Naltrexone vs nalmefene: which is right for you?

Naltrexone (50mg tablets) and nalmefene (Selincro, 18mg tablets) are both opioid antagonists. They work by the same mechanism: they sit at the brain's mu-opioid receptors and block the reward response that comes from drinking. Beyond that core similarity, they differ in licensing, dosing, half-life, liver effects and tolerability.

Licensing

Naltrexone has a UK marketing authorisation for opioid dependence; in the Sinclair Method it is prescribed off-licence for alcohol use disorder. This is legal and standard practice — many UK private providers prescribe it this way.

Nalmefene has a UK marketing authorisation specifically for reducing alcohol consumption in adults with alcohol dependence (NICE TA325, 2014). It is on-licence for this use.

Dosing

• Naltrexone: one 50mg tablet, one hour before drinking

• Nalmefene: one 18mg tablet, two hours before drinking

• Naltrexone half-life is 8-10 hours. If you're still drinking 8+ hours later you can take a second tablet.

• Nalmefene half-life is 12-14 hours. A second tablet in 24 hours is rarely needed.

Liver effects

Naltrexone is metabolised mainly by the liver and can occasionally cause transient changes in liver function tests (LFTs). Standard practice is to check LFTs at baseline and at 1 and 6 months.

Nalmefene is metabolised differently and is considered kinder to the liver. It does not require routine LFT monitoring. This makes it the preferred choice for patients with mild liver enzyme abnormalities, fatty liver, or other liver conditions where naltrexone wouldn't be ideal.

Tolerability and side effects

Both can cause mild nausea in the first week, headaches, and fatigue. Most patients find these settle within 7-14 days. Nalmefene's side effects are sometimes reported as more severe initially but the difference is small.

Our titration protocol — starting at a quarter tablet and building up over 2-3 weeks — significantly reduces side effects with both medications.

Cost

Both retail at around £99 per pack at LoveMyLife. Nalmefene packs are smaller (14 tablets vs 28 for naltrexone) but you typically take it on the days you drink, not every day.

Which one is right for you?

Naltrexone is our default. It's been studied more, has the larger evidence base for the Sinclair Method specifically, costs the same per pack, and the protocol is simpler.

We choose nalmefene if: you have mild LFT derangement, you've previously had tolerability issues with naltrexone, you'd benefit from the longer half-life, or there's a supply disruption.

During your consultation we'll discuss which fits you. You can also switch between them during your programme at no additional charge.

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