Gastrointestinal System Drug Classifications PDF

HSHG 2090 – Basic Principles of Pharmacology Drug Classifications – Gastrointestinal System Learning Outcomes 6.6 Distinguish the following drug classifications related to the gastrointestinal system: 6.6.1 Antiemetics 6.6.2 Antacids 6.6.3 Laxatives 6.6.4 Antidiarrheal agents 6.11 Iden...

HSHG 2090 – Basic Principles of Pharmacology Drug Classifications – Gastrointestinal System Learning Outcomes 6.6 Distinguish the following drug classifications related to the gastrointestinal system: 6.6.1 Antiemetics 6.6.2 Antacids 6.6.3 Laxatives 6.6.4 Antidiarrheal agents 6.11 Identify examples of each of the above classifications of medications https://www.yout ube.com/watch?v=Og5xAdC8EUI&t=42sications Peptic Ulcers and Disease Stomach contains hydrochloric acid to breakdown food and kill germs When protection from the gastric acid in the stomach is lost, open sores on the stomach and upper intestinal tract can develop Ulcers result from damage to the mucus membranes which line the stomach and upper portion of the small intestine Antacids MOA: decrease gastric acidity by neutralizing acid Ulcers are not healed, but reduced acidity decreases tissue irritation and provides relief of discomfort Can also be used for gastroesophageal reflux disease (GERD) Examples: calcium carbonate, aluminum hydroxide, magnesium hydroxide, sodium bicarbonate Side effects: Constipation or diarrhea Antacids (cont’d) Precautions: Excess calcium can cause: N&V, kidney stones, mental status changes Many contain sodium which can cause fluid retention and aggravate heart failure symptoms Some contain aluminum which can accumulate and cause aluminum toxicity in patients with kidney failure Acid Reducers H2 Histamine Receptor Antagonists (H2RAs) MOA: Block gastric acid and pepsin secretion Examples: ranitidine, famotidine, cimetidine Proton Pump Inhibitors (PPIs) MOA: reduces gastric acid secretions by blocking the proton pump More effective than H2RAs Examples: pantoprazole, omeprazole, esomeprazole https://www.yout ube.com/watch?v=RlNaAiumwSQ Constipation Abnormally delayed or infrequent passage of dry stool Many causes such as: Low dietary fiber Dehydration Medications GI diseases Laxatives Drugs that stimulate intestinal peristalsis and increase movement of material through the bowel 4 types: Bulk-forming Osmotic / Saline Stimulant Surfactant (Stool Softener) Laxatives (cont’d) Bulk-forming laxatives MOA: Indigestible materials which absorb and retain water  increased weight stimulates bowel to move Takes 2 or 3 days to work Example: psyllium Osmotic laxatives MOA: draw water into the stool resulting in softer stools making it easier to pass Onset varies (depends on drug and dose) Example: polyethylene glycol 3350 (PEG3350) Laxatives (cont’d) Stimulant MOA: Directly stimulate the nerves controlling muscles that line the GI tract and increase intestinal secretion Takes 6 to 12 hours to work Example: senna, bisacodyl Laxatives (cont’d) Common side effects: Bloating Flatulence Abdominal cramping Nausea Dehydration Precautions: Laxative abuse may occur Stimulant laxatives are the most commonly abused Dependence and tolerance occurs with frequent use  Diarrhea Excessive flow of loose stools Many causes such as: Bacterial or viral infections Parasites Medications GI diseases Can quickly lead to dehydration Affects absorption of drugs, vitamins, nutrients, and toxins Source: https://www.openmed.co.in/2021/09/bristol-stool-chart.html Anti-diarrheal Agents Diarrhea is a condition characterized by increased frequency and liquidity of bowel movements Anti-diarrheals relieve symptoms of diarrhea, not the cause Different mechanisms of action: Depressing the normal wave-like action of peristalsis to allow more fluid to reabsorb Example: loperamide Bulking up the stool to increase volume Example: psyllium Antidiarrheal Agents (cont’d) Side effects are more common for the elderly or those with health problems Abdominal pain Constipation Dizziness Nausea and vomiting Nausea and Vomiting https://www.yout ube.com/watch?app=desktop&v=GSHTLWbwKgo Emesis is a complex process that involves various parts of the brain as well as receptors and other structures in the stomach and inner ear. Vomiting center stimulates vomiting directly Chemoreceptor Trigger Zone (CTZ) Indirect stimulation Multiple transmitters are involved in the vomiting reflex including serotonin, dopamine, acetylcholine and histamine. Medications that interfere with any of these transmitters can decrease or prevent nausea and vomiting. Anti-emetics Emesis (vomiting) is a normal physiological response to the presence of irritating and potentially harmful substances Controlled by the emetic center in the CNS Anti-emetic drugs work by interfering with communications to and from the emetic center Ideally, should treat the cause and not the symptom Anti-emetics (cont’d) Serotonin receptor antagonists MOA: block serotonin receptors which stimulate nausea Example: ondansetron Anticholinergics/antihistamines MOA: block acetylcholine/muscarinic receptors and histamine receptors and therefore prevent signals in the CNS Example: scopolamine, dimenhydrinate Prokinetic agents MOA: Promote GI motility and increase emptying time Example: metoclopramide Anti-emetics (cont’d) Side effects depend on the type of antiemetic Drowsiness Dry mouth Indigestion Constipation Muscle weakness, spasms, or convulsions Hearing loss Palpitations Summary Antacids do not affect stomach acid production Laxatives increase intestinal smooth muscle work or increase moisture of stool Anti-diarrheal agents inhibit intestinal smooth muscle work or add bulk to stool to thicken it Anti-emetics block CNS emesis center from sensing nausea or block muscarinic sites to prevent nausea being signaled to the emetic center References 1. Flake, Z., et al. Practical Selection of Antiemetics. American Family Physician. March 2004. Accessed at https://www.aafp.org/afp/2004/0301/p1169.html 2. Hauser, J., et al. Antiemetic Medications. StatPearls [Internet]. August, 2020. Accessed at https://www.ncbi.nlm.nih.gov/books/NBK532303/ 3. Heathline, Antacids. March, 2019. Accessed at https://www.healthline.com/health/antacids#takeaway 4. Hughes C. Nausea and Vomiting. In: Minor Ailments [Internet]. Ottawa (ON): Canadian Pharmacists Association; c2016 [updated Apr 2021; cited 2022 Feb 14]. Available from: http://www.myrxtx.ca. Also available in paper copy from the publisher. 5. Portalatin, M., et al. Medical Management of Constipation, Clinics in Colon and Rectal Surgery. March 2012; 25(1)