Pharmacology: motility affecting drugs Flashcards
What is another name for laxatives?
Aperients
What are the 4 classes of laxatives?
Fibre supplements/bulking agents
Osmotic laxatives
Stimulant laxatives
Stool softeners
Fibre supplements/bulking agents
- What are they made of?
- What is their MOA
Poorly digested polysaccharide polymers - usually plant extracts
Not broken down in GIT. Forms bulky hydrated mass which maintains water and promotes peristalsis
Fibre supplements/bulking agents:
- Formulation?
- Main ADR?
- Can it interact with pharmacokinetics of other drugs?
- Examples?
Powder
Bloating
Yes
Psyllium husk (Metamucil), bran, ispaghula husk
Osmotic laxatives:
- What are they
- What is their mechanism of action?
Solutes that are poorly absorbed in the GIT
Draw water into the gut –> increase motility
Osmotic laxatives:
- ADRs?
- Examples?
Cramping, systemic effects of salts
Lactulose (sugars), macrogol (salts)
Stimulant laxatives
- What is their mechanism of action?
Irritates the mucosa –> stimulates peristalsis + water and electrolyte secretion from mucosa
Stimulant laxatives:
- Main ADR?
- Examples?
Cramping
Senna, bisacodyl, glycerol suppositories
Stool softeners
- What are they?
- What is their MOA?
Surfactants
Have detergent like effects, to reduce surface tension of water to produce softer feces
Stool softeners:
- Examples?
Docusate, glycerol suppositories
What are the 2 main classes of anti-diarrhoeal drugs?
Muscarinic receptor antagonists
Opioid derivatives
Muscarinic receptor antagonists:
MOA?
Blocks excitatory cholinergic stimulation in the ENS
Opioid derivates:
- MOA?
Activate opioid receptors in gut wall –> decrease motility and thus increases fluid absorption
Opioid derivates:
- Do they cross the BBB? Implications?
- Are they relatively selective for the GIT?
- Examples?
No - hence no CNS ADRs
Yes
Loperamide, diphenoxylate
