What is the recommended dosing of acyclovir (antiviral medication) for pregnant women with herpes simplex virus (HSV)?

Acyclovir Dosing in Pregnancy for HSV

For pregnant women with herpes simplex virus (HSV), oral acyclovir 400 mg three times daily is recommended for first clinical episodes of genital herpes, while intravenous acyclovir is indicated for life-threatening HSV infections. 1

Treatment Recommendations by Clinical Scenario

First Episode of Genital Herpes During Pregnancy

• Oral acyclovir is recommended for the first clinical episode of genital herpes during pregnancy 1
• Standard dosing: 400 mg orally three times daily until clinical resolution is attained 1

Life-Threatening HSV Infection in Pregnancy

• Intravenous acyclovir is indicated for disseminated infection, encephalitis, pneumonitis, or hepatitis 1
• Standard IV dosing: 5 mg/kg every 8 hours until clinical resolution 1

Recurrent Genital Herpes in Pregnancy

• Routine administration of acyclovir for recurrent genital herpes during pregnancy is not universally recommended in older guidelines 1
• However, more recent evidence suggests suppressive therapy near term (from 36 weeks until delivery) may reduce the need for cesarean delivery 2, 3, 4
• When suppressive therapy is used near term, the recommended dosage is acyclovir 400 mg orally three times daily 2, 3, 4

Safety Considerations

• The safety of systemic acyclovir in pregnant women has not been fully established, but registry findings do not indicate an increased risk for major birth defects compared to the general population 1
• Benefits may outweigh risks in certain clinical scenarios, particularly for severe infections 1, 5
• Women who receive acyclovir during pregnancy should be reported to the registry maintained by the manufacturer in cooperation with CDC 1

Pharmacokinetics in Pregnancy

• Acyclovir concentrates in amniotic fluid but does not show evidence of preferential fetal drug accumulation 6
• Maternal-to-umbilical vein plasma ratio at delivery is approximately 1.3 for acyclovir 6

Alternative Medications

• Valacyclovir (a prodrug of acyclovir) results in higher plasma acyclovir levels than direct acyclovir administration during pregnancy 6
• For HSV-1 exposure prophylaxis, valacyclovir 1g orally twice daily for 7-10 days is an alternative option 7
• Famciclovir 250mg orally three times daily for 7-10 days is another alternative for HSV prophylaxis 7

Common Pitfalls and Caveats

• Antiviral medications neither eradicate latent virus nor affect the risk, frequency, or severity of recurrences after discontinuation 7, 8
• Acyclovir resistance should be suspected if lesions persist during treatment, particularly in immunocompromised patients 1
• Asymptomatic viral shedding can still occur despite suppressive therapy, though at reduced rates 4
• The risk of HSV transmission to the neonate is highest among women who acquire genital herpes near the time of delivery (30%-50%) and lower among women with recurrent herpes (≤3%) 1

Monitoring

• At the onset of labor, all women should be examined and questioned regarding symptoms of genital herpes 1
• Viral cultures during pregnancy do not predict viral shedding at delivery and are not routinely indicated 1
• Monitor for development of lesions or symptoms during treatment 7