KEY POINTS
- 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
RESOURCES