62 Questions
Which type of drugs are used for the treatment of bowel motility disorders, gastric acidity, and peptic ulcers?
Gastrointestinal drugs
Which part of the gastrointestinal tract is responsible for increasing secretions and gut motility?
Small intestine
Which type of neurons project to the gut to decrease gut motility and contract sphincters?
Sympathetic neurons
Which exocrine gland is not part of the gastrointestinal tract?
Liver
What is the function of vagal afferent neurons in the gastrointestinal tract?
Receive sensory information from the gut
Which condition is NOT treated using drugs affecting the gastrointestinal system?
Urinary tract infection
Which enzyme is responsible for the formation of histamine from histidine?
Histidine decarboxylase
What stimulates the release of histamine?
Immunoglobulin E (IgE) complexes
Which of the following inhibits the release of histamine?
Histamine itself
What is the breakdown process of histamine known as?
Ring methylation and oxidative deamination
Which of the following activates H2 receptors?
Immunoglobulin E (IgE) complexes
What is the mechanism of action of H2 receptor antagonists?
Blocking the binding of acetylcholine, histamine, or gastrin to their receptors
Which drug is known as the first H2 receptor antagonist?
Cimetidine
What stimulates the gastric acid secretion by parietal cells of the gastric mucosa?
Acetylcholine, histamine, and gastrin only
What is the essential function of TRPML1 in gastric acid secretion?
Facilitating vesicle exocytosis
What might be a potential future therapy target in inhibiting gastric acid secretion?
TRPML1
What is the function of bulk-forming laxatives?
They retain water and make fecal material hydrated and soft
What triggers the stimulation of peristalsis in the intestines?
Intraluminal bolus distention
What condition is characterized by delayed gastric emptying?
Gastroparesis
How do stool softeners prevent tenesmus?
By retaining water and making fecal material hydrated and soft
What is the function of cathartics like bisacodyl and castor oil?
Acting as irritants on the small intestine
What is the effect of sodium salts used as cathartics?
Reducing drug absorption and causing electrolyte imbalance
What is the mechanism of action of magnesium hydroxide and other saline cathartics?
Retaining water and increasing peristalsis
How do prokinetic drugs affect GI motility?
Indirectly increasing Acetylcholine release
What are the clinical applications of prokinetic drugs?
Treatment for gastroparesis, gastroesophageal reflux disease, chronic dyspepsia, and as antiemetics
What are the side effects of prokinetic drugs?
Extrapyramidal symptoms similar to those seen with typical antipsychotics.
What hormone stimulates excitatory neurons and muscle cells to increase intestinal peristalsis?
Motilin
How do cathartics like castor oil act in the body?
By being activated by pancreatic lipases
What is the mechanism of action of Bismuth subsalicylate?
Absorbs intestinal toxins and microorganisms
Which drug should not be used in children or in patients with severe colitis due to the risk of toxic megacolon?
Loperamide
What is the clinical use of Aluminum hydroxide and Methylcellulose?
Adsorbing bacterial toxins and fluid in the gut
Which drug is an indirect cholinergic agonist and is used for acute colonic pseudo-obstruction in hospitalized patients?
Bathanechol
Which drug is also an agonist to Motilin receptors and increases gastrointestinal motility?
Erythromycin
Which drug activates presynaptic opioid receptors in the enteric nervous system and decreases peristalsis?
Diphenoxylate
Which of the following H2 receptor antagonists is more potent than Cimetidine and requires less frequent dosing?
Ranitidine
What is the primary reason for the withdrawal of H2 receptor antagonists like Ranitidine and Nizatidine from the market?
Prevalence of PPIs
Why are PPIs preferred over H2 receptor antagonists for treating NSAID-induced ulcers and preventing stress ulcers?
They suppress acid secretion more effectively
Which type of antacids, based on absorption, are not absorbed into the systemic circulation and are excreted in feces?
Non-systemic antacids
What is the approved use of Misoprostol, a prostaglandin E1 analog?
Treating NSAID-induced ulcers
Which H2 receptor antagonist has an increased T1/2 in patients with renal dysfunction, requiring dose adjustment?
Ranitidine
What is the primary function of Prostaglandins, such as Prostaglandin E?
Inhibit HCl secretion
What is the primary side effect of Misoprostol, a prostaglandin E1 analog?
Diarrhea
What is the preferred treatment for high-risk patients, including those with chronic NSAID use, the elderly, and a history of ulcers?
PPIs
What is the primary function of Gastric antacids like aluminum hydroxide and magnesium hydroxide?
Inhibit gastric acid secretion
What stimulates parietal cells to produce gastric acid?
Vagus nerve, acetylcholine, and histamine
How is hydrogen ions (H+) and bicarbonate (HCO3-) formed in parietal cells?
Through the action of carbonic anhydrase
How does H+/K+-ATPase function in parietal cells?
It pumps H+ out of parietal cells into the stomach lumen and secretes HCO3- into the bloodstream
What is the main component of gastric acid?
Hydrochloric acid (HCl)
How is the gastric mucosa protected from the acidic environment?
By mechanisms including mucus secretion, HCO3- secretion, and an impermeable gastric epithelium to H+
What are common causes of peptic ulcers?
Infection with Helicobacter pylori, use of nonsteroidal anti-inflammatory drugs, increased hydrochloric acid secretion
What is the first-line treatment for peptic ulcers?
Eradicating H. pylori infection, reducing gastric acid secretion, providing agents that protect the gastric mucosa
What is the cause of gastroesophageal reflux disease (GERD)?
Stomach acid continuously refluxing into the esophagus
How can GERD be treated?
Improving defense mechanisms, decreasing aggressive factors, and surgery to tighten the sphincter
Which of the following drugs is a mucosal protective agent that forms a paste when in contact with gastric acid and adheres to the mucosal defect, protecting it from acids and pepsin?
Sucralfate
What is the optimal treatment for patients with peptic ulcer disease infected with H. pylori?
Quadruple therapy involving antimicrobial drugs and a proton pump inhibitor (PPI)
What is the possible cause of constipation as a side effect?
Radiologic exams of the GI tract
Which type of laxatives work by increasing the water content of the feces?
Saline and osmotic laxatives
What is the role of H. pylori in peptic ulcers?
It secretes inflammatory mediators and increases gastrin release
Which group of drugs is used to relieve symptoms of peptic ulcer disease, heartburn, and GERD by neutralizing stomach acid?
Antacids
What is the percentage of patients with peptic ulcers who are infected with H. pylori?
~50%
What is the primary function of antacids?
Neutralizing stomach acid by combining with hydrogen ions (H+)
Which drug forms a paste when in contact with gastric acid and has antimicrobial properties against H. pylori?
Bismuth Subsalicylate
Study Notes
- Antacids: used to relieve symptoms of peptic ulcer disease, heartburn, and GERD. They neutralize stomach acid by combining with hydrogen ions (H+) and forming carbonic acid, which releases CO2 and causes belching. Cations in antacids, such as magnesium and aluminum, can have adverse effects in patients with renal failure.
- Antacids: cationic groups – sodium ions (Na+) – do not combine with bicarbonate ions (HCO3-) in the pancreas. Instead, they are absorbed in the duodenum, producing a metabolic alkalosis.
- Mucosal protective agents: improve the defense mechanisms of the gut, prevent mucosal injury, reduce inflammation, and promote healing of existing ulcers.
- Bismuth Subsalicylate: a mucosal protective agent that forms a paste when in contact with gastric acid. This paste adheres to the mucosal defect and protects it from acids and pepsin, improving healing. It is used to treat peptic ulcers and has antimicrobial properties against H. pylori.
- Sucralfate: a mucosal protective agent that forms a paste when it comes into contact with gastric acid. It protects the ulcer from acids and pepsin, improving healing. It is not absorbed, does not inhibit acid secretion, and does not neutralize acid. It cannot be used together with gastric neutralizing agents or gastric secretion lowering agents.
- H. pylori: a gram-negative spiral bacillus that is present in around 55 to 65% of patients with peptic ulcers. It secretes inflammatory mediators, which increase gastrin release and gastric pH, and urease activity, which produces ammonia and increases gastrin secretion. Optimal treatment for patients with peptic ulcer disease infected with H. pylori requires antimicrobial treatment, which eradicates the bacteria and results in rapid healing of active peptic ulcers and low recurrence rates.
- Antimicrobial agents: used to treat H. pylori infections. The most effective therapy involves the use of a combination of antimicrobial drugs, such as metronidazole, amoxicillin, clarithromycin, and tetracyclines, along with a proton pump inhibitor (PPI). Quadruple therapy is recommended for patients with clarithromycin resistance.
- Laxatives and Cathartic Drugs: drugs used to promote defecation. They can be irritants and stimulants, such as senna, bisacodyl, and castor oil, which directly stimulate the intestinal muscles and cause the intestines to contract. They can also be bulk-forming laxatives, such as bran, methylcellulose, and psyllium, which absorb water and increase the volume of stool. Saline and osmotic laxatives, such as magnesium citrate, magnesium hydroxide, and sodium phosphate, work by increasing the water content of the feces. Stool softeners, such as docusate sodium, docusate calcium, and docusate potassium, soften the stool by increasing the water content and making it easier to pass. Mineral oil and glycerin suppositories are lubricant laxatives that help lubricate the rectal area and facilitate the passage of stool.
- Constipation: possible causes include drugs, such as laxatives and cathartic drugs, which can cause constipation as a side effect. Other causes include radiologic exams of the GI tract, bowel surgery, proctologic exams, and anorectal disorders, such as hemorrhoids. Constipation can also be caused by colic, nausea, cramps, undiagnosed abdominal pain, patients with symptoms of appendicitis, and after anti-helminthic therapy or poisoning.
- Irritant laxatives: work by causing an irritant effect on the intestinal mucosa, which stimulates reflex peristalsis and fluid absorption, and directly stimulates peristalsis. They are also used to stimulate bowel movements before radiologic exams and surgeries.
- Peristalsis: the process by which the intestines contract to move food through the digestive tract. It is triggered by the passage of a bolus and involves the stretching of the intestinal wall, which triggers a reflex that results in the contraction of the intestinal muscles and the movement of the bolus through the intestines.
Test your knowledge of gastrointestinal motility with this quiz. Explore the mechanisms behind peristalsis, including the functions of circular and longitudinal muscles, as well as the role of bolus stimulation and cathartics in intestinal motor activity.
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