Naltrexone Injection: What Is it and What Does it Do?


Naltrexone is one of the most common medications to handle opioid and alcohol addiction. The drug is relatively safe to use, and it doesn’t cause addiction.

While it’s available in both pill and injection form, today’s topic will all be about the extended-release naltrexone injection, the dosing, mechanism of action, precautions, expected side effects, and interactions.

Naltrexone Injection: A Bird’s Eye View

Naltrexone injections are prescribed to people who suffer from opioid use disorder (OUD). The medication doesn’t treat the drug addiction itself but omits the pleasurable effect of opioids.

As such, naltrexone treatment should be used as a part of medication-assisted treatment along with counseling and therapy.

Naltrexone works by stopping the effect of opioids on the body by binding to the receptors that opioids bind to. By stopping that “high” feeling that makes patients crave opioids, the patient will be less likely to relapse.

Naltrexone doesn’t activate those receptors, so patients can safely use it without worrying about dependence.

It’s also a common medication for those struggling with alcohol use disorder (AUD) because it reduces alcohol cravings, as well.

The drug can be taken as a daily pill or as a monthly intramuscular injection. The 50 mg pill should be taken at fixed times daily, and the 380 mg extended release injectable naltrexone should be injected into the gluteal muscle.

Precautions and Expectations Before Using Naltrexone Injections

Naltrexone is a relatively safe drug. However, there are some precautions before using it:

1. Allergic Reactions

Like any other medication, some people might have allergic reactions to naltrexone. The patient needs to let their doctor know if they have a history of allergy to naltrexone or any other medications.

The doctor will then perform a sensitivity test to see whether the patient might have an allergy to naltrexone.

Giving an accurate history before taking systemic injections is of paramount importance. A systemic allergic reaction may put the patient in a life-threatening condition known as anaphylaxis.

2. Geriatric and Pediatric Patients

Patients who are too old or too young may want to find alternatives to naltrexone, as the drug lacks evidence-based studies that ensure its safety on either age extreme.

If injectable naltrexone is to be used in either age group, the patient must be hospitalized and monitored around the clock.

3. Breast-Feeding

Minimal data suggests that naltrexone can be expressed in breast milk in small amounts, which might have an adverse effect on breast-feeding babies.

If naltrexone is considered as a treatment option for a nursing mother, the patient’s doctor must weigh the risks and benefits to see if using the drug is beneficial before prescribing it.

Disclaimer: While the data in this post can give you an insight about the drug, it doesn’t replace a doctor’s opinion. Reach out to a certified healthcare professional for personal health advice.

4. Kidney or Liver Disease

Most medications are metabolized in the liver and filtered from the blood through the kidneys. If the patient has a liver or kidney disease, they must mention it in their medical history.

The doctor may reduce the dose of naltrexone or change the medication altogether to prevent any further harm to the kidney or liver.

5. Opioid Withdrawal Symptoms

Naltrexone is a supporting drug in opioid treatment. If it’s used while the withdrawal side effects are still active, it may prolong their duration for over two weeks.

As such, the patient must stop using any form of opioids for at least 7-10 days before beginning naltrexone therapy.

Expect that your doctor will perform a urine test before starting therapy to make sure that your body is opioid-free.

Keep in mind that if you’re using opioids concurrently with naltrexone, you might experience sudden opioid withdrawal symptoms even if you’re taking naltrexone for alcohol dependency.

Precautions While Using Naltrexone Injections

Assuming the patient has already started injectable naltrexone therapy, they should keep the following factors in mind to ensure safety and the best chances of success:

1. Monitoring Is Paramount

All long-term medications should be constantly monitored, especially if they’re injectable. If you or someone you know is on naltrexone therapy, it must be done under supervision from a certified doctor. If patients can’t maintain constant visits, telemedicine appointments are also viable.

The doctor may ask the patient for blood and urine tests as well to check if naltrexone is achieving the desired effects or if it’s causing any unwanted effects.

2. Expect Some Side Effects

Some of naltrexone’s side effects are common, but others need to be reported immediately to the supervising doctor.

If you face any of these side effects, you should let your doctor know:

  • Excessive bleeding at the site of injection
  • Open wounds or blistering
  • Lingering numbness or coldness
  • A painful burning sensation at the site of injection
  • Injection site reactions like swelling, burning, hives, or skin discoloration.
  • Dark urine or pain under the stomach (liver area)

These side effects may look scary, but they’re rare and can be quickly managed if you handle them early.

3. Expect Emotional Depression

Patients who are on naltrexone therapy likely won’t be in their best mental state because naltrexone blocks the effects of opioids, even endogenous ones. If the patient manages to go on opioids again, they won’t find the rewarding feeling they seek and it can lead to feelings of depression and despair.

For healthcare providers, iIt’s crucial to understand that the patient might experience some self-harm or suicidal thoughts during this time, especially if they expressed these thoughts before.

If you, or someone you know, are experiencing this, informing your doctor and asking for help can be life-saving. Don’t hesitate to reach out for help through the National Suicide Prevention Lifeline 988.

4. Going Back to Opioids Could Be Lethal

Naltrexone is often safe to use. However, it may indirectly lead to a fatal overdose if the patient gets their hands on some opioids while undergoing naltrexone therapy.

Due to the decreased sensitivity to opioids, the patient might try an additional opioid dose in hopes of achieving the euphoric feeling they seek.

That could easily lead to an opioid overdose, which is responsible for around 125,000 deaths in 2019 alone.

Naltrexone Injection Side Effects

As mentioned earlier, naltrexone has some side effects, which can be categorized as common and uncommon/rare.

Here are the common side effects of naltrexone:

  • Skin rash
  • Cold symptoms like sneezing, sore throat, and chills
  • Body aches or chest pain
  • Mental exhaustion or sadness
  • Difficult breathing
  • Generalized fatigue and joint pain
  • Constant nervousness
  • Occasional fever
  • Headaches
  • Nausea and/or vomiting
  • Ear congestion
  • Nervousness and ease of irritability

Some of the uncommon side effects (which usually require a doctor’s intervention) are:

  • Pain under the stomach
  • Jaundice
  • Dark Urine
  • Skin blisters and swellings
  • Open wounds
  • Raised lumps or hard areas at the injection site.

Injectable naltrexone is a monthly dose. Unlike oral naltrexone, which can sometimes be consumed twice a day by accident, the injectable form has a low chance of overdosing. However, should naltrexone overdose occur, you might experience:

  • Difficulty while moving
  • Redness, swelling, and pain in the joints
  • Muscle stiffness (as if they’re squeaking while moving)

Should you experience any of this, inform your doctor immediately.

Naltrexone Drug Interactions

The term “drug interaction” refers to an unpredictable reaction between two or more drugs that may result in undesirable and potentially dangerous results.

There’s a relatively extensive list of drugs that can interact with naltrexone. We’ll list most of these medications, but you shouldn’t use them as your only reference. Always inform your doctor about your complete medical history and any drugs you are currently taking.

That being said, the drugs that can interact with naltrexone are:

  • Hydrocodone
  • Ketobemidone
  • Morphine
  • Diacetylmorphine
  • Buprenorphine
  • Benzhydrocodone
  • Alphaprodine
  • Alfentanil
  • Meperidine
  • Morphine Sulfate Liposome
  • Methadone
  • Nicomorphine
  • Oxymorphone
  • Paregoric
  • Oxycodone
  • Tilidine
  • Tramadol
  • Propoxyphene
  • Piritramide
  • Levorphanol
  • Diphenoxylate
  • Sufentanil
  • Tapentadol

To Wrap Up

As a popular drug in helping with opioid and alcohol dependence, naltrexone can be a significant step in battling addiction if used within its safety parameters.

Its non-addictive mechanism of action that takes the joy out of opioid usage can discourage the patient from relapsing and help them make a full recovery.

Keep the precautions in mind, monitor your condition with your doctor, and report any side effects.


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