Gastrointestinal Drug Introduction Gastrointestinal medications can be broken down into the following categores antidiarrheals antiemetics H2 antagonists proton pump inhibitors other antiulcer medications laxitives Gastrointestinal Drug Table Antidiarrheals Name Mechanism of Action Key Indication Key Toxicity Lomotil (diphenoxylate + atropine) Opioid agonist + anti-muscarinic Diarrhea Constipation Dry eyes, mouth, skinv Urinary retention Loperamide Opioid agonist Constipation Antiemetics Dimenhydrinate 1st generation antihistamine Nausea/Vomitting Vertigo (ondansetron) Gastroprokinetic (metoclopramide) Motion sickness (scopolamine) Sedation Orthostatic hypotension Dry eyes, mouth Ondansetron 5-HT3 antagonist Headache Torsades QT prolongation Constipation Prochlorperazine D2 antagonist Dystonia Parkinsonism Akathisia EPS Metoclopramide Central D2 + 5-HT3 antagonists Peripheral 5-HT4 agonist Parkinsonian symptoms EPS Scopalamine Muscarinic antagonist Sedation Promethazine 1st generation antihistamine α-antagonist Anti-cholinergic properties Sedation Dry mouth, eyes Dystonia Parkinsonism Akathisia EPS H2 Antagonists Cimetadine H2 blocker Gastritis/GERD Anti-androgen P450 inhibitor Decreased creatinine clearance Famotidine Sedation Ranitidine Decreased creatinine clearance Proton Pump Inhibitors Lansoprazole Irreversible parietal H+/K+ ATPase inhibition Gastritis/GERD P-450 inhibition Increased risk of C. diff infection B12 and Mg2+ deficiency Omeprazole Other Anti-Ulcer Simethicone Coating agent Decreases surface tension of gas bubbles (simethicone) Gastric ulcer GI symptoms Sucralfate Constipation Flatulence Headache Carafate Laxatives Bulk-forming laxatives (psyllium, methylcellulose, fiber supplements) Bulk-forming Draws in water to gut lumen Constipation Bloating Osmotic laxatives (magnesium hydroxide, magnesium citrate, polyethylene glycol) Increases osmotic load in gut lumen drawing in water Decreased deep tendon reflexes (Mg2+) Diarrhea Alkalosis Stimulant laxatives (senna, bisacodyl) Stimulates enteric nerves causing colonic contraction Diarrhea Emollient laxatives (mineral oil, docusate) Osmotic draw into gut lumen