Osmotic Laxatives

Osmotic laxatives work by drawing fluid into or holding fluid within the intestinal lumen, which aids in gut motility and relief of constipation.  

Lactulose is unique in this class of medications. First, lactulose is a prodrug that is metabolized by gut bacteria to form acids, which increase osmotic pressure within the bowel lumen. Second, lactulose is used in the treatment of elevated ammonia levels, which is frequently seen in liver failure, by decreasing intestinal production and absorption of ammonia.  

Class Drugs

• Magnesium Citrate/Hydroxide

• Polyethylene Glycol

• Lactulose

Class Mechanism of Action

See individual drugs

Class Applications

Constipation

Class Adverse Effects

May decrease absorption of other drugs

Drug Table

Drug Name	Application	Comments	Image
Magnesium Citrate/Hydroxide		Mechanism; Increases retention of fluid in gut lumen by osmotic forces	"Magnum" "Citrus"
Polyethylene Glycol		Mechanism; Osmotic laxative with few GI cramping effects	"Polly" "Ethel"
Lactulose	Constipation; Hepatic encephalopathy	Mechanism; -Colonic bacteria metabolize lactulose into acids, which increases osmotic pressure; -Reduces Ammonia levels	"Lactation" "Lose"