Osmotic laxatives

Osmotic laxatives stay in the bowel and hold water there by osmosis. The extra water softens the stool, increases its volume and speeds its passage. Lactulose is also fermented by colonic bacteria into acids that add to this pull. They usually take 1 to 3 days to work, so they relieve constipation steadily rather than within hours.

• LactuloseA synthetic sugar laxative for constipation that also lowers blood ammonia in hepatic encephalopathy.
• MacrogolAn osmotic laxative (polyethylene glycol 3350) for constipation and fecal impaction, and with salts for bowel cleansing before colonoscopy.

• Constipation
• Hepatic encephalopathy (lactulose)
• Bowel cleansing before colonoscopy (macrogol)

• BloatingKnown for
• FlatulenceKnown for
• Abdominal cramps and pain
• Nausea and vomiting
• Diarrhea at high doses
• DehydrationSerious
• Low potassium from heavy diarrheaSerious
• Allergic reactions, including anaphylaxisSerious

What the class has in common. Each drug's card has its own, and Known for marks what an exam expects you to know.

• Do not use with bowel obstruction or perforation, or with ileus.
• Heavy or prolonged diarrhea can upset fluid and salt balance; watch potassium and sodium.

Written for biofideX in plain words, after checking these references:

• Laxative (NCI Thesaurus)
• Lactulose solution: label (DailyMed)
• Polyethylene glycol 3350 powder: label (DailyMed)
• PEG 3350 and electrolytes for oral solution: label (DailyMed)
• Lactulose (NHS)
• Macrogol (NHS)

For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.