Pharma 3 - Acid-Controlling Drugs (Chapter 50 ) Flashcards
Hydrochloric Acid (HCl)
- an acid that aids digestion and also serves as a barrier to infection.
- maintains stomach pH of 1 to 4.
- several substances stimulates secretion of the parietal cell to secrete HCl such as: food, caffeine, chocolate, & alcohol.
- excessive consumption of large, fatty meals or alcohol, also emotional stress, may result in excessive production of HCl and can lead to hypersecretory disorders like PUD.
Bicarbonate
a base that is a natural mechanism to prevent hyperacidity
Pepsinogen
an enzymatic precursor to PEPSIN, which is an enzyme that digests dietary proteins
Intrinsic Factor
a glycoprotein that facilitates gastric absorption of Vitamin B12
Mucus
protects the stomach lining from both HCl and digestive enzymes
Prostaglandins
have a variety of anti-inflammatory and protective functions
Glands in the Stomach:
➀ Cardiac
➁ Pyloric
➂ Gastric
➀ Cardiac Glands
→ located around the cardiac sphincter a.k.a. gastroesophageal sphincter
➁ Pyloric Glands
→ in the pyloric region and in the transitional area between the pyloric and the fundic zones
➂ Gastric Glands
→ in the fundus, also known as the greater part of the body of the stomach
→ largest in number
→ Primary importance in acid control
→ Composed of different types of Cells:
——– parietal, chief, mucous, endocrine, & enterochromaffin
Gastric Gland Cells
- the 3 most important cell types are:
1 - Parietal
2 - Chief
3 - Mucous
** These three cell types play an important role in the digestive process. When the balance of these cells and their secretions is impaired, acid-related diseases can occur.
** The most harmful these involve hypersecretion of acid and include peptic ulcer disease and esophageal cancer.
PARIETAL Cells
❶ PARIETAL Cells
→ produce and secrete Hydrochloric Acid (HCl)
→ primary site of action for many of the drugs used to treat acid-related disorders
→ Releases INtrinsic Factor, so B12 can be absorbed.
The wall of Parietal Cell contains 3 types of receptors:
== Acetylcholine (ACh), Histamine, and Gastrin.
* When any of these 3 receptors is occupied by its corresponding chemical stimulant, the parietal cell will produce and secrete Hydrochloric Acid (HCl).
CHIEF Cells
❷ CHIEF Cells
→ Secrete pepsinogen.
→ → Pepsinogen is a proenzyme (enzyme precursor) that becomes pepsin when activated by exposure to acid. Pepsin breaks down protein, therefore called a PROTEOLYTIC ENZYME.
MUCOUS Cells
❸ MUCOUS Cells
→ are mucous-secreting cells that are also called SURFACE EPITHELIAL CELLS. The secreted mucus serves as a protective coating against the digestive action of hydrochloric acid and digestive enzymes
Hyperacidity
Hyperacidity is often associated with Gastroesophageal Reflux Disease (GERD). This is the tendency of excessive and acidic stomach contents to back up or reflux, into the lower (and even upper) esophagus.
- Overtime, this condition can lead to more serious disorders such as erosive esophagitis and Barrett esophagus, a precancerous condition.
- Therefore, to prevent serious disorders from occurring and to promote patient comfort, GERD is aggressively treated.
Acid Related Diseases
Peptic Ulcer Disease (PUD) Helicobacter pylori (H. pylori)
Peptic Ulcer Disease
- term for gastric (stomach) or duodenal ulcers that involve digestion of the GI mucosa by the enzyme Pepsin.
- the defect can extend through the muscularis mucosa (smooth muscle layer)
- Because the process of ulceration is driven by the proteolytic (protein breakdown) actions of pepsin together with the caustic effects of hydrochloric acid, peptic ulcer disease and related problems are also referred to by the more general term = ACID-PEPTIC DISORDER
NSAID-Induced Peptic Ulcer Disease
≥ 60 yrs old history of PUD Concurrent steroid use Concurrent warfarin use Regular alcohol or tobacco use NSAID dosage higher than recommended Concurrent ASA-containing drugs/other NSAIDS Long-term NSAID use
PUD
- Etiology
No longer felt to be d/t
∙ Stress
∙ Diet (Spicy foods) – avoiding spicy foods may help healing of PUD
Most Caused by H. pylori infection (70%)
∙ Gastritis – inflammation of stomach
NSAIDS (25%)
∙ ASA, Ibuprofen, Naproxen, Ketoprofen, Celecoxib, Meloxicam
∙ Inhibits cyclooxygenase-1 (COX-1) → inhibits PGs → ↓ mucosal barrier maintenance & ↓ bicarbonate secretion
PUD
- Other causes
✧ Severe physiologic stress
- Burns
- CNS trauma
- Surgery
- Severe Medical illness
✧ Hypersecretory States (Uncommon)
- Zollinger-Ellison syndromeHelicobacter pylori
Endoscopy - EGD - definitive diagnosis of H. pylori/ Peptic Ulcer
Urease Breath Test - one way to diagnose H. pylori
Types of Acid-Controlling Drugs
☉ Antacids
☉ H2 antagonist
☉ Proton Pump Inhibitors
Antacids
• compounds used to neutralize stomach acid
• Salts of aluminum, magnesium, calcium, &/or sodium
☝ Aluminum - causes constipation; med of choice for patient with renal disease
☝ Magnesium - causes diarrhea
☝ Sodium - careful with patients with CVD
• many antacid preparations also contain the antiflatulent (antigas) drug simethicone
Antacid
- MOA
➧ Does not prevent the overproduction of acid
• Help to neutralize acid secretions
➧ Promote gastric mucosal defensive mechanisms
➧ Stimulate Secretions of:
• Mucus - protective barrier against HCl
• Bicarbonate - helps buffer acidic properties of HCl
• Prostaglandins - prevent activation of proton pump
Antacids: ALUMINUM SALTS
☘ Have constipating effects
☘ Often used with magnesium to counteract constipation
☘ Often recommended for patients with renal disease (more easily excreted)
☘ Examples:
• Aluminum carbonate: Basaljel
• Hydroxide salt: AlternaGEL
• Combination products (aluminum and magnesium): Gaviscon, Maalox, Mylanta, Di-Gel
Antacids: MAGNESIUM SALTS
☘ Dangerous when used to patients with renal failure
☘ Commonly cause diarrhea: usually used with other drugs to counteract this effect
☘ Dangerous when used to patients with renal failure
• Failing kidney cannot excrete extra Magnesium, resulting in accumulation
☘ Examples:
• Hydroxide salt: Magnesium hydroxide (Milk of Magnesia)
• Carbonate salt: Gaviscon (also a combination product)
• Combination products: Maalox, Mylanta
Antacids: CALCIUM SALTS
☠ not recommended for patients with renal disease
☛ Many forms but Carbonate is most common
☛ May cause constipation, kidney stones
☛ Also not recommended for patients with renal disease – may accumulate toxic levels
☛ Long duration of acid action – may cause increased gastric acid secretion (hyperacidity rebound)
☛Often advertised as an extra source of dietary calcium
☛ Examples:
• Tums (calcium carbonate)
Antacids: SODIUM BICARBONATE
☉ Highly soluble
☉ Buffers the acidic properties of HCl
☉ Quick onset, but short duration
☉ May cause metabolic alkalosis bec it makes more base
☉ Sodium content may cause problems in patients with heart failure, hypertension, or renal insufficiency
Antacids & Antiflatulents
☘ Antiflatulents – used to relieve the painful symptoms associated with gas
☘ Several drugs are used to bind or alter intestinal gas and are often added to antacid combination products
• Simethicone
Antacids: ADVERSE EFFECTS
☘ Minimal and depend on the compound used
￫ Aluminum & Calcium
• constipation
￫ Magnesium
• diarrhea
￫ Calcium carbonate
• Produces gas and belching; often combined with Simethicone
Antacids: DRUG INTERACTIONS
☘ Adsorption of other drugs to antacids
￫ Reduces the ability of the other drug to be absorbed into the body
☘ Chelation
￫ Chemical binding, or inactivation, of another drug
￫ Produces insoluble complexes
￫ Result: Reduced drug absorption
