Download Part 9: Drugs Affecting the GIT. DRUGS USED TO TREAT

Part 9: Drugs Affecting the GIT.
I. DRUGS USED TO TREAT GASTROESOPHAGEAL
REFLUX DISEASE AND ULCER DISEASE
The drugs used to treat gastroesophageal reflux disease (GERD) and ulcer disease include:
1- Histamine-2 (H2) antagonists, which block the release of hydrochloric acid in response to gastrin
2- Antacids, which interact with acids at the chemical level to neutralize them.
3- Proton pump inhibitors, which suppress the secretion of hydrochloric acid into the lumen of the
stomach.
4- GI protectants, which coat any injured area in the stomach to prevent further injury from acid.
5- Prostaglandins, which inhibit the secretion of gastrin and increase the secretion of the mucous
lining of the stomach, providing a buffer.
A. Antacids:
Antacids are a group of inorganic chemicals that neutralize stomach acid. Antacids are available over
the counter, and many patients use them to self-treat a variety of GI symptoms. There is no one
perfect antacid. The choice of an antacid depends on adverse effect and absorption factors.
Mechanism of Action
 Antacids DO NOT prevent the overproduction of acid
 Antacids DO neutralize the acid once it is in the stomach
Drug Effects
 Reduction of pain associated with acid-related disorders
Over-the-counter formulations available as Powders, Chewable tablets, Suspensions,
Effervescent granules and tablets
Antacids can be used alone or in combination
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Aluminum salts
Magnesium salts
Calcium salts
Sodium bicarbonate
1- Aluminum Salts
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Have constipating effects and often used with magnesium to counteract constipation
Often recommended for patients with renal disease (more easily excreted)
o Combination products (aluminum and magnesium): Gaviscon, Maalox.
2- Magnesium Salts
 Commonly cause diarrhea; usually used with other drugs to counteract this effect
3- Calcium Salts
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Many forms, but carbonate is most common
May cause constipation, kidney stones
4- Sodium Bicarbonate
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Buffers the acidic properties of HCl has quick onset, but short duration
May cause metabolic alkalosis
Sodium content may cause problems in patients with HF, hypertension, or renal insufficiency
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.
 Over-the-counter antiflatulents: Activated charcoal, Simethicone
Drug Interactions
 Reduces the ability of the other drug to be absorbed into the body by adsorption and chelation
(Chemical binding, or inactivation, of another drug, this produces insoluble complexes which
result: reduced drug absorption)
 Increased stomach pH this leads to increased absorption of basic drugs and decreased
absorption of acidic drugs
 Increased urinary pH this leads to increased excretion of acidic drugs and decreased excretion
of basic drugs
Nursing Implications:
 Assess for allergies and preexisting conditions that may restrict the use of antacids, such as:
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Fluid imbalances, renal disease, GI obstruction, and Heart failure (HF).
 Patients with HF or hypertension should not use antacids with high sodium content and use with
caution with other medications because of the many drug interactions
 Most medications should be given 1 to 2 hours after giving an antacid
 Antacids may cause premature dissolving of enteric-coated medications, resulting in stomach
upset
 Be sure that chewable tablets are chewed thoroughly, and liquid forms are shaken well before
giving
 Administer with at least 8 ounces of water to enhance absorption (except for “rapid-dissolve”
forms)
 Long-term self-medication with antacids may mask symptoms of serious underlying diseases, such
as cancer or bleeding ulcers
 If symptoms remain ongoing, patient should seek medical evaluation
 Monitor for adverse effects
 Monitor for therapeutic response
 Notify health care provider if symptoms are not relieved
B. Histamine Type 2 (H2) Antagonists:
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Block the release of hydrochloric acid in response to gastrin.
Most popular drugs for treatment of acid-related disorders
 Cimetidine (Tagamet)
 Nizatidine (Axid)
 Famotidine (Pepcid)
 Ranitidine (Zantac)
Mechanism of Action:
 Block histamine at the (H2) receptors of acid-producing parietal cells, Production of hydrogen ions
is reduced, resulting in decreased production of HCl
Indications
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GERD and PUD
Erosive esophagitis and as Adjunct therapy to control upper GI bleeding
Prophylaxis of stress-induced ulcers and acute upper GI bleeding in critical patients
Relief of symptoms of heartburn, acid indigestion, and sour stomach
Adverse Effects
 Overall, very few adverse effects. May cause headaches, lethargy, confusion, diarrhea, urticaria,
sweating, flushing, other effects
Drug Interactions
 Smoking has been shown to decrease the effectiveness of H2 blockers
Nursing Implications
 Assess for allergies and impaired renal or liver function.
 Use with caution in patients who are confused, disoriented, or elderly
 Give 1 hour before or after antacids.
 Give before or with meals or at bed time.
 For intravenous doses, follow administration guidelines
C. Proton Pump Inhibitors
 The parietal cells release positive hydrogen ions (protons) during HCl production, this process is
called the proton pump
 H2 blockers and antihistamines do not stop the action of this pump
Mechanism of Action
 Irreversibly bind to H+/K+ ATPase enzyme, this bond prevents the movement of hydrogen ions from
the parietal cell into the stomach. Results in achlorhydria—ALL gastric acid secretion is temporarily
blocked
 To return to normal acid secretion, the parietal cell must synthesize new H+/K+ ATPase
Proton Pump Inhibitors:
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lansoprazole (Prevacid)
omeprazole (Prilosec)*
rabeprazole (AcipHex)
pantoprazole (Protonix) (IV form available)
esomeprazole (Nexium)
*First in this new class of drugs
Indications
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GERD maintenance therapy
Erosive esophagitis
Short-term treatment of active duodenal and benign gastric ulcers
Zollinger-Ellison syndrome
Treatment of H. pylori–induced ulcers, given with an antibiotic
Adverse Effects
 Adverse effects uncommon
Nursing Implications
 Assess for allergies and history of liver disease
 Not all are available for parenteral administration
 The granules of pantoprazole capsules may be given via NG tubes, but the NG tube must be at
least 16 g or the tube may become clogged
 Capsule contents may be opened and mixed with apple juice, but do not chew or crush delayedrelease granules
 Proton pump inhibitors often work best when taken 30 to 60 minutes before meals
D. GI protectants:
Coat any injured area in the stomach to prevent further injury from acid. Sucralfate (Carafate) is the
only GI protectant currently available.
Sucralfate:
 Cytoprotective drug. Attracted to and binds to the base of ulcers and erosions, forming a protective
barrier over these areas and protects these areas from pepsin, which normally breaks down
proteins (making ulcers worse). This drug is little absorption from the gut and may cause
constipation, nausea, and dry mouth. This drug may impair absorption of other drugs—give other
drugs at least 2 hours before sucralfate so do not administer with other medications
E. Prostaglandin:
Prostaglandins are used to protect the stomach lining. The prostaglandin available for this use is the
synthetic prostaglandin E1 analogue misoprostol (Cytotec).
Misoprostol (Cytotec)
 Synthetic prostaglandin analog, prostaglandins have cytoprotective activity by enhancing local
production of mucus or bicarbonate, promote local cell regeneration, and help to maintain mucosal
blood flow, can be used for prevention of NSAID-induced gastric ulcers
II.
Antiemetics ans Antinusea:
Definitions:
 Nausea: Unpleasant feeling that often precedes vomiting
 Emesis (vomiting): Forcible emptying of gastric, and occasionally, intestinal contents
 Antiemetic drugs: Used to relieve nausea and vomiting
 Vomiting center (VC)
 Chemoreceptor trigger zone (CTZ)
o Both located in the brain
o Once stimulated, cause the vomiting reflex
The various pathways and the areas of the body that send the signals to the vomiting center are
illustrated in the figure below:
The sites at which antiemetics work in te vomiting pathway are shown in the figure below:
 Anticholinergic drugs (ACh blockers)
 Bind to and block acetylcholine (ACh) receptors in the inner ear labyrinth
 Block transmission of nauseating stimuli to CTZ
 Scopolamine: Also used for motion sickness (transdermal patch)
 Antihistamine drugs (H1 receptor blockers)
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 Inhibit ACh by binding to H1 receptors
 Prevent cholinergic stimulation in vestibular and reticular areas, thus preventing nausea
and vomiting
Cyclizine.
Cinnarizine.
Promethazine.
Meclizine.
Meclizine: used for the prevention of motion sickness also used in combination with B6 for
nausea and vomiting in pregnancy.
Cyclizine+ promethazine+ cinnarizine: prevent motion skinless.
Cinnarizine: prevent vertigo
 Antidopaminergic drugs
 Block dopamine receptors on the CTZ
 Also used for psychotic disorders, intractable hiccups
 Haloperidol.
 Domperidone.
 Metoclopramide.
 Domperidone and metoclopromide:
 Used in chemotherapy-induced nausea and vomiting.
 Postoperative nausea and vomiting.
 Side effects: sedating, restlessness, diarrhea.
 Serotonin blockers
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Block serotonin receptors in the GI tract, CTZ, and VC
Used for nausea and vomiting in patients receiving chemotherapy and for postoperative nausea
and vomiting
 Ondansetron (Zofran)
 Miscellaneous:
 Betahistine: Vertigo.
 Dexamethasone: Chemotherautic induced nausea and vomiting.
 Herbal Products: Ginger
 Used for nausea and vomiting including that caused by chemotherapy, morning sickness, and
motion sickness
 Adverse effects: Anorexia, nausea and vomiting, skin reactions
Drug interactions
 May increase absorption of oral medications
 Increase bleeding risk with anticoagulants