Recurrence and resistance patterns of herpes simplex virus following cessation of > or = 6 years of chronic suppression with acyclovir. Acyclovir Study Group.

Questions have arisen regarding the clinical outcome and the possible selection of resistant virus when patients with genital herpes discontinue prolonged chronic acyclovir; 239 immunocompetent patients with a history of frequently recurring genital herpes who stopped successful suppressive therapy after 6 years were studied. Of the patients, 85.8% had at least one recurrence and 75% had at least two recurrences in the subsequent year (median time to first and second recurrence, 68 and 180 days, respectively). Herpes simplex virus isolates recovered from these patients had a median acyclovir sensitivity of 0.79 micrograms/mL and 4 (3.5%) were resistant (> or = 3 micrograms/mL). These values are comparable to those of pretherapy isolates and to reported values of isolates from acyclovir-naive patients. Also, paired pre- and posttherapy isolates from 13 patients showed no trend toward development of resistance. Thus, even after 6 years of acyclovir suppression, most patients continue to have recurrences, but the selection of resistant virus has not been observed.