Laxatives - Osmotic laxatives

Question 1

There are 4 basic layers of the GIT. Organise them with the closest layer to the lumen 1st:

1 - mucosa
2 - serosa
3 - muscularis externa also known as muscularis propria
4 - submucoas

Answer 1

1 - mucosa
4 - submucoas
3 - muscularis externa also known as muscularis propria
2 - serosa

Question 2

In the 3rd layer of the GIT is the muscularis externa, contains smooth muscle. There are 2 layers of smooth muscle, an inner circular layer and an outer longitudinal layer. Together these perform peristalsis. Which of these layers is responsible for stopping food move backwards, and which is responsible for moving food forward?

Answer 2

• stopping food moving backwards = INNER CIRCULAR LAYER
• moving food forward = OUTER LONGITUDINAL LAYER

Question 3

The 3rd layer of the GIT is the muscularis externa, containing an inner circular and an outer longitudinal layer os smooth muscle. This is separated by what?

1 - submucosal nerve plexus
2 - lamina propria
3 - myenteric nerve plexus
4 - muscularis mucosa

Answer 3

3 - myenteric nerve plexus

Question 4

Which of the following is NOT contained within the dense submucosal layer?

1 - arteries
2 - veins
3 - submucosal nerve plexus
4 - lamina propria

Answer 4

4 - lamina propria

Question 5

Which 2 of the following are the functions of the submucosa plexus contained within the submucosal layer of the GIT?

1 - peristalsis of the GIT
2 - control of blood vessels
3 - secretion of mucus
4 - GIT secretions

Answer 5

2 - control of blood vessels
4 - GIT secretions

Question 6

The mucosa contains 3 separate layers. Which of the following is NOT a layer of the mucosa?

1 - muscularis mucosa
2 - submucosal nerve plexus
3 - lamina propria
4 - epithelial layers

Answer 6

2 - submucosal nerve plexus

• muscularis mucosa = break up food
• lamina propria = blood and lymph vessels
• epithelial layers = absorbs and secretes mucus and GIT secretions

Question 7

According to NICE, diarrhoea is the abnormal passage of loose or liquid stools. Which 2 of the following are needed in a patient to be diagnosed with acute diarrhoea?

1 - >3 times/day daily and/or a volume of stool >200g/day
2 - >10 times/day and/or stool volume >500g/day
3 - <14 days in duration
4 - >14 days in duration

Answer 7

1 - >3 times/day daily and/or a volume of stool >200g/day

3 - <14 days in duration

• chronic diarrhoea is >4 weeks

Question 8

Which of the following are included in the definition of constipation?

1 - <3 bowel movements/wk
2 - excessive straining
3 - abdominal pain or bloating
4 - all of the above

Answer 8

4 - all of the above

Question 9

Which of the following are included in the definition of chronic constipation?

1 - <3 bowel movements/wk
2 - excessive straining
3 - abdominal pain or bloating
4 - symptoms present in 12 weeks of the last 6 months
5 - all of the above

Answer 9

5 - all of the above

Question 10

Which of the following is NOT an osmotic laxative that we need to be aware of?

1 - Lactulose
2 - Macrogol
3 - Sodium phosphate
4 - Senna
5 - Enemas

Answer 10

4 - Senna

Question 11

How do osmotic laxatives improve bowel movements?

1 - contains compounds that are not digested or absorbed well
2 - epithelial cells secrete fluids to dilute compounds due to osmosis
3 - increase fluid and stool in bowels induces increased peristalsis
4 - all of the above

Answer 11

4 - all of the above

Question 12

Which 2 of the following are indications for the use of osmotic laxatives?

1 - diverticulosis
2 - bowel obstruction
3 - constipation
4 - bowel preparation prior to procedure

Answer 12

3 - constipation
4 - bowel preparation prior to procedure

Question 13

All the osmotic laxatives are indicated for the treatment of constipation and bowel preparation, prior to surgery. Which of the core laxatives is also used in the treatment of hepatic encephalopathy as it can reduce ammonia absorption?

1 - Lactulose
2 - Macrogol
3 - Sodium phosphate
4 - Enemas

Answer 13

1 - Lactulose

• once degraded becomes acetic and lactic acid, which stimulate peristalsis

Question 14

Which of the core osmotic laxatives is commonly used in enemas, which is when a fluid is injected into the rectum to cleans the lower colon and rectum?

1 - Lactulose
2 - Macrogol
3 - Sodium phosphate
4 - Enemas

Answer 14

3 - Sodium phosphate

Question 15

How are osmotic laxatives typically administered?

1 - orally
2 - IV
3 - suppository
4 - IM

Answer 15

1 - orally
3 - suppository

• need to ensure patient has adequate fluid levels prior to use

Question 16

When administering osmotic laxatives via the oral route. However, macrogels must not be consumed with starch based thickeners, why is this?

1 - accentuate the osmotic effect causing dehydration
2 - reduce lipid digestion and absorption
3 - inhibit the re-absorption of bile acids
4 - dilutes thickened foods that may cause aspiration

Answer 16

4 - dilutes thickened foods that may cause aspiration

• starch based thickeners are given to aid safe swallowing in patients with dysphagia

Question 17

Which of the following are common adverse events of osmotic laxatives?

1 - abdominal cramps
2 - diarrhoea
3 - nausea
4 - abnormal U&Es
5 - all of the above

Answer 17

5 - all of the above

Question 18

Osmotic laxative is contra-indicated in which of the following?

1 - GIT atony
2 - intestinal obstruction
3 - undiagnosed abdominal pain
4 - all of the above

Answer 18

2 - intestinal obstruction

Question 19

Osmotic laxatives in generally are contraindicated in GIT atony, intestinal obstruction and undiagnosed abdominal pain. One of the core laxatives should also be avoided in children, cardiac conditions, renal impairment and patients with abnormal U&Es as this drug can cause hypermagnesemia and hyperphosphatemia. Which laxative is this?

1 - Lactulose
2 - Macrogol
3 - Sodium phosphate
4 - Senna

Answer 19

3 - Sodium phosphate

• hypermagnesemia = heart block, neuromuscular block, and CNS depression
• hyperphosphatemia = AKI, metabolic acidosis, hypocalcemia, tetany, and even death

Question 20

Which drug class are laxatives generally prescribed alongside?

1 - NSAIDs
2 - Ca2+ channel blockers
3 - opioids
4 - benzodiazepines

Answer 20

3 - opioids