NR 293 // Ch 50 - Acid-Controlling Drugs Questions and answers + rationales

The stomach secretes...

-Hcl

-bicarb

-pepsinogen

-intrinsic factor

-mucus

-prostaglandins

Glands of the Stomach

-cardiac

-pyloric

-gastric (lrgst # of cells and size)

Cells of the Gastric Gland

-parietal

-chief

-mucous

-endocrine

-enterochromaffin

Hydrochloric Acid (HCl)

-secreted by parietal cells, stimulated by food

-maintains stomach's pH of 1-4

-secretion is also stimulated by: lg fatty meals, excessive alcohol, and emotional stress

Acid-Related Diseases

-caused by imbalance of 3 cells of gastric gland and their secretions

-most common is hyperacidity

Overproduction of HCl Dx

-indigestion

-sour stomach

-heartburn

-acid stomach

-PUD

-GERD

Helicobacter pylori (H. Pylori)

-found in GI tract of 90% of pts w duodenal ulcers, and 70% of pts w gastric ulcers

-can be detected by serum antibody tests

-antibiotics used to treat/eradicate

Types of Acid-Controlling Drugs

-antacids

-H2 antagonists

-proton pump inhibitors

-miscellaneous - coating, prostaglandin analogue, anticholinergics

Antacids - MOA

-neutralize stomach acid

-promote gastric mucosal defense mechanisms

-secretion of:

+mucus : protective barrier against HCl

+ bicarb : helps buffer acidic properties of HCl

+ prostaglandins : prevent activation of proton pump

-antacids DO NOT prevent overproduction of acid

-antacids DO neutralize the acid once its in the stomach

Antacids - Drug Effects

-reduction of pain associated w acid-related dx

-raising gastric pH from 1.3-1.6 neutralizes 50% of the gastric acid

-raising gastric pH 1 point neutralizes 90% of gastric acid

-reducing acidity reduces pain

Antacids

-OTC available as: capsules, tabs, powders, chewables, suspensions, effervescent granules/tabs

-used alone or in combo w/: aluminum salts, magnesium salts, calcium salts, sodium bicarb

Antacids - Aluminum Salts

-have constipating effects

-often used w magnesium to counteract the constipation

-often recommended for pts w renal dx (more easily excreted)

Antacids - Aluminum Salt Examples

-aluminum carbonate (Basaljel)

-hydroxide salt (AlternaGEL)

-combo products (Al and Mg) (Gaviscon, Maalox, Mylanta, Di-Gel)

Antacids - Magnesium Salts

-commonly cause diarrhea, usually taken w other drugs to counteract this

-dangerous w renal failure (failing kidneys can't excrete extra Mg - accumulation)

Antacids - Magnesium Salt Examples

-hydroxide salt: magnesium hydroxide (Milk of Magnesia)

-carbonate salt (Gaviscon)

-combo products like Maalox, Mylanta

Antacids - Calcium Salts

-many forms, but carbonate is most common

-may cause constipation, kidney stones

-not recommended for pt w renal dx (accumulation)

-long duration of acid action - may cause rebound hyperacidity)

-often advertised as extra source of dietary calcium

Antacids - Calcium Salt Examples

-Tums (calcium carbonate)

Antacids - Sodium Bicarbonate

-highly soluble

-buffers acidic properties of HCl

-quick onset, short duration

-may cause metabolic alkalosis

-sodium contact can cause problems w HF, htn, or renal insufficiency

Antacids & Antiflatulents

-antiflatulents: used to relieve pain assoc w gas

-several drugs are used to bind/alter intestinal gas and are often added to antacids

Antiflatulent OTCs

-activated charcoal

-simethicone - alters elasticity of mucus-coated bubbles, causing them to break; often used, but limited provable effectiveness

Antacids - Adverse Effects

-minimal, and depdn on compound used

-Al and Ca: constipation

-Mg: diarrhea

-Ca carbonate: produces gas, belching

Antacids - Drug Interactions

-absorption of other drugs to antacids - reduces ability of other drugs to be absorbed into the body

-chelation

-incr stomach pH (incr absorption of basic drugs, decr absorption of acidic drugs)

-incr urinary pH (incr excretion of acidic drugs, decr excretion of basic drugs)

Chelation

-chemical binding or inactivation of another drug

-produces insoluble complexes

-result = reduced drug absorption

Antacids - Nursing Implications

-assess for allergies/preexisting conditions that may restrict use of antacids such as...fluid imbalances, renal dx, GI obstruction, HF, pregnancy

-pt w HF or htn should not use antacids w high sodium content

-caution - many drug interactions

-most meds should be given 1-2 hrs after giving an antacid

-may cause premature dissolving of enteric-coated meds, resulting in stomach upset

-be sure chewable are chewed thoroughly, and liquid shaken well

-administer w at least 8 oz of water to enhance absorption (except for "rapid-dissolve" forms)

-long-term self medic can mask underlying dx like cancer or bleeding ulcers

Histamine Type 2 (H2) Antagonists

-reduce acid secretion

-all OTC in lower dosage forms

-most popular drugs for acid-related dx

H2 Antagonist Drugs

Cimetidine (Tagamet)

Nizatidine (Axid)

Famotidine (Pepcid)

Ranitidine (Zantac)

H2 Antagonists - MOA

-block histamine at the H2 receptors of acid-producing parietal cells

-production of hydrogen ions is reduced, resulting in decr production of HCl

H2 Antagonists - Drug Effect and Indications

-should suppress acid secretion in stomach

-inidcations: GERD, PUD, erosive esophagitis, upper GI bleeding, pathologic gastric hypersecretory conditions

H2 Antagonists - Adverse Effects

-very few

-cimetidine may induce impotence and gynecomastia

-may cause Ha, lethargy, confusion, diarrhea, urticaria, sweating, flushing, etc

H2 Antagonists - Drug Interactions

-cimetidine (Tagamet) - binds w p-450 microsomal oxidase system in the liver, resulting in inhibited oxidation of many drugs and INCR DRUG LEVELS

-all H2 drugs may inhibit the absorption of drugs that require an acidic GI environment

-Smoking has been shown to decr effectiveness of H2 blockers

H2 Antagonists - Nursing Implications

-assess for allergies/impaired renal or liver function

-caution w pt who are confused, disoriented, or elderly

-take 1 hr before or after antacids

-for IV doses, follow admin guidelines

Proton Pump Inhibitors

-parietal cells release H(+) ions during HCl production

-this process is called the PROTON PUMP

-H2 blockers and antihistamines DO NOT stop action of this pump

Proton Pump Inhibitors - MOA

-irreversibly bind to H+/K+ ATPase enzyme

-this bond prevents mvmnt of H ions from parietal cells into stomach

-result = achlorhydria: ALL gastric secretion is temporarily blocked

-to return to normal acid secretion, parietal cells must synthesize new H+/K+ATPase

Proton Pump Inhibitors - Drug Effects

-TOTAL inhibition of gastric acid secretion

-Drugs:

Lansoprazole (Prevacid)

Omeprazole (Prilosec-first in class)

Rabeprazole (AcipHex)

Pantoprazole (Protonix - IV form*****)

Esomeprazole (Nexium)

Proton Pump Inhibitors - Indications

-GERD maintenance therapy

-erosive esophagitis

-short-term tx of active duodenal and benign gastric ulcers

-Zollinger-Ellison syndrome

-tx of H. Pylori induced ulcers (given w antibiotic)

Proton Pump Inhibitors - Adverse Effects

-safe for short-term therapy

-some approved for long term

-adverse effects uncommon

Proton Pump Inhibitors - Nursing Implications

-assess for allergies and hx of liver dx

-not all are available for parenteral admin

-may incr serum levels of diazepam and phenytoin

-may incr chance for bleeding w warfarin

-granules of pantoprazole capsules may be given via NG tubes, but NG tube must be @ least 16g or tube will get clogged

-capsule contents may be opened and mixed w apple juice, but do not chew or crush delayed release

-often work best when taken 30-60 MIN BEFORE MEALS

Other Drugs

-sucralfate (Carafate)

-misoprostol (Cytotec)

-simethicone (Mylicon)

Sucralfate (Carafate)

-cytoprotective drug

-used for stress ulcers, PUD

-attracted to and binds to base of ulcers and erosions, forming protective barrier over areas

-protects these areas from pepsin, which normally breaks down proteins (making ulcers worse)

-little absorption from gut

-may cause: constipation, nausea, and dry mouth

-may impair absorption of other drugs

-give other drugs @ lease 2 HOURS BEFORE

-do not administer w other meds

-bnds w phosphate, may be used in chronic renal failure

Misoprostol (Cytotec)

-synthetic prostaglandin analog

-prostaglandins have cytoprotective activity (protect gastric mucosa from injury by enhancing local prod of mucous or bicarb, promote local cell regen, help maintain mucosal blood flow)

-used to prevent NSAID induced gastric ulcers

-doses that are therapeutic enough to treat duodenal ulcers often produce abdominal cramps, diarrhea

Simethicone (Mylicon)

-antiflatulent drug

-used to reduce discomfort of gastric/intestinal gas

-alters elasticity of mucus-coated gas bubbles, breaking them into smaller ones

-result is decr gas pain and incr expulsion via mouth or rectum