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Osmotic Laxative — Bowel Preparation / Constipation Pregnancy: The preparation should only be used during pregnancy and lactation if considered essential by the physician. There is no experience of use during pregnancy. The purpose and mechanisms of use should be borne in mind if the physician is considering administration.

Macrogol (Polyethylene Glycol)

Brand names: Klean-Prep, Moviprep, Laxido

Macrogol (polyethylene glycol) is an osmotic laxative used in the surgical setting to treat constipation and faecal loading and to relieve opioid-induced constipation after operations.

Adult dose

Dose: Colonic lavage (bowel cleansing) prior to diagnostic examination or surgical procedures requiring a clean colon, e.g. colonoscopy, barium enema or colonic resection. Klean-Prep sachets, powder for oral solution (each sachet contains macrogol 3350 59.000 g, anhydrous sodium sulfate 5.685 g, sodium bicarbonate 1.685 g, sodium chloride 1.465 g and potassium chloride 0.7425 g): adults - each sachet dissolved in 1 litre of water; the usual dose is up to 4 sachets taken at a rate of 250 ml every 10 to 15 minutes until the total volume is consumed or rectal effluent is clear, or as directed by the physician; the solutions from all 4 sachets should be drunk within 4 to 6 hours. Alternatively, administration may be divided, for example 2 sachets during the evening before the examination and the remaining 2 sachets on the morning of the examination. By nasogastric tube the usual rate is 20 to 30 ml/minute.
Route: Oral (each sachet dissolved in 1 litre of water); nasogastric tube is also described
Frequency: Single bowel-preparation course: up to 4 sachets over 4 to 6 hours, or divided as 2 sachets the evening before and 2 sachets on the morning of the examination
SCOPE - PINNED PRODUCT ONLY: KLEAN-PREP 69G SACHET POWDER FOR ORAL SOLUTION (MHRA PL003220068, Norgine Limited). This is a class page (macrogol bowel preparation and laxative products): other macrogol products, including Moviprep and Laxido, and macrogol laxatives for constipation, differ in composition and regimen and are NOT covered; the only indication of this SPC is colonic lavage before examination or surgery. No maximum dose is printed beyond the usual 'up to 4 sachets', which is stated above as printed. Section 4.4: the fluid content of Klean-Prep when reconstituted with water does not replace regular fluid intake and adequate fluid intake must be maintained; no solid food should be eaten for at least 2 hours before taking Klean-Prep; should nausea, vomiting, abdominal distension or pain arise, the rate of administration should be slowed down or temporarily stopped until symptoms subside. Children: 'There is no recommended dosage', so no paediatric figure is given. Renal patients: 'No dosage adjustment need be made.' Source note: the SPC was extracted from a PDF; all figures above are quoted as printed.

Dose adjustments

Renal

Renal patients: no dosage adjustment need be made (SPC section 4.2). Section 4.4: use with care in patients at risk of electrolyte disturbance, such as patients with renal failure; in patients with clinically significant renal impairment the physician should consider a baseline and post-treatment electrolyte and renal function test and ECG as appropriate.

Hepatic

Not stated - the SPC gives no hepatic-impairment dosing statement.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via MHRA Products — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Known or suspected hypersensitivity to the active substances or to any of the excipients
  • Gastrointestinal obstruction or perforation
  • Ileus
  • Gastric retention
  • Toxic colitis and toxic megacolon
  • Congestive cardiac failure (NYHA class III or IV)

Side effects

  • The most commonly experienced undesirable effects are gastrointestinal: vomiting, nausea, abdominal pain, anal discomfort, abdominal distension, flatulence (frequencies not known)
  • Allergic reactions including anaphylactic reaction, dyspnoea and skin reactions (angioedema, urticaria, pruritus, rash, erythema)
  • Electrolyte disturbances, specifically hypokalaemia, hyponatraemia and dehydration; convulsions associated with severe hyponatraemia, seizures, confusional state/disorientation
  • Headaches and dizziness; transient increase in blood pressure, arrhythmia, palpitations
  • Oesophageal rupture (Boerhaave syndrome) associated with excessive vomiting has been reported post-marketing, mostly in elderly patients
  • Rigors, malaise, pyrexia and thirst
  • Ischaemic colitis has been reported post-marketing in patients treated with macrogol for bowel preparation
  • Rare reports of serious arrhythmias including atrial fibrillation with ionic osmotic laxatives for bowel preparation, and of pulmonary oedema resulting from aspiration of macrogol lavage solutions

Interactions

  • The interaction of Klean-Prep with other medicinal products has not been studied; oral medication (e.g. the oral contraceptive pill) taken one hour before, during and one hour after administration may theoretically be flushed from the gastrointestinal tract and not absorbed, and the effect of drugs with a narrow therapeutic index or short half-life may be particularly affected
  • Starch-based food thickeners: the macrogol counteracts the thickening effect of starch, effectively liquefying preparations that need to remain thick for people with swallowing problems
  • Stimulant laxatives (such as bisacodyl or sodium picosulfate): use macrogol with caution because of the risk of ischaemic colitis
  • Diuretics: use with care because of the risk of electrolyte disturbance

Monitoring

  • In debilitated patients, patients with poor health, those with clinically significant renal impairment, arrhythmia and those at risk of electrolyte imbalance, consider a baseline and post-treatment electrolyte and renal function test and ECG as appropriate
  • In case of neurologic symptoms, correct fluid and electrolyte abnormalities
  • Unconscious, semi-conscious patients or patients prone to aspiration or regurgitation should be observed during administration, especially via the nasogastric route
  • Caution in patients with an impaired gag reflex, reflux oesophagitis, diminished levels of consciousness or ulcerative colitis
  • Patients with sudden abdominal pain, rectal bleeding or other symptoms of ischaemic colitis should be evaluated promptly
  • Advise patients to stop and seek immediate medical assistance for incoercible vomiting with chest, neck or abdominal pain, dysphagia, haematemesis or dyspnoea
  • Contains aspartame (a source of phenylalanine), which may be harmful in phenylketonuria; contains 125 mmol (2.9 g) sodium per sachet, to be considered by patients on a controlled sodium diet

Clinical monograph

How it works

As an inert, non-absorbed polymer it sequesters water within the bowel lumen by osmosis, increasing stool water content and volume to soften faeces and promote peristalsis.

Prescribing in practice

  • Do not use where intestinal obstruction, perforation, ileus or another acute surgical abdomen is suspected, as osmotic laxatives are hazardous in these settings; ensure mechanical obstruction is excluded before treating post-operative constipation.
  • Dissolve each sachet in water as directed and maintain adequate fluid intake; higher regimens used for faecal impaction deliver a substantial fluid and electrolyte load.
  • Use cautiously in patients with cardiovascular impairment or fluid-balance concerns when large-volume regimens are given.

Monitoring

Monitor bowel response and, when high-volume regimens are used or in frail patients, fluid balance and electrolytes.

Counselling the patient

  • Mix each sachet with water as instructed and keep drinking fluids while taking it.
  • Stop and seek advice if you develop abdominal pain, bloating or vomiting.

Evidence & guidelines

Macrogols are first-line osmotic laxatives with good evidence in chronic constipation and faecal impaction; the SPC contraindicates them in obstruction and perforation.

Reference: Moviprep SPC; BSG Bowel Preparation Guidelines; NICE NG90 (Childhood Constipation); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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