The Web Health



Generic name: methylnaltrexone (oral/injection) [METh-IL-nal-TREX-own]
Drug Class:Peripheral receptor antagonists

What is Relistor?

Relistor blocks opioid medication. Sometimes an opioid is called a drug.Relistor helps reduce constipation that is caused by opioid medication. Methylnaltrexone reduces constipation while maintaining the pain-relieving effect of opioids.Adults who are using opioid medication to treat chronic pain but not cancer-related pain should take Relistor.Adults with advanced illnesses who are receiving palliative treatment (treatments to relieve pain and improve quality-of-life during a serious illness) can also use Relistor.This medication is often prescribed after trying laxatives without success to treat constipation.

Side effects of Relistor

If you experience any of the following symptoms of an allergic reaction: hives, difficulty breathing, swelling of your lips, face, tongue, or throat, or hives, seek emergency medical attention.Methylnaltrexone can cause a perforation in your stomach or intestines. If you experience severe stomach pain that is getting worse or won't go away, stop using the medicine immediately and seek medical attention.

Relistor should be stopped immediately, and you need to consult your doctor if:

  • Severe or ongoing diarrhea;
  • Feeling dizzy or as if you could pass out is a sign of extreme
  • Bloody or tarry stool, vomiting blood, or vomit that looks like coffee grounds
  • Nausea or vomiting that is new or worsening;
  • Symptoms of opioid medicine withdrawal: anxiety, sweating, and chills

Side effects of Relistor include:

  • Bloating, stomach pain,
  • Mild nausea or diarrhea
  • Muscle spasms;
  • Dizziness, tremors, feeling anxious;
  • Runny nose;
  • Heat flashes, chills, or sweating

There may be other side effects. For medical advice on side effects, call your doctor. The FDA can be contacted at 1-800-FDA-1088 to report side effects.


Relistor can cause a perforation in your stomach or intestines. If you experience severe stomach pain, stop using the medicine immediately and seek medical attention.While using this drug, you may feel symptoms such as anxiety or diarrhea.If you experience severe or persistent diarrhea, stop using Relistor immediately and consult your doctor.

Before you take this drug

A Relistor should not be used if your stomach or intestines are blocked.

Tell your doctor about any of the following to ensure that this medicine will be safe for you:

  • A stomach ulcer
  • Perforation in the stomach or intestines (a hole or tear);
  • Kidney disease
  • Liver disease
  • Colitis and other intestinal disorders such as Crohn’s disease, diverticulitis, or Ogilvie’s syndrome.

Inform your doctor that you are expecting. Your newborn may experience withdrawal symptoms if you take Relistor during pregnancy.Breastfeeding is not recommended while taking methylnaltrexone.Anyone younger than 18 is not allowed to use Relistor.

How to take Relistor?

Relistor should be taken exactly as prescribed by your physician. Read all the instructions on the prescription label.Stop using laxatives before you start using methylnaltrexone.The Relistor will produce a bowel motion within 30 minutes. When using this medication, be sure to use it near a toilet.Take Relistor tablets at least 30 minutes prior to your first meal.Take the tablet with a glass of full water.A Relistor is injected into the skin. Your healthcare provider may give you your first dose and teach you how to use the medication properly.Please read and follow all instructions for use that come with your medication. Ask your pharmacist or doctor if you don't understand.You will be shown by your healthcare provider where to inject Relistor. Each time you inject, use a new place. Don't inject in the same spot twicePrepare an injection only when you are ready to administer the drug. If the medicine is cloudy, has changed color, or contains particles, do not use it. For new medicine, call your pharmacist.Each prefilled syringe or injection vial is only for one-time use. After one use, throw it out, even if the medicine is still inside.Use this medication no more than once every 24 hours.If your symptoms don't improve within 3 days, call your doctor. After 3 days, you may use other laxatives.Store the medicine at room temperature, away from moisture, light, and heat. Do not freeze. Do not freeze.Only use a needle or syringe once, and then store them in a "sharps container" that is puncture-proof. Be sure to follow local or state laws on how to properly dispose of the container. Keep the container out of reach of pets and children.Relistor should be stopped after you have stopped taking opioid pain medications.

Details on dosage

Usual Adult Dose for Constipation—Drug-Induced:

Constipation caused by opioids in patients with non-cancer chronic pain
Oral 450 mg once daily in the morning
Parenteral: 12 mg once daily subcutaneously
Prior to initiating, discontinue any laxative maintenance therapy. Laxatives may be used if the response is not optimal after 3 days.
Patients should be in close proximity to the bathroom after this medication is administered.
To avoid any adverse reactions, re-evaluate the need for this medication when changing your opioid regimen.
Patients with advanced illnesses may experience constipation caused by opioids.
Parenteral: weight-based dosing. Administer subcutaneously as needed every other day, but not more than once in a 24-hour period.
Less than 38 kg: 0.15 mg/kg
38 kg to less than 62 kg: 8 ml (0.4 mg)
Subcutaneously: 12 mg (0.6 mL).
Subcutaneously: More than 114 kg (0.15 mg/kg)
Comment: To calculate the injection volume of patients who weigh less than 38 kg or more than 112 kg, multiply the weight by 0.0075 kg and round to the nearest 0.01 mL.
When laxative therapy is not sufficient to treat opioid-induced constipation, it can be used in adults with chronic pain that is not cancerous or who have advanced illnesses and are receiving palliative treatment.

What happens if I miss the dose?

Take the missed dose as soon as you remember. Skip the missed dosage if your next dose is scheduled soon.Use this medicine no more than once every 24 hours.

What happens if I overdose?

For poison assistance, call 1-800-222-1222 or get immediate medical help.Withdrawal can be triggered by an overdose of methylnaltrexone when you are taking an opioid medication. Common withdrawal symptoms include yawning and irritability.

What should be avoided?

Use only the laxatives prescribed by your doctor.

Interaction with other drug

Other drugs, such as vitamins and herbal remedies, may also interact with methylnaltrexone. Inform your doctor of all the medicines you are taking, as well as any new ones.