Antiviral – aciclovir prodrug
ATC code: J05AB11 (Valacyclovir)
L-valine ester of aciclovir. After oral intake, rapidly hydrolyzed in gut and liver to aciclovir with 54% bioavailability – 3–5 times higher than oral aciclovir. Subsequent mechanism identical to aciclovir (viral TK phosphorylation, viral DNA polymerase inhibition). Convenient 2–3 times daily dosing is the main advantage over oral aciclovir.
First line
Used in recurrent herpes labialis as short courses. Dose 2000 mg twice daily for 1 day (total 4 g). Spruance 2003 showed this 1-day regimen shortens the episode by 1 day versus placebo. An alternative to longer aciclovir regimens.
Sources
First line
First-line for genital herpes. Primary episode: 1000 mg twice daily for 7–10 days; recurrences: 500 mg twice daily for 3 days. Suppressive therapy 500 mg once daily for more than 6 recurrences per year reduces them by 70–80% and partner transmission (Corey 2004 – 48% reduction).
First line
First-line for herpes zoster per 2024 and 2007. Dose 1000 mg three times daily for 7 days. Starting within 72 hours of rash reduces pain intensity, skin lesion duration, and postherpetic neuralgia risk. Convenient dosing improves adherence over aciclovir (five times daily).
The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.
Not recommended
Valaciclovir is a prodrug of aciclovir with better bioavailability. It is prescribed for infections caused by herpesviruses (HSV-1, HSV-2, VZV) – genital and orolabial herpes, and shingles (AEMPS Ficha Técnica). For common colds or flu, valaciclovir does not work – respiratory virus pathogens are not susceptible to drugs in this class. Taking valaciclovir at the first signs of any cold is not justified. The drug can cause nausea, headache, and in susceptible patients acute kidney injury and thrombotic microangiopathy (rare). If valaciclovir was prescribed for a cold, consider seeking a second opinion.
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FDA category B. Pregnancy use when indicated – accumulated data show no teratogenic effects. Suppressive therapy from week 36 in pregnant patients with genital herpes reduces neonatal transmission.
Compatible with breastfeeding.
Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.
Valacyclovir is evaluated for the following indications with varying evidence strength: Herpes simplex (evidence tier A), Herpes zoster (evidence tier A), Herpes labialis (evidence tier A). See the full indication matrix with dosing and citations above on this page.
Common side effects of Valacyclovir (≥ 1 in 100): Headache, Nausea, Abdominal pain, Fatigue, Skin rash. See the Safety section for uncommon and serious reactions.
FDA category B. FDA category B. Pregnancy use when indicated – accumulated data show no teratogenic effects. Suppressive therapy from week 36 in pregnant patients with genital herpes reduces neonatal transmission.
Compatible with breastfeeding.
Valacyclovir is contraindicated in: Valacyclovir or aciclovir hypersensitivity; Severe renal impairment without dose adjustment. Full list in the Safety section.