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Scottish Palliative Care Guidelines print pdf



A peripheral opioid antagonist used in palliative care for intractable opioid-induced constipation where response to usual laxative therapy has not been sufficient.


Injection containing 20mg of methylnaltrexone bromide per ml.
Each vial of 0.6ml contains 12mg of methylnaltrexone bromide for  subcutaneous injection.


May be recommended by a palliative care specialist for treatment of opioid-induced constipation in patients with advanced illness when optimum use of laxatives is ineffective.


Known or suspected mechanical gastrointestinal obstruction or acute surgical abdomen.

Known or suspected lesions of the GI tract.
Diverticular disease; faecal impaction; patients with colostomy or peritoneal catheter. Conditions which may predispose to perforation.
Dose reduction required in severe renal impairment. Avoid in patients in end stage renal impairment receiving dialysis and in severe hepatic impairment.
Assess risk versus benefit in pregnancy and breast feeding.

Drug interactions
No clinically significant interactions identified.

Side effects
Common: abdominal pain/colic, diarrhoea, flatulence, nausea, dizziness (postural hypotension can occur).
Rare: syncope, severe diarrhoea, cardiovascular collapse, GI perforation.

Dose and Administration

For patients weighing 38 to 61kg 8mg S.C.(0.4ml of solution) on alternate days.
For patients weighing 62 to 114kg 12mg S.C. (0.6ml of solution) on alternate days.
Outside this range give 150 micrograms/kg on alternate days.
The interval between administrations may be varied but not more than once a day.

Practice Points

Rotate injection sites.
Avoid hard or red areas and areas of tenderness or bruising.
Recommended injection sites are upper legs, abdomen and upper arms.
Treatment can result in the rapid onset of a bowel movement (i.e. within 30 to 60 minutes).
Treatment is added to usual laxative therapy which may subsequently require reviewed.

Patient and carer advice points
If severe or persistent diarrhoea occurs during treatment, patients should be advised to discontinue therapy and consult their doctor.
Patient Information leaflet (last revised 05/13) on the Electronic Medicines Compendium at


Further information
Specialist Palliative Care services/Palliative Medicine on-call advice service.