Acyclovir vs Valacyclovir vs Famciclovir: which herpes antiviral, and which strength

Three antivirals sit on the same shelf in our warehouse, and about once a day someone emails to ask which one to put in the cart. Acyclovir, valacyclovir, famciclovir. Six strengths between them. The product names sound like cousins, the prices don’t, and the leaflets are written for pharmacists rather than for someone with a tingling lip and a flight on Friday.

Here is the thing we wish every first-time buyer knew before ordering: all three drugs end up doing the same job in the same way. The differences are about how many tablets you swallow, how often, and what the course costs. Once you see the dosing schedules side by side, the choice mostly makes itself — and you’ll stop paying for a pack that’s the wrong size.

The short answer

If you want the fewest tablets and the simplest schedule: valacyclovir. If you want the cheapest possible course and don’t mind taking a tablet five times a day: acyclovir. If you’ve reacted badly to the other two, or your doctor specifically wants the single-dose cold-sore regimen: famciclovir. That’s genuinely most of it.

Strength is the second question. Acyclovir 400 is for genital herpes and suppression; acyclovir 800 is for shingles. Valacyclovir 500 is for recurrences and daily suppression; valacyclovir 1000 is for cold sores, first episodes and shingles. Famciclovir 250 is for first-episode genital herpes; famciclovir 500 is for shingles and the one-dose regimens. The rest of this guide is the detail behind those sentences.

Three drugs, one molecule doing the work

Acyclovir is the original. It was the first antiviral that actually worked against herpes viruses, and every generic on our shelf — Acyclovir 400 and Acyclovir 800 from Torrent and Cipla — is the same molecule that Zovirax made famous. It has one weakness. The gut absorbs only a small fraction of a swallowed dose, so you have to take it often. Five times a day, for most regimens.

Valacyclovir is acyclovir wearing a coat. Chemically it is a “prodrug”: the tablet contains valacyclovir, the gut absorbs it far more efficiently, and the liver strips the coat off and releases plain acyclovir into the blood. Same active drug, several times more of it per tablet. That is the whole reason a valacyclovir course is two or three tablets a day instead of five. Valacyclovir 500 and Valacyclovir 1000 are the generics of Valtrex.

Famciclovir is the same trick with a different molecule. It’s a prodrug of penciclovir, a close relative of acyclovir that stays inside infected cells longer. Well absorbed, three doses a day or fewer, and — uniquely — licensed for a single-dose cold-sore treatment. Famciclovir 250 and Famciclovir 500 are Cipla’s generics of Famvir.

None of the three cures herpes. They stop the virus copying itself while you take them — shortening an outbreak, and taken daily, cutting how often outbreaks return. Stop the tablets and the virus is still asleep in the nerve. That’s not a failure of the medicine. That’s herpes.

Cold sores: the one-day regimens

This is where the newer drugs win outright, and where most of our cold-sore customers land after one course of acyclovir. The acyclovir label for cold sores is five doses a day for five days. Valacyclovir and famciclovir compress the whole thing into a single day:

• → Valacyclovir: 2 g twice in one day, about 12 hours apart. That is two Valacyclovir 1000 tablets in the morning and two in the evening. Four tablets. Done.
• → Famciclovir: 1500 mg as a single dose. Three Famciclovir 500 tablets, once. Three tablets. Done.
• → Acyclovir: 400 mg five times daily for five days is a common regimen. Twenty-five tablets, and five alarms a day.

The catch is that the one-day regimens only work if you start at the tingle. Not when the blister appears. Customers who keep a strip in the bathroom cabinet and one in the travel bag get the full benefit; customers who order when the blister is already crusting have missed the window, and we tell them so.

Genital herpes: first episode, recurrence, suppression

Three situations, three quite different regimens. Getting the situation right matters more than picking the drug.

First episode

The first outbreak is usually the worst and the longest, and it gets the longest course. Standard label regimens:

Acyclovir is no longer the cheap option per course, and it’s the one people abandon halfway — five doses a day for ten days is a lot of alarms. If you know you’ll forget the lunchtime tablet, choose valacyclovir. A finished course of the dearer drug beats an abandoned course of the cheap one.

Recurrences

Recurrent outbreaks are shorter and milder, and so are the courses. Valacyclovir 500 mg twice daily for three days — six tablets. Famciclovir 1 g twice in a single day — four Famciclovir 500 tablets. Acyclovir 400 mg three times daily for five days — fifteen tablets. All three work; the newer two are simply less of a chore. Again, start at the first sign. The prodrome — tingling, itching, a shooting pain down the leg — is the signal.

Daily suppression

If you get six or more outbreaks a year, or you want to reduce the chance of passing the virus to a partner, a daily tablet is the option doctors reach for. Label regimens:

• → Acyclovir 400 mg twice daily (some doctors use three times) — 60–90 tablets a month
• → Valacyclovir 500 mg once daily (1 g daily if outbreaks are frequent) — 30 tablets a month
• → Famciclovir 250 mg twice daily — 60 tablets a month

Here the tablet count decides the cost. One valacyclovir a day is where most of our suppression customers settle: the 360-pack of Valacyclovir 500 is $600.99 — a year at $1.67 a day, delivery included. The 360-pack of Acyclovir 400 is $702.99, or $1.95 a tablet, and at two or three a day it’s four to six months, not twelve, so valacyclovir wins on both counts.

Shingles: where the higher strengths earn their keep

Shingles is the varicella-zoster virus — the chickenpox virus — waking up decades later in a single nerve. It needs much higher doses than herpes simplex, which is exactly why the 800 mg acyclovir, 1000 mg valacyclovir and 500 mg famciclovir tablets exist.

Shingles is where the timing rule is strictest. The antivirals reduce the risk of post-herpetic neuralgia — nerve pain that can linger for months — but only if started within 72 hours of the rash. A rash on the face or near the eye is a same-day medical appointment, not an online order.

The 48–72 hour rule nobody should ignore

Every regimen above shares one fine-print line that turns out to be the most important sentence on the leaflet: start within 48 to 72 hours of the first symptom. Herpes viruses do their copying early. By day four the virus has largely finished, the blisters are the aftermath, and an antiviral has little left to stop. Start on day one and you shorten the outbreak by days. Start on day four and you may shorten it by hours.

Three consequences. Order before you need it — tracked delivery is typically 10–18 working days, far too slow for an outbreak that started this morning. Learn your prodrome; the tingle is the start line, not the blister. And complete the course: stopping at day three of a seven-day shingles regimen is how people end up with a second, longer round.

Kidneys, water, pregnancy and side effects

All three are well-tolerated drugs with decades of use behind them. The usual complaints are mild: headache, nausea, a bit of dizziness, occasionally diarrhoea. Nothing that normally stops a course.

The organ that matters is the kidney. Acyclovir — and therefore valacyclovir — leaves the body through the kidneys and can crystallise inside them at high doses if you’re dehydrated. Two rules follow:

• → Drink water through the course. Especially on the shingles regimens and the 2 g cold-sore doses. This is the single piece of advice on the leaflet that people skip.
• → Reduced kidney function means reduced doses. Older customers, anyone with known kidney disease, and anyone on other kidney-cleared drugs need the regimen adjusted by a doctor. This is not a place to guess.

Rare but serious: confusion, hallucinations or unusual drowsiness on high doses — mostly in older people or those with kidney problems — is a same-day call to a doctor.

What a course actually costs, from our shelf

Price per tablet is what the product pages show. Price per course is what actually matters, so here it is, computed from the standard regimens above and our current pack prices.

Acyclovir is cheapest per tablet, but count the tablets a course needs and the gap closes — for suppression, valacyclovir costs about the same at one tablet a day. Famciclovir is the dear one for anything ongoing; keep it for the one-dose regimens. Delivery is free and tracked on every order to our supported countriesshipping policy and the full antiviral range.

Questions we get asked

Is valacyclovir stronger than acyclovir?

Not in the sense of a stronger drug — it becomes acyclovir once absorbed. It is better absorbed, so each valacyclovir tablet delivers more acyclovir to the blood than an acyclovir tablet does. That is why valacyclovir regimens need two or three doses a day instead of five, with the same effect on the outbreak.

Which is best for cold sores?

For convenience, valacyclovir or famciclovir: four Valacyclovir 1000 tablets over one day, or three Famciclovir 500 tablets as a single dose. Both must be started at the first tingle to work. Acyclovir works too but needs five doses a day for five days.

Can I use acyclovir 400 for shingles?

The shingles regimen is 800 mg five times daily, so you’d need two 400 mg tablets each time — ten tablets a day for seven days. It works but it’s clumsy, and a 60-pack of Acyclovir 800 ($157.99) or a 30-pack of Valacyclovir 1000 ($131.99) is simpler. Start within 72 hours of the rash.

What happens if I start after 72 hours?

The antiviral helps less, because most of the viral copying is over. It may still be worth taking for a severe outbreak or if new blisters are still appearing — that’s a doctor’s judgement. For next time, keep a pack at home so the first dose can go in at the tingle.

Can I take these while pregnant?

Only with a doctor’s say-so. Acyclovir and valacyclovir have the longest safety record in pregnancy and are what doctors normally choose when treatment is needed, particularly near delivery to reduce transmission. Famciclovir has less data. Don’t self-prescribe any of them in pregnancy.

What to do now

If it’s a cold sore or a recurrence you’ve had before, and a doctor has already confirmed the diagnosis, our pick is valacyclovir: the 1000 mg pack for cold sores and shingles, the 500 mg pack for recurrences and daily suppression — one tablet a day, no alarms, and the 360-pack covers a year. If cost per tablet is the only thing that matters and you’ll keep to five doses a day, Acyclovir 400 is hard to beat. If it’s your first ever outbreak, a rash near the eye, or you’re pregnant or have kidney trouble, see a doctor before anything goes in the cart. Not sure which pack? Email us — a person answers, any hour.

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