Macrogol 3350 with sulfate, ascorbate, KCl & NaCl (bowel prep)

How it works

The macrogol and sodium sulfate act as osmotic agents that draw large volumes of water into the colon to produce a watery purge, while the ascorbate component contributes additional osmotic effect, together evacuating the bowel without significant net absorption.

Prescribing in practice

• Bowel-cleansing solutions can cause clinically significant dehydration and electrolyte disturbance, so they are contraindicated in gut obstruction or perforation, ileus, toxic colitis and severe dehydration, and used with caution in frail, elderly, renally or cardiac-impaired patients.
• Adequate intake of clear fluids alongside the preparation is essential, and the ascorbic acid content makes it unsuitable for patients with glucose-6-phosphate dehydrogenase deficiency.
• Oral medicines taken around the time of the purge may be incompletely absorbed, so the timing of essential drugs should be reviewed.

Monitoring

Assess hydration, renal function and electrolytes before and, where indicated, after administration in patients at risk of fluid or electrolyte depletion.

Counselling the patient

• Follow the split-dose timing exactly and drink plenty of the recommended clear fluids to avoid dehydration.
• Expect frequent watery stools; stay near a toilet once you start.
• Report dizziness, palpitations, severe abdominal pain or persistent vomiting promptly.

Evidence & guidelines

Low-volume macrogol-ascorbate bowel preparations are widely used in UK endoscopy services as an effective alternative to standard-volume regimens, with MHRA advice emphasising hydration and electrolyte safety.