Aciclovir can be applied topically as a cream or taken orally in tablet form. For the cream, apply a thin layer to the affected area at the first sign of a cold sore outbreak, typically 5 times a day for 4 to 5 days. Follow your doctor's instructions for oral tablets, which are usually taken several times a day for a prescribed period.

Common side effects may include mild skin irritation, burning, or itching when using the cream. Oral aciclovir may cause nausea, diarrhea, headache, and dizziness. Contact your doctor if you experience severe side effects like rash, difficulty breathing, or unusual changes in mood.

Aciclovir can interact with other medications, including certain vaccines and medications that affect kidney function. Inform your healthcare provider about all medications and supplements you are taking to avoid potential interactions.

Avoid touching your eyes or mucous membranes after applying the cream to prevent spreading the virus. Stay hydrated, especially if taking oral aciclovir, as it can affect kidney function. If you have kidney issues or a weakened immune system, consult your doctor before use.

For oral aciclovir, take the missed dose as soon as you remember. If it’s almost time for your next dose, skip the missed dose and resume your regular schedule. Do not double up on doses.

Store aciclovir cream at room temperature, away from moisture and heat. Oral tablets should be kept in a cool, dry place. Keep all medications out of reach of children and do not use them past their expiration date.