Naltrexone (Intramuscular)


Naltrexone injection is used in the treatment of those who suffer from narcotic dependence who have stopped taking narcotics to stay drug-free. It's also used to help alcoholics stay alcohol-free. The medication cannot cure addiction. It's part of an overall program that will include attending support group meetings, counseling, and other treatments as recommended by a healthcare professional.

Naltrexone is not a narcotic. The injection works by blocking the effects of narcotics, and the "high'' feeling that encourages you to use them. It can also block the "high'' feeling that may make you want to consume alcohol. It won't cause physical or mental dependent or produce narcotic-like effects. It won't prevent you from becoming impaired if you drink alcohol.

This drug will cause withdrawal symptoms in those who suffer from dependence on narcotics. Treatment with this drug, therefore, is started after you no longer suffer from dependence on narcotics. How long you will take this medication and how long it will take to work will depend on the type of narcotic you took, and how long you've been taking it for. Before you begin using this medication, ensure you let your doctor know you think you are still suffering from withdrawal symptoms.

This medication can only be given under the supervision of a healthcare professional. It is available in the dosage form of powder for suspension.

Conditions treated

Type of medication

  • Powder for suspension

Side effects

Alongside its intended effects, this drug can produce some unwanted side effects. Not all of these may be present but if they are, you may need medical attention.

Seek advice from a healthcare professional if you suffer from any of the following side effects while taking Naltrexone:

More common

  • Unusual weakness or tiredness

Incidence not known

  • Chest discomfort or pain

Seek emergency help right away if you suffer from any of the following symptoms of overdose.

Symptoms of overdose

  • Sleepiness or unusual drowsiness

Some side effects that occur with this drug don't usually require medical attention. These side effects tend to disappear as your body starts adjusting to the medication. You can ask your local pharmacist for advice on reducing these side effects if they are giving you bother. Check with your doctor if any of the following side effects listed below continue to linger or become bothersome.

More common

  • Muscle stiffness

Incidence not known

  • Change in taste

You may suffer from other side effects not listed above. Contact your doctor if you notice anything unusual. You can report all side effects to the FDA regardless of severity.


The final dose of this medication will depend upon individual factors. This will include your age, weight and height, any other medical conditions you suffer from and corresponding treatment for those conditions. Your doctor will also consider the strength of this medication, the duration you are to receive it and your reaction to the first dose.

A trained healthcare professional or nurse will administer you this medication. This medicine is given as an injection into the buttocks muscle. It is typically given every four weeks or once a month.

Naltrexone injection can only be given to alcohol-dependent patients who can refrain from consuming alcohol and don't need an overnight stay in the hospital.

You should contact your doctor right away if you miss your scheduled dose, to make a new appointment.

This medication typically comes alongside a Medication Guide. You should read the information contained in this guide carefully and ask your doctor if you have any questions.


Drug interactions can occur with this drug. These could produce severe side effects or reduce the effectiveness of this drug in its treatment. To help limit these interactions, it's important to ensure your doctor knows about any other medications you are currently taking. This should include all over the counter drugs (prescription and nonprescription drugs), all herbal products and vitamin supplements. It's also a good idea to make your health care team aware of any other medical conditions you may suffer from as these too could increase your risk of interactions. In most cases, your doctor will avoid treating you with this drug when possible to avoid an interaction occurring, but in some circumstances, it may still be necessary.

The use of this medication alongside any of the following medications is not recommended. Your doctor may avoid treating you with this drug together or alter some of the other medicines you are taking.

  • Papaveretum

The use of this medication alongside any of the following medications is not typically recommended. However, in some cases, it may be necessary. If you are given both medications at the same time, your doctor may change the dose or frequency in which you use either medication.

  • Naloxegol

The use of this medication alongside any of the following medications could increase your risk of certain side effects. However, it may still be the best treatment option for you. If you are given both drugs at the same time, your doctor may change the frequency you use either drug or the final dose.

  • Yohimbine

Let your doctor or healthcare professional know if you are taking any of the following medications.

  • Moxifloxacin

Other Interactions

Some medications cannot be used around the time of eating food, or with certain types of food as it could increase the chance of interactions. The use of tobacco or alcohol may also increase interactions. You should discuss with your doctor about the use of alcohol, food, and tobacco with this drug.

Other Medical Problems

The presence of other medical conditions could affect the use of this medication. Ensure you tell your health care professional about any other medical problems, especially:

  • Bleeding problems (eg, hemophilia)



Let your doctor or healthcare professional know if you have ever suffered from an allergic reaction to this medication or other medications. You should also make them aware of any other allergies you suffer from including to animals, dyes, food or preservatives.

Pediatric population

Appropriate studies have not been conducted on the relationship of age to the effects of naltrexone injection in the younger population. Therefore efficacy and safety have not been established.

Geriatric population

Appropriate studies that have been conducted to date have not demonstrated a geriatric-specific problem that could limit the effectiveness of naltrexone injection in the elderly population.

Use in pregnancy and breastfeeding

This drug is under FDA pregnancy category C. It's currently unknown whether Naltrexone can harm an unborn baby. You should make your doctor aware if you are pregnant or intend on falling pregnant.

Naltrexone can pass into breast milk could potentially harm a nursing child. You should avoid breastfeeding whilst using this medication.

It's extremely important that your doctor monitors your progress at regular appointments. Your doctor may want to perform certain urine and blood tests to see if the medication is causing unwanted effects.

This medication can cause serious problems with your liver. You should call your doctor immediately if you notice any of the following signs: pain in the upper stomach, yellowing of the eyes or skin or darn urine while you are using this medicine.

This medication can increase your risk of having a lung disease known as eosinophilic pneumonia. You should inform your doctor immediately if you have trouble breathing or suffer from coughing after receiving this injection.

This medication can cause a serious type of allergic reaction known as anaphylaxis. This can be life-threatening and requires urgent medical attention. Seek medical attention immediately if you suffer from any of the following symptoms: itching, rash, hoarseness, trouble swallowing, trouble breathing or any swelling of your face, hands, or mouth while you are using this medication.

You will need to stop using opioids for at least seven to ten days before you can start receiving this injection. Your doctor may be required to do a urine test or the naloxone challenge test for opioids to ensure you are opioid-free.

This medication blocks the "high" feeling you get from narcotic drugs, including heroin. Since this injection may make you more sensitive to lower doses of opioids than your body is previously used to, you should avoid all narcotic drugs or heroin. You could develop serious problems or overdose.

This medication can increase thoughts of suicide. Let your doctor know immediately if you start to feel more depressed. You should also tell your doctor urgently if you have thoughts of hurting yourself. Report any unusual behaviors or thoughts that trouble you, especially if they worsen or are new. Ensure your caregiver knows if you sleep a lot more or less than usual, feel tired all the time, feel helpless or hopeless or if you have trouble sleeping, have a big increase in energy, or begin to act recklessly. You should also tell your doctor if you have strong or sudden or feelings, such as feeling angry, nervous, restless, scared or violent.

You should remember that use of naltrexone is only part of treatment.Ensure you follow all of your doctor's orders, including attending support group meetings or seeing your therapist on a regular basis.

Don't try to overcome the effects of this injection by taking narcotics. This could lead to death or coma. You could be more sensitive to the effects of narcotics than you were before.

This injection also blocks the useful effects of narcotics. Make sure you use a non-narcotic medicine to treat a cough, pain or diarrhea. Check with your doctor about what medication to use if you are unsure.

Naltrexone injection will not stop you from becoming impaired when you drink alcohol. Don't take naltrexone in order to perform activities or drive whilst under the influence of alcohol substance.

After this drug has been injected into your body, it's impossible to remove it.

It's recommended that you carry an identification card stating that you are currently taking naltrexone injection. You can also carry a letter that lets others know you are receiving this medication in a medical emergency.

You may experience a serious reaction at the site of the injection, including, tenderness, pain, swelling, itching, bruising, and redness. Seek advice from a healthcare professional immediacy if this reaction does not disappear or improve within 2 weeks of receiving the injection. Your doctor should refer you to a surgeon right away.

You may experience a feeling or nausea after you have received the first injection of this mediation. This will be mild and should disappear after a few days. Nausea will lessen with more injections.

This medication can cause some people to become drowsy, dizzy, or less alert than normal. If any of these side effects occur, don't use machinery, drive or anything else that could be dangerous if you feel dizzy or not alert whilst receiving this injection.

Ler your doctor know you are taking this infection before receiving any medical tests. The results of various tests could be affected by this medication.


You will not need to worry about the storage of this medication as it will be stored in a hospital or clinic setting. Typically medications for injection are refrigerated until use.


When used correctly, Naltrexone is successful in the blocking the effects of opioid medication. However, due to a large number of interactions possible, it's important you make your health care team aware of all the medications you are currently taking. This drug will not work on those who are still taking narcotics or alcohol. This drug is not for the use in children. You should let your doctor know if you are pregnant or intend on falling pregnant whilst using this drug. This drug can pass into breast milk so it's important to avoid using this drug if you are breastfeeding. This drug is not a cure, it is used alongside other programs to help dependence such as support groups and counseling. If you require any further information about the practical uses of this injection or you have any more questions, then contact your local health care professional or doctor for further advice.