Methylnaltrexone

• Injection containing 20mg of methylnaltrexone bromide per ml.
• Each vial of 0.6ml contains 12mg of methylnaltrexone bromide for subcutaneous (SC) 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 lesions of the gastrointestinal (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.

Contra-indications

• Known or suspected mechanical GI obstruction or acute surgical abdomen.

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.

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

• 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 (within 30 to 60 minutes).
• Treatment is added to usual laxative therapy which may subsequently require review.
• If severe or persistent diarrhoea occurs during treatment, patients should be advised to discontinue therapy and consult their doctor.
• Further information: Specialist Palliative Care services/Palliative Medicine on-call advice service.
• Patient Information leaflet on the Electronic Medicines Compendium.

Palliative Care Formulary (PCF) on the Knowledge Network via Athens password (http://www.knowledge.scot.nhs.uk/home/portals-and-topics/palliative-care.aspx).

Summary of Product Characteristics (revised Feb 2017) on the Electronic Medicines Compendium at www.medicines.org.uk.

Product information on the European Medicines Agency website at http://www.ema.europa.eu.

Candy B et al. (2011) Laxatives or methylnaltrexone for the management of constipation in palliative care patients. Cochrane Database of Systematic Reviews. 19: CD003448.