Laxatives Flashcards
What are the four main groups of laxatives?
Bulk forming, Osmotic, Stimulant, Stool softeners (BOSS).
Give some examples of bulk-forming laxatives.
Bran, ispaghula husk, methylcellulose, sterculia.
How do bulk-forming laxatives work?
Increase the bulk of the stool, increasing ease of passing.
What is the onset of action of bulk-forming laxatives?
72 hours (3 days).
What are the side effects of bulk forming laxatives?
Bloating, cramping, flatulence.
When are bulk-forming laxatives used?
Colostomy, ileostomy, haemorrhoids, anal fissure, IBS, diverticular disease, ulcerative colitis.
Give some examples of osmotic laxatives.
Lactulose and macrogols.
How do osmotic laxatives work?
By drawing water from the body into the bowel or retaining water in the bowel.
What is the onset of action for osmotic laxatives?
Up to 2 days for max effect.
What are the side effects of osmotic laxatives?
Abdominal pain and bloating.
Which osmotic laxatives act faster - macrogols or lactulose?
Macrogols.
Which fast acting osmotic laxatives are used to quickly clear the bowel?
Phosphate enemas and magnesium salts.
Give examples of stimulant laxatives.
Bosacodyl, sodium picosulfate, senna, glycerol, co-danthramer.
Which stimulant laxative is only used in the terminally-ill? Why?
Co-danthramer due to its carcinogenicity.
How do stimulant laxatives work?
By increasing intestinal motility.
What is the onset of action of stimulant laxatives?
8-12 hours - bedtime dose recommended.
Which form of stimulant laxatives act the quickest? In how long do they act?
Suppositories. 20-60 minutes.
What are the side effects of stimulant laxatives?
Abdominal cramps.
Co-danthramer can colour one’s urine. What colour should be expected?
Red.
Stimulant laxatives should not be used in which age group unless under the advice of a prescriber?
Children under 12.
Give some examples of stool softening laxatives.
Liquid paraffin, docusate sodium (weak stimulant), peanut (arachis) enemas.
How do stool softening laxatives work?
Decrease surface tension and increase the penetration of water into the stool. Softens and wets stool.
Which laxatives are first line?
Bulk forming (BOS).
Which laxatives should be used for opioid induced constipation?
Osmotic or stimulant. NOT bulk forming.
Describe the treatment of constipation in pregnant women.
Diet and lifestyle first line. Then bulk forming. Then osmotic. Stimulants can be used but cause abdominal pain and diarrhoea.
Describe the treatment of constipation in children.
Diet and lifestyle first. Macrogols are first line treatment, then stimulant if macrogols fail. Can try lactulose.
