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Osmotic bowel cleanser Pregnancy: §4.6: 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 3350 with KCl/NaHCO3/NaCl

Brand names: Klean-Prep

This is macrogol 3350 combined with potassium chloride, sodium bicarbonate and sodium chloride, an electrolyte-balanced osmotic laxative for chronic constipation and faecal impaction.

Adult dose

Dose: Bowel cleansing before examination — adults: each sachet should be 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, taking 2 sachets during the evening before the examination and the remaining 2 sachets on the morning of the examination.
Route: Oral. If administration is by nasogastric tube, the usual rate should be 20 to 30 ml/minute. No solid food should be eaten for at least 2 hours before taking Klean-Prep. The fluid content of the reconstituted solution does not replace regular fluid intake, and adequate fluid intake must be maintained.
Frequency: A single bowel-preparation course before the examination — either the whole volume in one session, or divided between the evening before and the morning of the examination
Max: Up to 4 sachets per course, each dissolved in 1 litre of water — §4.2 states 'The usual dose is up to 4 sachets'. No higher dose is given anywhere in this SPC.
The SPC states that the solutions from all 4 sachets should be DRUNK WITHIN 4 to 6 hours. TOLERABILITY: should nausea, vomiting, abdominal distension or pain arise, the rate of administration should be slowed down or temporarily stopped until symptoms subside. AT-RISK GROUPS (§4.4): administer with caution to patients with impaired gag reflex, reflux oesophagitis, diminished levels of consciousness, or ulcerative colitis; unconscious or semi-conscious patients and those prone to aspiration or regurgitation should be observed during administration, especially by the nasogastric route, because pulmonary oedema resulting from aspiration of macrogol lavage solutions has been reported and requires immediate treatment. There have been rare reports of serious arrhythmias, including atrial fibrillation, with ionic osmotic laxatives used for bowel preparation, predominantly in patients with underlying cardiac risk factors and electrolyte disturbance. Use with care in patients at risk of electrolyte disturbance — renal failure, mild (NYHA class I and II) congestive cardiac impairment, or concurrent diuretic treatment. Convulsions associated with severe hyponatraemia, and confusional state/disorientation associated with hyponatraemia, have been reported; use caution in patients with a history of seizures, at increased risk of seizure, or at risk of electrolyte disturbance, and correct fluid and electrolyte abnormalities if neurologic symptoms occur. CHILDREN (§4.2), verbatim: 'Children: There is no recommended dosage.' No paediatric dose exists in this SPC, which is why paedDose is null. Some sections of the product information we used were incomplete — check the full SPC.

Dose adjustments

Renal

§4.2, verbatim: 'Renal patients: No dosage adjustment need be made.' Note that §4.4 nevertheless directs that the product be used with care in patients at risk of electrolyte disturbance, including those with renal failure, and that a baseline and post-treatment electrolyte and renal function test and an ECG be considered in patients with clinically significant renal impairment.

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

  • Hypersensitivity to the active substances or to any of the excipients listed in section 6.1
  • Gastrointestinal obstruction or perforation (known or suspected)
  • 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 in nature. All the reactions below were observed in post-marketing experience, so their frequencies are not known
  • Gastrointestinal: vomiting, nausea, abdominal pain, anal discomfort, abdominal distension, flatulence; oesophageal rupture (Boerhaave syndrome)
  • Metabolism: electrolyte disturbances — specifically hypokalaemia, hyponatraemia and dehydration
  • Nervous system: seizures, convulsions, confusional state/disorientation, headaches, dizziness
  • Cardiac: transient increase in blood pressure, arrhythmia, palpitations
  • Immune system: allergic reactions including anaphylactic reaction, dyspnoea and skin reactions
  • Skin: allergic skin reactions including angioedema, urticaria, pruritus, rash, erythema
  • General: rigors, malaise, pyrexia and thirst

Monitoring

  • In debilitated patients, patients in poor health, those with clinically significant renal impairment or arrhythmia, and those at risk of electrolyte imbalance, the physician should consider a baseline and post-treatment electrolyte and renal function test and an ECG as appropriate
  • Maintain adequate fluid intake throughout — the reconstituted solution does not replace regular fluid intake
  • Observe unconscious or semi-conscious patients, and those prone to aspiration or regurgitation, during administration — especially by the nasogastric route
  • Slow down or temporarily stop administration if nausea, vomiting, abdominal distension or pain arise, until symptoms subside
  • Correct fluid and electrolyte abnormalities if neurologic symptoms (including seizures or confusional state) occur

Clinical monograph

How it works

The macrogol polymer osmotically retains water in the bowel lumen to soften and bulk the stool, while the added electrolytes are formulated to be near-isotonic and minimise net shifts of sodium, potassium and water across the gut wall.

Prescribing in practice

  • Contraindicated in intestinal obstruction or perforation, ileus and severe inflammatory bowel disease; use caution in significant cardiovascular impairment because of the added electrolyte and fluid load.
  • The electrolyte content means caution is needed in renal impairment and when co-prescribed with other drugs affecting fluid or electrolyte balance.
  • Each sachet must be dissolved in water before use; the reconstituted solution may be kept refrigerated for a limited period and discarded thereafter.

Monitoring

Consider monitoring serum electrolytes when used at high impaction doses, in renal impairment, or in patients taking diuretics or other drugs that disturb electrolyte balance.

Counselling the patient

  • Mix each sachet in water as directed and drink enough fluid through the day.
  • Tell your prescriber if you have kidney or heart problems before regular use.
  • Stop and seek advice if you get severe bloating, abdominal pain or vomiting.

Evidence & guidelines

Electrolyte-containing macrogol preparations are an established, evidence-based first-line treatment for chronic constipation and faecal impaction in UK practice.

Reference: Confirm identity and dosing against the manufacturer SPC (eMC) and NICE. 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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