Pharmacology of GI Drugs

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Questions and Answers

What is the primary mechanism of action of Infliximab?

Stimulates the production of anti-inflammatory cytokines

Blocks TNF alpha receptors on T lymphocytes (correct)

Neutralizes bacterial toxins in the gut

Inhibits the synthesis of epithelial cells

When is Infliximab indicated for use in Crohn's disease?

In severe acute cases when other treatments fail (correct)

For all patients with moderate symptoms

During maintenance therapy to prevent flare-ups

As a first-line therapy for mild cases

Which treatment is NOT typically included for acute management of Crohn's disease?

Antibiotics

Intravenous steroids

NSAIDs for analgesia (correct)

Bowel rest

What are the main treatment options classified for chronic Crohn's disease?

Immunosuppressants, 5-ASAs, and anti-TNF therapies Signup and view all the answers

Which medication is classified as an anti-TNF therapy for Crohn’s disease?

Infliximab Signup and view all the answers

Which medication used in the treatment of ulcerative colitis acts as an inhibitor of COX and 5-lipoxygenase?

Sulfasalazine Signup and view all the answers

What is the primary mechanism of action of ciclosporin in the treatment of ulcerative colitis?

Inhibits calcineurin to lower T-cell activity Signup and view all the answers

What significant lifestyle factor is associated with an increased prevalence of ulcerative colitis?

Smoking Signup and view all the answers

Which of the following is NOT a common symptom of ulcerative colitis?

Severe constipation Signup and view all the answers

What is the potential side effect associated with the medication Mercaptopurine?

Agranulocytosis Signup and view all the answers

Which of the following factors has been implicated as a contributing element to the onset of ulcerative colitis?

Deficient immunoregulation Signup and view all the answers

What is the age range at which most patients typically present with ulcerative colitis?

15-30 years Signup and view all the answers

What is a common associated symptom of ulcerative colitis that can occur alongside diarrhea?

Fever Signup and view all the answers

What is the mechanism of action of Lubiprostone in treating constipation?

It activates selective chloride channels leading to increased chloride efflux. Signup and view all the answers

Which of the following is an adverse effect associated with the use of mu opioid agonists for diarrhoea?

Respiratory depression in small children Signup and view all the answers

What classification does Irritable Bowel Syndrome (IBS) belong to?

Functional gastrointestinal disorder Signup and view all the answers

Which of the following is a potassium-sparing diuretic used in the treatment of mild to moderate ascites?

Spironolactone Signup and view all the answers

What is a potential long-term consequence of excessive laxative use?

Dehydration Signup and view all the answers

Which treatment is effective for achieving the disappearance of ascites in patients with cirrhosis?

Spironolactone and loop diuretics Signup and view all the answers

Which of the following actions does an antimuscarinic agent like atropine perform in treating gastrointestinal disorders?

Reduces gastrointestinal contractions Signup and view all the answers

What subtype classification does the term 'mixed subtype' refer to in IBS?

Alternating diarrhoea and constipation Signup and view all the answers

Study Notes

Drugs and the Gastrointestinal Tract

Drugs impact the gastrointestinal tract, affecting conditions like peptic ulceration, gastro-oesophageal reflux disease, diarrhoea, constipation & IBS and IBD.
Learning resources include materials by James M. Ritter, Rod Flower, Graeme Henderson, Yoon Kong Loke, David MacEwan, Humphrey P. Rang, Bertram G. Katzung and Todd W. Vanderah.
Key learning objectives include pharmacological management of various GI conditions, a list of main drug groups, descriptions of drug mechanism of action, identification of limitations of each drug.

Gastric Acid Secretion and Drug Targets

Gastric acid secretion involves several cellular mechanisms with specific receptor targets.
Different drugs such as histamine receptor antagonists, proton pump inhibitors, and antacids affect gastric acid secretion in different ways.

Proton Pump Inhibitors (PPIs)

PPIs like Omeprazole and Esomeprazole irreversibly inhibit the H+/K+ ATPase (proton pump).
Accumulation of the drug in the parietal cell is key to this mechanism.
PPIs inhibit basal and stimulated acid secretion, with effects lasting 2-3 days after a single dose.

Histamine H2 Receptor Antagonists

Cimetidine and Ranitidine, available over-the-counter in lower doses, competitively inhibit histamine H2 receptors.
These drugs reduce histamine, gastrin and ACh-stimulated acid secretions by 70%.

Antacids

Magnesium and Aluminum salts neutralize acidity by removing H+ ions by binding to them.
This leads to different reactions and side effects. Sodium bicarbonate produces CO2 and thus will cause bloating and alkalosis, Mg(OH)2 produces diarrhea, and Al(OH)3 has constipation as a side effect.

Helicobacter pylori Infection

Recommended first-line therapy usually involves a Proton Pump Inhibitor (PPI) plus a combination of antibiotics like Clarithromycin and Amoxicillin or Metronidazole.

Constipation and Diarrhoea

Purgatives, osmotic laxatives, and stimulant laxatives are used to treat constipation and diarrhea. Docusate sodium is an example of a fecal softener. Biscodyl and other stimulant laxatives are administered to stimulate intestinal motility and excretion.

Constipation: CIC-2 Activator

Lubiprostone is a selective chloride channel activator that increases intestinal motility and softens stool.

Oral Rehydration Therapy

Oral rehydration therapy involves co-transport of glucose and sodium in the small intestine to restore fluids and electrolytes.

Anti-diarrhoeal Agents

Codeine and Loperamide are mu opiod agonists prescribed to manage diarrhea, but may cause respiratory depression in small children and paralytic ileus.

Liver Ascites

Liver ascites is fluid buildup in the peritoneal cavity due to liver disease or sinusoidal portal hypertension. Treatment involves sodium restriction and diuretics, primarily spironolactone.

Irritable Bowel Syndrome (IBS)

IBS is a functional gastrointestinal disorder affecting ~20% of the population worldwide. IBS has a biopsychosocial basis, and three main subtypes (constipation-predominant, diarrhea-predominant, and mixed/alternating).
Diagnosis is established using criteria such as the Rome criteria and the Manning criteria.
Treatment approaches include fiber supplements, laxatives, anti-diarrhoeal medicines and a low-FODMAP diet.

Inflammatory Bowel Disease (IBD)

IBD (including Ulcerative Colitis (UC), and Crohn's disease), can be understood as stemming from an inappropriate and continuing inflammatory response to microbes.
Dysfunction of the epithelial barrier, innate immune cells, and adaptive T cells contribute to it. Differences in affected areas and presentation distinguish the two subtypes.
Key symptoms for UC includes: Crampy abdominal pain, diarrhoea, urgency, tenesmus, weight loss, fever, and anaemia.
Characteristics of Crohn's disease include: Crampy abdominal pain, diarrhoea, weight loss, fever, anaemia, obstruction, distension, vomiting and abscesses.
Treatment management for IBD often involves several approaches such as medications (5-ASA, corticosteroids, mercaptopurine, ciclosporine, biologics) and surgery.

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Description

Explore the impact of various drugs on the gastrointestinal tract and their roles in managing conditions such as peptic ulcers and IBS. This quiz covers drug mechanisms, targets for gastric acid secretion, and key pharmacological treatments including proton pump inhibitors. Understand the limitations and pathways of these pharmacological agents in GI management.