Methylnaltrexone (Subcutaneous)

Generic name: methylnaltrexone [ meth-il-nal-TREX-one ]
Brand name: Relistor
Drug class: Peripheral opioid receptor antagonists

Medically reviewed by Drugs.com. Last updated on Feb 19, 2024.

Uses for methylnaltrexone

Methylnaltrexone injection is used to treat constipation caused by opioids (narcotic pain medicines), in adults with long-lasting pain that is not caused by cancer, or in patients with long-lasting pain caused by a previous cancer or its treatment who do not need weekly increases in opioid dosage. It is also used to treat constipation caused by opioids in adults with an advanced illness or cancer who need an increase in their opioid dosage.

This medicine is available only with your doctor's prescription.

Before using methylnaltrexone

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:

Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Pediatric

Appropriate studies have not been performed on the relationship of age to the effects of methylnaltrexone injection in the pediatric population. Safety and efficacy have not been established.

Geriatric

Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of methylnaltrexone injection in the elderly.

Breast Feeding

There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Interactions with Medicines

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

• Morphine
• Morphine Sulfate Liposome
• Naldemedine
• Naloxegol
• Oxycodone
• Oxymorphone

Interactions with Food/Tobacco/Alcohol

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other Medical Problems

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

• Crohn's disease or
• Diverticulitis or
• Ogilvie's syndrome (decreased movement of food in the intestines) or
• Peptic ulcer or
• Stomach or bowel cancer—May increase risk for more serious side effects.

• Liver disease or
• Kidney disease, severe—Use with caution. The effects may be increased because of slower removal of the medicine from the body.

• Stomach or bowel blockage, known, suspected, or increased risk of—Should not be used in patients with these conditions.

Related/similar drugs

MiraLAX, docusate, lactulose, Colace, bisacodyl, polyethylene glycol 3350, lubiprostone

Proper use of methylnaltrexone

Your doctor will prescribe your exact dose and tell you how often this medicine should be given. It is given as a shot under your skin (usually in the upper arm, abdomen or stomach, or thighs) each day for long-lasting pain not caused by cancer or every other day for patients with an advanced illness.

Methylnaltrexone injection may be given at home to patients who do not need to be in the hospital. If you are using this medicine at home, your doctor will teach you how to prepare and inject the medicine. Be sure that you understand exactly how the medicine is prepared and injected.

This medicine comes with a Medication Guide and patient instructions. Read and follow these instructions carefully. Ask your doctor if you have any questions.

This medicine is available in three forms: a pre-filled syringe, a vial (glass container), or a vial and syringe with a retractable needle. You can use these dosage forms at home.

You will be shown the body areas where this shot can be given. Use a different body area each time you give yourself a shot. Keep track of where you give each shot to make sure you change body areas. This will help prevent skin problems from the injections. Do not inject into skin areas that are bruised, red, tender, hard, or have scars or stretch marks.

Use a new needle and syringe each time you inject your medicine.

You might not use all of the medicine in each vial (glass container). Use each vial or syringe only one time. Do not save an open vial or syringe. If the medicine in the vial or syringe has changed color, or if you see particles in it, do not use it.

Stop taking other laxatives before starting treatment with methylnaltrexone. You should also stop using this medicine if you have stopped taking narcotic pain medicines.

Dosing

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

• For injection dosage form:
  • For constipation caused by opioids in patients with long-lasting non-cancer pain:
    • Adults—Dose is based on body weight and must be determined by your doctor. The dose is 12 milligrams (mg) injected under the skin once a day for at least 4 weeks (with narcotic pain medicines).
    • Children—Use and dose must be determined by your doctor.
  • For constipation caused by opioids in patients with severe illness:
    • Adults weighing more than 114 kilograms (kg)—Dose is based on body weight and must be determined by your doctor. The dose is 0.15 milligram (mg) per kilogram (kg) of body weight injected under the skin every other day for 4 months.
    • Adults weighing 62 to 114 kg—Dose is based on body weight and must be determined by your doctor. The dose is usually 12 mg injected under the skin every other day for 4 months.
    • Adults weighing 38 to less than 62 kg—Dose is based on body weight and must be determined by your doctor. The dose is usually 8 mg injected under the skin every other day for 4 months.
    • Adults weighing less than 38 kg—Dose is based on body weight and must be determined by your doctor. The dose is 0.15 mg per kg of body weight injected under the skin every other day for 4 months.
    • Children—Use and dose must be determined by your doctor.

Missed Dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Store unopened vials of this medicine at room temperature, away from heat and direct light. Do not freeze. An open vial of this medicine must be used right away.

Throw away used needles in a hard, closed container that the needles cannot poke through. Keep this container away from children and pets.

Precautions while using methylnaltrexone

It is very important that your doctor check your progress at regular visits. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to use it.

This medicine may cause a tear (perforation) in your stomach or bowels. Check with your doctor right away if you have a severe stomach pain that does not go away.

If severe or persistent (non-stop) diarrhea occurs while using methylnaltrexone injection, check with your doctor right away.

Do not suddenly stop using this medicine without checking first with your doctor. Doing so may cause withdrawal symptoms, such as anxiety, chills, increased tearing, redness on the face, neck, arms, and upper chest, feeling cold, diarrhea, irritability, stomach pain, sweating, and yawning.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Side Effects of methylnaltrexone

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

More common

• Diarrhea
• increased sweating

Incidence not known

• Bloody, black, or tarry stools
• heartburn
• indigestion
• nausea
• severe abdominal or stomach pain, cramping, or burning
• trouble breathing
• vomiting of material that looks like coffee grounds, severe and continuous

Get emergency help immediately if any of the following symptoms of overdose occur:

Symptoms of overdose

• Chills
• cold sweats
• confusion
• dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

• Bloated
• dizziness
• excess air or gas in the stomach or intestines
• feeling of fullness
• passing of gas
• stomach pain

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Commonly used brand name(s)

In the U.S.

• Relistor

Available Dosage Forms:

• Solution

Therapeutic Class: Gastrointestinal Agent

Pharmacologic Class: Opioid Antagonist

Frequently asked questions

• Which drugs cause opioid-induced constipation?

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer