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Are strong painkillers causing constipation? Let's learn about methylnaltrexone pills

Are strong painkillers causing constipation? Let's learn about methylnaltrexone pills

Sometimes, after surgery or due to a serious medical condition, doctors give us strong painkillers. We call these 'Opioids'. These reduce the pain a lot, but they also come with a small problem. That is constipation, or simply put, difficulty going to the toilet. When you can't go to the toilet for days and have a full stomach and feel uncomfortable, that is also a big problem. So, today we are talking about a special medicine that doctors recommend in times like these.

What kind of medicine is Methylnaltrexone?

Simply put, methylnaltrexone is a pill that is given to treat constipation caused by the strong painkillers (Opioids) you are taking. You may sometimes find it under the brand name ``Relistor``.

Imagine that the opioid painkillers you take are slowing down your bowel movements a bit. It's like traffic jams. This is why the bowel movement process is slowed down. This is where Methylnaltrexone comes in.

This drug does a really cool thing. It goes straight to your intestines and "blocks" the effect of that painkiller. It tells your intestines, "Okay, now you can do your job." But the most important thing is, this drug doesn't interfere with the brain's ability to control pain. That means it only helps relieve constipation while the pain continues to decrease .

Things to tell your doctor before taking medication

Before starting this medication, it is very important to give your doctor a complete description of your health condition. This is because only then can he or she be able to determine exactly whether this medication is right for you and how it should be given.

Things to tell your doctor
Medical conditions

  • If you have kidney disease.
  • If you have any liver disease.
  • If you have other stomach or intestinal problems, such as an ulcer or blockage.

AllergiesTell your doctor if you are allergic to methylnaltrexone or any other medicine, food, or dye.
Special occasions

  • If you are pregnant or trying to get pregnant.
  • If you are a breastfeeding mother.

How should I use this medicine?

The method of using this medicine is very simple, but it is very important to follow the instructions exactly.

  • Take this pill with a glass of water .
  • For best results, take this medicine on an empty stomach , which means it is best to take it about 30 minutes before a meal .
  • Take the medicine exactly as prescribed by your doctor, at the right time . Never take more than the prescribed amount.
  • When you are given this medicine, you may receive a special information leaflet (MedGuide) with it. It contains important information about this medicine, so read it carefully each time.
  • If this medicine is given to children, you should talk to the medical team about it and get special advice.

Warning: If you have any suspicion that you have taken too much of this medicine, immediately call the National Poisons Information Centre at the Colombo National Hospital , or go to the nearest Emergency Treatment Unit (ETU) . Also, remember, this medicine has been prescribed for you only. Never share it with anyone else.

What do you do if you miss a medication appointment?

If you miss a dose, take it as soon as you remember. But if it is almost time for your next dose, skip the missed dose and take the next dose at the scheduled time. Never take a double dose.

Be careful of these things when taking medicine.

It's a good idea to pay a little attention to your body while taking this medicine.

  • Stay near a bathroom: This may sound a little funny, but it's really important. After taking this medicine, you may need to go to the bathroom quickly , maybe within 30 minutes or a few hours. So be prepared for that.
  • Drowsiness or dizziness: This medication may make some people feel drowsy or dizzy. Therefore , avoid driving or operating machinery until you know how this medication affects you.Stay away from. Especially if you are elderly, be careful when getting up from a sitting position and when sitting down from a standing position.
  • Avoid alcohol: Alcohol can interfere with the effectiveness of this medication, so it is best to avoid alcohol completely while taking this medication.

What are the possible side effects?

Like any medicine, methylnaltrexone can cause some side effects. Some of these are serious, while others are common.

Type of side effect Symptoms
Serious side effects that should be reported to your doctor immediately
Allergic reactions Skin rash, itching, swelling of the face, lips, tongue or throat.
Severe stomach pain A severe stomach ache that doesn't go away and gets worse.
Side effects that usually do not require medical attention (but should be reported to the doctor if they persist)
Other features

  • Chills
  • Indigestion/Diarrhea
  • Excessive sweating
  • Headache
  • Nausea
  • General stomach pain

If you experience any other unusual symptoms not mentioned in this list, talk to your doctor about them as well.

Can there be problems with other medications?

Yes, some medications can interact with Methylnaltrexone. In particular, medications like `Alvimopan`, `Naloxone`, and `Naltrexone` may interact with it.

It is very important to tell your doctor about all the medications you take, not just those prescribed by a doctor, but also painkillers, vitamins, traditional medicines, herbal products, or supplements you buy from a pharmacy.

Also, if you smoke or drink alcohol, inform your doctor about that as well.

How to store the medicine?

Keep this medicine out of the reach of children and pets . Store at room temperature (between 20-25 degrees Celsius). Dispose of expired medicine safely.

Take-Home Message

  • Methylnaltrexone is a special medication that is only given for constipation caused by strong painkillers (Opioids).
  • Always take this medicine on an empty stomach, as prescribed by your doctor.
  • Tell your doctor about all your medical conditions and all other medications you are taking.
  • Be prepared for the need to go to the bathroom quickly after taking the medicine.
  • If you experience severe stomach pain or allergic symptoms, seek medical advice immediately.
  • If you have any questions about this medicine, don't hesitate to ask your doctor.

Methylnaltrexone, Relistor, Opioid-induced constipation, Constipation, Painkiller Side Effects, Stomach Upset, Medication Information
⚠️ Important: The medical articles and information on Nirogi Lanka are for general awareness only, and are by no means a substitute for professional medical advice, diagnosis, or treatment. For any medical problem you have, consult a qualified physician immediately.

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Are strong painkillers causing constipation? Let's learn about methylnaltrexone pills
MedicationsMay 26, 2026

Are strong painkillers causing constipation? Let's learn about methylnaltrexone pills

Sometimes, after surgery or due to a serious medical condition, doctors give us strong painkillers. We call these 'Opioids'. These reduce the pain a lot, but they also come with a small problem. That is constipation, or simply put, difficulty going to the toilet. When you can't go to the toilet for days and have a full stomach and feel uncomfortable, that is also a big problem. So, today we are talking about a special medicine that doctors recommend in times like these.

What kind of medicine is Methylnaltrexone?

Simply put, methylnaltrexone is a pill that is given to treat constipation caused by the strong painkillers (Opioids) you are taking. You may sometimes find it under the brand name ``Relistor``.

Imagine that the opioid painkillers you take are slowing down your bowel movements a bit. It's like traffic jams. This is why the bowel movement process is slowed down. This is where Methylnaltrexone comes in.

This drug does a really cool thing. It goes straight to your intestines and "blocks" the effect of that painkiller. It tells your intestines, "Okay, now you can do your job." But the most important thing is, this drug doesn't interfere with the brain's ability to control pain. That means it only helps relieve constipation while the pain continues to decrease .

Things to tell your doctor before taking medication

Before starting this medication, it is very important to give your doctor a complete description of your health condition. This is because only then can he or she be able to determine exactly whether this medication is right for you and how it should be given.

Things to tell your doctor
Medical conditions

  • If you have kidney disease.
  • If you have any liver disease.
  • If you have other stomach or intestinal problems, such as an ulcer or blockage.

AllergiesTell your doctor if you are allergic to methylnaltrexone or any other medicine, food, or dye.
Special occasions

  • If you are pregnant or trying to get pregnant.
  • If you are a breastfeeding mother.

How should I use this medicine?

The method of using this medicine is very simple, but it is very important to follow the instructions exactly.

  • Take this pill with a glass of water .
  • For best results, take this medicine on an empty stomach , which means it is best to take it about 30 minutes before a meal .
  • Take the medicine exactly as prescribed by your doctor, at the right time . Never take more than the prescribed amount.
  • When you are given this medicine, you may receive a special information leaflet (MedGuide) with it. It contains important information about this medicine, so read it carefully each time.
  • If this medicine is given to children, you should talk to the medical team about it and get special advice.

Warning: If you have any suspicion that you have taken too much of this medicine, immediately call the National Poisons Information Centre at the Colombo National Hospital , or go to the nearest Emergency Treatment Unit (ETU) . Also, remember, this medicine has been prescribed for you only. Never share it with anyone else.

What do you do if you miss a medication appointment?

If you miss a dose, take it as soon as you remember. But if it is almost time for your next dose, skip the missed dose and take the next dose at the scheduled time. Never take a double dose.

Be careful of these things when taking medicine.

It's a good idea to pay a little attention to your body while taking this medicine.

  • Stay near a bathroom: This may sound a little funny, but it's really important. After taking this medicine, you may need to go to the bathroom quickly , maybe within 30 minutes or a few hours. So be prepared for that.
  • Drowsiness or dizziness: This medication may make some people feel drowsy or dizzy. Therefore , avoid driving or operating machinery until you know how this medication affects you.Stay away from. Especially if you are elderly, be careful when getting up from a sitting position and when sitting down from a standing position.
  • Avoid alcohol: Alcohol can interfere with the effectiveness of this medication, so it is best to avoid alcohol completely while taking this medication.

What are the possible side effects?

Like any medicine, methylnaltrexone can cause some side effects. Some of these are serious, while others are common.

Type of side effect Symptoms
Serious side effects that should be reported to your doctor immediately
Allergic reactions Skin rash, itching, swelling of the face, lips, tongue or throat.
Severe stomach pain A severe stomach ache that doesn't go away and gets worse.
Side effects that usually do not require medical attention (but should be reported to the doctor if they persist)
Other features

  • Chills
  • Indigestion/Diarrhea
  • Excessive sweating
  • Headache
  • Nausea
  • General stomach pain

If you experience any other unusual symptoms not mentioned in this list, talk to your doctor about them as well.

Can there be problems with other medications?

Yes, some medications can interact with Methylnaltrexone. In particular, medications like `Alvimopan`, `Naloxone`, and `Naltrexone` may interact with it.

It is very important to tell your doctor about all the medications you take, not just those prescribed by a doctor, but also painkillers, vitamins, traditional medicines, herbal products, or supplements you buy from a pharmacy.

Also, if you smoke or drink alcohol, inform your doctor about that as well.

How to store the medicine?

Keep this medicine out of the reach of children and pets . Store at room temperature (between 20-25 degrees Celsius). Dispose of expired medicine safely.

Take-Home Message

  • Methylnaltrexone is a special medication that is only given for constipation caused by strong painkillers (Opioids).
  • Always take this medicine on an empty stomach, as prescribed by your doctor.
  • Tell your doctor about all your medical conditions and all other medications you are taking.
  • Be prepared for the need to go to the bathroom quickly after taking the medicine.
  • If you experience severe stomach pain or allergic symptoms, seek medical advice immediately.
  • If you have any questions about this medicine, don't hesitate to ask your doctor.

Methylnaltrexone, Relistor, Opioid-induced constipation, Constipation, Painkiller Side Effects, Stomach Upset, Medication Information
⚠️ Important: The medical articles and information on Nirogi Lanka are for general awareness only, and are by no means a substitute for professional medical advice, diagnosis, or treatment. For any medical problem you have, consult a qualified physician immediately.

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