Valacyclovir

Valacyclovir is a prodrug converted to acyclovir by hepatic metabolism after oral administration and reaches plasma leveles 3–5 times greater than those achieved by acyclovir. Valcyclovir has a longer duration of action than acyclovir. it has greater bioavailability and at high doses or in a dehydrated patient receiving the drug IV. High-dose valacyclovir can cause GI problems and thrombotic thrombocytopenic purpura in patients with AIDS.