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DOSAGE
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Herpes Zoster: 800 mg PO q4hr (~5/day) for 7 to 10 days. Most effective when started within 48 hours after onset of symptoms.
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Herpes Simplex: 400mg PO q4hr (~5/day) for 7 to 10 days
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GENERIC
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acyclovir
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SIZE
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200mg, 400mg, 800mg
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TREATMENT REGIMEN
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HERPES ZOSTER
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HERPES SIMPLEX
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Conjunctivitis: (1) Oral Antiviral (Choose one): Acyclovir 800 mg PO 5x/day x 7-10 days, Valacyclovir 1000mg PO TID x 7-10 days or Famciclovir 500mg PO TID x 7-10 days (2) Cool compresses BID (3) Erythromycin ung BID
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Conjunctivitis: (1) Topical Antiviral (Choose one): Viroptic 1% 5x/day x 7 days or Zirgan 0.15% (gel) 5x/day x 7 days
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SPK Cornea: (1) Oral Antiviral (Choose one): Acyclovir 800 mg PO 5x/day x 7-10 days, Valacyclovir 1000mg PO TID x 7-10 days or Famciclovir 500mg PO TID x 7-10 days (2) Preservative-free artificial tears q1-2hrs + ung qHS
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Cornea Epithelial Dendrites (1) Topical Antiviral (Choose one): Viroptic 1% 9x/day x 7 days or Zirgan 0.15% (gel) 5x/day x 7 days (2) Oral Antiviral (choose one): Acyclovir 400 mg PO 5x/day x 7-10 days, Valacyclovir 500mg PO TID x 7-10 days or Famciclovir 250mg PO TID x 7-10 days (3) Consider Cyclopentolate 1% TID if AC reaction or photophobia (4) DO NOT use topical steroids with epithelial
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Cornea Pseudodendrites: (1) Oral Antiviral (Choose one): Acyclovir 800 mg PO 5x/day x 7-10 days, Valacyclovir 1000mg PO TID x 7-10 days or Famciclovir 500mg PO TID x 7-10 days (2) Preservative-free artificial tears q1-2hrs + ung qHS (3) Topical antiviral: Zirgan 0.15% (gel) TID-QID x 7-10 days
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Cornea Stromal (Disciform Keratitis) (1) Cyclopentolate 1% TID (2) Antiviral prophylaxis Oral (choose one): Acyclovir 400 mg PO BID or Valacyclovir 500mg PO qDay to BID (3) Antiviral prophylaxis Drops (choose one): Viroptic 1% TID or Zirgan 0.15% (gel) 3-5x/day (4) If moderate/Severe with central vision loss: Add on Predforte 1% q2hr to QID
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Stromal Cornea Keratitis: (1) Oral Antiviral (Choose one): Acyclovir 800 mg PO 5x/day x 7-10 days, Valacyclovir 1000mg PO TID x 7-10 days or Famciclovir 500mg PO TID x 7-10 days (2) Predforte 1% 4-8/day, then taper, usually with weaker steroid with goal of q1week.
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INDICATIONS
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Acyclovir is indicated for acute Herpes Zoster and Herpes Simplex keratitis and keratoconjunctivitis. Patients at high risk for recurrent HSV may be kept on low dose (400mg bid ) maintenance for extended periods.
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MECHANISM OF ACTION
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guanine analogue: The activated form inhibits viral DNA polymerase. Viral thymidine kinase activates acyclovir, so non-infected cells remain unaffected.
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MICROBIOLOGY
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Acyclovir is a synthetic purine nucleoside analogue with in vitro and in vivo inhibitory activity against herpes simplex virus types 1 (HSV-1), 2 (HSV-2), and varicella-zoster virus (VZV). The inhibitory activity of acyclovir is highly selective due to its affinity for the enzyme thymidine kinase (TK) encoded by HSV and VZV. This viral enzyme converts acyclovir into acyclovir monophosphate, a nucleotide analogue. The monophosphate is further converted into diphosphate by cellular guanylate kinase and into triphosphate by a number of cellular enzymes. In vitro, acyclovir triphosphate stops replication of herpes viral DNA. This is accomplished in 3 ways: 1) competitive inhibition of viral DNA polymerase, 2) incorporation into and termination of the growing viral DNA chain, and 3) inactivation of the viral DNA polymerase. The greater antiviral activity of acyclovir against HSV compared to VZV is due to its more efficient phosphorylation by the viral TK.
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CONTRAINDICATIONS & WARNINGS
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Acyclovir is contraindicated for patients who develop hypersensitivity to acyclovir or valacyclovir.
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PEDIATRIC USE
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> 2 years
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PREGNANCY
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There are no adequate studies in pregnant women. Animal studies have not demonstrated tertatogenicity.
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NOTE
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800mg dosing or 800mg loading dose is considered by some to be a more effective treatment for Simplex.
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Steroids are indicated for HSV stromal keratitis but must be avoided in the acute phase of active viral replication on the ocular surface as in acute epithelial keratitis.
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