抗病毒藥品
1. Treatment of acute herpes zoster (shingles), herpes labialis (cold sores), recurrent episodes of genital herpes in immunocompetent patients
2. Treatment of recurrent orolabial/genital (mucocutaneous) herpes simplex in adult patients with HIV

Antiviral Agent
Famciclovir undergoes rapid biotransformation to the active compound, penciclovir (prodrug), which is phosphorylated by viral thymidine kinase in HSV-1, HSV-2, and VZV-infected cells to a monophosphate form; this is then converted to penciclovir triphosphate and competes with deoxyguanosine triphosphate to inhibit HSV-2 polymerase, therefore, herpes viral DNA synthesis/replication is selectively inhibited.

1. Metabolism: Famciclovir is rapidly deacetylated and oxidized to penciclovir
2. Bioavailability: (Penciclovir) 69% to 85%
3. Protein binding:＜20%
4. Excretion: Urine (73% primarily as penciclovir)
5. Elimination half-life: (Penciclovir) 2-4 hours; prolonged in renal impairment

Known hypersensitivity to famciclovir, penciclovir or other constituents

B [FDA.AUS]

Avoided

Headache, dizziness, nausea, abdominal pain, diarrhea, pruritus

Herpes simplex virus infection (Immunocompetent patients):
1. Recurrent: 1 g twice daily for 1 day or 500 mg as a single dose, followed by 250 mg twice daily for 2 days or 125 mg twice daily for 5 days
2. Suppressive (eg, for severe and/or frequent recurrences): 250 mg twice daily
Herpes zoster (Immunocompetent patients):
500 mg every 8 hours for 7 days; treatment is most effective when initiated ≤72 hours after rash onset, but may initiate treatment >72 hours after rash onset if new lesions are continuing to appear

1. CrCl ≥30 mL/min/1.73 m2: No dosage adjustment necessary
2. CrCl 10-29 mL/min/1.73 m2: 125 mg Q8H
3. Hemodialysis: 250 mg after each dialysis session (herpes zoster ); 125 mg after each dialysis session (genital HSV infection)

1. Mild-to-moderate impairment: No dosage adjustment is necessary
2. Severe impairment: No dosage adjustment provided (has not been studied); However, a 44% decrease in the Cmax of penciclovir (active metabolite) was noted in patients with mild-to-moderate impairment