Famciclovir

CLINICAL USE

Antiviral agent

DOSE IN NORMAL RENAL FUNCTION

Zoster: 250 mg 3 times a day or 750 mg once daily(Immunocompromised: 500 mg 3 times daily)First genital herpes infection: 250 mg 3 times a dayAcute recurrent genital herpes: 125 mg twice a day(Immunocompromised: 500 mg twice a day)Suppression: 250 mg twice daily (HIV patients: 500 mg twice daily)

PHARMACOKINETICS

Molecular weight :321.3

%Protein binding :<20 as penciclovir

%Excreted unchanged in urine : 0

Volume of distribution (L/kg) :0.91–1.25

half-life – normal/ESRD (hrs) :2 (penciclovir)/3.2–23.6 (3.8–25: penciclovir)

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

For immunocompromised patients, see ‘Other Information’30–59 Zoster, and first episode genital herpes: 250 mg twice a day Recurrent genital herpes: Dose as in normal renal function 10–29 Zoster, and first episode genital herpes: 250 mg daily Recurrent genital herpes: 125 mg daily

<10 : Zoster, and first episode genital herpes: 250 mg 3 times a week Recurrent genital herpes: 125 mg 3 times a week

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD :Moderate dialysability likely. Dose as in GFR <10 mL/min

HD :Dialysed. Dose as in GFR

<10 : mL/min post dialysis on dialysis days

HDF/high flux :Dialysed. Dose as in GFR

<10 : mL/min post dialysis on dialysis days

CAV/VVHD :Likely dialysability. Dose as in GFR=10–29 mL/min

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugsProbenecid: decreased excretion of famciclovirIncreased famciclovir levels reported with mycophenolate mofetil

ADMINISTRATION

Reconstition

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Route

Oral

Rate of Administration

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Comments

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OTHER INFORMATION

Treatment of herpes infections in immuno compromised patients:GFR (mL/min) Dose Zoster Simplex>40 500 mg 3×/day 500 mg 2×/day30 39 250 mg 3×/day 250 mg 2×/day10 29 125 mg 3×/day 125 mg 2×/dayWell absorbed after oral administration; deacetylated and oxidised rapidly to form the potent and selective antiviral compound penciclovirFour hours’ haemodialysis results in approximately 75% reduction in plasma concentration of penciclovir.

See how to identify renal failure stages according to GFR calculation

See how to diagnose irreversible renal disease

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