Certain individuals should avoid famciclovir due to potential adverse effects and contraindications. Famciclovir is an antiviral medication used to treat various viral infections, such as chickenpox and shingles [1][2]. According to the information provided, individuals with certain health conditions or those who are taking specific medications should avoid famciclovir.

Individuals with kidney impairment or end-stage renal disease should avoid famciclovir, as it can further affect kidney function [1]. Additionally, people with allergies to famciclovir or related medications like acyclovir or valacyclovir should avoid taking famciclovir, as it may cause allergic reactions [1][3]. Pregnant or breastfeeding women should also avoid famciclovir, as its safety during pregnancy and lactation has not been established [1].

In summary, individuals should avoid famciclovir if they have kidney issues, allergies to the drug or related medications, or are pregnant or breastfeeding. Always consult a healthcare professional before starting any new medication.

Sources:
[1] <https://www.drugpatentwatch.com/p/tradename/FAMCICLOVIR>
[2] <https://www.cdc.gov/chickenpox/hcp/index.html>
[3] <https://medlineplus.gov/druginfo/meds/a681045.html>