GI Pharm 1

Antacids

• Neutralize or reduce acidity in the stomach and duodenum by combining with hydrochloric acid and increasing stomach pH.
• Used for hyperacidity caused by heartburn, acid indigestion, sour stomach (GERD), and peptic ulcers.
• Aluminum-containing antacids can cause constipation, anorexia, weakness, tremors, bone pain, and hypophosphatemia.
• Magnesium-containing antacids can cause severe diarrhea, dehydration, and hypermagnesemia, especially with impaired kidney function.
• Monitor for central nervous system (CNS) depression in patients with high magnesium levels.
• Hypermagnesemia can lead to CNS depression, indicated by lethargy and drowsiness.
• Calcium-containing antacids can cause rebound hyperacidity, metabolic alkalosis, headache, renal calculi, neurologic impairment, and hypercalcemia.
• Signs and symptoms of hypercalcemia include anorexia, nausea, vomiting, and confusion.
• Contraindications include severe abdominal pain of unknown origin and cardiovascular disease (for sodium-based antacids).
• Calcium-based antacids are contraindicated for individuals with kidney stones or pre-existing hypercalcemia.
• Aluminum-containing antacids can decrease the effectiveness of digoxin, tetracycline, and warfarin.
• As a standard practice, wait an hour between administering antacids and other medications due to decreased absorption.
• Chew antacids thoroughly and drink eight ounces of water or milk afterward.
• Liquid antacids should be shaken well before use.
• Examples of antacids: Amphigel, Tums, Mylanta, and Milk of Magnesia (this list is not exhaustive).

Histamine Antagonists (H2 Blockers)

• H2 blockers inhibit histamine action at H2 receptor cells in the stomach, reducing gastric acid secretion.
• Used for heartburn, acid indigestion, GERD, gastric and duodenal ulcers, and gastric hypersecretory conditions.
• Also used with antibiotics to treat H. pylori infections.
• Adverse reactions include dizziness, somnolence, headache, confusion, hallucinations, diarrhea, reversible impotence, lethargy, and restlessness.
• Cimetidine (Tagamet) can decrease libido, cause gynecomastia (breast development in men), and impotence; these effects are reversible upon discontinuation.
• Side effects are more common in older adults with kidney and liver dysfunction.
• Use with caution in clients at increased risk for pneumonia and COPD.
• Increased risk of GI bleed; monitor for frank bleeding, dark tarry stools, and coffee ground emesis.
• Limit aspirin products and NSAIDs due to the risk of GI bleed.
• Avoid alcohol and foods that increase GI irritation.
• Use cautiously in individuals with renal or hepatic impairment, especially the elderly.
• Antacids can decrease the absorption of many medications; separate administration times.
• Avoid taking antacids one hour before or after taking H2 antagonists to prevent decreased absorption.
• Opiates taken with H2 antagonists may increase respiratory depression risk.
• Oral anticoagulants (e.g., Warfarin) taken with H2 antagonists can increase the risk of bleeding, so monitor PT and INR.
• Digoxin levels may decrease; monitor levels.
• Antihistamines may increase phenytoin and theophylline levels; monitor blood levels.
• Smoking decreases the effectiveness of H2 antagonists.
• Drug examples: Cimetidine (Tagamet) and Famotidine (Pepcid) (this list is not exhaustive).

Proton Pump Inhibitors (PPIs)

• PPIs suppress gastric acid secretion by inhibiting the enzyme that produces gastric acid.
• Used for short-term treatment (4-8 weeks) of gastric and duodenal ulcers, GERD, and erosive esophagitis.
• Adverse reactions include headache, nausea, diarrhea, vomiting, and abdominal pain.
• Long-term use can cause pneumonia, osteoporosis, fractures, and decreased magnesium levels.
• Symptoms of decreased magnesium include tremors, muscle cramps, or seizures.
• Report any diarrhea, especially if accompanied by fever, abdominal cramps, or bloody stools, as it may indicate C. diff infection.
• Contraindications include allergy to the drug.
• Use with caution in older patients and those with hepatic or kidney impairment.
• Prolonged use may impair vitamin B12 absorption.
• Misoprostol and pantoprazole are generally contraindicated during lactation and pregnancy.
• Avoid during pregnancy unless the benefits outweigh the risks.
• Carafate can decrease the absorption of PPIs.
• PPIs increase the risk of bleeding with oral anticoagulants.
• PPIs increase the absorption of digoxin, potentially leading to toxicity; monitor levels.
• PPIs decrease the effect of Plavix (clopidogrel), a platelet inhibitor; monitor for potential clotting events.
• May increase the risk of toxicity with benzodiazepines, methotrexate, diazepam, antifungals, and phenytoin; monitor for signs and symptoms of toxicity and drug levels.
• Do not crush, chew, or break sustained-release capsules; do not open and sprinkle on food.
• Administer omeprazole once a day before meals in the morning.
• A typical treatment duration is four to eight weeks for active ulcers.
• Notify the provider of any signs of a GI bleed.
• Drug examples are Nexium, Prilosec, and Protonix (this list is not exhaustive).

Antiemetics

• Antiemetics are used to prevent vomiting caused by drugs, radiation, metabolic disorders, and chemotherapy.
• Common adverse reactions include varying degrees of drowsiness and anticholinergic effects, like dry mouth, urinary retention, and constipation.
• Ondansetron adverse effects include headache, diarrhea, dizziness, and prolonged QT interval.
• Prolonged QT interval can lead to a potentially lethal arrhythmia called Torsades de Pointes.
• Dimenhydrinate (Dramamine) and promethazine (Phenergan) can cause sedation and severe respiratory depression.
• Contraindications include severe CNS depression and, for promethazine (Phenergan), use in children under two years old.
• Use extreme caution in older children.
• Generally contraindicated in pregnancy and lactation.
• CNS depressants, such as opioids and alcohol, increase the risk of respiratory depression with antiemetics.
• Antihypertensives and antiemetics can worsen hypotension when used together.
• Encourage increased fluid intake to combat anticholinergic effects; encourage exercise to relieve constipation.
• Assess for bladder distention and address urinary retention promptly.
• Ask about the last bowel movement and consider a laxative or stool softener if needed.
• Suggest sucking on hard candy or chewing gum to relieve dry mouth.
• Metoclopramide (Reglan) carries a black box warning regarding the risk of developing tardive dyskinesia with use longer than 12 weeks.
• Tardive dyskinesia involves uncontrollable movements, often of the face, and can be permanent.
• Discontinue use of Metoclopramide if movements of face or extremities are noticed
• Scopolamine is used to prevent motion sickness.
• A transdermal patch can be applied behind the ear hours before travel; tablets should be taken at least one hour before travel.
• Drug examples include Metoclopramide (Reglan), promethazine (Phenergan), Ondansetron (Zofran), scopolamine, and Dimenhydrinate (Dramamine). (this list is not exhaustive).

Chemotherapy-Induced Nausea and Vomiting

• Additional medications for controlling nausea and vomiting in chemotherapy patients include lorazepam, dronabinol, aprepitant, and dexamethasone.