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Active Substance: methylnaltrexone bromide
Common Name: methylnaltrexone bromide
ATC Code: A06AH01
Marketing Authorisation Holder: PharmaSwiss Ceska Republika s.r.o
Active Substance: methylnaltrexone bromide
Status: Authorised
Authorisation Date: 2008-07-02
Therapeutic Area: Constipation Opioid-Related Disorders
Pharmacotherapeutic Group: Laxatives

Therapeutic Indication

Treatment of opioid-induced constipation in advanced-illness patients who are receiving palliative care when response to usual laxative therapy has not been sufficient.

What is Relistor?

Relistor is a solution for injection that contains the active substance methylnaltrexone bromide. It is available in vials or in prefilled syringes.

What is Relistor used for?

Relistor is used to treat the constipation caused by opioids (painkillers that are related to morphine and used to treat moderate to severe pain due to long-term or advanced diseases) in adults (aged 18 years or over) when the response to laxative medicines has not been sufficient.

The medicine can only be obtained with a prescription.

How is Relistor used?

In patients who are receiving palliative care (treatment of the symptoms of a serious disease that is not intended to lead to cure), Relistor is given as an injection under the skin, once every two days, in addition to the usual laxative medicines. The dose depends on the patient’s body weight and should be reduced in patients who have severe problems with their kidneys. In patients not on palliative care, Relistor is given as an injection under the skin at a dose of 12 mg once a day, for 4 to 7 days per week; treatment with usual laxatives should be stopped when starting Relistor.

The dose of Relistor should be reduced in patients who have severe kidney problems. Relistor is not recommended for patients who have very severe kidney problems that require dialysis (a blood clearance technique).

Patients can inject Relistor themselves once they have been trained appropriately.

How does Relistor work?

Opioids relieve pain by attaching to ‘opioid receptors’ in the brain and spinal cord. These receptors are also found in the gut. When opioids attach to the gut receptors, the mobility of the gut is reduced, leading to constipation.

The active substance in Relistor, methylnaltrexone bromide, is a ‘mu-opioid receptor antagonist’. This means that it blocks a specific type of opioid receptor called the ‘mu-opioid receptor’. Methylnaltrexone bromide is derived from naltrexone, a well-known substance that is used to block the action of opioids. Methylnaltrexone bromide is less able to enter the brain than naltrexone, meaning that it blocks the mu-opioid receptors in the gut but not in the brain. By blocking these receptors, Relistor reduces the constipation due to opioids, but does not interfere with their painkilling effects.

How has Relistor been studied?

Relistor has been compared with placebo (a dummy treatment) in two main studies involving a total of 288 patients with an advanced illness and constipation caused by opioids. The main measure of effectiveness in both studies was the number of patients whose bowels opened within four hours of the first dose. The second study also looked at the number of patients whose bowels opened at least twice within four hours of the first four doses.

Relistor has also been compared with placebo in 496 patients with constipation caused by opioids, but no advanced illness. The main measures of effectiveness were the number of patients whose bowels opened within four hours of the first dose, and the percentage of injections that were successful in producing a bowel movement.

What benefit has Relistor shown during the studies?

Relistor was more effective than placebo in stimulating the bowels to open in patients with an advanced illness. Looking at the results of the two studies taken together, 55% of the patients receiving Relistor opened their bowels within four hours after the first injection (91 out of 165), compared with 15% of the patients receiving placebo (18 out of 123). In the second study, 52% of the patients receiving Relistor opened their bowels at least twice within four hours of the first four doses (32 out of 62), compared with 8% of those receiving placebo (6 out of 71).

In the third study, 34% of patients (102 out of 298) with no advanced illness opened their bowels within four hours after the first injection, compared with 10% of those receiving placebo (16 out of 162). The percentages of successful injections for the two groups were around 30% and 9%, respectively.

What is the risk associated with Relistor?

The most common side effects with Relistor (seen in more than 1 patient in 10) are abdominal pain (stomach ache), nausea (feeling sick), diarrhoea and flatulence (gas). For the full list of all side effects reported with Relistor, see the package leaflet.

Relistor must not be used in patients whose bowel is blocked or who have a condition that needs immediate bowel surgery. For the full list of restrictions, see the package leaflet.

Why has Relistor been approved?

The CHMP decided that Relistor’s benefits are greater than its risks and recommended that it be given marketing authorisation.

What measures are being taken to ensure the safe and effective use of Relistor?

A risk management plan has been developed to ensure that Relistor is used as safely as possible. Based on this plan, safety information has been included in the summary of product characteristics and the package leaflet for Relistor, including the appropriate precautions to be followed by healthcare professionals and patients.

Other information about Relistor

The European Commission granted a marketing authorisation valid throughout the European Union for Relistor on 2 July 2008.

For more information about treatment with Relistor, read the package leaflet (also part of the EPAR) or contact your doctor or pharmacist.

Source: European Medicines Agency

Disclaimer: Every effort has been made to ensure that the information provided here is accurate, up-to-date and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. This information has been compiled for use by healthcare practitioners and consumers in the United States. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate that the drug or combination is safe, effective or appropriate for any given patient. If you have questions about the substances you are taking, check with your doctor, nurse or pharmacist.