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Stimulant + osmotic bowel cleanser Pregnancy: Avoid in pregnancy - as picosulfate is a stimulant laxative it is preferable, as a safety measure, to avoid use during pregnancy; no clinical or reproductive toxicity data are available. Breast-feeding: no experience in nursing mothers, but treatment may be considered given the pharmacokinetic properties of the active ingredients (UK SPC 4.6).

Magnesium citrate with sodium picosulfate

Brand names: Picolax, CitraFleet

This fixed combination of magnesium citrate with sodium picosulfate is a dual-action oral bowel-cleansing preparation taken before colonoscopy, surgery or radiological investigation of the colon.

Adult dose

Dose: Bowel cleansing prior to a procedure (adults, including the elderly, aged 18 years and over): a course of two sachets, each reconstituted in a cup of water - usually one sachet on the evening prior to the procedure and the second sachet in the morning of the day of the procedure
Route: Oral. Each sachet must be reconstituted in a cup of water, because the osmolarity of the product needs to be maintained to obtain the desired effect; do not further dilute the product by drinking liquid immediately after the intake of each sachet
Frequency: Two sachets per preparation course, with at least 5 hours between them. Alternative schedules in the SPC: both sachets on the afternoon and evening prior to the procedure (more suitable when the procedure is early in the morning), or both sachets in the morning of the day of the procedure (only suitable when the procedure is planned in the afternoon/evening)
Max: 2 sachets per bowel-preparation course
FLUID INTAKE: after a period of ten minutes following the administration of each reconstituted sachet, it is recommended to drink approximately 1.5-2 litres of a variety of clear fluids at a rate of approximately 250-400 ml/h; clear soups and/or balanced electrolyte solutions are recommended and it is advisable not to drink clear or demineralised water alone. DIET: a low residue diet or only clear liquids on the day before the procedure is recommended, and no solid food should be taken from the start of the course of treatment until after the procedure. The patient should be nil-by-mouth prior to the procedure (usually for at least 2 hours) in accordance with anaesthesia requirements. The period of bowel cleansing should not exceed 24 hours, because longer preparation may increase the risk of water and electrolyte imbalance. This product should not be used as a routine laxative. Each sachet contains 5 mmol (195 mg) potassium - relevant in reduced kidney function or a controlled potassium diet - and less than 1 mmol sodium (23 mg), i.e. essentially sodium-free. INTERACTIONS: absorption of other orally administered medicines (e.g. anti-epileptics, contraceptives, anti-diabetics, antibiotics) may be modified; tetracycline and fluoroquinolone antibiotics and penicillamine should be taken at least 2 hours before and not less than 6 hours after administration, to avoid chelation with magnesium; efficacy is lowered by bulk-forming laxatives. The SPC section retrieved states the dose in whole sachets and does not give the milligram content of either active substance, so no per-active figure is published. Some sections of the product information we used were incomplete — check the full SPC.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — 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
  • Congestive cardiac failure
  • Severe dehydration
  • Hypermagnesaemia
  • Gastric retention
  • Gastro-intestinal ulceration
  • Toxic colitis or toxic megacolon
  • Ileus
  • Nausea and vomiting
  • Ascites
  • Acute surgical abdominal conditions such as acute appendicitis
  • Known or suspected gastro-intestinal obstruction or perforation
  • Rhabdomyolysis - laxatives may induce rhabdomyolysis and may therefore exacerbate the condition
  • Active inflammatory bowel disease, e.g. Crohn's disease or ulcerative colitis
  • Severely reduced renal function - accumulation of magnesium in plasma may occur; another preparation should be used

Side effects

  • Abdominal pain (very common)
  • Dry mouth, nausea, abdominal distension, anal discomfort, proctalgia (common)
  • Sleep disorder (common)
  • Headache (common)
  • Thirst, fatigue (common)
  • Vomiting, faecal incontinence (uncommon)
  • Dizziness (uncommon)
  • Orthostatic hypotension (uncommon)
  • Diarrhoea - the primary clinical effect - and flatulence (frequency not known)
  • Hyponatraemia and hypokalaemia (frequency not known); hyponatraemia has been reported with or without associated convulsions
  • Epilepsy, grand mal convulsion, convulsion, confusional state (frequency not known) - seizures have been reported in epileptic patients even without hyponatraemia
  • Anaphylactoid reaction and hypersensitivity (frequency not known)
  • Rash (including erythematous and maculo-papular rash), urticaria, pruritus, purpura (frequency not known)

Monitoring

  • In at-risk populations, obtain baseline and post-treatment electrolyte levels; elderly and debilitated patients and those at risk of hypokalaemia or hyponatraemia may need particular attention
  • Emphasise adequate hydration - diarrhoea due to the evacuating effect may cause fluid and electrolyte losses, hypovolaemia and hypotension
  • Weigh the benefit/risk ratio carefully before initiating in frail or debilitated patients, in whom severe and potentially fatal electrolyte disorders or impaired renal function have rarely occurred
  • Use with caution in patients with known disorders of water and/or electrolyte balance or on drugs affecting them (e.g. diuretics, corticosteroids, lithium), recent gastrointestinal surgery, renal impairment, mild to moderate dehydration, hypotension or heart disease
  • Be alert to a vasovagal reflex triggered by abdominal stimuli such as pain, which may cause low blood pressure and loss of consciousness

Clinical monograph

How it works

Sodium picosulfate is a stimulant laxative activated by colonic bacteria to directly stimulate the mucosa and increase motility, while magnesium citrate provides an osmotic effect that retains water in the lumen; together they produce a thorough purge.

Prescribing in practice

  • As with all bowel-cleansing agents it carries a real risk of dehydration and electrolyte disturbance, so it is contraindicated in gut obstruction or perforation, ileus, toxic colitis and severe dehydration, and the magnesium component warrants caution in renal impairment.
  • Generous clear-fluid intake during cleansing is essential, with particular care in elderly, frail or cardiac patients.
  • Because picosulfate requires colonic bacteria for activation, concurrent antibiotics may reduce its effectiveness.

Monitoring

Check or consider renal function and electrolytes before use in at-risk patients, and ensure hydration is maintained throughout the cleansing process.

Counselling the patient

  • Take each dose at the times instructed and drink large amounts of clear fluid to stay hydrated.
  • Expect watery diarrhoea within hours and stay near a toilet.
  • Seek advice if you develop fainting, palpitations, severe pain or persistent vomiting.

Evidence & guidelines

Sodium picosulfate with magnesium citrate is a well-established bowel-preparation regimen in UK endoscopy practice, with safe use guided by attention to hydration and electrolytes.

Reference: NICE; 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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