Use of acyclovir for prophylaxis of herpes infections in severely immunocompromised patients

Two consecutive studies are reported. In study 1, 59 patients with acute leukaemia undergoing remission induction therapy or bone marrow transplantation were given either acyclovir (5 mg/kg) or placebo by intravenous infusion twice daily during the period of neutropenia. All patients were seropositive (greater than or equal to 1:8) for herpes simplex virus. Acyclovir provided total protection against herpes simplex virus infection in bone marrow transplant patients with 0/10 versus 5/10 infections in the placebo group (P = 0.033). For the remission induction therapy group 2/19 on acyclovir developed HSV versus 10/20 receiving placebo (P = 0.018). Only one episode of cytomegalovirus (CMV) infection was seen and this was in a patient on acyclovir. Epstein-Barr virus secretion studies were inconclusive. No varicella zoster virus (VZV) infections were seen. In Study 2, 20 consecutive HSV seropositive (greater than or equal to 1:8) bone marrow transplant recipients received oral acyclovir. Five (25%) developed HSV infections, one of which was in a non-compliant patient, who subsequently developed a fatal infection whilst receiving therapeutic (5 mg/kg 8 hourly) intravenous acyclovir for this HSV infection. Intravenous acyclovir is effective in preventing HSV infections in the immunocompromised host but it seems unlikely that CMV will be amenable to acyclovir in its present formulation.