Antiviral Therapies for Long-term Suppression of Genital Herpes

To the Editor: While we applaud Dr Engel's¹ assessment of the importance of suppressive antiviral therapy for genital herpes, we believe he has made several errors in his comparative analysis of the effectiveness of acyclovir, famciclovir, and valacyclovir hydrochloride. The data Engel uses to compare these drugs are derived from separate randomized clinical trials with markedly different patient populations performed more than a decade apart. Patients enrolled in the acyclovir study by Mattison et al² conducted in 1985 had a median frequency of recurrence of 13, for the valacyclovir study conducted by Patel et al³ a decade later it was 8, and for the famciclovir study more than 12 recurrences in 2 years.⁴ The median times to first recurrence in the placebo groups in the acyclovir, valacyclovir, and famciclovir studies were 23, 20, and 47 days, respectively, a 2-fold difference. As it is clear that severity of infection influences the antiviral response,⁵ the studies in Engel's table cannot be compared directly.