Famciclovir

Indications

Famciclovir is used for: Genital herpes, Herpes zoster, Herpes labialis, CMV infections, Mucocutaneous herpes

Adult Dose

Acute Herpes Zoster (Shingles) Treatment in immunocompetent adults 500 mg PO q8hr for 7 days; initiated within 72 hours of symptom or lesion onset Herpes Labialis Treatment of initial and recurrent episodes or suppressive therapy in immunocompetent adults Initial episode: 250 mg PO q8hr for 7-10 days Suppressive therapy: 250 mg PO q12hr for 12 months Recurrent episodes: 1500 mg PO once; initiate therapy at first sign (within 1 hour) of symptoms such as tingling, itching or burning Genital Herpes Treatment of initial and recurrent episodes or suppressive therapy in immunocompetent adults Initial episode: 250 mg PO q8hr for 7-10 days Suppressive therapy: 250 mg PO q12hr for up to 12 months Recurrent episodes: 1000 mg PO q12hr for 1 day; initiated within 6 hours of symptom or lesion onset Herpes (HIV-Infected Adults) Prevention of herpes simplex virus (HSV) reactivation and treatment of recurrent episodes Prevention of HSV reactivation: 500 mg PO q12hr Recurrent episodes: 500 mg PO q12hr for 5-10 days; initiated within 48 hours of symptom or lesion onset

Child Dose

Renal Dose

Acute herpes zoster CrCl >60 mL/min: Regular dosage CrCl 40-59 mL/min: 500 mg q12hr CrCl 20-39 mL/min: 500 mg once daily CrCl <20 mL/min: 250 mg once daily Hemodialysis: 250 mg after each session Herpes labialis CrCl >60 mL/min: Regular dosage CrCl 40-59 mL/min: 750 mg once CrCl 20-39 mL/min: 500 mg once CrCl <20 mL/min: 250 mg once Hemodialysis: 250 mg once after dialysis Genital herpes (treatment of recurrent disease) CrCl >60 mL/min: Regular dosage CrCl 40-59 mL/min: 500 mg q12hr for 1 day (2 doses total) CrCl 20-39 mL/min: 500 mg once CrCl <20 mL/min: 250 mg once Hemodialysis: 250 mg once after dialysis Genital herpes (suppressive therapy) CrCl >40 mL/min: Regular dosage CrCl 20-39 mL/min: 125 mg q12hr CrCl <20 mL/min: 125 mg/day Hemodialysis: 125 mg after each session Herpes (HIV-infected adults) CrCl >40 mL/min: Regular dosage CrCl 20-39 mL/min: 500 mg/day CrCl <20 mL/min: 250 mg/day Hemodialysis: 250 mg after each session

Administration

May be taken with or without food.

Contra Indications

Hypersensitivity. Lactation.

Precautions

Renal impairment. Pregnancy. Lactation: Unknown whether drug is excreted in breast milk; caution advised

Pregnancy-Lactation

Interactions

Reduced renal excretion resulting to increased plasma concentration w/ probenecid. Raloxifen may reduce the formation of penciclovir, the active metabolite of famciclovir.

Adverse Effects

Side effects of Famciclovir : >10% Headache (23%),Nausea (13%) 1-10% Diarrhea (2-9%),Abdominal pain (8%),Dysmenorrhea (<8%),Vomiting (1-5%),Flatulence (5%),Pruritus (4%),Rash (3%),Paresthesia (3%),Neutropenia (3%),Increased transaminases (2-3%),Increased bilirubin (2%),Fatigue (1%) <1% Arthralgia,Confusion,Dizziness,Erythema multiforme,Hallucinations,Jaundice,Rigors,Thrombocytopenia,Upper respiratory tract infection

Mechanism of Action

Famciclovir rapidly undergoes biotransformation to penciclovir, which has inhibitory activity against HSV types 1 (HSV-1) and 2 (HSV-2) varicella-zoster virus (VZV). Thymidine kinase then phosphorylates penciclovir to a monophosphate form, which is then converted to penciclovir triphosphate. This inhibits HSV-2 DNA polymerase by competing with deoxyguanosine triphosphate, thus inhibiting herpes viral DNA synthesis and replication.