Who Should Not Take Famciclovir?
Famciclovir is contraindicated in patients with known hypersensitivity to the drug or its components, such as penciclovir (its active metabolite).[1] This includes anyone who has experienced allergic reactions like rash, hives, or anaphylaxis from prior exposure.
What About Kidney Problems?
No absolute contraindication exists for renal impairment, but dosage adjustments are required for patients with creatinine clearance below 40 mL/min to avoid accumulation and toxicity.[1][2] It's not recommended without monitoring in severe cases.
Is It Safe in Pregnancy or Breastfeeding?
Famciclovir lacks a formal contraindication in pregnancy (Category B; limited human data shows no clear risk), but use only if benefits outweigh risks, as animal studies showed no fetal harm.[1] Avoid breastfeeding during treatment and for 24 hours after the last dose, due to excretion in milk.[2]
Any Issues with Children or Elderly?
Not contraindicated in pediatrics for approved indications (e.g., herpes zoster in ages 1+), though safety data is limited under age 1.[1] Elderly patients need no specific contraindication but require renal function checks due to age-related decline.[2]
Drug Interactions Leading to Avoidance?
No strict contraindications from interactions, but caution with probenecid (increases famciclovir levels) or drugs affecting renal clearance like cimetidine. Not contraindicated with antiretrovirals or other antivirals.[1][3]
[1]: Famciclovir Prescribing Information (FDA)
[2]: Lexicomp: Famciclovir
[3]: Drugs.com: Famciclovir