Naltrexone Medications

Naltrexone Info

What Is Naltrexone?

Naltrexone belongs to a group of medicines called opioid antagonists. Its main job is to block the effects of opioid substances in the body. By doing this, it can help manage conditions where the body’s response to certain chemicals needs to be reduced. Naltrexone is available in several UK-registered products, including Revia, the generic tablet called Naltrexone, and the combination medicine Contrave (which pairs bupropion with naltrexone).

Medicines That Contain Naltrexone

A number of UK-licensed products use naltrexone as the active ingredient:

• Revia - a film-coated tablet that contains only naltrexone.
• Naltrexone (generic) - sold under various pharmacy-brand names, usually as 50 mg tablets.
• Contrave - a fixed-dose combination of bupropion and naltrexone, supplied as extended-release tablets.
• Bupropion + Naltrexone - other brand-name formulations that pair the two agents in a single tablet.

These medicines are offered in oral tablet form, with strengths ranging from 25 mg to 100 mg for the single-ingredient versions and a combined 8 mg bupropion/375 mg naltrexone dose in Contrave. Availability may differ between NHS prescriptions and private pharmacies, and some products are only supplied with a prescription from a qualified prescriber.

What Does Naltrexone Treat?

Naltrexone is primarily used for two recognised purposes in the UK:

• Alcohol dependence - it reduces cravings and the urge to drink by blocking the rewarding feelings that alcohol can produce.
• Opioid dependence - after a person has stopped using opioid drugs (such as heroin or prescription opioids), naltrexone helps prevent relapse by eliminating the “high” that would otherwise be felt if the drug is taken again.

In addition to these approved uses, some clinicians may consider naltrexone for other conditions where its ability to modulate the brain’s reward pathways is thought to be helpful. Such uses are typically described as off-label and are decided on a case-by-case basis.

How Naltrexone Works

When taken, naltrexone attaches to the same receptors in the brain that opioids would normally bind to. By occupying those spots, it stops opioids from activating them, which means the usual pleasurable effects are blocked. With alcohol, the exact way naltrexone reduces cravings isn’t fully understood, but it is believed to interfere with the brain chemicals that signal reward, helping people feel less compelled to drink.

The medication starts to act within a few hours of a dose, and its blocking effect can last for up to 24 hours, which is why it is usually taken once daily. The extended-release combination in Contrave is designed to release the ingredients gradually over the day.

Safety Information

Common Side Effects

Most people who take naltrexone experience only mild, short-lasting reactions. Typical reports include:

• Nausea or an upset stomach
• Headache
• Dizziness or light-headedness
• Fatigue or a feeling of low energy

These effects often improve as the body gets used to the medicine.

Serious Reactions

Although rare, some reactions need urgent attention:

• Severe skin rash or swelling, especially of the face, lips, or throat
• Trouble breathing or shortness of breath
• Sudden, marked drop in blood pressure
• Liver problems, signalled by yellowing of the skin or eyes (jaundice)

If any of these occur, seeking immediate medical help is essential.

Who Should Be Cautious

People with certain health conditions should discuss naltrexone with a prescriber before starting:

• Liver disease - because naltrexone is processed by the liver, impaired function can raise the risk of complications.
• Kidney problems - dose adjustments may be needed.
• Pregnancy or breastfeeding - safety data are limited, so the benefits and risks must be weighed carefully.
• Allergy to naltrexone or any ingredient in the specific tablet - an allergic reaction can develop.

Interaction Awareness

Naltrexone can interact with other medicines and substances:

• Opioid painkillers (e.g., morphine, codeine) - the antagonist effect of naltrexone can make these drugs less effective and may cause withdrawal symptoms.
• Alcohol - while naltrexone reduces cravings, drinking large amounts while on the medication can increase the risk of liver strain.
• Certain antidepressants and antipsychotics - may require monitoring, especially when combined with the bupropion component in Contrave.
• Alcohol or sedating drugs - can enhance drowsiness or dizziness.

For a full interaction list, refer to the specific product’s information leaf-let.

What to Know Before Using

• Storage - keep tablets in a dry place away from direct sunlight and out of reach of children.
• Treatment length - some courses may be short-term (for acute relapse prevention), while others can continue for many months under medical supervision.
• Follow the label - each medicine containing naltrexone may have different directions for use, strength, and timing. Always read the patient information that comes with your particular product.
• Monitoring - regular check-ups, especially of liver function, are common practice when using naltrexone for longer periods.

For detailed instructions on dosing, administration, and monitoring, see the specific medication sheet that accompanies your prescription.

Information Disclaimer

This article offers general educational information about naltrexone as an active substance used in various medicines. Its purpose is to help patients better understand the ingredient and the conditions it is used to treat. It is not a substitute for professional medical advice or for the specific instructions provided with individual products. Medicines containing naltrexone may differ in formulation, strength, and directions for use. Always consult the labeling of your particular medication and follow your healthcare provider’s guidance for complete information on proper use, dosage, and safety.