Movantik (naloxegol) is a prescription medication used to treat opioid-induced constipation (OIC) in adults with chronic non-cancer pain. It belongs to a class of drugs designed to reverse the constipation caused by opioid pain medications without reducing their ability to control pain.
How Opioid-Induced Constipation Works
Opioids relieve pain by binding to receptors in the brain, but the same type of receptor also exists throughout the digestive tract. When opioids bind to gut receptors, they slow down the muscle contractions that move food and waste through the intestines. The result is constipation that doesn’t respond well to typical remedies like fiber supplements or over-the-counter laxatives. This is one of the most common and persistent side effects of long-term opioid use, and unlike other opioid side effects, the body rarely adjusts to it over time.
How Movantik Relieves Constipation
Movantik works by blocking opioid receptors specifically in the gut wall. Its chemical structure includes a modification (called PEGylation) that prevents it from crossing into the brain in meaningful amounts. This selectivity is substantial: naloxegol shows more than 6,000-fold preference for opioid receptors in the body’s periphery over those in the central nervous system. That means it can restore normal bowel function without interfering with the pain relief your opioid medication provides.
This makes Movantik fundamentally different from general opioid-blocking drugs like naloxone, which would reverse both the constipation and the pain control.
How to Take It
The recommended dose is 25 mg taken once daily in the morning. You should take it on an empty stomach, either one hour before your first meal or two hours after eating. If you have trouble tolerating the 25 mg dose, your prescriber may lower it to 12.5 mg daily. People with reduced kidney function (creatinine clearance below 60 mL/min) typically start at the lower 12.5 mg dose, with the option to increase if tolerated.
Movantik is meant to be used while you’re still taking opioid medications. If you stop your opioid treatment, there’s no reason to continue taking Movantik.
Common Side Effects
The most frequently reported side effects in clinical trials, each occurring in 3% or more of patients, were abdominal pain, diarrhea, nausea, gas, vomiting, and headache. These are largely gut-related, which makes sense given where the drug acts. In studies testing a higher dose of 50 mg (twice the recommended amount), these digestive side effects occurred more often and were more intense.
If you experience severe abdominal pain or diarrhea, that may be a signal to stop taking the medication and contact your prescriber.
Opioid Withdrawal Risk
Although Movantik is designed to stay out of the brain, there’s a small risk of opioid withdrawal symptoms in certain situations. This risk increases if you take Movantik alongside another opioid-blocking medication, or if you have a condition that compromises the blood-brain barrier, such as brain tumors or certain vascular conditions affecting the central nervous system. Withdrawal symptoms can include sweating, chills, diarrhea, abdominal pain, anxiety, irritability, and yawning.
Drug Interactions to Know About
Movantik is broken down in the body by a specific liver enzyme, and certain medications or foods that interfere with that enzyme can cause dangerously high levels of the drug in your system. This matters because elevated levels could push enough of the drug past the blood-brain barrier to trigger opioid withdrawal.
Several interactions are important:
- Strong enzyme inhibitors like ketoconazole, itraconazole, and clarithromycin are contraindicated entirely. You cannot take Movantik with these drugs.
- Moderate enzyme inhibitors like diltiazem, erythromycin, and verapamil should be avoided when possible. If your prescriber determines the combination is necessary, the Movantik dose is reduced to 12.5 mg.
- Grapefruit and grapefruit juice also inhibit the same enzyme and should be avoided during treatment.
- Other opioid-blocking medications should not be combined with Movantik due to increased withdrawal risk.
Who Should Not Take Movantik
Movantik is specifically approved for adults with chronic non-cancer pain. The indication does extend to patients whose chronic pain is related to a prior cancer diagnosis or past cancer treatment, as long as they don’t need frequent increases in their opioid dose (such as weekly escalations). It is not intended for people actively being treated for cancer pain that requires ongoing dose adjustments.
People with known or suspected gastrointestinal obstruction should not take Movantik. Caution is also warranted for anyone at increased risk of bowel perforation, including those with conditions that weaken the intestinal wall such as peptic ulcers. Additional caution applies to patients taking methadone or those with cardiovascular disease.