Valaciclovir

CLINICAL USE

Antiviral: Herpes zoster and simplex Prevention of cytomegalovirus (CMV) disease after renal transplantation

DOSE IN NORMAL RENAL FUNCTION

Herpes simplex: 500 mg twice daily for 5–10 days Herpes zoster: 1 g 3 times a day for 7 days Herpes simplex suppression: 500 mg daily in 1–2 divided doses (500 mg twice daily in the immunocompromised) Prevention of CMV disease: 1 g 3 times a day for 90 days

PHARMACOKINETICS

Molecular weight : 360.8 (as hydrochloride)

%Protein binding : 15

%Excreted unchanged in urine : <1

Volume of distribution (L/kg) : 0.7

half-life – normal/ESRD (hrs) : 3/14

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

30–50 Dose as in normal renal function 15–30 Herpes simplex: Dose as in normal renal function Herpes zoster: 1 g every 12 hours CMV prophylaxis: 1 g every 12 hours <15 Herpes simplex: 500 mg daily Herpes zoster: 1 g every 24 hours CMV prophylaxis: 1 g every 24 hours Herpes simplex suppression: Immunocompetent – 250 mg daily Immunocompromised – 500 mg daily

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD : Likely dialysability. Dose as in GFR<15 mL/min

HD : Dialysed. Dose as in GFR<15 mL/min post dialysis

HDF/high flux : Dialysed. Dose as in GFR<15 mL/min post dialysis

CAV/VVHD : Likely dialysability. Dose as in GFR=15–30 mL/min

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugs

Ciclosporin: may alter ciclosporin levels Mycophenolate: higher concentrations of both aciclovir and mycophenolic acid on concomitant administration

ADMINISTRATION

Reconstition

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Route

Oral

Rate of Administration

–

Comments

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OTHER INFORMATION

Almost completely (80%) converted to aciclovir – see aciclovir monograph for further information

Bioavailability of aciclovir from 1 g oral dose of valaciclovir is 54% Mean peak aciclovir concentrations occur 1.5 hours post dose; peak plasma concentrations of valaciclovir are 4% of aciclovir levels, occur at a median of 30–60 minutes post dose, and are at or below the limit of quantification 3 hours post dose The dose quoted in the literature for CMV prophylaxis in transplant recipients is 2 g 4 times a day. However, in practice this results in severe aciclovir toxicity, especially in patients with poorly functioning grafts .

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