252 Pharmacology - Acid Controlling Drugs Flashcards
Which glands of the stomach are the largest in number and of primary importance when discussing acid control?
Gastric glands
What is the function of parietal cells?
- Produce and secrete hydrochloric acid
- Primary site of action for many of the drugs used to treat acid-related disorders
What do chief cells do?
- Secrete pepsinogen, a proenzyme
- Pepsinogen becomes pepsin when activated by exposure to acid.
- Pepsin breaks down proteins (proteolytic).
What are the purposes of mucous cells?
- Mucus-secreting cells (surface epithelial cells)
- Provide a protective mucus coat
- Protect against self-digestion by hydrochloric acid and digestive enzymes
When is hydrochloric acid secreted?
- Secreted by parietal cells when stimulated by food, caffeine, chocolate, and alcohol
- Secretion also stimulated by
- Large fatty meals
- Emotional stress
What pH does HCl keep the stomach at?
Maintains stomach at pH of 1 to 4
What does HCl do?
Acidity aids in the proper digestion of food and defenses against microbial infection via the gastrointestinal tract
What does triple therapy for H. pylori involve?
Triple therapy includes a 7- to 14-day course of a proton pump inhibitor (PPI) and the antibiotics clarithromycin and either amoxicillin or metronidazole or quadruple therapy of a PPI, bismuth subsalicylate, and the antibiotics tetracycline and metronidazole.
What are the characteristics of stress-related mucosal damage in hospitalized patients?
- Gastrointestinal lesions are a common finding in Critical Care Unit patients, especially within the first 24 hours after admission.
- Factors include decreased blood flow, mucosal ischemia, hypoperfusion, and reperfusion injury.
- Nasogastric tubes and ventilators predispose patients to gastrointestinal bleeding.
- A histamine receptor–blocking drug or a PPI are given for prevention.
What are the classes of acid controlling drugs?
- Antacids
- H2 antagonists
- PPIs
How do antacids help with acid controlling?
- Basic compounds used to neutralize stomach acid
- Salts of aluminum, magnesium, calcium, or sodium bicarbonate, or all of these
- Many antacid preparations also contain the antiflatulent (antigas) drug simethicone.
- Many aluminum- and calcium-based formulations also include magnesium, which not only contributes to the acid-neutralizing capacity but also counteracts the constipating effects of aluminum and calcium.
Antacids that may lead to the development of kidney stones and increased gastric acid secretion.
Calcium antacids
What kind of antacid must be avoided in patients with renal failure?
Antacids containing magnesium
Which antacid is a highly soluble antacid form with a quick onset but a short duration of action.
Sodium bicarbonate
What is the mechanism of action of antacids?
- Do not prevent the overproduction of acid but instead help to neutralize acid secretions
- Promote gastric mucosal defensive mechanisms
- Stimulate secretion of:
- Mucus: protective barrier against hydrochloric acid
- Bicarbonate: helps buffer acidic properties of hydrochloric acid
- Prostaglandins: prevent activation of proton pump
What is the drug effect of antacids?
- Reduction of pain and reflux associated with acid-related disorders
- Raising the gastric pH 1 point (1.3 to 2.3) neutralizes 90% of the gastric acid.
- Reducing acidity reduces pain as a result of:
- Base-mediated inhibition of the protein-digesting ability of pepsin
- Increase in the resistance of the stomach lining to irritation
- Increase in the tone of the cardiac sphincter
What are the indications for antacids?
- Acute relief of symptoms associated with peptic ulcer, gastritis, gastric hyperacidity, and heartburn
What contraindications are there for antacids?
- Known allergy to a specific drug product
- Severe renal failure or electrolyte disturbances: potential toxic accumulation of electrolytes in the antacids themselves
- Gastrointestinal obstruction: Antacids may stimulate gastrointestinal motility when they are undesirable because of the presence of an obstructive process requiring surgical intervention.
What OTC antacid formulations are available?
- Capsules and tablets
- Powders
- Chewable tablets
- Suspensions
- Effervescent granules and tablets
List the types of antacids.
- Aluminum hydroxide
- Magnesium hydroxide
- simethicone
- Combination aluminum hydroxide and magnesium hydroxide contain a local anaesthetic (Mucaine®).
What are the characteristics and examples of aluminum salts?
- Have constipating effects
- Often used with magnesium to counteract constipation
- Often recommended for patients with renal disease (more easily excreted)
- Examples
- Combination products (aluminum and magnesium): Antacid Plus®, Diovol®, Gelusil®, Maalox®, Multiaction®
What are the characteristics and examples of magnesium salts?
- Commonly cause diarrhea; usually used with other drugs to counteract this effect
- Dangerous when used with renal failure; the failing kidney cannot excrete extra magnesium, resulting in accumulation
- Magnesium hydroxide and mineral oil (Magnolox®)
What are the characteristics and examples of calcium salts?
- Many forms but carbonate is most common
- May cause constipation, kidney stones
- Also not recommended for patients with renal disease—may accumulate to toxic levels
- Long duration of acid action—may cause increased gastric acid secretion (hyperacidity rebound)
- Often advertised as an extra source of dietary calcium
- Example: calcium carbonate and simethicone (Maalox, Rolaids®)
What are the characteristics of sodium bicarbonate as an antacid?
- Highly soluble
- Buffers the acidic properties of hydrochloric acid
- Quick onset but short duration
- May cause metabolic alkalosis
- Sodium content may cause problems in patients with heart failure, hypertension, or renal insufficiency.
What are the adverse effects of the various antacids?
- Minimal and depend on the compound used
- Overuse: metabolic alkalosis
- Aluminum and calcium: constipation
- Magnesium: diarrhea
- Calcium: kidney stones, rebound hyperacidity
- Calcium carbonate: produces gas and belching; often combined with simethicone
What are the drug interactions for antacids?
- 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
- Increased stomach pH
- Increased absorption of basic drugs
- Decreased absorption of acidic drugs
- Increased urinary pH
- Increased excretion of acidic drugs
- Decreased excretion of basic drugs
