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DOSAGE
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Herpes Zoster: Famciclovir 500mg PO TID for 7-10 days
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Herpes Simplex: Famciclovir 250mg PO TID x 7-10 days
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GENERIC
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famciclovir
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SIZE
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125mg, 250mg, 500mg
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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% 5/day x 7 days or Zirgan 0.15% (gel) 5/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 Dendrites Epithelial (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 5/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) 3-5/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 5/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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Indicated for acute herpes zoster and herpes simplex infections Use oral treatment when topical toxicity is encountered. Initiate treatment within 6 hrs of symptom onset if possible
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MECHANISM OF ACTION
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guanine analogue antiviral: Famciclovir is a prodrug of penciclovir which is absorbed poorly when given orally. Activated form inhibits viral DNA polymerase, impairing virus replication within the cell.
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MICROBIOLOGY
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Famciclovir is a prodrug of penciclovir, which has demonstrated inhibitory activity against herpes simplex virus types 1 (HSV-1) and 2 (HSV-2). In cells infected with HSV-1 or HSV-2 the viral thymidine kinase phosphorylates penciclovir to a monophosphate form that, in turn, is converted by cellular kinases to the active form penciclovir triphosphate. Biochemical studies demonstrate that penciclovir triphosphate inhibits HSV-2 DNA polymerase competitively with deoxyguanosine triphosphate. Consequently, herpes viral DNA synthesis and, therefore, replication are selectively inhibited. Penciclovir triphosphate has an intracellular half-life of 10 hours in HSV-1- and 20 hours in HSV-2-infected cells grown in culture. However, the clinical significance of the intracellular half-life is unknown.
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CONTRAINDICATIONS & WARNINGS
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Famciclovir tablets are contraindicated in patients with known hypersensitivity to the product, its components, or penciclovir cream. Acute renal failure: Cases of acute renal failure have been reported in patients with underlying renal disease who have received inappropriately high doses of famciclovir for their level of renal function.
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PEDIATRIC USE
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The efficacy of famciclovir tablets have not been established in pediatric patients.
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PREGNANCY
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Category B. After oral administration, famciclovir (prodrug) is converted to penciclovir (active drug). There are no adequate and well-controlled studies of famciclovir or penciclovir use in pregnant women. No adverse effects on embryofetal development were observed in animal reproduction studies using famciclovir and penciclovir at doses higher than the maximum recommended human dose (MRHD) and human exposure. Because animal reproduction studies are not always predictive of human response, famciclovir should be used during pregnancy only if needed.
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NOTE
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Steroids are indicated with stromal involvement, maintaining antiviral coverage if the epithelium is compromised.
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Two thirds of early Acanthamoeba keratitis are misdiagnosed as HSV
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