Acyclovir: What It Treats, How to Use It, and Safe Alternatives

Got a cold sore, shingles, or genital herpes and heard about acyclovir? This antiviral is a common go-to. Here’s a clear, no-nonsense look at when it helps, how people take it, what side effects to watch for, and practical alternatives you can discuss with your doctor.

Acyclovir fights herpes viruses: herpes simplex type 1 (oral cold sores), type 2 (genital herpes), varicella (chickenpox) and herpes zoster (shingles). Timing matters. For shingles, starting acyclovir within 72 hours of the first rash usually gives the best results. For cold sores, beginning at the first tingle can stop a blister from forming. For first-time or severe genital outbreaks, doctors usually prescribe a longer course.

Doses vary by condition and kidney health. Examples adults commonly get: for cold sores 200 mg five times a day for 5 days; for initial genital herpes 400 mg three times daily for 7–10 days; for shingles 800 mg five times daily for 7–10 days. If you have reduced kidney function or are older, your clinician may lower the dose or stretch dosing intervals. Never guess—check with a clinician or pharmacist if you’re unsure.

Side Effects and Safety

Most people tolerate acyclovir well. Mild side effects include nausea, headache, and dizziness. Serious issues are less common but can happen—kidney problems, confusion, or unusual tiredness—especially if you’re dehydrated or already have kidney disease. Drink plenty of water while taking the drug and report unusual symptoms right away.

Pregnancy and breastfeeding? Acyclovir is sometimes recommended in pregnancy for outbreaks, but you should only take it under medical advice. If you’re on other drugs that affect kidney function, tell your prescriber—some interactions raise risk. If you notice an allergic reaction like a rash or breathing trouble, stop the medicine and seek emergency care.

Alternatives, Buying Tips, and Practical Advice

Valacyclovir (brand: Valtrex) converts to acyclovir in the body and usually needs fewer daily doses—many people prefer it for convenience. Famciclovir is another effective option. For resistant or severe infections, hospitals may give intravenous antivirals under supervision.

Thinking of buying antivirals online? Use licensed pharmacies that require a prescription. Legit sites will ask for one and show verifiable contact details. Avoid offers that look too cheap or ship without proper credentials. Store pills in a cool, dry place and finish the prescribed course for active infections.

For frequent outbreaks, suppressive daily therapy can reduce episodes and lower transmission risk to partners. Use condoms and be open with partners—medication lowers risk but doesn’t remove it completely. If you’re unsure whether acyclovir or another antiviral fits your situation, get a short consult with your provider. With the right timing and dose, you’ll get the most benefit and the least hassle.