Pharmacological Basis For Treatment of GI Disorders II
• The mechanism of action of two different types of laxative agent
• The mechanism of action of one anti-diarrhoeal agent
Constipation
Constipation is a subjective complaint (differs between people) and is an obstructive
problem where digested material is not coming out.
This needs to be investigated because it could be something sinister.
Normal bowel opening is 1-3x per day, if you go once this is still okay. One does not
have to be regular to be physiologically adequate, no toxic substances accumulate
upon prolonged constipation.
The consequences of constipation as a result of rectal distension include: Headache,
loss of appetite, nausea and abdominal distension and stomach pain.
Holding of faecal matter leads to increased water loss from the faeces leading to a
drier faeces. As a result it can make it more painful and harder to defecate.
Constipation is caused by decreased motility of the large intestine, this is often a
product of old age or damage to the enteric nervous system of the colon.
Factors that can increase colonic motility (increase distension of the large intestine, as
this helps with the motility) and improve symptoms of constipation include
-> Increased fibre, cellulose and complex polysaccharides
-> Bran, some fruits and vegetables with high fibre
-> Laxatives, but excessive use will lead to decreased responsiveness to them
-> Mineral oil lubricates faeces
-> Castor oil, stimulates motility of the colon
Causes, management and alarm signs of constipation—
Causes of constipation in elderly
- Diet
- Inactivity
- Drugs (polypharmacy), some drugs will decrease colon motility
Alarm signs and symptoms of patients with chronic constipation include
-> Acute onset constipation in older individuals
-> Weight loss
-> Blood in stool
-> Anaemia
-> Family history of colon cancer or inflammatory bowel disease
Management of constipation
, Lifestyle changes
-> Diet, fluid intake and exercise (more appealing)
-> Increase fibre intake (can lead to bloating and flatulence which may not be
appealing)
-> Increase water intake
In terms of drugs
-> Purgatives: they are laxatives that act as faecal softners and stimulant purgatives can
modulate/hasten food transit in the intestine
-> Bulk-forming and osmotic laxatives
-> Bulk laxatives e.g. methylcellulose
-> Plant gums which retain water in gut lumen, these promote peristalsis but take a
few days to work
-> These increase stool’s solid content
Bloating and flatulence is associated with these
Osmotic laxatives include lactulose
- This increases and maintains the volume of fluid in the lumen of the bowel by osmosis,
it increases the transfer of gut contents into the intestine.
It increases the volume of gut content entering the colon which causes a big distension
leading to purgation in one hour
However, high doses can lead to flatulence, cramps, diarrhoea, vomiting and tolerance
• The mechanism of action of two different types of laxative agent
• The mechanism of action of one anti-diarrhoeal agent
Constipation
Constipation is a subjective complaint (differs between people) and is an obstructive
problem where digested material is not coming out.
This needs to be investigated because it could be something sinister.
Normal bowel opening is 1-3x per day, if you go once this is still okay. One does not
have to be regular to be physiologically adequate, no toxic substances accumulate
upon prolonged constipation.
The consequences of constipation as a result of rectal distension include: Headache,
loss of appetite, nausea and abdominal distension and stomach pain.
Holding of faecal matter leads to increased water loss from the faeces leading to a
drier faeces. As a result it can make it more painful and harder to defecate.
Constipation is caused by decreased motility of the large intestine, this is often a
product of old age or damage to the enteric nervous system of the colon.
Factors that can increase colonic motility (increase distension of the large intestine, as
this helps with the motility) and improve symptoms of constipation include
-> Increased fibre, cellulose and complex polysaccharides
-> Bran, some fruits and vegetables with high fibre
-> Laxatives, but excessive use will lead to decreased responsiveness to them
-> Mineral oil lubricates faeces
-> Castor oil, stimulates motility of the colon
Causes, management and alarm signs of constipation—
Causes of constipation in elderly
- Diet
- Inactivity
- Drugs (polypharmacy), some drugs will decrease colon motility
Alarm signs and symptoms of patients with chronic constipation include
-> Acute onset constipation in older individuals
-> Weight loss
-> Blood in stool
-> Anaemia
-> Family history of colon cancer or inflammatory bowel disease
Management of constipation
, Lifestyle changes
-> Diet, fluid intake and exercise (more appealing)
-> Increase fibre intake (can lead to bloating and flatulence which may not be
appealing)
-> Increase water intake
In terms of drugs
-> Purgatives: they are laxatives that act as faecal softners and stimulant purgatives can
modulate/hasten food transit in the intestine
-> Bulk-forming and osmotic laxatives
-> Bulk laxatives e.g. methylcellulose
-> Plant gums which retain water in gut lumen, these promote peristalsis but take a
few days to work
-> These increase stool’s solid content
Bloating and flatulence is associated with these
Osmotic laxatives include lactulose
- This increases and maintains the volume of fluid in the lumen of the bowel by osmosis,
it increases the transfer of gut contents into the intestine.
It increases the volume of gut content entering the colon which causes a big distension
leading to purgation in one hour
However, high doses can lead to flatulence, cramps, diarrhoea, vomiting and tolerance
