Acyclovir Treatment Duration and Non-Herpes Indications
Acyclovir treatment duration varies by condition, with standard courses ranging from 5-21 days for herpes infections, while it is also indicated for viral encephalitis, herpes zoster (shingles), and varicella (chickenpox) infections.
Duration of Acyclovir Treatment for Herpes Infections
The duration of acyclovir treatment depends on the specific herpes manifestation and whether it's an initial or recurrent episode:
Genital Herpes
- First clinical episode: 7-10 days or until clinical resolution 1
- First episode of herpes proctitis: 10 days or until clinical resolution 1
- Recurrent episodes: 5 days (using one of these regimens) 1:
- 200 mg orally 5 times daily
- 400 mg orally 3 times daily
- 800 mg orally twice daily
Oral/Mucocutaneous Herpes
- Mild gingivostomatitis: 5-10 days 1
- Moderate to severe gingivostomatitis: IV therapy until lesions begin to regress, then oral therapy until complete healing 1
Severe Disease
- CNS or disseminated disease: 21 days for children outside neonatal period 1
- Severe disease requiring hospitalization: 5-7 days or until clinical resolution 1
Suppressive Therapy
- For patients with frequent recurrences (≥6 episodes/year), daily suppressive therapy is recommended for up to 1 year, after which it should be discontinued to reassess recurrence rate 1
Non-Herpes Indications for Acyclovir
1. Herpes Zoster (Shingles)
- Standard treatment: 800 mg orally 5 times daily for 7-10 days 2
- Acyclovir shortens the time to lesion scabbing, healing, and cessation of pain 3
- Most effective when started within 48 hours of rash onset, particularly in adults over 50 3
2. Viral Encephalitis
- Proven HSV encephalitis: 14-21 days of intravenous therapy 1
- A repeat lumbar puncture should be performed at the end of treatment to confirm CSF is negative for HSV by PCR 1
- If CSF remains positive, treatment should continue with weekly PCR testing until negative 1
- For children aged 3 months-12 years, a minimum of 21 days of treatment is recommended before repeating LP 1
3. Chickenpox (Varicella)
- Pediatric patients: 20 mg/kg 4 times daily (up to 3,200 mg per day) for 5 days 3
- Treatment shortens healing time, reduces maximum number of lesions, and decreases fever and constitutional symptoms 3
4. Immunocompromised Patients
- Herpes virus infections: Continuous IV infusion for 3-5 days has shown benefit 4
- Varicella-zoster infections: Prevents new vesicle formation and stops viral shedding 4
Important Clinical Considerations
Dosage Adjustments
- Renal impairment requires dose adjustment due to acyclovir's renal elimination 3
- Geriatric patients may require dose reduction due to age-related changes in renal function 3
Monitoring
- Monitor renal function, particularly after 4 days of IV therapy, as crystalluria and obstructive nephropathy can affect up to 20% of patients 1
- Maintain adequate hydration to reduce risk of nephropathy 1
Treatment Limitations
- Acyclovir neither eradicates latent virus nor affects subsequent risk, frequency, or severity of recurrences after discontinuation 1
- For herpes zoster, while acyclovir reduces acute pain, it does not significantly impact postherpetic neuralgia 2, 5
Resistance Concerns
- For acyclovir-resistant HSV infections, foscarnet (40 mg/kg IV 3 times daily or 60 mg/kg IV twice daily) is the recommended alternative 1
Common Pitfalls
- Delaying treatment for herpes zoster beyond 72 hours significantly reduces efficacy 3
- Oral acyclovir has limited bioavailability (10-20%) that decreases with increasing dose 3, 6
- Presumptive treatment without proper diagnosis may delay identification of other treatable conditions 1
- Discontinuing treatment for HSV encephalitis too early can lead to relapse, particularly in children 1