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Methylnaltrexone bromide parenteral


Solution for injection containing methylnaltrexone bromide

Drugs List

  • methylnaltrexone bromide 12mg/0.6ml injection
  • RELISTOR 12mg/0.6ml injection
  • Therapeutic Indications


    Treatment of opioid-induced constipation in patients with chronic pain
    Treatment of opioid-induced constipation in terminally ill patients



    Opioid-induced constipation in adult patients with chronic pain (except palliative care patients with advanced illness)
    12 mg (0.6 ml) subcutaneously, as needed, given as at least 4 doses weekly, up to once daily (7 doses weekly).

    Treatment with usual laxatives should be stopped when commencing treatment with methylnaltrexone bromide.

    Opioid-induced constipation in adult patients with advanced illness (palliative care patients)
    Body weight 38 to 62 kg: 8 mg (0.4 ml)
    Body weight 62 to 114 kg: 12 mg (0.6 ml)

    The usual administration schedule is one single dose to be injected subcutaneously every other day.

    Patients may receive two consecutive doses 24 hours apart, only when there has been no bowel response to the dose on the preceding day. Likewise, the doses can be given at longer intervals, depending on the clinical need.

    Where patient's body weight falls outside of the above ranges, they should be dosed at 0.15 mg/kg. The injection volume should be calculated as follows:

    Dose (ml) = patient weight (kg) x 0.0075


    (See 'Dosage; Adult)

    Patients with Renal Impairment

    The dose should be reduced in patients with severe renal impairment (creatinine clearance less than 30 ml/minute) as follows:

    Body weight 62 to 114 kg
    8 mg (0.4 ml) on alternate days.

    Body weight outside the 62 to 114 kg range
    0.075 mg/kg on alternate days.


    For subcutaneous injection.

    Can be injected without regard to food.

    The upper legs, upper arms and the abdomen are recommended as the injection sites and these should be rotated regularly. Areas where the skin is tender, bruised, red, hard, has scars or stretch marks should be avoided.


    Children under 18 years
    Predisposition to gastrointestinal obstruction
    Acute surgical abdomen
    End stage renal disease
    Mechanical gastrointestinal obstruction
    Severe hepatic impairment - Child-Pugh score greater than or equal to 10

    Precautions and Warnings

    Faecal impaction
    Gastric mucosa lesion
    Gastrointestinal diverticula
    Renal impairment - creatinine clearance below 30 ml/minute

    Reduce dose in patients with creatinine clearance below 30ml/min
    Advise patient dizziness may affect ability to drive or operate machinery
    Rotate injection sites to minimise the risk of lipoatrophy
    May result in rapid onset of bowel movement
    Discontinue if severe and persistent abdominal pain occurs
    Discontinue if severe and persistent diarrhoea develops
    Treatment should be limited to 4 months. No data for longer periods.

    Should not be used to treat constipation unrelated to opioid use.

    Methylnaltrexone bromide should be added to the usual laxative treatment in palliative care patients.

    Cases of gastrointestinal perforation have been reported in patients using methylnaltrexone bromide. Although patients had medical conditions that may be associated with localised or diffuse reduction of structural integrity in the wall of the gastrointestinal tract (e.g., peptic ulcer disease, pseudo obstruction, diverticular disease, infiltrative gastrointestinal tract malignancies or peritoneal metastases), the use of methylnaltrexone bromide may have contributed to these events. The overall risk-benefit profile should be taken into account when using methylnaltrexone bromide in patients with these conditions or other conditions which might result in impaired integrity of the gastrointestinal tract wall e.g. Crohn's disease.

    Symptoms consistent with opioid withdrawal (hyperhidrosis, chills, vomiting, abdominal pain, palpitations, blushing) have occurred with methylnaltrexone bromide. Patients with disruptions to the blood-brain barrier may be at increased risk for opioid withdrawal and/or reduced analgesia.

    Pregnancy and Lactation


    Methylnaltrexone bromide is contraindicated during pregnancy.

    At the time of writing, there are no adequate data regarding the use of methylnaltrexone bromide during pregnancy and the potential risk to human pregnancies is unknown.

    Data from animal studies have shown reproductive toxicity and reduced birth weights in rats at high doses. The clinical significance for humans is unknown and as such should only be used if clearly necessary.

    The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( ) or if this is unavailable at the backup site ( ).


    Methylnaltrexone bromide is contraindicated during breastfeeding.

    At the time of writing it is unknown whether methylnaltrexone bromide is excreted in human milk. Studies in animals have shown excretion of methylnaltrexone bromide in breast milk. The manufacturer advises that a decision as to whether to discontinue breastfeeding or whether to discontinue methylnaltrexone bromide while breastfeeding should be made.

    Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
    Specialist advice is available from the UK Drugs in Lactation Advisory Service at


    Advise patients that rapid onset of a bowel movement can occur following treatment with methylnaltrexone bromide (within 30 to 60 minutes on average).

    Advise patients that methylnaltrexone bromide may cause dizziness and as such may have an effect on driving and/or operating machinery.

    Advise patients to promptly report severe, persistent or worsening symptoms.

    Side Effects

    Abdominal pain
    Burning (injection site)
    Gastro-intestinal perforation
    Hot flushes
    Injection site reactions
    Local pain (injection site)
    Oedema (injection site)
    Stinging (injection site)


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Further Information

    Last Full Review Date: September 2015

    Reference Sources

    Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press Accessed on 4 September 2015.

    Martindale: The Complete Drug Reference (online) London: Brayfield A (ed). Pharmaceutical Press Accessed on 4 September 2015.

    Summary of Product Characteristics: Relistor 12mg/0.6ml solution for injection. Swedish Orphan Biovitrum Ltd. Revised January 2017.

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    Medscape UK | Univadis prescription drug monographs & interactions are based on FDB Multilex Content

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