Valacyclovir (Valtrex)

Description

Valacyclovir (Valtrex) is an antiviral agent and pro-drug that is converted to acyclovir in vivo by intestinal and hepatic metabolism
Works by inhibiting DNA synthesis and viral replication by competing with deoxyguanosine triphosphate for viral DNA polymerase
Can be used for herpes simplex virus (HSV) 1 or HSV-2, cytomegalovirus (CMV) and varicella zoster virus (VZV)
Only available oral and doses can range from 500mg to 2gm given between one and four times per day, depending on the indication
Dosing with valacyclovir is less frequent and therefore more convenient as compared to acyclovir
Requires dose adjustment for renal dysfunction but not for hepatic dysfunction
Comes as 500mg and 1000mg tablets for oral administration
Intravenous acyclovir is the injectable counterpart to oral valacyclovir
In general it is best to begin therapy when tingling, itching or burning starts (i.e., before visual manifestations)
Adverse effects may include?
CNS effects (e.g., headache, agitation, confusion, delirium, seizures), particularly in elderly patients
Renal toxicity
Best to drink plenty of water when taking valacyclovir
Thrombotic thrombocytopenia purpura / hemolytic uremic syndrome
Hepatic effects such as increased liver enzymes (AST/ALT)
Nausea and abdominal discomfort
Pregnancy category B