What medications are used for bowel prep?

Medications Used for Bowel Preparation for Colonoscopy

For most patients undergoing colonoscopy, a split-dose 2L polyethylene glycol (PEG) preparation is recommended as the first-line bowel preparation regimen due to its superior tolerability while maintaining adequate bowel cleansing efficacy. 1

Primary Bowel Preparation Medications

Polyethylene Glycol (PEG) Formulations

• High-volume PEG (4L):

  • FDA-approved formulations: Colyte, Gavilyte, Golytely, Nulytely 1
  • Provides excellent cleansing but lower patient compliance due to volume
  • Preferred for patients with renal insufficiency, congestive heart failure, or advanced liver disease due to iso-osmotic properties 1

• Low-volume PEG (2L):

  • FDA-approved formulations: MoviPrep (2L PEG with ascorbate) 1
  • Similar efficacy to 4L PEG in healthy non-constipated individuals 1
  • Better patient tolerance and compliance (91.9% vs 66.9% willingness to repeat) 1

• Ultra-low-volume PEG (1L):

  • FDA-approved: 1L PEG with ascorbate 1
  • May be combined with adjuncts like linaclotide for comparable efficacy to 2L preparations 1
  • Not recommended for routine use without adjuncts 1

Hyperosmotic Agents

• Oral Sulfate Solution (OSS):

  • FDA-approved: SUPREP 1
  • Approved for split-dose administration only 1
  • 92% adequate bowel preparation rate when used as split-dose 1

• Sodium Phosphate (NaP):

  • Prescription tablet formulation (Osmo-Prep) available with boxed warning 1
  • OTC liquid formulation withdrawn from market due to risk of phosphate nephropathy 1
  • Contraindicated in patients with renal insufficiency 2

• Sodium Picosulfate/Magnesium Citrate:

  • FDA-approved: Prepopik 1
  • Lower adequate preparation rates (75%) when used as ultra-low volume (<1L) 1

Adjunctive Medications

• Stimulant Laxatives:

  • Bisacodyl: Often combined with PEG to reduce required volume 3
  • Senna/Sennosides: Can be used with reduced volume PEG 4, 5
  • Both allow reduction of PEG volume while maintaining cleansing efficacy

• Antiemetics:

  • Domperidone or sulpiride can improve tolerance and completion rates of PEG preparations 6
  • Consider for patients with history of nausea with bowel preparations

Dosing Regimens

Split-Dose Regimens (Preferred)

• 4L PEG split-dose: 2L evening before, 2L morning of procedure

  • Provides significantly better cleansing than non-split regimens (OR 4.38) 1
  • Recommended for high-risk patients 2

• 2L PEG split-dose: 1L evening before, 1L morning of procedure

  • Recommended for most average-risk patients 1
  • Complete final dose 2-4 hours before procedure

Same-Day Regimens

• Acceptable alternative for afternoon colonoscopies 1
• Entire preparation taken morning of procedure
• Better sleep quality but may have more side effects like nausea 1

Patient Selection Considerations

High-Risk Patients (Consider 4L Split-Dose PEG)

• Prior inadequate preparation
• History of constipation
• Use of opioids or constipating medications
• Prior colon resection
• Diabetes mellitus
• Spinal cord injury 2

Patients with Comorbidities

• Renal insufficiency: Use iso-osmotic PEG; avoid sodium phosphate 2
• Heart failure: Use iso-osmotic PEG; avoid high sodium preparations 1
• Advanced liver disease: Use iso-osmotic PEG 1

Medication Management During Preparation

• Hold ACE inhibitors/ARBs on day of preparation and procedure 2
• GLP-1 receptor agonists may need to be stopped 1-7 days before procedure 2
• Review metformin in patients with borderline GFR 2

Practical Tips for Improved Efficacy and Tolerance

• Add bisacodyl (15mg) to reduce required PEG volume 3
• Consider antiemetics for patients with history of nausea 6
• Use split-dose regimens whenever possible 1
• Ensure adequate hydration with additional clear liquids 2
• Follow low-residue diet 2-3 days before colonoscopy 2

Common Pitfalls to Avoid

• Using sodium phosphate preparations in patients with renal insufficiency
• Non-split dosing, which results in inferior bowel cleansing
• Inadequate fluid intake during preparation
• Failing to adjust medication regimens for high-risk patients
• Not allowing sufficient time between last dose and procedure (should not exceed 5 hours) 2

By selecting the appropriate bowel preparation regimen based on patient characteristics and using split-dosing when possible, adequate bowel preparation can be achieved in most patients while minimizing discomfort and adverse effects.