SIDE EFFECTS: Stomach/abdominal pain may occur. If this effect lasts or gets worse, tell your doctor or pharmacist promptly. Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Stop taking methylnaltrexone and tell your doctor right away if you have diarrhea that doesn't stop. Opioid withdrawal symptoms may occur in some people. Tell your doctor right away if any of these withdrawal symptoms occur: sweating, chills, abdominal cramps, diarrhea, mental/mood changes (such as anxiety, confusion, extreme sleepiness, visual hallucinations), yawning. This drug may rarely cause a serious tear in the stomach or intestinal wall (perforation). Stop taking this medication and get medical help right away if any of these very serious side effects occur: severe stomach/abdominal pain that doesn't go away, fever, severe dizziness, fainting, severe nausea/vomiting. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

HOW TO USE: Read the Medication Guide provided by your pharmacist before you start taking methylnaltrexone and each time you get a refill. If you have any questions, ask your doctor or pharmacist. Take this medication by mouth on an empty stomach as directed by your doctor, usually once daily at least 30 minutes before your first meal of the day. The dosage is based on your medical condition and response to treatment. Ask your doctor if you should continue using your usual medications for constipation. This medication is used only for constipation caused by opioids. Stop taking methylnaltrexone when you stop using opioid pain medication unless otherwise directed by your doctor. Make sure you are close to a bathroom after taking this medication. This medication works quickly. Most people have a bowel movement within a few minutes to a few hours after taking this medication. Tell your doctor if your condition lasts or gets worse.

PRECAUTIONS: Before taking methylnaltrexone, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details. Before using this medication, tell your doctor or pharmacist your medical history, especially of: stomach/intestinal problems (such as blockage, ulcers, tumors, Crohn's disease, diverticulitis), kidney disease, liver disease. Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). Older adults may be at greater risk for diarrhea while taking this drug. During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor. It is unknown if this medication passes into breast milk. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center.