Magnesium hydroxide versus macrogol/electrolytes in the prevention of opioid-induced constipation in incurable cancer patients: study protocol for an open-label, randomized controlled trial (the OMAMA study)

K R J Kistemaker, Alexander de Graeff, M Crul, G de Klerk, P M van de Ven, M P van der Meulen, L van Zuylen, M A H Steegers

Research output: Contribution to journalArticleAcademicpeer-review


Background: Opioid-induced constipation (OIC) is a common symptom in cancer patients treated with opioids with a prevalence of up to 59%. International guidelines recommend standard laxatives such as macrogol/electrolytes and magnesium hydroxide to prevent OIC, although evidence from randomized controlled trials is largely lacking. The aim of our study is to compare magnesium hydroxide with macrogol /electrolytes in the prevention of OIC in patients with incurable cancer and to compare side-effects, tolerability and cost-effectiveness. Methods: Our study is an open-label, randomized, multicenter study to examine if magnesium hydroxide is non-inferior to macrogol/electrolytes in the prevention of OIC. In total, 330 patients with incurable cancer, starting with opioids for pain management, will be randomized to treatment with either macrogol/electrolytes or magnesium hydroxide. The primary outcome measure is the proportion of patients with a score of < 30 on the Bowel Function Index (BFI), measured on day 14. The Rome IV criteria for constipation, side effects of and satisfaction with laxatives, pain scores, quality of life (using the EQ-5D-5L), daily use of laxatives and escape medication, and cost-effectiveness will also be assessed. Discussion: In this study we aim to examine if magnesium hydroxide is non-inferior to macrogol/electrolytes in the prevention of OIC. The outcome of our study will contribute to prevention of OIC and scientific evidence of guidelines on (opioid-induced) constipation. Trial registration: This trial is registered at NCT05216328 and in the Dutch trial register: NTR80508. EudraCT number 2022–000408-36.

Original languageEnglish
Article number22
Pages (from-to)22
Number of pages1
JournalBMC palliative care
Issue number1
Publication statusPublished - Dec 2023


  • Analgesics, Opioid/adverse effects
  • Cancer
  • Clinical trial
  • Constipation
  • Constipation/chemically induced
  • Humans
  • Laxative
  • Laxatives/therapeutic use
  • Macrogol/electrolytes
  • Magnesium Hydroxide/adverse effects
  • Magnesium hydroxide
  • Multicenter Studies as Topic
  • Neoplasms/complications
  • Opioid-Induced Constipation/drug therapy
  • Opioids
  • Palliative care
  • Polyethylene Glycols/adverse effects
  • Quality of Life
  • Randomized Controlled Trials as Topic

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