Letters to the Editor
Famciclovir and Valacyclovir
Am Fam Physician. 1998 Mar 1;57(5):947.
to the editor: We are writing in response to the article by Dr. Stott about famciclovir (Famvir).1 Several comparisons of famciclovir and acyclovir (Zovirax) were made; however, there was no mention of valacyclovir (Valtrex).
It is worth noting the following: both famciclovir and valacyclovir were available in 1995; both drugs are dosed less frequently than acyclovir; both drugs have better bioavailability than acyclovir; both are pro-drugs, and both may have effects on postherpetic neuralgia.
In addition to omitting information about valacyclovir, the article included several comments that were incorrect or were not clinically relevant.
The author implies that the intracellular pharmacokinetics of famciclovir may be responsible for its reduced dosing frequency and its effects on postherpetic neuralgia (compared with placebo) in patients with herpes zoster. Although valacyclovir has quite different intracellular pharmacokinetics, it still demonstrates an effect on postherpetic neuralgia, not only when compared with placebo, but also when compared with acyclovir. Moreover, a trial comparing famciclovir with acyclovir2 in otherwise healthy patients (one not mentioned in the article) showed no difference between famciclovir and acyclovir in terms of efficacy for postherpetic neuralgia despite the high intracellular concentrations of drug. If intracellular pharmacokinetics of antivirals were indeed clinically relevant, one would expect an improvement in efficacy; however, no additional clinical benefit seems apparent.
In addition, the author states that famciclovir has been compared with placebo in two clinical trials in immunocompromised patients with herpes zoster. To our knowledge, the trials to which the author refers were conducted in immunocompetent patients and formed the basis for the current use of famciclovir in immunocompetent patients.
1. Stott GA. Famciclovir: a new systemic antiviral agent for herpesvirus infections. Am Fam Physician. 1997;55:2501–4.
2. Package insert. Famciclovir. Philadelphia: Smith-Kline Beecham, 1997.
editor's note: This letter was sent to the author of “Famciclovir: A New Systemic Antiviral Agent for Herpesvirus Infections,” who declined to reply.
Send letters to firstname.lastname@example.org, or 11400 Tomahawk Creek Pkwy., Leawood, KS 66211-2680. Include your complete address, e-mail address, and telephone number. Letters should be fewer than 400 words and limited to six references, one table or figure, and three authors.
Letters submitted for publication in AFP must not be submitted to any other publication. Possible conflicts of interest must be disclosed at time of submission. Submission of a letter will be construed as granting the AAFP permission to publish the letter in any of its publications in any form. The editors may edit letters to meet style and space requirements.
This series is coordinated by Kenny Lin, MD, MPH, Associate Deputy Editor for AFP Online.
Copyright © 1998 by the American Academy of Family Physicians.
This content is owned by the AAFP. A person viewing it online may make one printout of the material and may use that printout only for his or her personal, non-commercial reference. This material may not otherwise be downloaded, copied, printed, stored, transmitted or reproduced in any medium, whether now known or later invented, except as authorized in writing by the AAFP. Contact email@example.com for copyright questions and/or permission requests.
Want to use this article elsewhere? Get Permissions