Acyclovir prophylaxis in bone marrow transplant recipients.

Forty-two patients undergoing bone marrow transplantation were included in a randomised, double-blind and placebo controlled trial of prolonged acyclovir prophylaxis against infections with viruses of the herpes group. Twenty patients were allocated to receive acyclovir and 22 to receive placebo. Acyclovir or placebo was administered i.v. at a dose of 250 mg/m2 twice daily, starting 5 days before transplantation. At 5 weeks after transplantation, administration was changed to tablets, 400 mg three times daily (children less than 6 years, 200 mg three times daily) and continued until 6 months after transplantation. In the placebo group, 10 acute herpes simplex virus (HSV) infections occurred in 7 patients (5 HSV-1 and 2 HSV-2), and another patient repeatedly shed HSV in throat washings. Five patients developed herpes zoster. Among patients receiving acyclovir only one episode of HSV infection occurred and no herpes zoster. The difference in the number of infection episodes and the number of infected patients was strongly significant (p = 0.0002 and 0.0017, respectively). The only acyclovir patient who reactivated HSV was terminally ill, and it is highly likely that she did not absorb a sufficient amount of the orally administered drug to control infection. All HSV and varicella zoster virus (VZV) infections were reactivations, and 9 of 10 patients who developed HSV infections or shed virus had a pre-transplantation HSV IgG titer of greater than 10 000 (ELISA). Acyclovir had no effect on cytomegalovirus (CMV), time of engraftment, or graft versus host disease (GVHD). Apart from a possible allergic reaction (skin rash) to acyclovir tablets, no adverse reactions were seen during this long prophylaxis with acyclovir.