famciclovir: clinical use

Prescribing considerations

• Confirm the indication, immune status and whether zoster is ophthalmic, disseminated or otherwise complicated.
• Assess renal function where impairment is known or possible; penciclovir clearance falls with renal function.
• Oral treatment may be inadequate for complicated zoster or high-risk immunocompromised patients; assess the need for intravenous antiviral management.
• For genital herpes, counsel that viral transmission remains possible despite treatment or suppression.

Contraindications and cautions

• Hypersensitivity to famciclovir, penciclovir or a listed excipient.
• Use caution in renal impairment and severe hepatic impairment; conversion to penciclovir may be reduced in severe liver disease.

Monitoring

• Review renal function when clinically relevant and before selecting therapy in renal impairment.
• Monitor clinical response closely in immunocompromised patients.
• When combined with probenecid, watch for clinically significant central nervous system toxicity.
• No universal routine laboratory-monitoring schedule is specified in the selected SmPC.

Clinical pharmacology

Famciclovir is an orally absorbed prodrug rapidly converted to penciclovir. Viral and cellular kinases generate penciclovir triphosphate within infected cells, where it inhibits viral DNA-chain extension. Penciclovir and its precursor are predominantly eliminated in urine.

Formulation and product differences

• The selected presentation is a white, oval film-coated tablet.
• Its listed excipients do not include lactose; other Famvir tablet presentations may have different excipients.
• Store in the original package, protected from moisture and below the stated pack storage limit.

Tablet

Route: Oral

Strengths: 125 mg, 250 mg, 500 mg