Overview
This lecture covers drugs and treatments for lower gastrointestinal (GI) disorders, focusing on constipation, diarrhea, irritable and inflammatory bowel diseases, hemorrhoids, and gas, with emphasis on drug categories, mechanisms, and practical management.
Lower GI Disorders Overview
- Focus on conditions affecting the lower small intestine, large intestine, colon, and rectum.
- Common issues include constipation, diarrhea, irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), flatulence, and hemorrhoids.
Constipation: Causes, Signs, and Drug Therapy
- Constipation defined as less than 3 bowel movements per week, often with hard, dry stools and straining.
- Causes: dehydration, stress, pregnancy, obesity, low fiber diet, inactivity, medications (especially codeine), and schedule changes.
- Goal of drug therapy: increase stool softness and promote normal bowel movements.
- Four main drug categories:
- Bulk forming laxatives (e.g., Metamucil): Fiber-based, need lots of water, slow onset (12–24 hrs), interact with tetracyclines, warfarin, aspirin.
- Stool softeners (e.g., Colace): Oil-water surfactants, slow onset, ideal post-surgery or childbirth.
- Hyperosmotic agents (e.g., magnesium citrate, glycerin suppositories): Draw water into intestine, faster onset (1–6 hrs or less).
- Stimulant laxatives (e.g., Ex-Lax, Dulcolax): Increase GI motility, onset 6–10 hrs, risk of abuse and dehydration.
Diarrhea: Causes, Signs, and Drug Therapy
- Diarrhea involves increased frequency and decreased consistency of bowel movements.
- Two types: acute (<2 weeks) from infection or toxins; chronic (>2 weeks).
- Key risk: dehydration and electrolyte loss.
- Drug classes:
- Opioids (e.g., Imodium, Lomotil): Slow GI motility, do not cross blood-brain barrier.
- Bismuth subsalicylate (Pepto-Bismol): Anti-inflammatory, possible mild antibiotic effect, short onset and half-life.
IBS and IBD Management
- Irritable Bowel Syndrome (IBS): Types: IBS-D (diarrhea), IBS-C (constipation), IBS-M (mixed); triggers include hormone changes, stress, and certain foods.
- Treatment: match drugs to symptoms (anti-diarrheals for IBS-D, laxatives for IBS-C), plus lifestyle modifications.
- Inflammatory Bowel Disease (IBD): Includes Crohn’s disease (patchy, non-continuous lesions throughout GI) and ulcerative colitis (continuous lesions in colon/rectum).
- IBD requires anti-inflammatory drugs (e.g., Humira, Flagyl) and often surgery.
Hemorrhoids
- Hemorrhoids are swollen rectal veins (internal/external), caused by pressure, straining, constipation, or diarrhea.
- Symptoms: pain, itching, bleeding, visible polyps.
- Treatment: topical corticosteroids, lubricants, anti-inflammatory creams, surgical removal for severe cases.
Gas and Flatulence
- Gas arises from swallowed air, food digestion, and diffusion; main symptoms: belching and flatulence.
- Beano: Use for food-related gas, especially after beans, whole grains, leafy vegetables.
- Gas-X: Use for non-food-related gas, works as an anti-foaming agent.
Key Terms & Definitions
- Peristalsis — Coordinated muscle contractions moving contents through the GI tract.
- Bulk forming laxative — Fiber supplement that increases stool mass with water, easing passage.
- Stool softener — Surfactant drug that mixes water and oil into stool to soften it.
- Hyperosmotic agent — Drug that draws water into the intestine or rectum to soften stool.
- Stimulant laxative — Medication that increases intestinal motility to induce bowel movements.
- IBS (Irritable Bowel Syndrome) — Functional disorder with alternating diarrhea, constipation, or both.
- IBD (Inflammatory Bowel Disease) — Chronic inflammatory GI diseases (Crohn’s & ulcerative colitis).
Action Items / Next Steps
- Review medication onset times and contraindications for bulk forming laxatives.
- Know symptom profiles for constipation, diarrhea, IBS, and IBD.
- Refer patients with prolonged self-medication (>2 weeks) for further evaluation.
- Complete assigned textbook readings on GI drugs and diseases.