What is Naltrexone?

Naltrexone is a drug that blocks the effects of heroin, methadone (Physeptone) and all other opiates, such as morphine, codeine, DF118 and Temgesic. 

How does it work?

Naltrexone enters the brain and nervous system and attaches itself to small areas called receptor sites. For heroin to produce  its effects, it must bind to the same receptors, but Naltrexone stops heroin getting to them for up to three days after an oral dose. These receptors are part of the complex reward mechanisms that motivate us and lead to repetitive behaviour. If the reward is blocked the craving and dependence behaviour reduces and new ones reassert themselves with time. It works well for opiate addiction and often but less predictably in alcohol dependence.

Why take it?

Naltrexone helps prevent relapse. Most opioid dependents will have at least one relapse after getting detoxified. Research indicates that taking Naltrexone regularly provides a better chance to prevent relapse.

How effective is it?

Completely. Some patients try using heroin soon after starting Naltrexone. Once they realise that smoking or injecting even several grams of heroin has no effect, they do not usually waste their money by trying again.


How long do I take it for?

We recommend you take it for at least twelve months and that you agree to let a responsible family member, friend or workmate see you take it regularly if you are taking tablets.


Why does it have to be supervised?

Some days, your motivation may slip. Getting someone you trust to give it to you helps you stay clean at times when you feel tempted to use. Supervision also has the advantage that your carer or mentor can let us know if things are not going well. Having your medication supervised may be annoying at times, but it is much less annoying than a relapse. If supervision is difficult, you should consider other prevention strategies options.


Is Naltrexone addictive?

Definitely not. Even after several months, there are no withdrawal symptoms if you stop suddenly.


Is it a new drug?

No. Naltrexone has been used in the USA for over 40 years and in Britain for over 30 years.


Does it have side effects?

Very few and none of them serious. A few patients experience slight tiredness and indigestion. However, if you take Naltrexone while you are physically addicted to heroin or other opiates it will cause withdrawal symptoms within a few minutes. If you stop taking Naltrexone and start using heroin again, you are likely to kill yourself if you take your usual dose of heroin right away. People always wonder if it will stop them enjoying life if their reward mechanisms are blocked but, interestingly, in everyday circumstances it seems to have little or no impact on this. Instead, people are usually very happy and pleased to be opiate or alcohol free and protected from relapse.


Who should think of taking Naltrexone?

Any opioid user who wants to stop using opiates but who has never managed it for long, or who thinks that relying on will-power, NA or counselling alone will not work for them.


Problem drinkers hoping to gain control rather than abstain from drinking.

Is counselling needed as well?

We advise all patients to attend two or three sessions during the first month and at least one session every month or two for the next six months. Some people may need to come more often, but if you stay clean for a few months and keep yourself occupied, a lot of your problems will probably disappear without much help. We like to involve your family in treatment. If you already have a counsellor, we are happy to work with them. NA (Narcotics Anonymous) do not mind people attending NA meetings while on Naltrexone. You could also attend ‘Smart’ groups.


How often does it have to be taken?

The usual dose is one tablet every day, but you can take two or three tablets every two or three days respectively if this makes for easier supervision.


Liver Function Test

The national guidelines on naltrexone use advice to take a liver function test before prescribing.

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