Proper Use

Drug information provided by: Merative, Micromedex®

Your doctor will prescribe your exact dose and tell you how often this medicine should be given. It is given as a shot under your skin (usually in the upper arm, abdomen or stomach, or thighs) each day for long-lasting pain not caused by cancer or every other day for patients with an advanced illness.

Methylnaltrexone injection 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 a Medication Guide and patient instructions. Read and follow these instructions carefully. Ask your doctor if you have any questions.

This medicine is available in three forms: a pre-filled syringe, a vial (glass container), or a vial and syringe with a retractable needle. You can use these dosage forms at home.

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, hard, or have scars or stretch marks.

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.

Stop taking other laxatives before starting treatment with methylnaltrexone. You should also stop using this medicine if you have stopped taking narcotic pain medicines.

Dosing

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 in patients with long-lasting non-cancer pain:
      • Adults—Dose is based on body weight and must be determined by your doctor. The dose is 12 milligrams (mg) injected under the skin once a day for at least 4 weeks (with narcotic pain medicines).
      • Children—Use and dose must be determined by your doctor.
    • For constipation caused by opioids in patients with severe illness:
      • Adults weighing more than 114 kilograms (kg)—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 for 4 months.
      • Adults weighing 62 to 114 kg—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 for 4 months.
      • Adults weighing 38 to less than 62 kg—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 for 4 months.
      • Adults weighing less than 38 kg—Dose is based on body weight and must be determined by your doctor. The dose is 0.15 mg per kg of body weight injected under the skin every other day for 4 months.
      • Children—Use and dose must be determined by your doctor.

Missed Dose

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.

Storage

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.

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Store unopened vials of this medicine at room temperature, away from heat and direct light. Do not freeze. An open vial of this medicine must be used right away.

Throw away used needles in a hard, closed container that the needles cannot poke through. Keep this container away from children and pets.

Portions of this document last updated: Feb. 01, 2024

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