Naltrexone to Treat Alcohol Use Disorder
Naltrexone is a drug or pharmacotherapy for treating alcohol use disorders (AUDs). It is one of the most common forms of medication used in the treatment of AUDs. It was first made in 1965, and goes by the brand names ReVia and Vivitrol.
Naltrexone is what is known as an opioid antagonist. This means that it interferes with the mu-opioid receptors in the brain in order to make drinking alcohol less appealing and less pleasurable (more on this later).
Also used for the treatment of opioid use disorders, such as heroin use disorder, naltrexone can be taken either orally or as an injection. It has been the subject of countless studies, most of which have found it to be moderately effective, although it does appear to be less effective in some people than others.
Naltrexone should be used in concert with a broader treatment regime for AUDs. This should incorporate rehab and detox under professional care.
Patients need to be clean for 7 days before they begin a course of naltrexone.
Naltrexone for alcohol
As mentioned above, naltrexone was originally designed for patients with opioid use disorders. It has, however, become common in AUD treatment.
In alcohol treatment, it is important for patients to detox first in a rehab facility before starting naltrexone treatment. This is partly so that medical staff can distinguish between alcohol withdrawal symptoms and the adverse consequences which sometimes accompany naltrexone treatment.
Withdrawal symptoms for alcohol can be extreme. They may include:
- Fever and excessive sweating
- High blood pressure
- Nausea and vomiting
It is usually advisable to wait for withdrawal symptoms to die down before taking naltrexone, for the reason given above.
What does naltrexone do?
In patients with AUDs, naltrexone is said to have three effects. They are:
- Reducing a patient’s urge or desire to drink
- Helping patients remain abstinent
- Interfering with the patient’s desire to continue drinking more if he/she slips and has a drink 
These effects of naltrexone can be very helpful for someone in the early stages of abstinence.
How does naltrexone work?
The exact manner in which naltrexone works is not fully understood, but we know that it reduces cravings for alcohol and reduces the pleasure achieved by drinking alcohol.
One theory is that it decreases the reinforcing effects of alcohol by interfering with the brain’s neural pathways.  It does so by blocking opioid receptors, which are crucial to the role of dopamine in producing feelings of pleasure.
Ways to take naltrexone
Naltrexone is available in three different forms: an injection, a tablet and, most recently, an implant. There are pros and cons of each option. We discuss them below:
Naltrexone injection. The injectable form of naltrexone, which goes by the brand name Vivitrol, is taken once a month. The injection can cause redness and swelling which lasts for a few days. The main benefit of taking naltrexone as a an injection – rather than, say, a tablet – is that there is a greater chance of completing the course of medication. With a tablet, that has to be taken daily, there is always a risk that you forget to take the tablet or stop taking the tablets because of relapse. An injection takes this decision out of your hands.
Tablet of naltrexone. Naltrexone in tablet form, which goes by the brand names Depade and ReVia, needs to be taken once a day. In an inpatient rehab, this is the most common way to take naltrexone as there will be medical staff to remind you to take your pills. It’s important not to miss a dose, or take too many naltrexone tablets, as this can cause problems.
Naltrexone implant. This relatively new way of taking naltrexone involves inserting an implant under the skin, where it will remain active for eight weeks. This carries obvious benefits: you do not need to remember anything, nor are any medical staff required to make sure that you are getting the correct dosage.
One study, which looked at oral naltrexone versus the naltrexone implant for opioid use disorder, found that the implant was much more effective, with patients more likely to complete the course of treatment and reduce drug use when given the implant.  This was for opioid treatment, rather than alcohol treatment, but some of the conclusions may hold true in the case of AUD treatment too.
Who should not take naltrexone?
Certain groups of people should not take naltrexone. That includes the following:
People who currently use opioids. If you are currently taking opioids, this will interfere with naltrexone. Only take naltrexone if you have stopped drinking and taking opioids.
People with opioid withdrawal symptoms. If you still have opioids withdrawal symptoms, such as anxiety, fever, sweating, muscle aches, hot flushes and so on, you should not take naltrexone. It is best to wait until withdrawal symptoms (from alcohol or opioids) have settled down before taking naltrexone.
People who are pregnant or breastfeeding.
People who are taking medications that include opioids, perhaps for a chronic disorder.
People with liver failure or alcoholic hepatitis. 
How effective is naltrexone?
The consensus among the scientific community seems to be that naltrexone does reduce cravings, both for opioids and alcohol, but it does not work for everyone. This may be due to genetic factors.
One study found that ‘there is considerable heterogeneity in treatment response to naltrexone, which may vary in efficacy in some individuals.’  It seems that there are a variety of factors which determine how effective naltrexone will be for an individual, but we have yet to fully work out what these factors are. One study suggests that there is a certain allele that makes patients have a better response to naltrexone.  Another found that naltrexone is more effective among heavy smokers.  A third found that it is effective for those with lots of heavy drinkers in their social circle.  In summary, there is little consensus on what exactly makes people more likely to reap the benefits of naltrexone.
In order to be most effective, naltrexone needs to be accompanied by proper treatment, including a full course of therapy. Good forms of therapy for AUDs include cognitive behavioural therapy (CBT), motivational enhancement therapy and contingency management. Other useful forms of therapy include dialectical behavioural therapy (for suicidal patients and patients with borderline personality disorder) and alternative therapies like acupuncture, reiki, mindfulness and more.
Dosage and duration of treatment
For naltrexone taken in tablet form, the starting dose is normally 25 mg a day, for around a week. After the end of this week, the dose should go up to 50 mg.
Naltrexone tablets are best taken just after eating, as the drug can cause nausea if taken during a period of fasting.
If abdominal symptoms occur, the dose can be lowered and combined with a specific treatment such as bismuth subsalicylate in order to counter these symptoms. 
With oral naltrexone, three to four months of treatment is the typical duration. This ensures that naltrexone has a chance to make a positive impact. Under the circumstances where a patient who has been taking naltrexone becomes abstinent, for instance during the last few months of treatment, naltrexone can be stopped. The patient should then be monitored for four to six months in case of relapse. In a case where a patient begins using again, having previously stopped naltrexone during a period of abstinence, they can start taking naltrexone again without any problems.
Should the patient carry on drinking despite naltrexone, the dose can be increased to 100 mg, or an injectable form of naltrexone can be considered. This is to make sure that the patient is complying with treatment.
Side effects for naltrexone include common ones, such as nausea, and more serious ones such as opioid overdose. We list common and serious side effects below.
Common side effects include:
- cold symptoms
- decreased appetite
- muscle cramps
- painful joints
- trouble sleeping
More serious side effects include the following.
Painful reactions due to injection. Sometimes patients who get the naltrexone injection experience a reaction. This might just be a bit of swelling but, in some cases, it can cause tissue death. This condition which may need surgery to rectify. If a reaction does occur, it can cause:
- a dark scab
- an open wound
- intense pain
- large area of swelling
- the area feels hard
In case of a reaction, the patient should notify a doctor immediately.
Liver damage can also be caused by naltrexone. Symptoms of liver damage include:
- Dark urine
- Stomach area pain lasting more than a few days
- Yellowing of the whites of your eyes
Again, if any signs of liver damage occur, the patient should let their doctor now as soon as possible.
A third serious side effect of naltrexone can be opioid overdose. This is more common in those who are taking naltrexone for an opioid use disorder but is still possible in those with AUDs.
Opioid overdoses come about in this context because naltrexone reduces the effects of opioids. Someone who is dependent on opioids may decide to increase their normal dose of e.g. heroin to make up for the naltrexone. This can lead to death. For this reason, patients must be informed about the risks of opioid overdose before they agree to naltrexone treatment.
This is also one risk with injectable naltrexone: someone who is seriously dependent on opioids cannot choose to stop the naltrexone dose, and maybe decide to take a massive dose of opioids instead. This could be fatal.
Other side effects include:
- Low mood
- Allergic reactions 
Can you take other medications with naltrexone?
Those who are taking naltrexone need to carry a card that alerts medical staff to this fact. This is so that medical staff know not to prescribe e.g. an opiate painkiller.
The main form of medication which interacts with naltrexone is opiates. However, there are lots of alternatives to opiate painkiller so as long as doctors are made aware of this, it should not be an issue.
The majority of medications should have no reaction with naltrexone, but patients should still tell the doctor what medication they are taking prior to starting naltrexone treatment in case there is a problem. Medications that have an impact on the liver can determine the dose of naltrexone, as the liver is responsible for breaking it down. .
Naltrexone is one of the best forms of medication for people with AUDs. Although it does carry some side effects, some of which can be serious, it is effective for large numbers of people.
As noted earlier, naltrexone is most effective as part of a full treatment regime, including therapy, counselling, and support groups.