Macrogol

Overview

Macrogol, also known as polyethylene glycol (PEG), is an osmotic laxative widely used for the management of constipation and for bowel cleansing prior to diagnostic or surgical procedures. It is a polymer of ethylene oxide, pharmacologically inert, and works by retaining water in the bowel lumen, softening stools and promoting bowel motility.

Macrogol is often formulated with electrolytes to prevent disturbances in sodium, potassium, or bicarbonate balance during use. It is well tolerated and considered safe for both short-term and long-term management of constipation, including in children and older adults.

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Pharmacological Class and Formulations

• Class: Osmotic laxative

• ATC Code: A06AD15

• Formulations:

  • Sachets or powder for oral solution (commonly macrogol 3350 or macrogol 4000)

  • Oral solutions with electrolytes for constipation (e.g., macrogol + sodium bicarbonate + sodium chloride + potassium chloride)

  • High-volume bowel preparations for colonoscopy (e.g., 2–4 L of macrogol-electrolyte solution)

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Mechanism of Action

Macrogol is not absorbed or metabolized in the gastrointestinal tract. Its effects include:

• Osmotic water retention: Binds water molecules, increasing stool water content.

• Stool softening: Produces softer stools that are easier to pass.

• Increased bowel motility: Expands stool volume, stimulating peristalsis.

• Electrolyte balance (when combined with electrolytes): Prevents dehydration and electrolyte shifts during high-volume bowel cleansing.

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Pharmacokinetics

• Absorption: Minimal systemic absorption.

• Metabolism: Not metabolized; remains pharmacologically inert.

• Elimination: Excreted unchanged in the feces.

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Clinical Indications

1. Constipation

   • Chronic idiopathic constipation

   • Constipation associated with opioid therapy (often combined with stimulants such as senna)

   • Constipation in children and older adults

2. Faecal impaction

   • High-dose regimens are used for clearance.

3. Bowel cleansing

   • Preoperative or pre-endoscopic preparation (e.g., colonoscopy, bowel surgery).

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Contraindications

• Known hypersensitivity to macrogol or components of the formulation

• Gastrointestinal perforation or obstruction

• Paralytic ileus

• Severe inflammatory bowel disease (e.g., toxic megacolon, Crohn’s flare, ulcerative colitis exacerbation)

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Precautions

• Cardiovascular disease: High-volume preparations may increase strain due to fluid shifts.

• Renal impairment: Monitor electrolytes closely with macrogol–electrolyte solutions.

• Children: Effective and safe but dose must be age- and weight-adjusted.

• Pregnancy and breastfeeding: Considered safe due to minimal systemic absorption.

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Adverse Effects

Common

• Bloating, abdominal discomfort

• Flatulence

• Loose stools or diarrhea

Less Common

• Nausea, vomiting

• Electrolyte disturbances (mainly with prolonged use or electrolyte-free formulations)

Rare but Serious

• Severe dehydration and electrolyte imbalance if improperly used

• Allergic reactions (rare)

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Drug Interactions

• Reduced absorption of oral drugs: Macrogol may delay or reduce absorption of concomitant oral medications (especially narrow therapeutic index drugs such as antiepileptics).

• Avoid simultaneous dosing: Separate macrogol and other oral medicines by at least 1–2 hours.

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Dosage

Constipation (Adults)

• 1 sachet (usually containing 10–13 g macrogol 3350) once to three times daily.

• Dissolve sachet contents in ~125 mL water before ingestion.

Chronic Constipation (Children ≥2 years)

• 2–6 years: ½–2 sachets daily, adjusted to response.

• 6–12 years: 1–4 sachets daily.

• Sachet contents should be dissolved in water or juice.

Faecal Impaction (Adults and Children)

• Adults: Up to 8 sachets daily, taken within 6 hours for up to 3 days.

• Children (5–11 years): Dose escalates from 4 sachets on day 1 to up to 12 sachets/day by day 4–7, depending on response.

Bowel Cleansing Prior to Colonoscopy/Surgery

• Large-volume regimens: 2–4 L macrogol–electrolyte solution taken over several hours, usually in split doses the day before and the morning of the procedure.

• Clear fluids allowed until 2 hours before procedure.

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Monitoring

• Short-term use: Generally no monitoring required.

• Long-term or high-dose use: Periodic electrolyte monitoring, especially in elderly, renal impairment, or those on diuretics.

• Clinical monitoring: Relief of constipation, stool consistency, frequency of bowel movements.

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Patient Counseling Points

• Dissolve sachets fully in water before taking.

• May take 1–2 days to achieve desired laxative effect.

• Maintain adequate hydration throughout treatment.

• Separate other oral medicines by at least 1–2 hours.

• For faecal impaction or bowel cleansing, follow dosing instructions precisely; incomplete intake reduces efficacy.