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 Diarrhea Constipation Antiemetics Name Mechanism of Action Key Indication Key Toxicity Dimenhydrinate 1st generation antihistamine Nausea/Vomiting Vertigo (ondansetron) Gastroprokinetic (metoclopramide) Motion sickness (scopolamine) Sedation Orthostatic hypotension Dry eyes, mouth Ondansetron 5-HT3 antagonist Nausea/Vomiting Vertigo (ondansetron) Gastroprokinetic (metoclopramide) Motion sickness (scopolamine) Headache Torsades QT prolongation Constipation Prochlorperazine D2 antagonist Nausea/Vomiting Vertigo (ondansetron) Gastroprokinetic (metoclopramide) Motion sickness (scopolamine) Dystonia Parkinsonism Akathisia EPS Metoclopramide Central D2 + 5-HT3 antagonists Peripheral 5-HT4 agonist Nausea/Vomiting Vertigo (ondansetron) Gastroprokinetic (metoclopramide) Motion sickness (scopolamine) Parkinsonian symptoms EPS Scopalamine Muscarinic antagonist Nausea/Vomiting Vertigo (ondansetron) Gastroprokinetic (metoclopramide) Motion sickness (scopolamine) Sedation Promethazine 1st generation antihistamine α-antagonist Anti-cholinergic properties Nausea/Vomiting Vertigo (ondansetron) Gastroprokinetic (metoclopramide) Motion sickness (scopolamine) Sedation Dry mouth, eyes Dystonia Parkinsonism Akathisia EPS H2 Antagonists Name Mechanism of Action Key Indication Key Toxicity Cimetadine H2 blocker Gastritis/GERD Anti-androgen P450 inhibitor Decreased creatinine clearance Famotidine H2 blocker Gastritis/GERD Sedation Ranitidine H2 blocker Gastritis/GERD Decreased creatinine clearance Proton Pump Inhibitors Name Mechanism of Action Key Indication Key Toxicity Lansoprazole Omeprazole Irreversible parietal H+/K+ ATPase inhibition Gastritis/GERD P-450 inhibition Increased risk of C. diff infection B12 and Mg2+ deficiency Other Anti-Ulcer Name Mechanism of Action Key Indication Key Toxicity Simethicone Coating agent Decreases surface tension of gas bubbles (simethicone) Gastric GI symptoms Sucralfate Carafate Coating agent Decreases surface tension of gas bubbles (simethicone) Gastric Constipation Flatulence Headache Laxatives Name Mechanism of Action Key Indication Key Toxicity 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 Constipation Decreased deep tendon reflexes (Mg2+) Diarrhea Alkalosis Stimulant laxatives (senna, bisacodyl) Stimulates enteric nerves causing colonic contraction Constipation Diarrhea Emollient laxatives (mineral oil, docusate) Osmotic draw into gut lumen Constipation Diarrhea