Brand Name(s):

  • Relistor®

WHY is this medicine prescribed?

Methylnaltrexone injection is used to treat constipation caused by opioid (narcotic) pain medications in patients with advanced illnesses when laxatives have not worked. Methylnaltrexone injection is in a class of medications called peripherally acting mu-opioid receptor antagonists. It works by protecting the bowel from the effects of opioid (narcotic) medications.

HOW should this medicine be used?

Methylnaltrexone injection comes as a solution (liquid) to inject subcutaneously (under the skin). It is usually injected once every other day as needed, but it can be used up to once every 24 hours if needed. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Use methylnaltrexone injection exactly as directed. Do not use more or less of it or use it more often than prescribed by your doctor.

Methylnaltrexone is to be used by people who are taking opioid (narcotic) medications. If you stop taking opioid medications, talk to your doctor about whether you should stop using methylnaltrexone.

You can inject methylnaltrexone injection yourself or have a friend or relative perform the injections. Carefully read the manufacturer's instructions that describe how to prepare and inject a dose of methylnaltrexone. Ask your doctor or pharmacist to show you or the person who will be injecting the medication how to inject it. Be sure to ask your pharmacist or doctor if you have any questions about how to prepare or inject this medication.

Methylnaltrexone injection comes in vials to use with disposable syringes. Your medication may come on a tray with a syringe, or you may need to buy syringes separately. Ask your doctor or pharmacist if you have questions about the type of syringes to use. Use vials and disposable syringes only once. Throw away the vial and syringe after one use, even if they are not empty. Throw away used syringes and vials in a puncture-resistant container, out of the reach of children. Do not throw a filled container into the household trash or recycling. Talk to your doctor or pharmacist about how to throw away the puncture-resistant container. There may be special state and local laws for throwing away used needles and syringes.

You can inject methylnaltrexone under the skin on your stomach or thighs. If someone else will be injecting the medication for you, that person can also inject it into your upper arm. Choose a new spot each time you use methylnaltrexone injection. Do not inject methylnaltrexone into a spot that is tender, bruised, red, or hard. Also, do not inject into areas with scars or stretch marks.

Ask your pharmacist or doctor for a copy of the manufacturer's information for the patient.

Are there OTHER USES for this medicine?

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

What SPECIAL PRECAUTIONS should I follow?

Before using methylnaltrexone injection,

  • tell your doctor and pharmacist if you are allergic to methylnaltrexone or any other medications.
  • tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take.
  • tell your doctor if you have a gastrointestinal obstruction (a blockage in your intestine). Your doctor will probably tell you not to use methylnaltrexone injection.
  • tell your doctor if you have or have ever had kidney disease.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while using methylnaltrexone injection, call your doctor.
  • you should know that most people have a bowel movement within a few minutes to a few hours after using methylnaltrexone injection. Make sure that you are close to a bathroom when you use this medication.

What SPECIAL DIETARY instructions should I follow?

Unless your doctor tells you otherwise, continue your normal diet.

What should I do IF I FORGET to take a dose?

This medication is usually used as needed. If your doctor has told you to use methylnaltrexone injection regularly, use the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not use a double dose to make up for a missed one.

What SIDE EFFECTS can this medicine cause?

Methylnaltrexone injection may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • stomach pain
  • gas
  • nausea
  • vomiting
  • diarrhea
  • dizziness

Some side effects can be serious. If you experience this symptom, stop using methylnaltrexone and call your doctor immediately:

  • severe diarrhea

Methylnaltrexone injection may cause other side effects. Call your doctor if you have any unusual problems while using this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online [at Web Site] or by phone [1-800-332-1088].

What should I know about STORAGE and DISPOSAL of this medication?

Keep this medication in the carton it came in, tightly closed, and out of reach of children. Store it at room temperature and do not freeze it. Protect it from light. If you draw methylnaltrexone up into a syringe but are not able to use it right away, the syringe may be stored at room temperature for up to 24 hours. The syringe does not need to be protected from light during this time. Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.

What should I do in case of OVERDOSE?

In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.

Symptoms of overdose may include:

  • dizziness, lightheadedness, and fainting when you get up too quickly from a lying position

What OTHER INFORMATION should I know?

Keep all appointments with your doctor.

Do not let anyone else use your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

AHFS® Consumer Medication Information. © Copyright, The American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

Selected Revisions: December 1, 2008.