Flashcards in Laxative And Diarrhoeals Deck (19):
Purpose of laxatives?
How is constipation caused?
1) drug induced - e.g. Morphine
2) not enough fibre in diet
3) where straining exacerbates other conditions - e.g. Haemorrhoids
PK of laxatives
-but stimulant laxatives are available as suppositories or enemas
S/E of laxatives
Cramps (peristalsis stimulation)
bowel perforation in patients with intestinal obstruction
Excessive use may cause hypokalaemia and further colon impairments
Types of laxatives
- faecal softener (emollient)
Lactulose is what type of laxative and how does it work
- it is a synthetic disaccharide
- non-absorbable sugar that increases osmolality in gut
- retain fluid in bowel
- also increase faecal bulk, softens and lubricate stool
Bran and methylcellulose are what type of laxatives and how do they work ?
Both are bulk laxatives that increases faecal bulk thereby stimulating local reflexes (peristalsis)
Also soften hard stools but requires adequate fluid intake to prevent intestinal obstruction
Safest and most generally administrated laxative?
Emollient laxative can cause what unwanted effect
Anal Seepage and irritation
Example of stimulant laxatives
Properties of stimulant laxatives
Irritate intestinal mucosa thereby stimulating fluid secretion and peristalsis. (Increase motility via chemoreceptor activation and myenteric nerve plexus)
Very potent and seldom required
Normally used in terminal care and to evacuate bowel pre-surgery
Mimic parasympathetic effects therefore stimulates peristalsis
Have simulator effects to stimulant laxatives
What type of laxatives are muscarinic agonists and AChE inhibitors
Types of antidiarrhoeal drugs
- bulk laxatives
- fluid and salt replacements
How does salt and fluid replacement work ?
Treats diarrhoea by retaining Na ions back into the enterocyte via SGLT1 and SGLT2 (increase cell osmolality thereby causes water retention)
When does bulk forming laxatives become especially useful in treating diarrhoea?
In diverticular dieases
How does loperamide work
Binds to m-receptors in myenteric plexus , activate Gi protein and inhibits AC
Less cAMP therefore Decrease motility (decrease chronotropy and decrease dromotropy)