Gastroenterological Drugs

Gastroenterological Drugs Video

Welcome to this video tutorial over gastrointestinal medications. In this video, we are going to discuss some of the common drugs used to treat a wide variety of gastrointestinal disorders ranging from stomach ulcers to diarrhea.


Most gastrointestinal symptoms are minor, short-lived, and can be relieved with over-the-counter drugs such as antacids. Other ailments such as stomach ulcers, chronic diarrhea, and uncontrollable vomiting may need something stronger that requires a prescription from the doctor. Regardless, both over-the-counter and prescription gastrointestinal drugs, come with their fair share of side effects and must be monitored by the physician.


Histamine 2 Receptor Antagonists, also known as H2-blockers, are used in the treatment of duodenal and gastric ulcers. These medications are usually effective and work by suppressing the secretion of gastric acid. H2 blockers are cheap and serious side effects are uncommon making these drugs a good choice for the treatment of ulcers, sour stomachs, and indigestion. The four most commonly used H2 blockers include Cimetidine, Ranitidine, Famotidine, and Nizatidine. Cimetidine (Tagamet) works by blocking H2 receptors which reduces the volume of gastric juices that are secreted. Cimetidine is best used for the treatment of gastric and duodenal ulcers but can also aid in relieving symptoms associated with gastroesophageal reflux disease, Zollinger-Ellison syndrome, and heartburn. Adverse effects associated with this medication include antiandrogenic effects such as gynecomastia, reduced libido, and impotence. With the use of Cimetidine, the elevation of the gastric pH can cause an ideal environment for bacterial colonization of the respiratory tract and stomach. Therefore, a slight risk of pneumonia is also present. Cimetidine also interacts with many drugs and can cause levels of Warfarin, Phenytoin, Theophylline, and Lidocaine to rise, requiring a decrease in the dosage of these medications. Ranitidine (Zantac) has many of the same properties of Cimetidine but with fewer drug interactions and fewer adverse effects. Ranitidine does not cross the blood brain barrier easily and it does not bind to androgen receptors. This decreases the risk of gynecomastia. This drug is best used in the short-term treatment of ulcers, gastrointestinal reflux, and Zollinger-Ellison syndrome. Other drugs in the H2 blocker class include Famotidine (Pepcid) and Nizatidine (Axid). Both work similarly to the other H2 blockers and aid in the treatment of indigestion and sour stomachs.

Even more effective than H2 blockers in the treatment of peptic ulcer disease, GERD, and Zollinger-Ellison syndrome, are the proton pump inhibitors, or PPIs, which can completely inhibit acid secretion as well as have a long duration of action. PPIs have higher ulcer healing rates, faster control of peptic ulcer disease symptoms, and are more effective in preventing NSAID-induced gastroduodenal toxicity. PPI’s are used for short-term therapies and are generally well tolerated. However, long-term use has been associated with several safety concerns, such as increased risk of fractures, pneumonia, and intestinal infections. Common PPIs include Omeprazole, Esomeprazole, Lansoprazole, and Pantoprazole. Omeprazole (Prilosec) is one of the oldest PPIs on the market and is used for the short-term treatment of ulcers and reflux. Adverse effects associated with this medication include headaches, pneumonia, and fractures. Esomeprazole (Nexium) works like Omeprazole and is used for the treatment of erosive esophagitis, duodenal ulcers, NSAID-induced ulcers, and H. Pylori infections. Adverse effects include headaches, diarrhea, nausea, and abdominal pain. Lansoprazole (Prevacid) is a very effective over-the-counter remedy for treating acid reflux but also carries a strong risk for fractures. Pantoprazole (Protonix) is a PPI that is available in oral and IV form. It’s best used in hypersecretory states such as GERD. Adverse effects include diarrhea, fractures, and hypomagnesemia. Note that all the above PPIs include a risk for fractures. Fractures are a huge risk with the long-term use of PPIs due to the reduction of acid secretion which may decrease absorption of calcium. Additionally, long-term use of PPIs can lower magnesium levels and should not be used with other drugs that lower magnesium such as Thiazide and loop diuretics. Rebound acid hypersecretion is another risk that is increased with long-term use and can significantly raise the risk of gastric cancer and chance of a C. Difficile infection. Due to the serious adverse effects associated with long-term use of Proton Pump Inhibitors, the use of these medications should be used for the shortest amount of time at the lowest effective dose.

Other antiulcer drugs include Sucralfate, Misoprostol, and Antacids. Sucralfate (Carafate) is a medication that works by creating a protective barrier in the stomach that promotes ulcer healing. A common side effect with Sucralfate is constipation. Misoprostol (Cytotec) is used in the prevention of gastric ulcers caused by the long-term use of NSAIDs. Diarrhea and abdominal pain are common with this medication. Misoprostol is a category X medication and should not be used in a pregnant patient. Antacids are over-the-counter alkaline compounds that neutralize stomach acid and help combat GERD and peptic ulcer disease. Adverse effects of these include constipation, diarrhea, and hypernatremia. These should be used in caution in patients with renal impairments.

Antiemetic drugs are used to combat nausea and vomiting and work by suppressing the dopamine receptors in the chemoreceptor trigger zone. Ondansetron (Zofran) is an effective drug for treating nausea and vomiting that occurs postoperatively. It is also recognized as one of the first approved medications that is used to prevent chemotherapy-induced nausea and vomiting. Ondansetron can be administered orally, intramuscularly, or intravenously. Adverse effects associated with this medication include headaches, diarrhea, and a prolonged QT interval. Promethazine (Phenergan) is a widely used antiemetic and works by blocking dopamine receptors. This medication has a high risk of extrapyramidal reactions, hypotension, and sedation. It should be used in caution with children and the elderly. Metoclopramide (Reglan) is another antiemetic and is the main-line treatment for chemotherapy-induced nausea and vomiting. It is worth noting that with these antiemetics, effectiveness depends on the timing. Antiemetics are more effective in preventing chemotherapy-induced nausea than suppressing it.

Antidiarrheal agents work to suppress or prevent diarrhetic episodes. Diphenoxylate (Lomotil) and loperamide (Imodium) are the most commonly used. These work by activating opioid receptors in the gastrointestinal tract which reduce intestinal motility, slow intestinal transit, and allow more fluid to be absorbed. Diphenoxylate is only used for diarrhea and has no significant effect on the central nervous system unless taken in high doses in which the drug can elicit sedation. Loperamide is used to treat diarrhea and reduce the volume of discharge from ileostomies. This drug works by suppressing bowel motility and fluid suppression and has little to no potential for abuse. Bismuth subsalicylate, also known as Pepto-Bismol, is effective for the treatment of mild diarrhea. However, users should be aware that the drug has the potential to blacken the stools and the tongue.

The last type of gastrointestinal drugs discussed in this video is laxatives. Laxatives are used to ease, increase, and stimulate defecation. They work by softening the stool, increasing stool volume, and hastening fecal passage through the intestines. Bulk-forming laxatives such as Psyllium (Metamucil) work by softening and increasing fecal mass. Surfactant laxatives such as Docusate Sodium (Colace) alter the stool consistency which facilities water into the feces and produces soft stool. Stimulant laxatives such as Bisacodyl (Dulcolax) stimulate intestinal motility and osmotic laxatives (sodium phosphate, Milk of Magnesia) rely on the osmotic movement of salt into the intestinal lumen that stimulates peristalsis. Adverse effects associated with laxative use include dehydration, acute renal failure, and symptoms of sodium retention which will have to be used in caution in heart failure patients.

So now that we have an overview of some gastrointestinal drugs that can treat a wide variety of disorders, let’s do some review questions:

Review Questions

Thomas has been using Pepto Bismol for preventative diarrhea episodes while traveling out of the country. He reports to the physician with concerns of a dark appearance of his stool and a black tongue. The physician should:

  1. Discourage the use of Pepto Bismol due to the serious side effects presented.
  2. Direct patient to the emergency room for an evaluation.
  3. Realize that this is a common harmless side effect associated with bismuth subsalicylate.
  4. Swab his tongue to assess for bacteria growth.
The correct answer is #3.

Pepto Bismol can cause the appearance of black stool and a black tongue, both which are harmless.


What are the concerns associated with long-term use of Proton Pump Inhibitors? Pick all that apply:

  1. Fractures
  2. Hypomagnesemia
  3. Gastric cancer
  4. Rebound acid hypersecretion
  5. All the above
The correct answer is #5.

The long-term use of Proton Pump Inhibitors can cause fractures, hypomagnesemia, gastric cancer, and rebound acid hypersecretion.

I hope this helps summarize some of the common gastrointestinal drugs and their associated uses. See you next time!


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by Mometrix Test Preparation | Last Updated: January 30, 2024