Constipation

Question 1

What are the 7 drug groups used to treat constipation?

Answer 1

1. Bulk-forming laxatives
2. Stool surfactant agents
3. Osmotic laxatives
4. Stimulant laxatives
5. Cl- channel activators
6. Opoid receptor antagonists
7. Serotonin 5-HT4 receptor agonists

Question 2

What is the MOA of 5-HT4 receptor agonists?

Answer 2

Stimulation of 5-HT4 receptors on nerve terminals in the GI walls increases neurotransmitter release & smooth muscle activity

Question 3

What is an example of an opoid receptor antagonist?

Answer 3

Methylnaltrexone

Question 4

What is an example of a 5-HT4 receptor agonist?

Answer 4

Prucalopride

Question 5

What is methylnaltrexone indicated in?

Answer 5

Opoid-induced constipation in patients receiving palliative care

Question 6

MOA of methylnaltrexone?

Answer 6

Blockade of intestinal mu opoid receptors

Question 7

What is an example of a Cl- channel activator?

Answer 7

Lubiprostone

Question 8

MOA of lubiprostone?

Answer 8

Stimulate type-2 Cl- channels in small intestine, increasing Cl- rich fluid secretions and stimulating motility

Question 9

What group of patients is lubiprostone contraindicated in?

Answer 9

Pregnancy

Question 10

What is senna associated with?

Answer 10

Brown pigmentation of colon
(melanosis coli)

Question 11

What are 2 examples of stimulant laxatives?

Answer 11

Senna
Bisacodyl (dulcolax)

Question 12

Onset of action of bisacodyl (supp)?

Answer 12

30-60min

Question 13

MOA of stimulant laxatives?

Answer 13

Produce migrating colonic contractions via direct stimulation of the enteric nervous system

Question 14

Why should bisacodyl not be taken with milk?

Answer 14

Cause the enteric coating of oral bisacodyl to break down prematurely, causing gastric irritation/dyspepsia

Question 15

Name 3 examples of osmotic laxatives

Answer 15

Lactulose
Macrogol
Magnesium hydroxide
Sodium phosphate

Question 16

MOA of osmotic laxatives?

Answer 16

Nonabsorbable sugar/salt that stimulates water movement into bowel, increasing stool liquidity & volume

Question 17

Adverse effect of osmotic laxatives?

Answer 17

Electrolyte imbalance due to solute drag

Question 18

What groups of patients are sodium phosphates contraindicated in?

Answer 18

Elderly
Patients on diuretics
Renal insufficiency
Cardiac disease

Question 19

Adverse effects of sodium phosphate

Answer 19

The 4 hypers

Na/Ca/PO4/K

Question 20

Name 2 examples of stool surfactant agents

Answer 20

Glycerin (enema)
Mineral oil (PO)

Question 21

MOA of stool surfactant agents?

Answer 21

Lowers surface tension of stool, allowing water & lipids to penetrate

Increases stool volume & liquidity, promoting peristalsis

Question 22

Adverse effect of long-term mineral oil use?

Answer 22

Impairment of vit ADEK absorption

Question 23

Name an example of a bulk-forming agent

Answer 23

Psyllium

Question 24

MOA of psyllium?

Answer 24

Indigestible fiber, absorbes water forming bulk which distends colon, promoting peristalsis

Question 26

Which drug should not be taken within 2hrs of other oral drugs?

Answer 26

Psyllium

Prevents absorption of other oral drugs

Question 27

What are the general adverse effects of all constipation medications?

Answer 27

Diarrhoea, flatulence, bloating, abdominal pain, nausea

Question 28

What group of patients should NOT be given constipation meds?

Answer 28

Patients with intestinal obstruction