Gastrointestinal System - Drugs Overview

Gastrointestinal System - Drugs

• Drugs used to treat ulcer disease: Various drugs are used to treat ulcer disease.
• Histamine-2 Antagonists: H2 antagonists selectively block H2 receptors on parietal cells, preventing gastrin release, histamine release, and ultimately decreasing hydrochloric acid production. This also reduces pepsin production. High doses can cause cardiac arrhythmias.
  • Cimetidine (Tagamet, Tagamet HB): Used for duodenal ulcers, benign gastric ulcers, pathological hypersecretory syndromes, GERD, prophylaxis of stress ulcers, relief of heartburn, acid indigestion, and sour stomach. Not typically used in children under 16.
  • Famotidine (Pepcid, Pepcid AC): Used for duodenal ulcers, benign gastric ulcers, pathological hypersecretory syndromes, GERD, relief of heartburn, acid indigestion, and sour stomach. Not typically used in children under 16.
  • Nizatidine (Axid): Used for duodenal ulcers, benign gastric ulcers, pathological hypersecretory syndromes, GERD, relief of heartburn, acid indigestion, and sour stomach in adults.
  • Ranitidine (Zantac): Same usage as other histamine-2 antagonists listed above. Not typically used in children.
• Pharmacokinetics of Histamine-2 Antagonists: Available in oral and injectable forms. Cimetidine is the first developed and is associated with antiandrogenic effects, including gynecomastia and galactorrhea. It is metabolized in the liver, slowing down the metabolism of other drugs. It is excreted in the urine. Ranitidine and famotidine are longer-acting and more potent, less associated with these antiandrogenic effects, and metabolized and excreted in the urine. Nizatidine elimination differs, predominantly through the kidneys.
• Contraindications: Caution is advised during pregnancy, lactation, or with hepatic or renal dysfunction due to potential impacts on drug metabolism and excretion.
• **Adverse effects:**Common side effects include GI distress (diarrhea, constipation) CNS effects (dizziness, headache, confusion), cardiac arrhythmias, and hypotension. Gynecomastia and impotence are possible with long-term use of cimetidine.
• Proton Pump Inhibitors (PPIs): PPIs suppress gastric acid secretion by inhibiting the H+, K+-ATPase enzyme, lowering stomach acid levels.
  • Dexlansoprazole (Kapidex): Treatment of erosive esophagitis maintenance and treatment of heartburn associated with GERD.
  • Esomeprazole (Nexium): Treatment of GERD, severe erosive esophagitis, duodenal ulcers, and pathological hypersecretory conditions.
  • Lansoprazole (Prevacid): Treatment of gastric ulcer, GERD, pathological hypersecretory syndromes, maintenance to heal ulcers/esophagitis, and combined H pylori eradication therapy. Approved for use in children.
  • Omeprazole (Prilosec): Treatment of gastric ulcers, GERD, pathological hypersecretory syndromes, maintenance therapy to heal ulcers/esophagitis, combined H pylori eradication therapy. OTC available for heartburn relief.
  • Pantoprazole (Protonix): Treatment of GERD in adults, healing of erosive esophagitis, treatment for hypersecretory syndrome.
  • Rabeprazole (Aciphex): Treatment of GERD and duodenal ulcers, maintenance therapy for healing duodenal ulcers, and to treat pathological hypersecretory conditions; combined therapy for eradicating H. pylori infection.
• Pharmacokinetics of PPIs: These drugs are acid labile, rapidly absorbed in the GI tract, reach peak levels within 3 to 5 hours, and undergo substantial liver metabolism. Omeprazole is a faster-acting and more quickly excreted drug.
• Contraindications & Cautions of PPI use for pregnant/lactating women and for patients under 18 (except lansoprazole)
• Adverse Effects: Possible CNS effects (dizziness, headache, weakness). Includes GI effects (diarrhea, abdominal pain, nausea, vomiting), upper respiratory tract symptoms (cough, congestion), and other effects like rash, alopecia, pruritus, dry skin and fever.
  • Increased risk of bone loss, decreased calcium and magnesium, and an increased possibility of C. difficile and pneumonia with long-term use.

Gastrointestinal System - Constipation Treatment

• Laxatives: Laxatives (cathartic drugs) are indicated for short-term constipation relief. Several types exist:
  • Chemical stimulants: irritate the GI tract lining, increasing motility. Examples include castor oil, bisacodyl, and cascara.
  • Bulk stimulants: increase fecal bulk, inducing distension of the GI tract. Examples include lactulose, magnesium citrate and hydroxide, polyethylene glycol-electrolyte solution, and psyllium.
  • Lubricants: lubricate the stool, facilitating easier passage. Examples include mineral oil and docusate.
• Pharmacokinetics of laxatives: Most laxatives are minimally absorbed and exert their effects directly within the GI tract, but changes can occur for patients with underlying issues.
• Contraindications & Cautions: Caution is advised for pregnant and lactating women.
• Adverse effects: Common adverse effects among laxatives include diarrhea, abdominal cramping, nausea, dizziness, headache, weakness, sweating, palpitations, flushing, and fainting.

Gastrointestinal System - Lubricants

• Lubricants: These medications make defecation easier, without stimulating the GI tract, useful for people with rectal surgery or hemorrhoids; Docusate, mineral oil, and glycerin serve these functions.
• Pharmacokinetics of lubricators: These do not generally absorb and are excreted in feces.
• Contraindications & Cautions: Caution is advised for acute abdominal disorders, heart block, CAD, debilitation, pregnancy, and lactation.