GI Pharmacology Chapters 56–59: Secretions, Bowel Management & Antiemetics

What are the three sections of the small intestine?

Duodenum, Jejunum, Ileum

What do parietal cells produce?

Hydrochloric acid

What do chief cells produce?

Pepsinogen

What do mucous cells produce?

Mucus

What does the duodenum receive bile from?

The liver

What does the duodenum receive enzymes from?

The pancreas

What does the jejunum primarily absorb?

Nutrients

What does the ileum absorb that is special?

Vitamin B12 and bile salts

What does the liver produce and where is it stored?

Bile, stored in the gallbladder

What are the three enzymes secreted by the pancreas?

Amylase, lipase, protease

What is first-pass metabolism?

Drugs absorbed from the GI tract go to the liver before reaching systemic circulation.

What are the three normal protective mechanisms of the gastric mucosa?

Mucus production, bicarbonate secretion, and epithelial cell regeneration

What are the three disrupted factors that can cause ulcers?

Increased acid production, decreased mucus production, and H. pylori infection

What are the drug names for H2 antagonists?

Ranitidine, famotidine, nizatidine

What is the mechanism of action for H2 antagonists?

They block histamine H2 receptors, reducing gastric acid secretion.

What is the #1 drug to know among H2 antagonists and why?

Cimetidine, due to its drug interactions and side effects.

What is the mechanism of antacids?

They neutralize existing stomach acid.

What is the timing rule for taking antacids with other medications?

Antacids should be taken at least 1-2 hours apart from other medications.

What are the three drug names for proton pump inhibitors (PPIs)?

Omeprazole, esomeprazole, lansoprazole

What is the mechanism of action for PPIs?

They irreversibly inhibit the H+/K+ ATPase in gastric parietal cells.

What are the long-term side effects of PPIs?

Increased risk of Clostridium difficile infection, bone fractures, and kidney disease.

What is the mechanism of action for sucralfate?

It forms a protective barrier over ulcers without reducing acid.

What is misoprostol used for?

To prevent NSAID-induced gastric ulcers.

What is the black box warning associated with misoprostol?

It can cause uterine contractions and should not be used in pregnancy.

What is H. pylori and why does it cause ulcers?

H. pylori is a bacterium that disrupts the gastric mucosal barrier, leading to ulcer formation.

What is included in the triple therapy for H. pylori treatment?

Antibiotic, PPI, and bismuth compound.

What is the indication for pancrelipase?

It is needed for patients with pancreatic insufficiency.

What is the important allergy to ask about when prescribing pancrelipase?

Pork allergy, as it is derived from porcine sources.

What is the mechanism of stimulants used for constipation?

Stimulants act by increasing peristalsis in the intestines.

What are stool softeners/lubricants used for?

They are used to ease bowel movements by softening the stool.

What should not be used with stool softeners?

They should not be used with mineral oil.

Why do opioids cause constipation?

Opioids bind to receptors in the gut, decreasing gut motility.

What is the standard prevention for opioid-induced constipation?

Start prophylactically with a laxative with every opioid prescription.

What is methylnaltrexone and how is it different?

Methylnaltrexone is a targeted drug for OIC that does not cross the blood-brain barrier.

Does tolerance develop to opioid-induced constipation?

No, tolerance does not develop to opioid-induced constipation.

What drug class does Metoclopramide (Reglan) belong to?

It belongs to the class of prokinetic agents.

What is the mechanism of Metoclopramide?

It increases gut motility and accelerates gastric emptying.

List three uses of Metoclopramide.

1. Nausea and vomiting 2. Gastroparesis 3. GERD.

What does EPS stand for in relation to Metoclopramide?

Extrapyramidal symptoms.

What is the treatment for acute EPS?

Anticholinergic medications such as benztropine.

What is the black box warning for Metoclopramide?

Risk of tardive dyskinesia with long-term use.

What is the maximum duration of therapy for Metoclopramide?

The maximum duration is typically 12 weeks.

What is the mechanism of Loperamide (Imodium)?

It decreases gut motility and increases transit time.

What are two important contraindications for Loperamide?

1. Bloody diarrhea 2. Bacterial enterocolitis.

Is Loperamide available over-the-counter?

Yes, it is available OTC.

What is the mechanism of Bismuth Subsalicylate (Pepto-Bismol)?

It has anti-inflammatory and antimicrobial properties.

Why should Bismuth Subsalicylate be avoided in children?

It can cause Reye's syndrome in children recovering from viral infections.

What is the primary use of Ondansetron (Zofran)?

It is primarily used for preventing nausea and vomiting associated with chemotherapy.

What is an important cardiac concern with Ondansetron?

It can cause QT prolongation.

What is the maximum IV dose of Ondansetron?

The maximum IV dose is 16 mg.

What lab should be checked before using Ondansetron IV?

Electrolytes, particularly potassium and magnesium.

What does Aprepitant target in antiemetic therapy?

It targets the neurokinin-1 (NK1) receptor.

When is triple antiemetic therapy used?

It is used for highly emetogenic chemotherapy.

What are the components of triple antiemetic therapy?

Aprepitant + 5-HT3 antagonist + corticosteroid.

What is the controlled substance class for Cannabinoids?

Schedule III.

What type of nausea are antihistamines best for?

Motion sickness.

What is the pathway of the GI tract from mouth to rectum?

Mouth → Esophagus → Stomach → Small intestine (duodenum, jejunum, ileum) → Large intestine → Rectum

What are the main functions of the stomach?

The stomach acts as an acid factory, producing HCl and pepsinogen.

Which cells in the stomach produce hydrochloric acid?

Parietal cells

What is the primary site of nutrient absorption in the small intestine?

Jejunum

What is the role of the ileum in the GI tract?

Absorbs B12 and bile acids; the last 10 cm is the terminal ileum.

What is peristalsis?

Wave-like muscle contractions that move food along the GI tract.

What is the goal of therapy regarding acid in the stomach?

Restore acid-mucus balance, not eliminate all acid.

What are the main drug classes affecting GI secretions?

H2 antagonists, Proton Pump Inhibitors (PPIs), Antacids, Sucralfate, Misoprostol.

How do H2 antagonists work?

They block H2 receptors on parietal cells, reducing HCl production.

What are common adverse effects of H2 antagonists?

Headache, dizziness, diarrhea/constipation, and potential drug interactions.

What is the mechanism of action for Proton Pump Inhibitors (PPIs)?

They irreversibly block H+/K+-ATPase, shutting down acid production.

What are common indications for PPIs?

GERD, erosive esophagitis, peptic ulcer disease, and Zollinger-Ellison syndrome.

What is a significant risk associated with long-term PPI use?

Increased risk of Clostridium difficile infection and decreased magnesium and calcium levels.

What is the primary use of Sucralfate?

To form a protective paste that binds to the ulcer base, providing a barrier against acid.

What is a critical nursing consideration for Misoprostol?

It has a black box warning for causing uterine contractions; avoid in pregnant patients.

What should patients be advised regarding the timing of H2 antagonists?

Take 30-60 minutes before meals for best effect.

What are the common side effects of antacids?

Constipation (calcium carbonate), diarrhea (magnesium hydroxide), and potential electrolyte imbalances.

What is the effect of antacids on drug absorption?

Antacids can alter the absorption of many drugs; space doses by 1-2 hours.

What is the nursing assessment focus for patients on acid-suppression therapy?

Assess epigastric pain, triggers, and renal function; educate on timing and lifestyle changes.

What is the recommended administration route for H2 antagonists?

IV administration should be infused slowly over 15-30 minutes to avoid cardiac arrhythmias.

What are the adverse effects of Cimetidine?

Gynecomastia, impotence, and the highest potential for drug interactions among H2 antagonists.

What is the importance of renal dosing for H2 antagonists?

All H2 antagonists are renally excreted; dose must be reduced in patients with impaired renal function.

What is the mechanism of action for antacids?

They chemically neutralize existing HCl in the stomach.

What is the effect of PPIs on the gastric pH?

PPIs significantly raise gastric pH, reducing acidity and affecting drug absorption.

What bacterium is responsible for most peptic ulcers?

Helicobacter pylori (H. pylori)

What percentage of duodenal ulcers are caused by H. pylori?

70-90%

What is the primary method for diagnosing H. pylori?

Urea breath test, stool antigen, or biopsy

What is the standard treatment regimen for H. pylori?

Triple therapy: PPI, clarithromycin, and amoxicillin for 14 days

What is the role of PPIs in H. pylori treatment?

They raise pH, allowing antibiotics to work better in an alkaline environment.

What is the purpose of using multiple drugs in H. pylori treatment?

To prevent resistance and ensure effective eradication of the bacterium.

What should patients avoid while taking metronidazole?

Alcohol, due to the risk of a disulfiram reaction.

What are the nursing implications for H. pylori treatment?

Stress the importance of completing the full 14-day course and confirm eradication 4 weeks post-treatment.

What is pancrelipase used for?

It is used for exocrine pancreatic insufficiency (EPI).

How should pancrelipase be administered?

With every meal and snack, and not crushed or chewed.

What are common causes of xerostomia?

Radiation to head/neck, Sjögren's syndrome, and anticholinergic drugs.

What is the mechanism of action for bulk-forming laxatives?

They absorb water, swell, and stimulate peristalsis.

What is the primary risk of bulk-forming laxatives?

Esophageal or bowel obstruction if taken without enough fluid.

What is the fastest type of laxative?

Stimulant laxatives like bisacodyl and senna.

What is the recommended prophylactic treatment for opioid-induced constipation (OIC)?

A stimulant laxative (senna) combined with a stool softener (docusate).

What are the side effects of metoclopramide?

Extrapyramidal symptoms (EPS), drowsiness, fatigue, and hyperprolactinemia.

What should be monitored in patients taking metoclopramide?

Involuntary movements and adherence to the 12-week maximum therapy limit.

What is the mechanism of action for loperamide?

It acts as an opioid receptor agonist in the GI tract, slowing peristalsis.

What is a key nursing point for administering loperamide?

Do not use in cases of bloody diarrhea or suspected infection.

What is the primary use of bismuth subsalicylate?

It is used for traveler's diarrhea and has anti-secretory, antimicrobial, and anti-inflammatory properties.