Side Effects and What to Avoid When Taking Naltrexone

Naltrexone (Vivitrol) is a versatile medication. It is prescribed at a higher dose to treat alcohol use disorder and opioid use disorder. Naltrexone blocks opioid receptor sites in the brain and decreases pleasure and euphoria when taking opioids or consuming alcohol. When taken regularly, naltrexone can reduce cravings and prevent relapses.

Naltrexone is prescribed off-label in lower doses to reduce inflammation and treat chronic pain. Low-dose naltrexone may also help inhibit cancer growth, reduce fatigue, improve depressive symptoms, and help with autoimmune conditions.

Naltrexone is also prescribed with other medications. For example, naltrexone-bupropion is prescribed for weight loss treatment as an adjunct to a low-calorie diet and exercise.

Naltrexone has many benefits, but like all medications, it has the potential for side effects and drug interactions. Depending on your medical history, you may be at increased risk for some side effects, so it is important to be aware of any potential naltrexone side effects and interactions.

Possible Side Effects of Naltrexone

Naltrexone has been tested for safety and effectiveness in clinical trials.¹

Physical side effects associated with naltrexone use include:²

• Abdominal pain or cramps
• Anxiety
• Difficulty sleeping
• Headache
• Joint and muscle pain
• Low energy
• Nausea
• Nervousness
• Vomiting

In clinical trials, more than 10% of people taking naltrexone experienced these side effects.

Less common physical side effects associated with naltrexone use during clinical trials include:

• Chills
• Constipation
• Decreased appetite
• Decreased potency
• Delayed ejaculation
• Diarrhea
• Dizziness
• Increased thirst
• Skin rash

Side effects reported after clinical trials include:

• Changes in blood pressure
• Chest pain
• Fast or irregular heartbeat
• Fatigue
• Hot flashes
• Indigestion
• Malaise
• Tremor
• Vision abnormalities

Psychological side effects associated with naltrexone use include:

• Abnormal thinking
• Agitation
• Confusion
• Euphoria
• Feeling down
• Hallucinations
• Increased energy
• Irritability
• Nervousness

According to the Substance Abuse and Mental Health Services Administration, the following serious side effects may also occur:

• Injection site reactions: intense pain, scabbing, blistering, swelling
• Liver injury: liver damage or hepatitis causing stomach pain, dark urine, fatigue, and a yellow tinge to eyes and skin
• Serious allergic reactions: skin rash, swelling of face, eyes, mouth or tongue, trouble breathing, chest pain, feeling dizzy or faint
• Pneumonia: shortness of breath, cough
• Depressed mood: monitor for depression and suicidality

This is not the complete list of side effects known to occur with naltrexone use. Consult with your doctor if you are experiencing any persistent or concerning side effects.

Naltrexone shares some side effects with other weight loss medications. However, since each medication has a unique way of working, they do not all cause the same side effects.

Drug Interactions: What To Avoid When Taking Naltrexone

Naltrexone adversely interacts with other medications. To reduce your risk, talk to a healthcare professional, either in person or using Invigor Medical’s online health clinic before mixing any medications. This can minimize your risk of a serious reaction.

Certain Cough Medications

Naltrexone binds to opioid receptors and therefore negates the effects of opioid-containing medications such as cough and cold medication.

Codeine is often found in cough medications and combination cold medications. It may be combined with antihistamines, decongestants, and acetaminophen, such as in promethazine with codeine cough syrup.

Hydrocodone is another narcotic cough suppressant. It is commonly combined with antihistamines. An example is Tussionex cough syrup.

Hydromorphone is found in Dilaudid cough syrup.

Antidiarrheal Medications

Naltrexone can negate the effects of antidiarrheal medications that bind to opioid receptors, including the following:  

• Loperamide: acts mainly on gut opioid receptors to reduce bowel movements.
• Diphenoxylate: acts on gut opioid receptors.
• Difexoxin: contains an opioid that reduces bowel motility.
• Eluxadoline: a mixed opioid receptor agonist-antagonist that is used to treat irritable bowel syndrome with diarrhea.

Besides blocking the effects of these medications and increasing potential side effects, in people who are physically dependent on opioids, naltrexone can precipitate sudden and severe withdrawal symptoms.

Naltrexone is metabolized in the liver. It may cause changes in drug levels for other medications that are metabolized in the liver.

Prescription Opioid Medications

Since naltrexone is an opioid antagonist, it can reduce or even block the effects of other medications that contain opioids.

Examples of medications containing opioids include:

• Codeine: Tylenol with codeine, Fiorinal with codeine
• Morphine: MS Contin
• Oxycodone: Oxycontin, Percocet, Roxicodone
• Hydrocodone: Vicodin, Lorcet, Lortab, Norco
• Hydromorphone: Dilaudid, Exalgo
• Fentanyl
• Oxymorphone: Opana, Numorphan
• Methadone
• Tramadol
• Tapentadol
• Meperidine
• Buprenorphine

Combining opioid medications and naltrexone is dangerous. Taking naltrexone with opioids increases your risk of an overdose, coma, and death.

Do not take naltrexone if you are dependent on opioids or if you are experiencing opioid withdrawal symptoms.

Naltrexone should not be used within 7 to 14 days of taking an opioid.

Alcohol 

Naltrexone blocks the euphoric feelings of intoxication from alcohol use. This can make it dangerous to combine Naltrexone and alcohol use.

The benefit of taking naltrexone to treat alcohol use disorder is that it reduces the pleasant feelings associated with alcohol use. It can reduce cravings and the potential for a relapse.

The drawback is that if people continue to drink alcohol while taking naltrexone, they may lose track of how much they are drinking. While naltrexone reduces the “buzz” associated with consuming alcohol, it does not prevent you from becoming impaired while drinking alcohol.

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