Test your understanding of the basic pharmacology of the large intestine and some clinical reasoning.
Reviewed by Lena Berger and Jonathan Loomes-Vrdoljak
Pharmacology of the large intestine
Congratulations - you have completed Pharmacology of the large intestine. You scored %%SCORE%% out of %%TOTAL%%. Your performance has been rated as %%RATING%%
Your answers are highlighted below.
A patient on longstanding loperamide presents with new onset constipation. Which of the following best explains this?
Myenteric plexus antagonism
Submucosal plexus antagonism
Question 1 Explanation:
Loperamide is a mu receptor agonist - it stimulates opioid mu receptors in the myenteric plexus which slows their activity. Other opioids, like codeine and morphine, also bind to the same receptors, which is why these forms of pain relief can cause constipation.
A patient with congenital volvulus has silent bowel sounds in the RLQ. But loud sounds heard in the LUQ. Where is the most likely site of the obstruction?
Ligament of Trietz
Which of the following general examination signs indicates late stage constipation?
Enhanced bowel sounds
What class of drug is docusate?
Bulk forming laxative
Question 4 Explanation:
Docusate is a faecal softener. It makes it easier for the stool to hold water and therefore easier to pass. It arguably also has an osmotic laxative effect but it's major mechanism of action it to make the stool easier to move. See DrugBank.
Senna works by what mechanism?
Increasing the volume of non-absorbable material
Increasing stool water content
Altering faecal consistency
Innervating the myenteric plexus
A patient with flatus, abdominal pain that is diffuse and umbilical with fatigue and constipation is diagnosed with IBS after a negative colonoscopy and endoscopy. Which is the best first line treatment?
Question 6 Explanation:
Isphagula husk is a soluble fibre supplement. Other first line management for IBS with constipation include dietary changes including more soluble fibres (like oats and linseeds) and increase water intake.
Magnesium sulphate and magnesium hydroxide are given to this patient to relieve his non-responsive constipation. What type of receptor does this rely upon?
Question 7 Explanation:
These drugs are osmotic laxatives. They draw water into the gut. This stretches the walls of the GI tract, triggering peristalsis and the defecation reflex.
A patient with faecal impaction is given an osmotic laxative that is an inert polymer of ethylene glycol. What is this name of this medication?
A patient with constipation, liver flap on general examination, generalised confusion and day-night somnolence inversion is given a medication to treat their condition. As this medication is fermented, it is converted into...
Question 9 Explanation:
The stem is describing the drug lactulose which is converted by microbiota of the patient's gut to lactic acid and acetic acid. It is readily used in chronic constipation patients and to treat hepatic encephalopathy.
Once you are finished, click the button below. Any items you have not completed will be marked incorrect.
There are 9 questions to complete.