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

    Route

    Oral

    Rate of Administration

    Comments

    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.

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