Acyclovir: What It Treats and How to Use It Safely

Want a quick, no-nonsense look at acyclovir? This is the antiviral doctors often use for herpes simplex (cold sores, genital herpes), shingles, and chickenpox. It works best when you start early and follow the right dose for your situation.

How and when to take acyclovir

Acyclovir comes as tablets, a topical cream, and an IV. For oral use, common adult doses are: 400 mg three times a day for initial genital herpes, 800 mg five times a day for shingles, or shorter courses for recurring outbreaks. For cold sores many people use topical cream at first tingle. The exact dose depends on the infection type, how severe it is, and your kidney function. Try to begin treatment within 48–72 hours of symptoms for best results. If you have repeated outbreaks, your doctor might offer a suppression plan with a lower daily dose.

If you or a family member have kidney problems, doses must be adjusted. Acyclovir is cleared by the kidneys. Too much for your kidneys to handle can lead to harm. You may need blood tests or a lower dose schedule—don’t guess. If you’re hospitalized and receiving IV acyclovir, your care team will monitor fluids and kidney tests closely.

Side effects, interactions, and safety tips

Most people tolerate acyclovir well. Common side effects include nausea, headache, and sometimes mild stomach upset. Rare but serious issues include kidney problems, confusion, or seizures—these are more likely in elderly patients or those with poor kidney function. Drink water while taking acyclovir to help your kidneys clear the drug.

Acyclovir can interact with other medicines that affect the kidneys or raise levels of the drug. Tell your provider if you use NSAIDs, certain antibiotics, or drugs like cyclosporine. Also mention pregnancy or breastfeeding. Acyclovir is often considered when needed in pregnancy, but the decision should be clinical—talk to your doctor.

Don’t use topical and oral forms at the same time unless your provider says so. Topical cream can help minor cold sores but won’t treat systemic infections. Never share prescription medication, and don’t stop or change the dose without checking with your prescriber.

If you get any signs of allergic reaction (rash, swelling, trouble breathing), or dark urine, sudden weakness, or severe dizziness, seek medical care right away. For mild side effects, call your pharmacist for advice on managing symptoms.

Thinking of buying acyclovir online? Use only verified pharmacies and always keep a prescription. Fake or low-quality drugs can be ineffective or dangerous. If you’re unsure, contact your clinic or local pharmacist first.

Bottom line: acyclovir is a useful, well-established antiviral when used correctly. Start early, follow dosing guidelines, stay hydrated, and check with your provider about kidney function and other medicines. That keeps treatment effective and lowers risks.