Pharmacotherapeutics for GI Disorders

Questions and Answers

What is a significant contraindication for the use of prucalopride?

Short term diarrhoea

Chronic idiopathic constipation

Severe inflammatory bowel condition (correct)

Mild abdominal cramping

Which adverse effect is commonly associated with loperamide?

Dehydration

Intestinal obstruction

Dizziness (correct)

Severe abdominal cramping

What is the main mechanism of action for 5HT3 receptor antagonists?

They enhance the action of serotonin on 5-HT3 receptors.

They increase excitability of vagal afferent nerves.

They stimulate the release of substance P in the CTZ.

They block the action of serotonin on 5-HT3 receptors. (correct)

What mechanism do D2 receptor antagonists use to decrease vomiting?

Block dopamine on D2 receptors Signup and view all the answers

Which pharmacokinetic characteristic is true for Ondansetron?

It is predominantly renally excreted. Signup and view all the answers

Which of the following pharmacokinetic properties applies to prucalopride?

Renal excretion of 84% Signup and view all the answers

What is one of the unique features of domperidone compared to other D2 receptor antagonists?

It does not cross the blood-brain barrier Signup and view all the answers

What adverse effect is commonly associated with NK-1 receptor antagonists?

Diarrhoea Signup and view all the answers

Which condition is an indication for the use of metoclopramide?

Gastric stasis Signup and view all the answers

Which drug has the longest half-life among the mentioned antiemetics?

Aprepitant Signup and view all the answers

What common adverse effect is associated with the use of prochlorperazine?

Galactorrhoea Signup and view all the answers

What is the action of corticosteroids in the context of nausea and vomiting?

They inhibit PG synthesis and alter serotonin turnover. Signup and view all the answers

What is a common contraindication for the administration of corticosteroids?

Diabetes Signup and view all the answers

What is the primary action of loperamide in treating diarrhea?

Decreasing peristaltic contractions Signup and view all the answers

What pharmacokinetic characteristic applies to Aprepitant?

It has negligible renal excretion. Signup and view all the answers

Which mechanism is NOT associated with the action of NK-1 receptor antagonists?

Increased excitability of vagal afferent nerves. Signup and view all the answers

What is the primary mechanism by which Propranolol decreases portal blood flow?

Unopposed α1-mediated vasoconstriction Signup and view all the answers

Which patient precautions are associated with the use of Terlipressin?

Ischaemic cardiovascular disease Signup and view all the answers

What is a common adverse effect of Octreotide?

Flatulence Signup and view all the answers

How does Terlipressin primarily affect variceal bleeding?

By causing arterial vasoconstriction Signup and view all the answers

Which of the following is an indication for the use of Octreotide?

Oesophageal varices Signup and view all the answers

What is the half-life of Propranolol?

8 hours Signup and view all the answers

Which route of administration is used for Terlipressin?

Intravenous Signup and view all the answers

Which adverse effect is most likely associated with Propranolol?

Cold extremities Signup and view all the answers

What is a common adverse effect associated with 5-aminosalicylates?

Nausea Signup and view all the answers

Which of the following mechanisms describes the action of 5-aminosalicylates?

Exerting local inflammatory effects Signup and view all the answers

What is the primary indication for the use of immunosuppressants like azathioprine and mercaptopurine?

Inflammatory bowel disease (IBD) Signup and view all the answers

What could happen if mercaptopurine is administered alongside allopurinol?

Increased risk of bone marrow toxicity Signup and view all the answers

Which administration method is preferred for 5-aminosalicylates when treating ulcerative colitis?

Oral and rectal Signup and view all the answers

What is the primary pharmacological action of methotrexate?

Competing with dihydrofolate reductase Signup and view all the answers

What adverse effect is specifically noted in azathioprine use?

Dose-related myelosuppression Signup and view all the answers

How is mesalazine primarily cleared from the body?

Intestinal metabolism Signup and view all the answers

What is the primary mechanism of action for spironolactone?

Inhibits aldosterone-induced Na+ channel increase Signup and view all the answers

Which of the following describes the pharmacokinetics of spironolactone?

Extensively metabolized with renal excretion being primarily Signup and view all the answers

What role does albumin play in the treatment with terlipressin?

Acts as a colloid intravenous fluid to increase central blood volume Signup and view all the answers

Which side effects are associated with spironolactone?

Hyperkalemia and menstrual disorders Signup and view all the answers

How does lactulose help in hepatic encephalopathy?

Decreases colonic pH leading to reduced ammonia absorption Signup and view all the answers

Study Notes

Pharmacotherapeutics for Chronic Constipation

Indicated for chronic idiopathic constipation when other laxatives are ineffective.
Contraindicated in cases of intestinal obstruction and severe inflammatory bowel conditions.
Administered orally.
Adverse effects include abdominal cramping and diarrhea.
Pharmacokinetics for Prucalopride:
- Metabolism: None (nil)
- Renal Excretion: 84%
- Half-life: 18-20 hours

Treatment of Diarrhea

Antidiarrhoeals: Common drugs include Loperamide and diphenoxylate (with atropine).
Pharmacodynamics:
- Opioid receptor agonists reduce cAMP, leading to decreased Ca²⁺ and inhibiting peristalsis.
Indicated for short-term diarrhea relief, contraindicated in children.
Administration is oral.
Common adverse effects include abdominal pain, bloating, nausea, constipation, dizziness, and drowsiness.
Pharmacokinetics for Loperamide:
- Metabolism: Extensive
- Renal Excretion: 1%
- Half-life: 10.8 hours

Treatment of Nausea and Vomiting

D² Receptor Antagonists: Includes Metoclopramide, Domperidone, Prochlorperazine.
Pharmacodynamics:
- Block dopamine action on D² receptors, decreasing vomiting center stimulation.
- Metoclopramide and Domperidone activate 5-HT₄ receptors, increasing gut motility.
- Prochlorperazine additionally blocks H₁ and M₁ receptors.
Indications: General nausea and vomiting, gastric stasis.
Contraindications: GI obstruction, Parkinson's disease.
Routes: Oral, IM, IV.
Adverse effects: Drowsiness, movement disorders, galactorrhea.
Pharmacokinetics for Metoclopramide:
- Metabolism: Yes
- Renal Excretion: Predominantly
- Half-life: 5-6 hours
5-HT₃ Receptor Antagonists: Ondansetron and Dolastron.
Blocks serotonin action in CTZ and vagal afferents, reducing vomiting.
Indicated for nausea, particularly post-chemotherapy.
Administered orally, IM, or IV.
Adverse effects: Constipation, headache, dizziness.
Pharmacokinetics for Ondansetron:
- Metabolism: Yes
- Renal Excretion: Yes
- Half-life: 3-4 hours
NK-1 Receptor Antagonists: Aprepitant and Fosaprepitant.
Mechanism involves blocking substance P to reduce vomiting.
Indicated primarily for chemotherapy-induced nausea.
Routes of administration: Oral, IV.
Adverse effects: Diarrhea, fatigue, headache.
Significant interactions with CYP3A4 and CYP2C9 enzymes.
Pharmacokinetics for Aprepitant:
- Metabolism: Yes
- Renal Excretion: None
- Half-life: 9-13 hours
Corticosteroids: Dexamethasone and Prednisolone.
Action mechanism involves unclear pathways affecting inflammation and serotonin.
Indications include prevention of nausea in postoperative situations and IBD.
Administration methods: Oral, suppository, IV.
Adverse effects: Fluid retention, hypertension, Cushing's syndrome.

5-Aminosalicylates for Inflammatory Bowel Disease

Examples: Mesalazine and Olsalazine.
Mechanism involves local anti-inflammatory effects in the colon.
Indicated for ulcerative colitis and Crohn's with colonic involvement.
Administration methods: Oral, rectal.
Common adverse effects: Nausea, headache, diarrhea.
Pharmacokinetics for Mesalazine:
- Metabolism: Mostly intestinal
- Renal Excretion: Predominantly
- Half-life: 40 minutes

Immunosuppressants

Examples: Azathioprine and Mercaptopurine.
Mechanism of action: Inhibition of B and T cells, anti-inflammatory properties.
Indicated for inflammatory bowel diseases.
Interactions with Allopurinol increase risk of toxicity from mercaptopurine.
Adverse effects include myelosuppression, infections, hair loss, gastrointestinal disturbances.
Pharmacokinetics for Azathioprine:
- Metabolism: Yes
- Renal Excretion: None
- Half-life: 5 hours
Methotrexate:
- Mechanism: Antifolate action inhibiting cell division.
- Indication: Refractory inflammatory bowel disease.
- Administration: Oral, SC, IM.

Management of Liver Disease Complications

Oesophageal Varices Treatment:
- Non-selective Beta Blockers: Propranolol, decreases portal blood flow, indicated for oesophageal varices.
- Pharmacokinetics for Propranolol:
  - Metabolism: Yes
  - Renal Excretion: Predominantly
  - Half-life: 8 hours
Vasopressin Analogues: Terlipressin, activates V1 receptors for vasoconstriction.
Somatostatin Analogues: Octreotide inhibits hormone release, reducing portal blood flow.

Other Treatments

Ascites: Treated with Spironolactone, an aldosterone antagonist; indicated for excessive fluid accumulation.
Pharmacokinetics for Spironolactone:
- Metabolism: Extensively
- Renal Excretion: Primarily
- Half-life: 1.4 hours
Hepatic Encephalopathy: Managed with Lactulose, reducing ammonia absorption.

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Description

Explore the pharmacotherapeutics involved in the treatment of chronic constipation and diarrhea. This quiz covers the indications, contraindications, pharmacokinetics, and potential adverse effects for medications like Prucalopride and Loperamide. Test your knowledge on how these medications function and their appropriate use in clinical settings.