Acyclovir prophylaxis of herpes-simplex-virus infections.

We conducted a double-blind, placebo-controlled study of acyclovir prophylaxis against infection with herpes simplex virus (HSV) in 20 seropositive recipients of bone-marrow transplants. Acyclovir or placebo was administered for 18 days, starting three days before transplantation. Culture-positive HSV lesions developed during the study in seven of the 10 patients who received placebo. In contrast, no such lesions appeared in the 10 patients who received acyclovir (P congruent to 0.003). None of the patients had evidence of drug toxicity. Five of the patients treated with acyclovir had mild culture-positive HSV infections after cessation of the drug, and two additional patients shed virus without having lesions. Acyclovir appears to be a potent inhibitor of HSV replication. Although acyclovir does no appear to eradicate latent infection, it can provide effective prophylaxis against reactivated infections.