Common Side Effects of Famciclovir
Famciclovir, used to treat herpes viruses like shingles (herpes zoster) and genital herpes, commonly causes headache, nausea, and diarrhea. These affect 1-10% of users and are usually mild.[1]
Serious Side Effects and Rare Risks
Less common but serious effects include dizziness, fatigue, abdominal pain, vomiting, fever, itching, rash, and confusion. Thrombotic thrombocytopenic purpura (TTP)/hemolytic uremic syndrome (HUS), involving low platelets and kidney issues, is rare and mainly seen in immunocompromised patients with herpes zoster. Allergic reactions like swelling or trouble breathing require immediate medical attention.[1][2]
Side Effects in Specific Groups
Pregnant or breastfeeding individuals should consult doctors, as safety data is limited—animal studies show no fetal harm, but human trials are sparse. Kidney impairment raises risks, so dose adjustments are needed. Elderly patients report higher rates of nervous system effects like dizziness.[1][3]
How Famciclovir Causes Side Effects
It converts to penciclovir in the body to inhibit viral DNA replication. Side effects often stem from this process or individual sensitivity, not direct toxicity. They typically resolve after stopping treatment.[2]
Managing and Reporting Side Effects
Most effects are short-term; stay hydrated and take with food to ease nausea. Report severe symptoms to a doctor. Overdose can worsen nausea or confusion—seek emergency care. Long-term use data is limited beyond episodic therapy.[1]
Sources
[1]: Drugs.com - Famciclovir Side Effects
[2]: MedlinePlus - Famciclovir
[3]: FDA Label - Famvir (Famciclovir)