Constipation Flashcards
What are the 7 drug groups used to treat constipation?
- Bulk-forming laxatives
- Stool surfactant agents
- Osmotic laxatives
- Stimulant laxatives
- Cl- channel activators
- Opoid receptor antagonists
- Serotonin 5-HT4 receptor agonists
What is the MOA of 5-HT4 receptor agonists?
Stimulation of 5-HT4 receptors on nerve terminals in the GI walls increases neurotransmitter release & smooth muscle activity
What is an example of an opoid receptor antagonist?
Methylnaltrexone
What is an example of a 5-HT4 receptor agonist?
Prucalopride
What is methylnaltrexone indicated in?
Opoid-induced constipation in patients receiving palliative care
MOA of methylnaltrexone?
Blockade of intestinal mu opoid receptors
What is an example of a Cl- channel activator?
Lubiprostone
MOA of lubiprostone?
Stimulate type-2 Cl- channels in small intestine, increasing Cl- rich fluid secretions and stimulating motility
What group of patients is lubiprostone contraindicated in?
Pregnancy
What is senna associated with?
Brown pigmentation of colon
(melanosis coli)
What are 2 examples of stimulant laxatives?
Senna
Bisacodyl (dulcolax)
Onset of action of bisacodyl (supp)?
30-60min
MOA of stimulant laxatives?
Produce migrating colonic contractions via direct stimulation of the enteric nervous system
Why should bisacodyl not be taken with milk?
Cause the enteric coating of oral bisacodyl to break down prematurely, causing gastric irritation/dyspepsia
Name 3 examples of osmotic laxatives
Lactulose
Macrogol
Magnesium hydroxide
Sodium phosphate
MOA of osmotic laxatives?
Nonabsorbable sugar/salt that stimulates water movement into bowel, increasing stool liquidity & volume
Adverse effect of osmotic laxatives?
Electrolyte imbalance due to solute drag
What groups of patients are sodium phosphates contraindicated in?
Elderly
Patients on diuretics
Renal insufficiency
Cardiac disease
Adverse effects of sodium phosphate
The 4 hypers
Na/Ca/PO4/K
Name 2 examples of stool surfactant agents
Glycerin (enema)
Mineral oil (PO)
MOA of stool surfactant agents?
Lowers surface tension of stool, allowing water & lipids to penetrate
Increases stool volume & liquidity, promoting peristalsis
Adverse effect of long-term mineral oil use?
Impairment of vit ADEK absorption
Name an example of a bulk-forming agent
Psyllium
MOA of psyllium?
Indigestible fiber, absorbes water forming bulk which distends colon, promoting peristalsis
Which drug should not be taken within 2hrs of other oral drugs?
Psyllium
Prevents absorption of other oral drugs
What are the general adverse effects of all constipation medications?
Diarrhoea, flatulence, bloating, abdominal pain, nausea
What group of patients should NOT be given constipation meds?
Patients with intestinal obstruction
