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Naltrexone (injection)

Generic Name: Naltrexone (injection) [nal-TREX-own]
Name of the Brand: Vivitrol
Dosage Format: Intramuscular powder for injection, extended release (380 mg)
Drug Classes: Antidotes, drugs used in alcohol dependence

What is Naltrexone?

Naltrexone blocks the effects of opioids, which can cause pain relief or feelings of wellbeing that could result in the abuse of opioids.Naltrexone injections can be used to stop relapses in people who have become dependent on opioids and later quit using them. Naltrexone is a way to prevent your body from experiencing the "need" to use opioids.

Naltrexone injections are also employed to help treat alcohol dependence by reducing the urge for alcohol consumption. It can aid in reducing your drinking or even stopping entirely. It is not recommended to drink when you get the first injection of naltrexone.Naltrexone isn't a permanent solution for drug dependence and alcoholism.Naltrexone can also be used for reasons not mentioned in this guideline.

Side effects of Naltrexone

Take immediate medical care in the event that you exhibit symptoms that are warning signs of an allergic response, such as hives, discomfort in your chest, breathing problems, trouble breathing, feeling lightheaded, and swelling of your mouth, lips, or throat.

Utilising opioids while you receive naltrexone injections can trigger withdrawal symptoms. Common withdrawal symptoms include sweating, yawning, stomach pain, fever, diarrhoea, and  vomiting, as well as watery eyes, dry nasal passages, goosebumps, shakes, body aches, difficulty sleeping, and feeling agitated or anxious.

Naltrexone could result in serious side effects. Contact your doctor immediately if you suffer from:

  • Breath that is weak or shallow;
  • New or worsening cough or wheezing; trouble breathing;
  • Extreme pain, swelling, burning, skin changes, an elongated scab, or a large lump in the area at the site of injection;
  • Stomach symptoms, stomach pain (upper right side) dark urine, fatigue, jaundice (yellowing of the eyes or skin),
  • Symptoms of depression: unusual moods or behaviors that shift, loss of interest in things that you used to enjoyed, insomnia, crying or thoughts of self-harming

You might feel nauseated the first time you have an injection of naltrexone. It is also possible to experience headaches and fatigue, as well as joint and muscle discomfort, nausea, and vomiting.

Common negative side effects of naltrexone include:

  • Nausea and vomiting and the loss of appetite.
  • Joint pain, muscle cramps;
  • Dizziness, drowsiness;
  • Sleep problems (insomnia);
  • Toothache
  • Signs of a cold, like nasal stuffiness, sneezing, and a sore throat.

This isn't a complete list of possible side effects, and other effects may also be present. Contact your physician to seek medical advice on the effects. You can report any symptoms to the FDA at 1-800-FDA-1088.


It is recommended to treat yourself with naltrexone only when you haven't recently taken any opioid drug, buprenorphine, methadone, or any other medicine to treat the symptoms of a cold, diarrhoea, cough, or pain. Utilising these medications within the period of 7 to 14 days prior to starting naltrexone could result in sudden withdrawal symptoms from opioids.

Avoid using opioids such as heroin, narcotics, or any other street drugs while taking naltrexone. If you do, it could cause dangerous effects, such as the death of a patient or a coma.

Contact your physician if you suffer from persistent or recurring discomfort, redness, itching, or swelling. You may also experience bruising, swelling, or a lump in the area where the medicine was administered.

Naltrexone could affect your liver. Consult your physician if you suffer from stomach pain or dark urine. You may also notice yellowing in the whites of your eyes.

Following the administration of naltrexone, your body is more susceptible to opioids when you take an opioid medication in the near future. Utilising the same dosage that you did before can cause an overdose or even death.

Before you take this drug

It is not recommended to get a naltrexone injection if you are still taking opioids or are experiencing extreme withdrawal symptoms that are sudden and intense.

It is not recommended to treat with naltrexone if you are intolerant to it or

  • You are currently dependent on opioids.
  • You're experiencing withdrawal symptoms as a result of addiction to opioids.
  • You have taken any opioid medication in the last 7–14 weeks (including fentanyl, Vicodin, OxyContin, and many more);
  • You've taken buprenorphine or methadone (Subutex, Butrans, Suboxone, Zubsolv) in the last 14 days; you have used methadone or buprenorphine in the past 14 days;
  • You've taken any medicine in the treatment of a cold, diarrhoea, cough, or pain in the past 7–14 days.

Speak to your doctor if you have ever suffered from:

  • The liver condition;
  • Kidney disease
  • Problems with bleeding, for example, haemophilia.

Consult your physician if you are breastfeeding or pregnant.

It is unclear if the drug will cause harm to a baby who is not yet born. However, if you use opioids while pregnant, your child could develop dependence on the medication. This can cause dangerous withdrawal symptoms in the newborn after it's born. Children who are dependent on opioids might require medical attention for several weeks.

How to take Naltrexone?

Naltrexone is injected directly into a muscle. The injection is typically given every month (every four weeks) and can be administered only by a medical professional. Make sure you get your naltrexone injection on a regular basis to reap the maximum benefits.

There may be a sensation of itching, redness, pain, swelling, bruising, or a hard lump at the site where the medication was injectable. Consult your doctor if you experience this type of reaction, particularly when it becomes worse or doesn't go away within two weeks.

Naltrexone injections can be part of a comprehensive treatment plan that may include other methods of monitoring or counselling. Follow your doctor's directions carefully.In the event of a crisis Wear or carry a medical ID to notify others that you're using naltrexone.

Following the use of naltrexone, your body is more vulnerable to opioids. If you decide to use an opioid medication in the near future, it is recommended to reduce the amount you used prior to using naltrexone. Utilising the same dosage that you did before can result in death or overdose.

Details on dosage

Usual Adult Dose for Alcohol Dependence:

Average dosage: 50 mg daily, orally.
Time of treatment 12 weeks
380 mg intramuscularly once every 4 weeks or once per month
There are no studies specifically on the subject of switching from methadone or buprenorphine to Naltrexone. However, certain patients have reported serious symptoms of withdrawal that were precipitated when they switched from an opioid agonist to an opioid antagonist.
Patients who are switching to buprenorphine or methadone are at risk of abrupt withdrawal for as long as 2 weeks.
Prepare yourself to treat withdrawal symptoms with non-opioid medication.
To achieve the best results, employ techniques to improve compliance, including the ability to comply with medication.

Usual Adult Dose for Opiate Dependence:

Initial dose: 25 mg taken orally every day, once
Maintaining dose: 50 mg every day (if there are no withdrawals after 25 mg/day).
380 mg intramuscularly, every 4 weeks, once a month
There are no studies specifically on the subject of switching from methadone or buprenorphine to the naltrexone drug, but some patients have experienced severe symptoms of withdrawal that were precipitated when they transitioned from an opioid agonist treatment with opioid antagonists.
Patients who are switching to buprenorphine or methadone could be susceptible to abrupt withdrawal for as long as two weeks.
Be prepared to treat withdrawal symptomatically using non-opioid drugs.
The drug is effective only when it is part of a comprehensive treatment plan that includes measures to make sure that the patient is taking it.
Use(s) to block the effects of the exogenously administered opioids

What happens If I Miss a dose?

Contact your doctor for advice. If you do not make an appointment to receive your Naltrexone injection.

What happens If I overdose?

Because naltrexone is administered by a doctor in a medical environment, an overdose isn't likely to happen. However, the symptoms of overdose can include stomach pain, nausea or drowsiness, dizziness, or an allergic reaction after injections were administered (such as intense skin or joint pain).

What should be avoided?

Do not take heroin, opioids, or any other street drug during the time you are taking naltrexone. After naltrexone has been injected into your body, it is not able to be eliminated completely from the body. Don't try to combat these effects using large doses of opioids. If you do, it could cause dangerous effects, such as the death of a patient or a coma.

Talk to your doctor prior to using any medication to treat a cough, cold, or diarrhoea. The medicines could contain opioids, and they may not be effective if you're taking Naltrexone.

Avoid driving or engaging in hazardous activities until you are aware of the effects of this medication. Drowsiness, dizziness, or confusion can lead to accidents, falls, or serious injuries.

Interaction with other drugs

Other medications can affect naltrexone, such as prescription and over-the-counter medicines, vitamins, and herbal products. Inform your physician about your current medications and any medications you begin or stop taking.



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