GI

What are the three major classes of drugs that decrease gastric acid?

Antacids, H₂ receptor antagonists (H₂ blockers), and proton pump inhibitors (PPIs)

Which acid-reducing drug class is the weakest?

Antacids

Which acid-reducing drug class is the strongest?

Proton pump inhibitors (PPIs)

What is the order of acid-suppressing drugs from weakest to strongest?

Antacids → H₂ blockers → PPIs

What are the major GI drug classes covered in this lecture?

Antacids, H₂ blockers, PPIs, antidiarrheals, laxatives, antiemetics

What do parietal cells secrete?

Hydrochloric acid (HCl)

What is the normal stomach pH?

Approximately 1–4

What is the function of hydrochloric acid?

Digestion, activation of pepsin, and protection against infection

What is the function of bicarbonate in the stomach?

Neutralizes acid and protects against hyperacidity

Which stomach cells secrete pepsinogen?

Chief cells

What converts pepsinogen into pepsin?

Hydrochloric acid

What do mucous neck cells secrete?

Protective mucus

Which stomach cell is the primary drug target for acid-reducing medications?

Parietal cell

What disorders commonly result from gastric hyperacidity?

GERD, peptic ulcers, gastritis, erosive esophagitis, esophageal damage/cancer

Which foods commonly trigger increased gastric acid secretion?

Caffeine, chocolate, alcohol, large fatty meals, acidic foods

Besides food, what can increase gastric acid secretion?

Emotional stress

Which three substances stimulate parietal cells to secrete acid?

Acetylcholine, histamine, and gastrin

Which receptor is the primary target of H₂ blockers?

Histamine H₂ receptor

Which structure is directly inhibited by PPIs?

H⁺/K⁺ ATPase proton pump

What intracellular messengers activate the proton pump?

cAMP and calcium

What does the proton pump transport?

Hydrogen ions (H⁺) into the stomach lumen

Why is the H⁺/K⁺ ATPase called a proton pump?

Hydrogen ions are protons

What are common antacid medications?

Tums, Rolaids, Maalox, Mylanta

What are antacids primarily used for?

Acute relief of heartburn, acid reflux, gastritis, and hyperacidity

Are antacids appropriate for long-term treatment of GERD?

No; they provide symptom relief but do not treat the underlying cause

What is the mechanism of action of antacids?

Neutralize existing stomach acid by acting as weak bases

Do antacids decrease acid production?

No, they only neutralize acid already present

What common ingredient is found in Tums?

Calcium carbonate

What reaction occurs when calcium carbonate reacts with HCl?

Neutralization producing calcium chloride, water, and carbon dioxide

How do antacids reduce pain?

Raise gastric pH, reduce pepsin activity, protect the stomach lining, and reduce reflux

Why does a small increase in gastric pH greatly decrease acidity?

The pH scale is logarithmic

Which antacid ingredients commonly cause constipation?

Calcium and aluminum

Which antacid ingredient commonly causes diarrhea?

Magnesium

Why does Maalox contain both magnesium and aluminum?

To balance diarrhea and constipation effects

What electrolyte problem may occur with prolonged antacid use?

Electrolyte imbalance

What rebound effect can occur after stopping chronic antacid use?

Rebound hyperacidity

Why should antacids be separated from other medications by 1–2 hours?

They can decrease absorption or activation of other medications

A patient takes Tums with every medication they take. What should the PT educate them about?

Separate antacids from other medications by 1–2 hours because they reduce medication absorption.

A patient has frequent heartburn and uses Tums several times daily for months. What should the PT recommend?

Encourage the patient to discuss persistent symptoms with their healthcare provider because chronic antacid use may mask a more serious disorder.

What are common H₂ receptor antagonists?

Cimetidine, famotidine, ranitidine

Which H₂ blocker is the prototype?

Cimetidine

What common generic ending identifies many H₂ blockers?

-tidine

How do H₂ blockers work?

Block histamine H₂ receptors on parietal cells, decreasing acid production

Do H₂ blockers directly block the proton pump?

No; they indirectly decrease proton pump activity

How do H₂ blockers affect gastric pH?

Increase gastric pH by reducing acid secretion

Which conditions are commonly treated with H₂ blockers?

GERD, reflux, ulcers, esophagitis

Are H₂ blockers stronger than PPIs?

No; they are less potent

What common adverse effects occur with H₂ blockers?

Headache, dizziness, nausea, diarrhea, constipation

What long-term problem may occur with H₂ blockers?

Tolerance

A patient reports Pepcid is no longer controlling GERD symptoms after prolonged use. What is the most likely explanation?

Tolerance may have developed, requiring reassessment by the healthcare provider.

What are common PPIs?

Omeprazole, esomeprazole, lansoprazole

Which PPI is the prototype?

Omeprazole

What common generic ending identifies PPIs?

-prazole

How do PPIs work?

Irreversibly inhibit the H⁺/K⁺ ATPase proton pump

Why are PPIs considered the strongest acid-suppressing drugs?

They directly inhibit the final step of acid secretion

Why must new proton pumps be synthesized after PPI therapy?

The inhibited pumps remain permanently inactive

Approximately what percentage of acid secretion can PPIs suppress?

About 90%

What is achlorhydria?

Absence or near absence of stomach acid

What conditions are commonly treated with PPIs?

GERD, Barrett’s esophagus, ulcers, NSAID ulcers, erosive esophagitis, stress ulcer prophylaxis

What common adverse effect may occur when stopping PPIs after prolonged use?

Rebound acid secretion

What infection is associated with chronic PPI use?

Clostridium difficile

What respiratory infection is associated with chronic PPI use?

Pneumonia

What electrolyte deficiency may occur with long-term PPI use?

Hypomagnesemia

How do chronic PPIs affect bone health?

Decrease bone mineralization and increase fracture risk

A patient on long-term omeprazole has osteoporosis. What PT consideration is most important?

Monitor fracture risk and emphasize safe weight-bearing exercise.

Why should a PT ask about fracture history in someone taking chronic PPIs?

PPIs increase the risk of wrist, hip, and spine fractures.

What are the two major categories of drugs that alter gut motility?

Antidiarrheals and laxatives

What is the purpose of antidiarrheal medications?

Slow intestinal transit and reduce fluid loss from diarrhea.

Why can chronic diarrhea reduce exercise tolerance?

It decreases nutrient, water, and electrolyte absorption, leading to dehydration and fatigue.

When is diarrhea considered chronic?

Lasting 4 weeks or longer.

What are common causes for using antidiarrheal medications?

Acute diarrhea, traveler’s diarrhea, chronic diarrhea, inflammatory bowel conditions, and excessive fluid loss.

What are the two major types of antidiarrheal medications emphasized in this lecture?

Bismuth subsalicylate and opioid derivatives.

What is the generic name for Pepto-Bismol?

Bismuth subsalicylate.

How does bismuth subsalicylate reduce diarrhea?

Increases water and electrolyte absorption, has antibacterial effects, and decreases inflammation.

What aspirin-like component is found in Pepto-Bismol?

Salicylate.

Why should patients with aspirin sensitivity use caution when taking Pepto-Bismol?

Because it contains a salicylate similar to aspirin.

Besides diarrhea, what else is Pepto-Bismol commonly used to treat?

Upset stomach, mild heartburn, and traveler’s diarrhea.

What are the opioid-derived antidiarrheals discussed in lecture?

Diphenoxylate (Lomotil) and loperamide (Imodium).

Which antidiarrheal is available over the counter?

Loperamide (Imodium).

How do opioid-derived antidiarrheals decrease diarrhea?

Slow GI motility, increase anal sphincter tone, and increase water absorption.

How does loperamide differ from most opioids?

It acts primarily on peripheral intestinal opioid receptors and has minimal CNS effects.

Why doesn’t loperamide typically cause euphoria?

It does not significantly cross the blood-brain barrier.

What are common adverse effects of opioid-derived antidiarrheals?

Constipation, abdominal pain, and excessive slowing of GI motility.

A patient taking excessive doses of Imodium develops constipation. What caused this?

Excessive slowing of intestinal motility.

Why is dehydration a concern in patients with diarrhea?

Excessive water and electrolyte losses impair normal body function and exercise tolerance.

What is the overall purpose of laxatives?

Promote bowel movements and relieve constipation.

What four classes of laxatives were discussed?

Bulk-forming, emollient (stool softeners), hyperosmotic, and stimulant laxatives.

Which two laxative classes were emphasized in this lecture?

Bulk-forming and emollient laxatives.

What is the general mechanism shared by most laxatives?

Increase water within the bowel, stimulate peristalsis, and promote defecation.

What is the major contraindication for laxative use?

Mechanical bowel obstruction.

Why should laxatives not be used in bowel obstruction?

Increased motility cannot overcome the obstruction and may worsen the condition.

How do bulk-forming laxatives work?

Absorb water, increase stool bulk, stretch the bowel wall, and stimulate normal peristalsis.

What are common examples of bulk-forming laxatives?

Psyllium (Metamucil) and methylcellulose (Citrucel).

Which bulk-forming laxative contains natural fiber?

Psyllium (Metamucil).

Which bulk-forming laxative contains synthetic fiber?

Methylcellulose (Citrucel).

Why should patients drink adequate water while taking bulk-forming laxatives?

Water is required for the fiber to swell and soften stool.

Which laxatives are considered safest for long-term use?

Bulk-forming laxatives.

What are emollient laxatives also called?

Stool softeners or lubricant laxatives.

What is the prototype stool softener discussed?

Docusate sodium (Colace).

How do stool softeners work?

Lower surface tension, allowing water and fat to soften stool.