Nalmefene (brand name Selincro) is an opioid antagonist closely related to naltrexone, approved by the European Medicines Agency for alcohol dependence. It’s the same class of drug, the same mechanism, but with a different label and dosing profile. If you live in Europe and have looked into alcohol medication, you may have come across nalmefene first; if you live in the US or UK, you may not have heard of it. This article is part of our Naltrexone hub, the complete guide to using naltrexone for alcohol use disorder.

This article walks through what nalmefene is, how it differs from naltrexone in practice, and which patients tend to do better on which.

# What nalmefene is

Nalmefene is a mu-opioid receptor antagonist. So is naltrexone. Both block the dopamine-reward pathway that alcohol normally activates. Mechanistically, they do the same thing: drink alcohol while either drug is active, and you don’t get the same buzz, the same urge to keep drinking, or the same drinking-feedback reinforcement.

The differences come from molecular details:

  • Nalmefene also has partial agonist activity at the kappa-opioid receptor, where naltrexone is a pure antagonist. The clinical relevance of this is debated.
  • Nalmefene has slightly higher oral bioavailability and a longer effective duration of action per dose.
  • Nalmefene is dosed at 18mg per tablet (vs naltrexone’s 50mg) but the lower number reflects different potency, not weaker effect.

# Where each is approved

Naltrexone is approved in the US (FDA, 1994), UK (MHRA), Australia (TGA), Canada, most of Europe, and most other developed markets. It’s the global standard for alcohol use disorder pharmacotherapy.

Nalmefene (Selincro) is approved by the EMA (European Medicines Agency) for alcohol dependence, available in most EU countries. It is not FDA-approved in the US for alcohol use disorder; it’s available there only for opioid overdose reversal in different formulations. UK approval was granted but Selincro was withdrawn from NHS recommended use by NICE in 2014 after a cost-effectiveness review found insufficient evidence of advantage over naltrexone. It’s still available privately in the UK.

For most patients in the US, UK, Australia, or Canada, nalmefene is functionally unavailable for alcohol use disorder. If you’re reading this from an EU country, it may be your prescriber’s first suggestion. From elsewhere, naltrexone is what you’ll be offered.

A pharmacy interior with shelves of medication bottles.
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# The dosing difference

This is where nalmefene and naltrexone diverge most clearly.

Naltrexone is typically prescribed in two patterns: daily 50mg, or the Sinclair Method (50mg an hour before each drinking session). Both are legitimate evidence-based protocols.

Nalmefene is licensed specifically as an as-needed medication: you take 18mg about an hour or two before drinking, only on days you plan to drink. There is no licensed daily-nalmefene protocol equivalent to daily naltrexone.

In effect, nalmefene’s licensed use is structurally similar to TSM but with the as-needed framing built into the regulatory approval rather than relying on a clinician to apply naltrexone in a TSM-style way. For European patients who want a targeted-dose approach without entering the off-label TSM conversation, nalmefene is the cleaner regulatory route.

# Real-world adherence

Both drugs require you to remember to take a tablet before drinking. The compliance challenge is identical.

Per-dose: Nalmefene’s 18mg vs naltrexone’s 50mg makes no practical adherence difference. Both are single tablets.

Per-month: If you drink 3-4 times a week, you take 12-16 tablets a month on either drug.

Per-bottle: Nalmefene packaging in the EU is typically 14 or 28 tablets per pack. Naltrexone is typically 30 tablets per bottle. Again, no meaningful difference.

The only real adherence wedge between the two: nalmefene’s regulatory framing as “as-needed” may make it psychologically easier for patients who haven’t decided to fully commit to a protocol. Naltrexone for TSM requires the prescriber to explain off-label use, the patient to understand the targeted-dose mechanism, and both to be comfortable with that. Nalmefene’s licensed indication is closer to “take it when you’re going to drink”; the framing is built in.

# Side effects

Largely similar. Both can cause:

  • Nausea (common, especially in first 1-2 weeks)
  • Headache (transient)
  • Insomnia or vivid dreams
  • Fatigue
  • Dizziness

Nalmefene is sometimes reported to cause dizziness more frequently than naltrexone in head-to-head studies, though the difference is small.

The most important shared caution: both drugs are absolutely contraindicated with opioid medications. Both will trigger acute opioid withdrawal in patients on buprenorphine, methadone, or other opioid agonists. Both will leave acute pain unmanageable in patients trying to take prescription opioid analgesics simultaneously.

A pill bottle with a single tablet visible on a wooden surface.
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# Cost comparison

Naltrexone: Generic. Cheap globally. £10-25/month UK private, $4-50/month US, AUD $40-80/month Australia.

Nalmefene (Selincro): Branded, more expensive, and varies by country. In Germany and France, around €40-80/month at full price; available through statutory health insurance in many EU countries with a co-pay. UK private: £80-150/month (one of the reasons NICE didn’t recommend it for NHS use; the cost premium over naltrexone wasn’t justified by improved outcomes). Not available in the US for alcohol indication.

For patients with realistic access to both, naltrexone is several times cheaper. For patients in EU countries where Selincro is on formulary, the out-of-pocket gap may be small and nalmefene’s targeted-dose licensing may be the deciding factor.

# Which should you choose?

Default answer: Naltrexone, unless you have a specific reason to prefer nalmefene.

Choose nalmefene if:

  • You’re in an EU country where Selincro is on formulary and your prescriber is comfortable with it
  • Your prescriber is reluctant to prescribe naltrexone for off-label TSM, but is comfortable prescribing nalmefene because it’s licensed for the same approach
  • You’ve tried naltrexone and the side effect profile didn’t suit (the small differences in side effect rates may be relevant for individuals)

Choose naltrexone if:

  • You’re in the US, UK (NHS), Australia, Canada, or anywhere else nalmefene isn’t easily accessible
  • You’re cost-sensitive (naltrexone is dramatically cheaper)
  • You want flexibility between daily and TSM protocols
  • You’re considering long-acting injectable Vivitrol; there’s no nalmefene equivalent

In practice, the choice often depends entirely on what your prescriber is comfortable with and what’s accessible in your jurisdiction. The clinical difference between them for the average patient is small.

# How AlcoLog tracks both

AlcoLog’s Medications card supports both nalmefene and naltrexone, alongside five other alcohol-related preparations. Each medication has its own colour, dose log via the 24-hour time picker, last-24h dose list, and redose timer set in hours and minutes.

The dose-tracking workflow is the same regardless of which medication you’re on. Take the tablet, log the time, watch the redose timer countdown if you need a second dose during a long session.

Pro-tier location reminders fire when you arrive at a saved location: useful for the targeted-dose pattern that both nalmefene and TSM-style naltrexone share.

AlcoScore deliberately excludes medication use from its scoring. Your dose log informs you, not your score. Data stays on your device. CSV export is free for the last 10 sessions; unlimited export and PDF reports are on Pro for sharing with your prescriber at follow-up appointments.

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