Antiviral – aciclovir prodrug
Updated · Methodology
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
ICD-10: B00.1 · ICD-11: 1F00.01
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).
Sources
ICD-10: B00 · ICD-11: 1F00.Z
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).
Sources
ICD-10: B02 · ICD-11: 1E91
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.
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.
AEMPS summary of product characteristics (section 4.6): data on valaciclovir use in pregnancy are limited. Pregnancy registries have documented 111 outcomes after exposure to valaciclovir and 1,246 after oral or intravenous aciclovir (its active metabolite), with 29 and 756 of these exposed in the first trimester. Neither these registries nor post-marketing experience indicate malformations or fetal or neonatal toxicity. Animal studies show no reproductive toxicity of valaciclovir. Valaciclovir is used in pregnancy only if the potential benefits of treatment outweigh the potential risk.
Compatible with breastfeeding.
Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.
Verbatim lines from the interaction sections, in the language of the label
«La combinación de v alaciclovir con medicamentos nefrotóxicos se debe usar con precaución, especialmente en sujetos con la función renal deteriorada y hay que garantizar un control regular de la…»AEMPS, section 4.5 · Open on CIMA
«La combinación de v alaciclovir con medicamentos nefrotóxicos se debe usar con precaución, especialmente en sujetos con la función renal deteriorada y hay que garantizar un control regular de la…»AEMPS, section 4.5 · Open on CIMA
«La combinación de v alaciclovir con medicamentos nefrotóxicos se debe usar con precaución, especialmente en sujetos con la función renal deteriorada y hay que garantizar un control regular de la…»AEMPS, section 4.5 · Open on CIMA
«La combinación de v alaciclovir con medicamentos nefrotóxicos se debe usar con precaución, especialmente en sujetos con la función renal deteriorada y hay que garantizar un control regular de la…»AEMPS, section 4.5 · Open on CIMA
«Se han mostrado aumentos en las AUCs plasmáticas de aciclovir y del metabolito inactivo de micofenolato de mofetilo, un agente inmunosupresor usado en pacientes trasplantados, cuando estos fármacos…»AEMPS, section 4.5 · Open on CIMA
«Se han mostrado aumentos en las AUCs plasmáticas de aciclovir y del metabolito inactivo de micofenolato de mofetilo, un agente inmunosupresor usado en pacientes trasplantados, cuando estos fármacos…»AEMPS, section 4.5 · Open on CIMA
«Aciclovir: Se observaron concentraciones plasmáticas más altas de aciclovir cuando micofenolato de mofetilo se administró con aciclovir, en comparación con la administración de aciclovir sólo. Los…»AEMPS, section 4.5 · Open on CIMA
«Effect of Mycophenolate Mofetil on Other Drugs: Examples Acyclovir, ganciclovir, probenecid, valacyclovir, valganciclovir»FDA, section 7 · Open on DailyMed
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Valacyclovir is evaluated for the following indications with varying evidence strength: Herpes simplex (evidence tier A), Herpes zoster (evidence tier A), Cold sores (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.
AEMPS summary of product characteristics (section 4.6): data on valaciclovir use in pregnancy are limited. Pregnancy registries have documented 111 outcomes after exposure to valaciclovir and 1,246 after oral or intravenous aciclovir (its active metabolite), with 29 and 756 of these exposed in the first trimester. Neither these registries nor post-marketing experience indicate malformations or fetal or neonatal toxicity. Animal studies show no reproductive toxicity of valaciclovir. Valaciclovir is used in pregnancy only if the potential benefits of treatment outweigh the potential risk.
Compatible with breastfeeding.
Valacyclovir is contraindicated in: Valacyclovir or aciclovir hypersensitivity; Severe renal impairment without dose adjustment. Full list in the Safety section.
Direct links to regulator labels. Open in a new tab.
Vitaglutam, Aciclovir, Atazanavir, Brivudine, Efavirenz, Kagocel, Oseltamivir, Darunavir