Low-dose acyclovir prophylaxis for the prevention of herpes simplex virus disease after allogeneic hematopoietic stem cell transplantation

Background: Currently, acyclovir (ACV) at 1000 mg/day is widely used as prophylaxis in the early phase of hematopoietic stem cell transplant (HSCT) in Japan. However, low-dose ACV (200 mg/day) has been shown to prevent varicella zoster virus reactivation in the middle and late phases of HSCT. Methods: Therefore, in this study, we decreased the dose of ACV to 200 mg/day in the early phase after HSCT. We analyzed 93 consecutive herpes simplex virus (HSV)-seropositive patients who underwent allogeneic HSCT for the first time in our center between June 2007 and December 2011. Results: Before August 2009, 38 patients received oral ACV at 1000 mg/day (ACV1000) until day 35 after HSCT, whereas 55 patients received oral ACV at 200 mg/day (ACV200) after September 2009. We compared the cumulative incidence of HSV infection in the 2 groups. Oral ACV was changed to intravenous administration because of intolerance in 66% and 45% of the patients in the ACV1000 and ACV200 groups, respectively (P = 0.060). The probability of severe stomatitis (Bearman grade II-III) was 76% and 60% in the ACV1000 and ACV200 groups, respectively (P = 0.12). The number of patients who developed HSV disease before day 100 after HSCT was 0 in the ACV1000 group and 2 in the ACV200 group, with a cumulative incidence of 3.6% (P = 0.43). HSV disease in the latter 2 patients was limited to the lips and tongue and was successfully treated with ACV or valacyclovir at a treatment dose. Conclusion: ACV at 200 mg/day appeared to be effective for preventing HSV disease in the early phase after HSCT.