Valacyclovir

Action and Spectrum

Action 

Valacyclovir prevents the herpes virus from replicating. It is a prodrug of acyclovir which interferes with DNA synthesis. It is effective in treating HSV-1, HSV-2 and varicella-zoster virus as well as cytomegalovirus and Epstein-Barr virus.

Drug Interaction

Adverse Reaction

Frequency defined 

>10% 

Headache (14-35%) 

Neutropenia (<18%) 

Elevated aspartate transaminase (AST) (2-16%) 

Elevated alanine transaminase (ALT) (<14%) 

Abdominal pain (2-11%) 

Nasopharyngitis (<16%) 

Nausea (6-15%) 

1-10% 

Dysmenorrhea (1-8%) 

Depression (<7%) 

Arthralgia (<1-6%) 

Rhinorrhea (<2%) 

Thrombocytopenia (<3%) 

Leukopenia (≤1%) 

Vomiting (<1-6%) 

Dizziness (2-4%) 

Rash (≤8%) 

<1% 

Confusion 

Erythema multiforme 

Hypertension 

Tachycardia 

Tremor 

Visual disturbances 

Agitation 

Aggression 

Alopecia 

Black Box Warning

Black Box Warning: 

None  

Contraindication / Caution

Contraindication 

Hypersensitivity  

Pregnancy / Lactation

Pregnancy consideration:  

Pregnancy category: NA 

Lactation: The excretion of drug into human milk is unknown 

Pregnancy Categories:         

• Category A: Studies that were well-controlled and met expectations revealed no risk to the fetus in either the first or second trimester. 
• Category B: There were lack of studies on pregnant women and no evidence of risk to the fetus in animal experiments.   
• Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    
• Category D: adequate data available with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.   
• Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.    
• Category N: There is no data available for the drug under this category 

Pharmacology

Pharmacology: 

Pharmacodynamics:  

Acyclovir is an active metabolite of valacyclovir which interferes with viral DNA synthesis to prevent herpes virus replication. It transforms into acyclovir triphosphate which competes with dGTP for DNA polymerase leading to chain termination and preventing further viral DNA creation. 

Pharmacokinetics: 

Absorption 

Bioavailability is 54%. 

Distribution 

The extracellular fluid are largely distributed. 

Metabolism 

Liver converts acyclovir into an inactive metabolite which is eliminated through the urine.  

Elimination and Excretion

It is mostly excreted through the kidneys.  

Adminstartion

Administration: 

It is typically administered as a tablet; the recommended dose is usually 1 gram taken orally three times daily for 7-10 days. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: valacyclovir  

Pronounced: [val-a-SYE-kloe-veer ]  

Why do we use valacyclovir? 

Valacyclovir treats herpes virus by converting into acyclovir in the body that works by inhibiting the replication of the herpes virus.