles); initial and recurrent episodes of genital herpes; suppression of recurrent genital herpes; cold sores. Valtrex helps prevent genital herpes from being passed on to a partner who does not have genital herpes if it is used with 'safer sex' practices.

Valtrex does not cure herpes virus infections. It is unable to eliminate the latent virus in sensory nerve roots.


Hypersensitivity to valacyclovir or acyclovir.


Valtrex may be given without regard to meals. It is advised to maintain adequate hydration. In patients with reduced renal function, reduction in dosage is recommended.

Herpes zoster: 1 gram orally 3 times daily for 7 days. Therapy should be initiated at the earliest sign or symptom of herpes zoster and is most effective when started within 48 hours of the onset of zoster rash. No data are available on efficacy of treatment started greater than 72 hours after rash onset.

Initial genital herpes: 1 gram twice daily for 10 days. There are no data on the effectiveness of treatment with Valtrex when initiated more than 72 hours after the onset of signs and symptoms. Therapy was most effective when administered within 48 hours of the onset of signs and symptoms.

Recurrent episodes of genital herpes: 500 mg twice daily for 3 days. Patients should be advised to initiate therapy at the first sign or symptom of an episode. There are no data on the effectiveness of treatment with Valtrex when initiated more than 24 hours after the onset of signs or symptoms.

Suppressive therapy of recurrent genital herpes: 1 gram once daily in patients with normal immune function. In patients with a history of 9 or fewer recurrences per year, an alternative dose is 500 mg once daily. Suppressive therapy with Valtrex greatly cuts down recurrences of genital herpes.

Reduction of transmission of genital herpes: 500 mg once daily for the source partner (in those with a history of 9 or fewer recurrences per year). Patients should be counseled to use safer sex practices in combination with suppressive therapy. Valtrex halves sexual transmission rates of herpes in heterosexual, monogamous couples.

Cold sores (herpes labialis): 2 grams twice daily for 1 day taken about 12 hours apart. Therapy should be initiated at the earliest symptom of a cold sore (e.g., tingling, itching, or burning). There are no data on the effectiveness of treatment initiated after the development of clinical signs of a cold sore (e.g., papule, vesicle, or ulcer).

Warnings & Precautions

  • Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS) has occurred.
  • Valacyclovir may precipitate in renal tubules if solubility is exceeded in intratubular fluid.
  • Safety and effectiveness of Valtrex in pre-pubertal pediatric patients have not been established.

Side Effects

  • headache (38%)
  • neutropenia (18%)
  • nasopharyngitis (16%)
  • nausea (15%)
  • abdominal discomfort (11%)
  • tiredness (8%)
  • vomiting (6%)

Pregnancy & Breastfeeding

Pregnancy Category: B. Valacyclovir is generally safe during pregnancy and breastfeeding. It was not teratogenic in rats or rabbits at 10 and 7 times human plasma levels, respectively, during the period of major organogenesis.

There are no adequate and well-controlled studies of Valtrex in pregnant women. A prospective epidemiologic study was established in 1984 and completed in April 1999. There were 749 pregnancies followed in women exposed to systemic acyclovir during the first trimester of pregnancy resulting in 756 outcomes. The occurrence of birth defects approximates that found in the general population.

Valtrex may be used during pregnancy or breastfeeding.


  • Probenecid, cimetidine: Decreased renal clearance of valacyclovir; no dosage adjustment needed in patients with normal renal function. [2]
  • Zoster Vaccine: valacyclovir may diminish the therapeutic effect of Zoster Vaccine. When possible, discontinue antiviral agent for at least 24 hours prior to and 14 days after receiving a live attenuated zoster vaccine.


  • 1. U.S. FDA. Valtrex Prescribing Information
  • 2. De Bony F, Tod M, Bidault R, On NT, Posner J, Rolan P. Multiple interactions of cimetidine and probenecid with valaciclovir and its metabolite. Antimicrob Agents Chemother. 2002 Feb;46(2):458-63. PubMedCentral

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