Famciclovir (Famvir): What It Does and How to Use It

Want faster relief from shingles or a shorter herpes outbreak? Famciclovir is an oral antiviral many doctors use for shingles (herpes zoster), genital herpes, and some cold sore cases. It works by stopping the virus from multiplying, which helps the body clear the infection faster and can lower symptom severity when started early.

How to take famciclovir

Timing matters. For shingles, the typical regimen prescribed by clinicians is 500 mg every 8 hours for 7 days. For genital herpes there are different ways to use it: episodic treatment or suppression. Your doctor will pick a plan based on how often you get outbreaks and your medical history. Always follow the specific dose and length your prescriber gives you—don’t guess.

Start treatment as soon as possible. For best results with shingles, try to begin famciclovir within 72 hours of the rash appearing. Take the tablets with or without food, swallow whole, and keep taking the course even if you feel better. Missing doses can reduce effectiveness.

Side effects and safety tips

Common side effects are usually mild: headache, nausea, tiredness, and dizziness. Serious reactions are rare but can include mood changes, confusion, or allergic reactions—older adults and people with kidney problems are more likely to have stronger side effects. If you notice severe confusion, hallucinations, or allergic signs (rash, swelling, trouble breathing), get medical help right away.

Kidney function matters. Famciclovir is cleared by the kidneys, so your doctor may lower the dose if you have reduced kidney function. Tell your prescriber about all medicines you take—some drugs and supplements change how your body handles antivirals. Don’t share your pills, and store them at room temperature away from moisture.

Pregnancy and breastfeeding: data is limited. If you’re pregnant, planning pregnancy, or breastfeeding, talk to your doctor about the risks and benefits rather than starting the drug on your own.

Practical tips that help: keep a photo of the first signs of your typical outbreak so you can show your doctor, set phone alarms for doses, and refill prescriptions before you run out if you use famciclovir for suppression. If outbreaks change in pattern or get worse despite treatment, schedule a follow-up—sometimes a different approach or specialist care is needed.

Want more details specific to your situation? Bring a list of your medications and health issues to your appointment and ask about dosing for kidney problems, possible drug interactions, and what to expect day-by-day after starting treatment.