Acyclovir buccal: cold sores, how to take it, side effects
Last updated September 7, 2026.
**Acyclovir buccal is a prescription antiviral tablet that dissolves against your gum to treat recurring cold sores.** It blocks the herpes virus from copying its DNA. Do not use it if you are allergic to acyclovir, milk protein, or another tablet ingredient.
What does it treat?
You may be prescribed acyclovir buccal, labeled as Sitavig, for recurring cold sores if you are an adult with a normal immune system. These episodes often begin with familiar tingling, itching, or burning near your lip before blisters appear. This formulation does not treat canker sores and is not the labeled treatment for genital herpes, shingles, or chickenpox.
How do you take it?
Apply one 50 mg tablet once per episode, within 1 hour of the first symptoms and before a visible cold sore appears. With a dry finger, place its rounded side against your upper gum above an incisor on the affected side, then press gently through your lip for 30 seconds. Let it dissolve; do not chew, crush, suck, or intentionally swallow it. You can eat and drink normally, but avoid gum, upper dentures, brushing, and touching the tablet while it is attached. There is no daily repeat schedule: use only the single dose except for the replacement instructions below. If you miss the early treatment window, contact your prescriber rather than doubling up. Stop using it and seek help for allergy symptoms; call your doctor if symptoms worsen or fail to improve.
Side effects to know
- Common: You may have a headache or pain or irritation where the tablet touches your gum.
- Serious: Stop using it and get immediate help for hives, facial or throat swelling, or trouble swallowing or breathing. A blistering or peeling rash also needs immediate medical evaluation.
Who should not take it?
Do not use this tablet if you have an allergy to acyclovir, milk protein concentrate, or another ingredient; lactose intolerance is different from milk protein allergy. Talk to your doctor first if you have a weakened immune system, kidney disease, or trouble keeping a tablet attached safely. Safety and effectiveness in children are not established, and young children can choke on it. Review your medicines and supplements with your clinician. During pregnancy or breastfeeding, discuss your treatment needs and the limited information specific to this formulation. The label gives no specific alcohol restriction.
When is it an emergency?
For an overdose or a child swallowing tablets, call Poison Control at 1-800-222-1222 without waiting for symptoms. Serious overdose is unlikely with normal buccal use because little medicine reaches your bloodstream, but acyclovir overdose can cause agitation, extreme sleepiness, seizures, or reduced urination. Call 911 for collapse, breathing trouble, a seizure, or inability to wake up. Facial or throat swelling with breathing trouble can signal anaphylaxis.
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Common questions
What is the maximum dose, and what if the tablet falls off?
The labeled treatment is one 50 mg tablet per episode, not a daily course. Within the first 6 hours, reposition a detached tablet immediately; use a new one if it cannot be repositioned. If you swallow it within those 6 hours, drink a glass of water and apply a new tablet. After 6 hours, do not replace a tablet that falls off or is swallowed.
Can you drink alcohol while using it?
The Sitavig label does not specify an alcohol restriction. It does not establish a safe alcohol amount with this medicine. Avoid alcohol if it irritates your sore or worsens a headache.
Can you use it during pregnancy or breastfeeding?
Ask your clinician before use. The label reports no pregnancy data for Sitavig itself, while observational studies of acyclovir have not identified increased risks of major birth defects or miscarriage. Bloodstream exposure from the buccal tablet is minimal. Milk levels after buccal use and effects on nursing babies are unknown, so your clinician should weigh your treatment need alongside breastfeeding benefits.
Do you need food, and can you brush your teeth?
You do not need a meal before applying it. You can eat and drink with the tablet in place. Avoid brushing and chewing gum while it is attached; gently rinse your mouth if needed.
What overdose signs should you watch for?
Call Poison Control at 1-800-222-1222 for excess use, even without symptoms. Acyclovir overdose symptoms include agitation, extreme tiredness, seizures, and reduced urination. These are not expected effects of one correctly used buccal tablet. Call 911 for collapse, breathing trouble, seizures, or inability to wake up.
Does it interact with other medicines?
Interactions are unlikely because little acyclovir enters your bloodstream from this tablet, but formal interaction studies were not performed. Medicines that compete for kidney elimination could increase acyclovir levels. Give your clinician your full medication list, including any other acyclovir or valacyclovir treatment, before combining them.