To the Editor.
—Drs Dover and Arndt infer equivalent efficacy for topical penciclovir and acyclovir and also for famciclovir and valacyclovir in their Contempo article on dermatology.1 These inferences are inconsistent with the results of controlled clinical trials and product labeling for these antiviral agents. The authors indicated that topical penciclovir (Denavir, Smith-Kline Beecham Pharmaceuticals, Collegeville, Pa) is no more effective than topical acyclovir (Zovirax, Glaxo Wellcome, Research Triangle Park, NC) in the management of herpes labialis. It is important to note that comparative efficacy trials have not been conducted between these 2 agents, despite the statement in the article to this effect that Mr Ziegler cited as unpublished data. However, 2 randomized, double-blind, placebo-controlled trials have documented significant reductions in the time to healing and loss of pain of herpes labialis in immunocompetent patients treated with penciclovir.2,3 This clinical trial data supported penciclovir in becoming the