[CAS NO. 124832-27-5]  Valaciclovir HCl

Valaciclovir inhibits the uptake of substrates of dipeptide transporters, such as cefalexin. The metabolism of Valaciclovir to Aciclovir probably occurs within the gut lumen prior to absorption, in the small intestine after uptake but before entry into the portal blood system, and in the liver before entry into systemic circulation. Valaciclovir (Valtrex, Zelitrex), the L-valine ester of aciclovir, increases aciclovir bioavailability by 3- to 5-fold over that achievable with oral aciclovir. Valaciclovir extends the efficacy of aciclovir in the treatment of herpes zoster and genital HSV infections, using less frequent dose regimens but retaining the highly acceptable safety profile established for aciclovir. Valaciclovir is rapidly absorbed and extensively converted to aciclovir and L-valine, the essential amino acid after oral administration.