Naltrexone is a drug that is primarily indicated in the prevention of substance abuse especially among individuals who are already showing signs of addiction to alcohol or prescription opioid analgesics like codeine, hydrocodone, and oxycodone.

In some cases, naltrexone has also been indicated in the management of tobacco addiction, impulse control disorders, and even a few developmental disorders like autism.

The drug, while effective in the management of addictions, should not be the be-all, end-all of addiction treatment. Instead, it should form part of a comprehensive program for substance abuse and addiction treatment that include counseling, therapy, lifestyle changes, and psycho-social support.

Indications of Naltrexone

The drug, more popularly known for its brand name Vivitrol, is also indicated in the following conditions.

  • Fibromyalgia
  • Multiple sclerosis
  • Crohn’s disease
  • Complex regional pain syndrome

Naltrexone, given in low doses, has been shown to reduce the severity of the symptoms of the above health conditions as well as other chronic pain syndromes or disorders. However, it should be noted that these indications are considered as off-label. As such, it is often advised to seek medical opinion if naltrexone can work for you.

Low doses of naltrexone have also been used in the management of obesity. There is a drug that is a combination of sustained-release naltrexone and sustained-release bupropion which is being marketed as a possible treatment for obesity. Unfortunately, the FDA has not certified it use because of concerns about the possible adverse effects on the cardiovascular system. Nevertheless, overweight and obese individuals have been given the option of taking naltrexone only as a weight loss remedy.

While naltrexone is primarily an oral formulation, there is another preparation which is being increasingly used in the management of opioid abuse, misuse, or addiction. This preparation is implanted into the wall of the lower abdominal region. Known as naltrexone implants, these provide a steady supply of highly controlled amounts of naltrexone for the body’s benefit for a good 3 to 6 months. However, the FDA has not yet issued approval for these types of implants. Nonetheless, they are often provided by alcohol and drug rehabilitation facilities as well as other clinical settings that provide 24 hour round the clock supervision and monitoring.

Mechanism of Action of Naltrexone

The drug is classified as an opiate antagonist or a substance that blocks the effects of opiates or narcotic drugs. It acts by binding to the opiate receptors in the brain so that it prevents the development of opiate-induced reactions which can include respiratory depression, euphoria, miosis, and drug craving. Its metabolite, 6-ß-naltrexol, is also considered as a very potent antagonist or blocker of opiate receptors which can further enhance the therapeutic effectiveness of naltrexone.

Side Effects of Naltrexone

Like all medications, Naltrexone does carry with it quite a number of side effects stemming from the blockage of opiate receptors in the central nervous system. These can include the following.

  • Anxiety
  • Changes in energy levels
  • Decreased or loss of appetite
  • Diarrhea or constipation
  • Dizziness
  • Drowsiness
  • Headache
  • Insomnia and other sleep problems
  • Irritability or agitation
  • Joint pain
  • Muscle pain
  • Nausea and vomiting
  • Nervousness or jitteriness
  • Rashes
  • Tearfulness

There are also more serious side effects of naltrexone. It is generally advised that if you experience any of the following signs and symptoms, you should see your doctor at once.

  • Allergic reactions like rashes, itchiness, chest tightness, swelling of face, mouth, tongue or lips
  • Blurred vision or any other eye problems
  • Confusion
  • Diarrhea
  • Hallucinations
  • Respiratory problems including coughing, difficulty breathing, shortness of breath, or wheezing
  • Severe vomiting

Special Precautions When Taking Naltrexone

The drug is a very powerful narcotic antagonist as such it can be particularly dangerous if taken in substantially larger doses. It is a must that individuals who are taking naltrexone should use it according to the specific instructions of a doctor.

Generally, naltrexone should not be used if you are still taking any opioids as this can lead to coma or even death. It is recommended that you should have not taken any opioids in the past 10 days before your doctor can recommend naltrexone. In most cases, you will undergo a drug test to determine the presence of opioids or any other substance in your body which may have a deleterious effect when naltrexone is added. It has been shown that if you take naltrexone while opiates are still in your system, you may develop heightened sensitivity to opiate effects upon culmination of your treatment substantially increasing your risk of relapse.

If you are still consuming large quantities of alcohol, naltrexone may also not be recommended. Other situations where further consultation with your doctor is required before taking naltrexone include the following:

  • Hepatitis and other serious liver problems
  • Kidney disease
  • Bleeding disorders
  • Depression
  • Surgical procedures including those in dentistry
  • Pregnant
  • Breastfeeding

It is important to talk with your doctor about these conditions before taking naltrexone. While the effects of naltrexone on either the unborn baby or the breastfeeding infant have not been established, it is always a lot better to err on the side of safety.

It is equally crucial to always carry a naltrexone ID card or even a medical alert tag so that, in case of a medical emergency, the healthcare providers will know what to do.

Taking Naltrexone

Naltrexone is typically administered orally or as an injection. For off-label uses, naltrexone is usually administered at a rate of 4.5 mg per day. For addiction treatment purposes, the usual daily dose is 50 mg. It is also not uncommon that you may be given up to a maximum of 150 mg but only on certain days. Depending on your clinical assessment, you can receive naltrexone daily, every other day, or every 3 days. Naltrexone can be taken with or without food. For the inject-able preparation of naltrexone, it is usually administered once a month either by a doctor or by an advanced nurse practitioner but only in a clinical setting.

It is crucial to understand that naltrexone is a part of a comprehensive opiate addiction treatment program. It should never be used as a stand-alone treatment regimen. Additionally, it is vital to take naltrexone as instructed by your doctor, no more, no less.