What is this medication for?
Methylnaltrexone belongs to a group of medications known as opioid receptor antagonists (opioid receptor blockers). It is used to treat constipation caused by prescription pain medications called opioids, also know as narcotic analgesics (e.g., codeine, morphine, hydromorphone), for people with serious illnesses who are receiving narcotic analgesics for relief of pain. If laxatives are not working, methylnaltrexone is used to help produce a bowel movement.
It works by preventing opioid medications from binding to the opioid receptors in the intestinal tract. It does not reduce the pain-relieving effects of opioid pain medications. For most people, methylnaltrexone usually works within 30 minutes, but it may take longer. Make sure you are close to toilet facilities once you take the medication.
Your doctor may have suggested this medication for conditions other than those listed here. As well, some forms of this medication may not be used for all of the conditions discussed here. If you are not sure why you are being given this medication, speak to your doctor. Do not stop using this medication without consulting your doctor.
Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to use this medication if their doctor has not prescribed it.
What form(s) does this medication come in?
Relistor is available as:
Some medications may have other generic brands available. Always ask your doctor or pharmacist about the safety of switching between brands of the same medication.
How should I use this medication?
The usual recommended dose of methylnaltrexone is based on body weight and is injected once every other day under the skin (subcutaneous injection) of the upper arm, abdomen, or thigh.
For people who weigh 84 lbs to less than 136 lbs, the usual dose of methylnaltrexone is 8 mg.
For people who weigh 136 lbs to 251 lbs, the usual dose of methylnaltrexone is 12 mg.
For people who weigh less than 84 lbs or more than 251 lbs, your doctor will calculate the dose of this medication that is appropriate for you.
If you (or a family member or friend) are injecting this medication, a health care professional will show you how to inject the medication properly. Read the instructions provided in the package insert carefully. If you are not sure how to use this medication, contact your doctor or pharmacist.
It is recommended that you use a different site for each injection. Do not inject into skin that is tender, red, bruised, or hard, or has stretch marks or scars. If you are self-injecting, do not inject into the upper arm. An injection into the upper arm should be done by another person. You should be sitting or lying down when you receive this medication. Do not stand up quickly after the injection as you may feel dizzy.
If you do not notice improvement within a week, contact your doctor.
Do not take this medication if you are no longer taking a narcotic analgesic.
Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are using the medication without consulting your doctor.
It is important to use this medication exactly as prescribed by your doctor. If you miss a dose, inject it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not inject a double dose to make up for a missed one. Do not take more than 1 dose in a 24-hour period. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.
Store this medication at room temperature, protect it from light, and keep it out of the reach of children. Do not allow it to freeze.
Who should NOT take this medication?
Do not use this medication if you:
- are allergic to methylnaltrexone or any ingredients of this medication
- have or may have a blockage of the intestines (symptoms of intestine blockage include vomiting, stomach pain, and swelling of the stomach)