Understanding Relistor and Opioid-Induced Constipation (OIC)
Opioid medications are effective for pain management but frequently cause a distressing side effect known as opioid-induced constipation (OIC). This condition affects a significant portion of patients, with studies indicating a prevalence between 41% and 87% in those taking opioids for chronic pain. Unlike regular constipation, OIC occurs because opioids bind to mu-opioid receptors in the gastrointestinal (GI) tract, slowing down gut motility.
Relistor, with the active ingredient methylnaltrexone bromide, is a prescription medication specifically designed to treat OIC. It belongs to a class of drugs called peripherally acting mu-opioid receptor antagonists (PAMORAs). Because methylnaltrexone is a quaternary amine, its ability to cross the blood-brain barrier is restricted. This allows it to block the effects of opioids in the gut without interfering with their pain-relieving effects on the central nervous system.
How Quickly Does Relistor Injection Work?
The primary concern for patients suffering from OIC is the speed of relief. Clinical studies consistently demonstrate that the subcutaneous (under the skin) injection of Relistor works rapidly.
- General Onset: Many patients can expect to have a bowel movement within 4 hours of receiving a Relistor injection.
- Rapid Response: A significant portion of responders experience relief much faster. In clinical trials involving patients with advanced illness, about half of those who had a bowel movement within 4 hours did so within 30 minutes of the injection.
- Clinical Evidence: In one study of patients with advanced illness, 48% of those treated with Relistor had a laxation within 4 hours of the first dose, compared to only 15% of those on placebo. A long-term study on patients with chronic non-cancer pain found that 34.1% of all injections administered resulted in a bowel movement within four hours.
Due to this rapid onset, patients are advised to be near a toilet after administering the medication.
Indications for Use
Relistor is approved for two main patient groups:
- Adults with Chronic Non-Cancer Pain: Both Relistor injections and tablets are indicated for the treatment of OIC in this population.
- Adults with Advanced Illness: The injection form is also indicated for treating OIC in adults with advanced illness or pain from active cancer who require escalating opioid doses for palliative care.
Dosage and Administration
Appropriate dosage and administration for Relistor depend on the patient's specific condition and should always be determined by a healthcare professional. Relistor is administered subcutaneously, and injection sites should be rotated. Patients should typically discuss their current laxative use with their doctor before starting Relistor, as adjustments may be necessary.
Comparison of Relistor Formulations
Relistor is available as both a subcutaneous injection and an oral tablet. While both are effective, their onset and usage differ.
| Feature | Relistor Injection | Relistor Tablets |
|---|---|---|
| Primary Use | Chronic non-cancer pain, Advanced illness/palliative care | Chronic non-cancer pain |
| Typical Onset | Within 30 minutes to 4 hours | May work within 4 hours, but generally not as rapid or reliable as the injection |
| Administration | Subcutaneous injection in upper arm, abdomen, or thigh | Taken with water on an empty stomach, typically 30 minutes before the first meal |
Potential Side Effects and Important Safety Information
As with any medication, Relistor has potential side effects. The most common are related to its effects on the gastrointestinal system.
Common Side Effects for the injection include:
- Abdominal pain
- Nausea
- Diarrhea
- Sweating (hyperhidrosis)
- Hot flush
- Gas (flatulence)
- Dizziness
Serious Side Effects:
- Gastrointestinal Perforation: There is a risk of a tear in the stomach or intestinal wall, especially in patients with known issues like peptic ulcers or diverticulitis. Patients should seek emergency help for severe, persistent, or worsening stomach pain.
- Severe Diarrhea: If severe or persistent diarrhea occurs, treatment should be stopped and a healthcare provider consulted.
- Opioid Withdrawal: Symptoms such as chills, sweating, anxiety, stomach pain, and yawning can occur. This risk is higher in patients with a compromised blood-brain barrier.
Relistor is contraindicated in patients with a known or suspected bowel obstruction.
Conclusion
Relistor injection offers a rapid and targeted solution for the management of opioid-induced constipation. By selectively blocking mu-opioid receptors in the gut, it effectively induces a bowel movement—often within 30 minutes to four hours—without compromising the analgesic effects of opioid therapy. This makes it a valuable tool for improving the quality of life for patients with chronic non-cancer pain and those in palliative care who suffer from OIC. Patients should always use this medication under the guidance of a healthcare provider to ensure it is appropriate for their specific condition and to monitor for any potential side effects.
For full prescribing information, you can refer to the official documentation on the FDA's website.
