Lower GI Conditions and Pharmacology
Constipation
What is it: the passage of hard stools less frequent than normal. Typically, less than 3
bowel movements per week.
Symptoms: abdominal pain, cramps, bloating, nausea and difficulty passing the stool.
Most common in women (especially pregnant) and older people.
How do we measure it in practice: Bristol stool chart types 1-7
Type 1-2 is constipation.
Types 5-7 are diarrhoea.
Causes of Constipation:
o No cause (functional)
o Medication
o Non-medical factors e.g., diet and dehydration
o Medical conditions e.g., IBS, IBD etc.
Non-pharmacological advice:
o Increase fluid intake.
o Exercise
Red Flags for Constipation
Loss of weight
Blood in stools or vomit
Bleeding from rectum
Family history
, Obstruction signs
Nausea and vomiting
Aged>40
No cause but, persistent for >14 days
Bulk-forming Laxatives
Insoluble polysaccharide polymers that are not digested by the upper GI tract.
They expand when taking up water in the small intestine making a bulky mass.
Due to the walls expanding this promotes peristalsis (contractions in the GI tract)
They take several days to work but have no serious or unwanted effects.
Makes it easier for faecal matter to pass.
Examples: methylcellulose, the brand fybogel.
Safe in pregnant and the elderly for long-term medication.
Osmotic laxatives
Example: lactulose
These are poorly absorbed solutes made of salts such as magnesium sulfate and
magnesium hydroxide.
Once these agents enter the intestine the concentration of solutes increases: known
as an osmotic load.
So, water is drawn in via osmosis.
So, the stool volume increases and so does the flow of stools in the intestines.
And the Walls of the intestine expand so peristalsis occurs.
Distention (swollen stomach) and purgation (evacuation of the faecal matter) occurs
when the laxatives take their effect.
Lactulose on the other hand takes 2-3 days to act.
Abdominal cramps are common.
Magnesium should be avoided in small children and patients with poor renal
function as it can cause heart block and have other effects on the CNS.
Stimulant Laxatives
Constipation
What is it: the passage of hard stools less frequent than normal. Typically, less than 3
bowel movements per week.
Symptoms: abdominal pain, cramps, bloating, nausea and difficulty passing the stool.
Most common in women (especially pregnant) and older people.
How do we measure it in practice: Bristol stool chart types 1-7
Type 1-2 is constipation.
Types 5-7 are diarrhoea.
Causes of Constipation:
o No cause (functional)
o Medication
o Non-medical factors e.g., diet and dehydration
o Medical conditions e.g., IBS, IBD etc.
Non-pharmacological advice:
o Increase fluid intake.
o Exercise
Red Flags for Constipation
Loss of weight
Blood in stools or vomit
Bleeding from rectum
Family history
, Obstruction signs
Nausea and vomiting
Aged>40
No cause but, persistent for >14 days
Bulk-forming Laxatives
Insoluble polysaccharide polymers that are not digested by the upper GI tract.
They expand when taking up water in the small intestine making a bulky mass.
Due to the walls expanding this promotes peristalsis (contractions in the GI tract)
They take several days to work but have no serious or unwanted effects.
Makes it easier for faecal matter to pass.
Examples: methylcellulose, the brand fybogel.
Safe in pregnant and the elderly for long-term medication.
Osmotic laxatives
Example: lactulose
These are poorly absorbed solutes made of salts such as magnesium sulfate and
magnesium hydroxide.
Once these agents enter the intestine the concentration of solutes increases: known
as an osmotic load.
So, water is drawn in via osmosis.
So, the stool volume increases and so does the flow of stools in the intestines.
And the Walls of the intestine expand so peristalsis occurs.
Distention (swollen stomach) and purgation (evacuation of the faecal matter) occurs
when the laxatives take their effect.
Lactulose on the other hand takes 2-3 days to act.
Abdominal cramps are common.
Magnesium should be avoided in small children and patients with poor renal
function as it can cause heart block and have other effects on the CNS.
Stimulant Laxatives
