Methylnaltrexone (Subcutaneous Route)
Original Article: http://www.mayoclinic.com/health/drug-information/DR602671
US Brand Names
Methylnaltrexone injection is used to treat constipation caused by pain medicines called opioids (narcotics) in patients with severe illness. This medicine is used when other medicines for constipation (laxatives) have not worked well.
This medicine is available only with your doctor's prescription.
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Appropriate studies have not been performed on the relationship of age to the effects of methylnaltrexone injection in the pediatric population. Safety and efficacy have not been established.
Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of methylnaltrexone injection in the elderly.
|All Trimesters||B||Animal studies have revealed no evidence of harm to the fetus, however, there are no adequate studies in pregnant women OR animal studies have shown an adverse effect, but adequate studies in pregnant women have failed to demonstrate a risk to the fetus.|
There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your healthcare professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.
Other Medical Problems
The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:
- Bowel blockage—Should not be used in patients with this condition.
- Kidney disease, severe—Use with caution. The effects may be increased because of slower removal of the medicine from the body.
- Ogilvie's syndrome (decreased movement of food in the intestines) or
- Stomach or intestinal ulcers or problems (e.g., cancer, perforation)—Use with caution. May make these conditions worse.
Your doctor will prescribe your exact dose and tell you how often it should be given. This medicine is given as a shot under your skin (usually in the upper arm, abdomen, or thighs). Methylnaltrexone may be given at home to patients who do not need to be in the hospital. If you are using this medicine at home, your doctor will teach you how to prepare and inject the medicine. Be sure that you understand exactly how the medicine is prepared and injected.
This medicine comes with patient instructions. Read and follow these instructions carefully. Ask your doctor if you have any questions.
You will be shown the body areas where this shot can be given. Use a different body area each time you give yourself a shot. Keep track of where you give each shot to make sure you change body areas. This will help prevent skin problems from the injections. Do not inject into skin areas that are bruised, red, tender, or hard.
Use a new needle and syringe each time you inject your medicine.
You might not use all of the medicine in each vial (glass container). Use each vial or syringe only one time. Do not save an open vial or syringe. If the medicine in the vial or syringe has changed color, or if you see particles in it, do not use it.
The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For injection dosage form:
- For constipation caused by opioids:
- Adults weighing more than 114 kilograms (more than 251 pounds)—Dose is based on body weight and must be determined by your doctor. The dose is 0.15 milligram (mg) per kilogram (kg) of body weight injected under the skin every other day.
- Adults weighing 62 to 114 kg (136 to 251 pounds)—Dose is based on body weight and must be determined by your doctor. The dose is usually 12 mg injected under the skin every other day.
- Adults weighing 38 to less than 62 kg (84 to less than 136 pounds)—Dose is based on body weight and must be determined by your doctor. The dose is usually 8 mg injected under the skin every other day.
- Adults weighing less than 38 kg (less than 84 pounds)—Dose is based on body weight and must be determined by your doctor. The dose is 0.15 milligram (mg) per kilogram (kg) of body weight injected under the skin every other day.
- Children—Use and dose must be determined by your doctor.
- For constipation caused by opioids:
If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
Store unopened vials of this medicine at room temperature, away from heat and direct light. Do not freeze. An open vial of medicine must be used right away.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Throw away used needles in a hard, closed container that the needles cannot poke through. Keep this container away from children and pets.
It is very important that your doctor check your progress at regular visits. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it.
If severe or persistent (non-stop) diarrhea occurs while using methylnaltrexone injection, stop using this medicine and check with your doctor right away.
Stop using this medicine and check with your doctor right away if you have severe abdominal or stomach pain or cramps; bloody, black, or tarry stools; heartburn; indigestion; nausea; or vomiting of material that looks like coffee grounds. These could be symptoms of a serious bowel problem called intestinal perforation.
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:More common
- Increased sweating
- Bloody, black, or tarry stools
- Severe abdominal or stomach pain, cramping, or burning
- Trouble breathing
- Vomiting of material that looks like coffee grounds, severe and continuing
Get emergency help immediately if any of the following symptoms of overdose occur:Symptoms of overdose
- Cold sweats
- Dizziness, faintness, or lightheadedness when getting up from lying or sitting position
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:More common
- Excess air or gas in the stomach or intestines
- Full feeling
- Passing gas
- Stomach pain
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.