The L-Valine ester prodrug of Acyclovir.
Valacyclovir (Valtrex) is the 1-valine ester (prodrug) of acyclovir that exhibits no activity until hydrolyzed in the intestinal wall or liver to acyclovir and its active metabolite. Its modified structure allows increased intestinal absorption and concomitant higher plasma levels of acyclovir. It demonstrates activity against HSV types 1 and 2, varicella-zoster virus, and cytomegalovirus. It exerts its effects by interfering with DNA synthesis through phosphorylation by viral thymidine kinase and subsequent inhibition of viral DNA polymerase, thereby inhibiting viral replication. Valtrex is indicated for the treatment of acute herpes zoster and recurrent genital herpes in immunocompetent adults. The most common side effects are headache, nausea, and vomiting.
Indications
Valacyclovir (Valtrex) is the 1-valine ester (prodrug) of acyclovir that exhibits
no activity until hydrolyzed in the intestinal wall or liver to acyclovir and its
active metabolite. Its modified structure allows increased intestinal absorption
and concomitant higher plasma levels of acyclovir. It demonstrates activity
against HSV types 1 and 2, varicella-zoster virus, and cytomegalovirus.
It exerts its effects by interfering with DNA synthesis through phosphorylation
by viral thymidine kinase and subsequent inhibition of viral DNA
polymerase, thereby inhibiting viral replication. Valtrex is indicated for the
treatment of acute herpes zoster and recurrent genital herpes in immunocompetent
adults. The most common side effects are headache, nausea, and
vomiting. Valacyclovir is the only antiviral agent approved for herpes labialis,
for a 3-day course in the episodic treatment of recurrent genital herpes (2).
Valacyclovir is indicated for recurrent genital herpes and is administered at
500 mg twice daily for 3 days at the onset of prodromal symptoms or at the first
sign of infection.
Pharmacology
Valacyclovir (Valtrex), a valine ester prodrug of acyclovir, has
a bioavailability three to five times that of acyclovir. This is due to its improved
gastrointestinal absorption compared to acyclovir. Valacyclovir is rapidly and
almost completely converted to acyclovir after oral administration, with levels
comparable to those of intravenous acyclovir. This allows for twice-daily dosing,
which may improve compliance and ultimate clinical efficacy. It is more costly
than acyclovir.
