When Is Famciclovir Contraindicated?
Famciclovir is contraindicated in patients with known hypersensitivity to the drug or its components, such as penciclovir (its active metabolite).[1][2]
What About Cross-Hypersensitivity Risks?
Patients with prior hypersensitivity to penciclovir or related nucleoside analogs like acyclovir or ganciclovir should avoid famciclovir due to potential cross-reactivity.[1][2]
Can It Be Used in Pregnancy or Breastfeeding?
No absolute contraindication exists for pregnancy (Category B), but use only if benefits outweigh risks; limited human data available. Contraindicated in nursing mothers as it passes into breast milk.[1][3]
What If There's Kidney Impairment?
Not contraindicated, but dose adjustment required for creatinine clearance below 40 mL/min to prevent accumulation and toxicity.[1][2]
Are There Drug Interactions That Make It Unsafe?
No major contraindications, but caution with probenecid (increases penciclovir levels) or nephrotoxic drugs; monitor renal function.[1]
[1]: Famciclovir Prescribing Information (Famvir) - Novartis
[2]: Drugs.com - Famciclovir
[3]: Medscape - Famciclovir Dosing