Valtrex or valacyclovir
Intra- and interindividual variabilities of valacyclovir oral bioavailability and effect of coadministration of an hPEPT1 inhibitor.

Guglielmo BJ.

School of Pharmacy, University of California, San Francisco, California 94143, USA.

Variability in valacyclovir bioavailability and the potential for cephalexin-valacyclovir interaction were evaluated. The intraindividual acyclovir area under the concentration-time curve (AUC) varied minimally, whereas interindividual differences were substantial. Coadministration of the human peptide transporter 1 (hPEPT1) substrates valacyclovir and cephalexin minimally reduced the acyclovir AUC. These results suggest a stable valacyclovir absorption phenotype, significant interindividual variability, and minimal interaction between these hPEPT1 substrates.

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Valtrex or valacyclovir
Acyclovir levels in serum and cerebrospinal fluid after oral administration of valacyclovir.

Stahle L.

Institute of Clinical Neuroscience, Department of Neurology, Goteborg University, Sahlgrenska University Hospital, SE-413 45 Goteborg, Sweden. jan.lycke neuro.gu.se

The possible involvement of herpesviruses in the pathogenesis of multiple sclerosis (MS) was recently investigated in a clinical trial of valacyclovir in patients with MS. As an important part of that survey we performed an independent pharmacokinetic study in order to determine the concentration of acyclovir in cerebrospinal fluid (CSF). The concentrations of acyclovir in serum and CSF were measured at steady state after 6 days of oral treatment with 1,000 mg of valacyclovir three times a day. Samples were obtained from 10 patients with MS. All patients had normal renal function, and none had signs of a damaged blood-CSF barrier. The maximum concentration of acyclovir in serum was reached after 1 to 3 h (mean +/- standard deviation [SD], 27.1 +/- 5.6 micro M), and the minimum concentration in serum was 3.1 +/- 1.1 micro M (mean +/- SD). The acyclovir concentrations in CSF at 2 and 8 h were essentially stable, with the mean +/- SD levels being 2.5 +/- 0.9 and 2.3 +/- 0.7 micro M, respectively. Similar levels were recorded in serum and CSF samples from five other MS patients after 6 months of oral treatment with valacyclovir at identical dosages. The area under the concentration-time curve (AUC) for acyclovir in CSF to the AUC for acyclovir in serum (CSF/serum AUC ratio) was approximately 20%. We conclude that the improved bioavailability previously reported for valacyclovir in plasma results in higher concentrations in CSF, while the CSF/serum AUC ratio remains constant.

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Valtrex or valacyclovir
Epstein-Barr virus replication in oral hairy leukoplakia: response, persistence, and resistance to treatment with valacyclovir.

Nichols CM.

Department of Internal Medicine, Division of Infectious Diseases, University of Texas Medical Branch, Galveston 77555-0435, USA. dwalling utmb.edu

Nineteen cases of human immunodeficiency virus (HIV)-associated oral hairy leukoplakia (HLP) and Epstein-Barr virus (EBV) replication were treated with high-dose oral valacyclovir to inhibit productive EBV replication. The clinical, histopathological, and molecular viral responses to treatment were assessed in surgical biopsy specimens obtained before, during, and after treatment. In the majority of treated cases, HLP was resolved, and EBV replication was terminated. In many cases, the initial response to inhibition of replication was a persistent, nonproductive, EBV infection of the oral mucosa, characterized by limited expression of replicative EBV genes, especially BZLF1. In some cases, productive EBV replication recurred after discontinuation of treatment with valacyclovir. In a few treated cases, treatment failed, and productive EBV replication persisted, possibly because of the evolution of acyclovir-resistant EBV. In summary, safe treatment of HLP and of EBV replication, with valacyclovir, provides new insight into the mechanisms of EBV persistence in oral mucosa.

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Valtrex or valacyclovir
Inhibition of sickling in vitro by three purine-based antiviral agents: an approach to the treatment of sickle cell disease.

Erlanger BF.

Department of Medicine, Columbia University, New York, NY 10032, USA.

As a result of an in vitro screening effort the antiviral agent acyclovir was found to inhibit aggregation of hemoglobin S and the sickling of erythrocytes from individuals with sickle cell disease. Sickling of the erythrocytes was significantly inhibited at 200 microg/ml under essentially anaerobic conditions, considerably more hypoxic than the conditions in which sickling occurs in sickle cell patients. The structurally related guanine-based antiviral agents ganciclovir, valacyclovir, and penciclovir were also tested. Valacyclovir and ganciclovir showed comparable anti-sickling activity at concentrations similar to that of acyclovir. An examination of the shared structural characteristics of the four guanine derivatives linked anti-sickling activity to the presence of an oxygen atom alpha to the N9 of the guanine moiety. These findings suggest a new approach in the search for new agents for the treatment of patients with sickle cell disease.

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Valtrex or valacyclovir
Valacyclovir in the treatment of herpes simplex, herpes zoster, and other viral infections.

Tyring SK.

Department of Internal Medicine, Baylor College of Medicine, Houston, Texas, USA.

BACKGROUND: Genital herpes and herpes labialis are prevalent, physically and psychologically painful, and often disabling. Herpes zoster is often very painful and may result in months or years of postherpetic neuralgia (PHN). Over the past two decades, the treatment of these conditions has been transformed by guanosine nucleoside antivirals such as valacyclovir (Valtrex, a highly bioavailable prodrug of acyclovir (Zovirax, and famciclovir (Famvir), a highly bioavailable prodrug of penciclovir (Denavir). OBJECTIVE: We describe the pharmacology, pharmacokinetics, and clinical efficacy of valacyclovir for the treatment of herpes simplex, herpes zoster, and other viral infections. Valacyclovir is also compared with acyclovir and famciclovir. METHODS: All published literature containing the word "valacyclovir" was reviewed and summarized. RESULTS: Valacyclovir is the only oral antiviral agent approved for therapy of herpes labialis, the only antiviral drug approved for a 3-day course in the episodic treatment of recurrent genital herpes, as well as the only antiviral drug approved for once daily dosing for suppressive therapy. In herpes zoster, valacyclovir is more effective than acyclovir and equally effective as famciclovir at hastening the healing of zoster-associated pain and PHN. CONCLUSION: Valacyclovir is safe and effective in the therapy of patients with herpes simplex and herpes zoster and may be useful in other viral infections.

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