Safety of short-term valacyclovir as an anti-sickling agent in sickle-cell anemia.

To assess safety and tolerability, we administered valacyclovir, an oral anti-viral medication that inhibits erythrocyte sickling in vitro, to 14 subjects with sickle-cell anemia for 1 week at a standard dose of 1,000 mg every 8 hr. No clinically significant adverse effects occurred. In 11 subjects in steady state, the mean hemoglobin concentration was almost constant while the absolute reticulocyte count decreased in eight (P = 0.1) and the overall mean fell slightly although not significantly (10%, P = 0.2). These results suggest that valacyclovir is safe and well tolerated in patients with sickle-cell anemia and that a longer duration of therapy merits investigation.