Methylnaltrexone injection is used to treat constipation caused by opioid (narcotic) pain medications in people with chronic (on-going) pain that is not caused by cancer but may be related to a previous cancer or cancer treatment. It is also used to treat constipation caused by opioid pain medications in people with an advanced illness or for active cancer pain. 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.

Methylnaltrexone injection comes as a solution (liquid) to inject subcutaneously (under the skin). When used to treat constipation caused by opioid medications in people with chronic (on-going) pain that is not caused by cancer, it is usually injected once a day. When used to treat constipation caused by opioid medications in people with an advanced illness or cancer, 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 injection is to be used by people who are taking opioid (narcotic) medications. Talk to your doctor if you change how much or how often you take your opioid medications. If you stop taking opioid medications, you should stop using methylnaltrexone injection as well.

You should stop taking other laxative medications when you start using methylnaltrexone injection. However, be sure to let your doctor know if methylnaltrexone injection does not work for you after using it for 3 days. Your doctor may tell you to take other laxative medication(s).

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 prefilled syringes and in vials to use with disposable syringes. The vial 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 prefilled syringes, vials and disposable syringes only once. Discard the prefilled syringe, or vial and syringe after one use, even if they are not empty. They should be disposed of in a puncture-resistant container, out of the reach of children. Do not discard a filled puncture resistant container into the household trash or recycling. Talk to your doctor or pharmacist about how to throw away the puncture-resistant container.

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.

Your doctor or pharmacist will give you the manufacturer’s patient information sheet (Medication Guide) when you begin treatment with methylnaltrexone injection and each time you refill your prescription. Read the information carefully and ask your doctor or pharmacist if you have any questions. You can also visit the Food and Drug Administration (FDA) website (http://www.fda.gov/Drugs/DrugSafety/ucm085729.htm) to obtain the Medication Guide.

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

Before using methylnaltrexone injection,

• tell your doctor and pharmacist if you are allergic to methylnaltrexone, any other medications, or any of the ingredients in methylnaltrexone injection. Ask your pharmacist for a list of the ingredients.
• tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: alvimopan (Entereg), naldemedine (Symproic), naloxegol (Movantik), naloxone (Evzio, Narcan, in Bunavail, Suboxone, Zubsolv) or naltrexone (Vivitrol, in Contrave, Embeda). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• tell your doctor if you have or have ever had 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 stomach or bowel problems including stomach ulcer (sores in the lining of the stomach), cancer of the stomach or bowel, Crohn’s disease (a condition in which the body attacks the lining of the digestive tract, causing pain, diarrhea, weight loss, and fever), diverticulitis (small pouches in the lining of the large intestine that can become inflamed), Ogilvie’s syndrome (a condition in which there is a bulge in the bowel), or kidney or liver disease.
• tell your doctor if you are pregnant or plan to become pregnant. If you become pregnant while using methylnaltrexone injection, call your doctor. If you receive methylnaltrexone during your pregnancy, your baby may experience opioid withdrawal symptoms.
• tell your doctor if you are breastfeeding. Do not breastfeed while you are using methylnaltrexone injection.
• 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.

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

For certain people this medication is used as needed, but for other patients this medication is used daily. 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.

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

• abdominal pain
• gas
• nausea
• vomiting
• diarrhea
• dizziness
• sweating
• chills
• anxiety
• yawning
• tremor
• hot flushes

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

• severe diarrhea
• severe abdominal pain

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 (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

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.

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA’s Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

Symptoms of overdose may include the following:

• dizziness, lightheadedness, and fainting when you get up too quickly from a lying position
• chills
• sweating
• runny nose
• diarrhea
• abdominal pain
• anxiety
• yawning
• decrease in the pain relieving effects of the opioid medication

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.

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