For how many days can Acyclovir (antiviral medication) be taken?

Duration of Acyclovir Treatment

The duration of acyclovir therapy ranges from 5 to 21 days depending on the specific indication, with most common conditions requiring 5-10 days of treatment. 1

Treatment Duration by Indication

Genital Herpes

• Initial episode: 7-10 days of oral acyclovir (200 mg five times daily or 400 mg three times daily) 2, 3, 1
• Recurrent episodes: 5 days of oral acyclovir (200 mg five times daily, 400 mg three times daily, or 800 mg twice daily) 2, 3, 1
• Chronic suppressive therapy: Can be continued for up to 12 months, followed by re-evaluation of the need for ongoing therapy 1
• Treatment may be extended beyond 10 days if healing is incomplete 3

Herpes Zoster (Shingles)

• Standard treatment: 7-10 days of oral acyclovir 800 mg five times daily 1, 4
• The 7-day regimen is as effective as longer courses for immunocompetent patients 5
• Treatment should be initiated within 72 hours of rash onset, ideally within 48 hours for maximum benefit 2

HSV Encephalitis

• Children with proven HSV encephalitis: 14-21 days of intravenous acyclovir 2
• Children aged 3 months-12 years: Minimum of 21 days due to higher relapse rates (up to 29%) 2
• Adults with proven HSV encephalitis: 14-21 days of intravenous acyclovir 2
• If CSF remains PCR-positive: Continue acyclovir with weekly CSF PCR testing until negative 2

Chickenpox

• 5 days of oral acyclovir (20 mg/kg four times daily for children, or 800 mg four times daily for adults and children over 40 kg) 1
• Treatment should be initiated within 24 hours of rash onset 1

Severe or Life-Threatening HSV Infections

• 5-7 days of intravenous acyclovir (5-10 mg/kg every 8 hours) for severe disease requiring hospitalization, including disseminated infection, hepatitis, pneumonitis, or encephalitis 2, 6
• Treatment continues until clinical resolution is achieved 2, 6

Important Clinical Considerations

Monitoring During Treatment

• Renal function monitoring is essential, as reversible nephropathy can occur after 4 days of intravenous therapy in up to 20% of patients 2
• Maintain adequate hydration to reduce crystalluria risk 2
• Dose adjustment required in patients with renal impairment 2, 1

When to Extend Treatment Beyond Standard Duration

• HSV encephalitis: If CSF PCR remains positive at 14-21 days, continue treatment with weekly monitoring until negative 2
• Immunocompromised patients: May require prolonged therapy due to extensive disease 2
• Incomplete healing: Treatment may be extended if lesions have not fully resolved 3

Common Pitfalls to Avoid

• Do not use 10-day regimens for HSV encephalitis: Relapse rates are significantly higher (26-29% in children) with treatment durations less than 14 days 2
• Do not use oral acyclovir for severe/disseminated infections: Intravenous administration is essential for life-threatening disease 6
• Do not stop treatment prematurely in encephalitis: Even if clinical improvement occurs, complete the full 14-21 day course and confirm CSF clearance 2
• Avoid stopping suppressive therapy without reassessment: After 1 year of continuous suppressive therapy, discontinue to evaluate the patient's recurrence rate 2, 1

Hemodialysis Patients

• Administer an additional dose after each dialysis session, as hemodialysis reduces plasma concentrations by 60% over 6 hours 1