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Osmotic Laxative
Aka: Osmotic Laxative, Osmotic Cathartic, Magnesium Hydroxide, Milk of Magnesia, Magnesium Citrate, Polyethylene glycol, PEG, Miralax, Sorbitol, Fleets Enema, Fleet Enema, Phospho-Soda, Pink Lady Enema
- See Also
- Laxative
- Constipation
- Functional Constipation
- Pediatric Constipation
- Mechanism
- Poorly absorbed, they act as hyperosmolar agents
- Stimulate colonic activity (via cholecystokinin)
- Complications
- Hypermagnesemia (in patients with Renal Failure)
- Hypocalcemia (phosphate Overdose)
- Contraindications
- Renal Failure (except Lactulose and Sorbitol)
- Preparations: Poorly-absorbed sugars (may be used in Renal Failure)
- Lactulose (Chronulac)
- Easier to administer to young children
- May cause abdominal cramping and Flatus
- More expensive then Sorbitol ($10-30 per 480 ml)
- Onset of action within 24-48 hours
- Dose
- Adults: 15-60 ml PO daily
- Child (10 mg/15 ml): 1-3 cc/kg/day divided qd-bid
- Lactitol
- As effective as Lactulose with less pain and Flatus
- Pitzalis (1995) Pediatr Med Chir 17(3):223-6 [PubMed]
- Sorbitol 70%
- Less expensive than Lactulose ($7 per 480 ml)
- Sweet taste
- Dosing
- Adult: 15-60 ml PO daily
- Child: 1-3 ml/kg/day divided twice daily
- Preparations: Magnesium salt Osmotic Laxatives
- Rapid onset (within 3 hours)
- Avoid longterm use due to Electrolyte loss risk
- Milk of Magnesia (Magnesium Hydroxide)
- Cost: $3 per 360 ml
- Concentration: 400 mg/5 ml
- Adults: 15-60 ml PO qd prn
- Children: 1-3 cc/kg/day divided bid prn
- Concentration 800 mg/5 ml
- Children: 0.5 cc/kg/day divided bid prn
- Adverse effects
- May cause abdominal cramping in higher doses
- Magnesium Citrate (Citroma)
- Cost: $1.50 per 300 ml
- Dose
- Adult: 8 ounces PO daily prn
- Child: 4 ml/kg up to 200 ml PO daily prn
- Preparations: Mineral Oil
- Child: 1-3 cc/kg/day divided daily to twice daily
- Contraindicated if aspiration risk
- Not recommended under age 18 months
- Give chilled in juice to maximize tolerability
- Coadminister Multivitamin daily if used chronically
- Preparations: Sodium salt Osmotic Laxatives
- Phopho-Soda (Osmoprep, Visicol) 2 tablespoons in 4 ounces water orally
- Fleets Enema (Sodium phosphate) 120 ml enema
- Pink Lady Enema (1/2 Fleet Enema, 100 ml Docusate, 60 ml Mineral Oil, 60 ml Magnesium Citrate)
- Alternative agent: Tap Water Enema
- Precaution: Acute phosphate nephropathy (FDA Black Box Warning)
- Risk of permanent impact on Renal Function following use
- Risk Factors
- Diabetes Mellitus
- Age over 65 years
- Dehydration
- Concurrent NSAID, ACE Inhibitor, ARB or Diuretic
- Prevention of Renal Function impact
- Consider alternative Bowel Preparation if risk factors above
- Maintain clear fluid intake to replace fluid losses from Diarrhea
- Preparations: Polyethylene glycol 3350 (PEG, Miralax)
- Similar to bowel prep solution (GoLytely, Colyte)
- Onset of action with 24-48 hours
- No salty taste
- More expensive then Sorbitol: $2/day
- Preparation
- Use PEG powder 17 grams (one capful)
- Dissolve in 240 ml (8 ounces) water or juice
- May chill PEG solution or mix with flavoring (e.g. Crystal Light) to improve taste
- If for Colonoscopy prep, avoid colored flavoring that might interfere with visibility
- Dose:
- Adult: 17 grams (1 capful) daily
- Child
- Start 0.8-1 g/kg/day (15 ml/kg/day) divided bid
- Adjust dose for two soft painless stools per day
- Taper dose over time
- Efficacy
- Safe, well tolerated and effective
- More effective and better tolerated than Lactulose
- Safety
- Appears safe in children and adults
- In 2017, studies initiated to determine if young children absorb Ethylene Glycol with neurotoxicity based on case reports
- No evidence at this point that this is a significant concern
- (2017) Presc Lett 24(4): 23
- References
- Gremse (2002) Clin Pediatr 41:225-9 [PubMed]
- Pashankar (2003) Arch Pediatr Adolesc Med 157:661-4 [PubMed]
- Voskuijl (2004) Gut 53:1590-4 [PubMed]
- Preparations: Not recommended
- Castor oil or Ricinoleic Acid (Purge)
- Avoid due to Electrolyte disturbance
- Adult: 15-30 ml PO qhs
- Child: 5-15 ml PO qhs
- Soapsuds Enemas (never use)
- Risk of irritation or hemorrhagic colitis