Valacyclovir vs Acyclovir: What’s the Real Difference?

If you’ve ever Googled "valacyclovir vs acyclovir," you’re probably trying to pick the better pill for a cold sore, genital herpes, or shingles outbreak. Both drugs fight the same viruses, but they aren’t identical twins. Below we break down how they work, when doctors usually prescribe each, and what you should watch out for.

Valacyclovir is basically a pro‑drug. Your body turns it into acyclovir after you swallow it, but it starts out as a more absorbable molecule. That means you can take fewer pills for the same effect. Most adults use 1,000 mg twice daily for shingles or 500 mg once daily for suppressing recurrent genital herpes. Because it stays in the bloodstream longer, you often finish a short course in just three days for a cold sore.

Acyclovir is the older kid on the block. It’s been around since the 1980s and works directly without conversion. Doctors usually prescribe 200 mg five times a day for a cold sore, or 400 mg three times daily for genital herpes. For shingles, the dose jumps to 800 mg five times a day for a week. The frequent dosing can feel annoying, but it’s cheap and widely available.

How They Work and When to Use Them

Both medicines block the viral DNA polymerase enzyme, which stops the virus from making copies of itself. Valacyclovir’s higher bioavailability (about 55% versus 15‑30% for acyclovir) means you get more drug in your system with each pill. That’s why doctors often choose valacyclovir for people who want fewer daily doses or need rapid suppression, like during a shingles flare‑up. Acyclovir stays the go‑to for patients on a tight budget or when insurance only covers the older drug.

Key Differences You Should Know

Dosage simplicity: Valacyclovir usually needs just two doses a day, while acyclovir can require up to five. If you hate remembering multiple alarms, valacyclovir wins.

Cost: Acyclovir tablets are often under $10 for a supply of 20–30 pills, whereas valacyclovir can run $30‑$50 for the same amount. Check your pharmacy’s price list; sometimes a generic valacyclovir brings the gap down.

Side‑effects: Both can cause headache, nausea, and mild kidney irritation. Valacyclovir may cause a slightly higher rate of dizziness, while acyclovir sometimes leads to a tingling feeling in the fingers if you’re dehydrated. Stay hydrated and tell your doctor if you notice persistent symptoms.

Kidney safety: If you have reduced kidney function, your doctor will adjust the dose for either drug, but the adjustment is more critical with valacyclovir because of its higher concentration in the blood.

Here are a few practical tips to get the most out of whichever antiviral you’re prescribed:

• Take the pill with a full glass of water, especially if you’re on acyclovir multiple times a day.
• Don’t skip doses – the virus can bounce back quickly.
• Start treatment at the first sign of a sore or rash; early use cuts the outbreak length in half.
• If you’re on chronic suppressive therapy, keep a medication calendar to avoid missed days.

Bottom line: valacyclovir offers convenience and a stronger punch per tablet, making it a solid choice for busy folks or severe shingles. Acyclovir is the budget‑friendly option that works just as well when you’re diligent about dosing. Talk to your healthcare provider about your lifestyle, kidney health, and insurance coverage to decide which one fits you best.