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Laxative and Antidiarrheal Agents reviewed by Clare Shalders 2007

Laxative and Antidiarrheal Agents reviewed by Clare Shalders 2007. Actions of Drugs Used to Affect Motor Activity of the GI Tract. Speed up or improve movement of intestinal contents when movement becomes slow or sluggish (constipation)

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Laxative and Antidiarrheal Agents reviewed by Clare Shalders 2007

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  1. Laxative and Antidiarrheal Agentsreviewed by Clare Shalders 2007

  2. Actions of Drugs Used to Affect Motor Activity of the GI Tract • Speed up or improve movement of intestinal contents when movement becomes slow or sluggish (constipation) • Increase the tone of the GI tract and stimulate motility throughout the system • Decrease movement along the GI tract when rapid movement decreases the time for absorption of nutrients (diarrhea)

  3. Site of Action of Drugs Affecting GI Motility

  4. Types of Laxatives • Chemical stimulants • Chemically irritate the lining of the GI tract • Bulk stimulants • Cause the fecal matter to increase in bulk, natural plant gums. Stimulate peristalsis by increasing bulk in stool through absorption of water in the colon • Lubricants • Help the intestinal contents move more smoothly

  5. Types of Chemical Stimulants • Ducosate: Faecal softening agent, acute constipation and prevent straining • Senna (Senokot): Reliable drug, similar to cascara (OTC) Produces bowel action in 6-12 hours • Castor oil (Neoloid): Old standby for thorough evacuation of the intestine • Bisacodyl (Dulcolax): Very popular OTC laxative; Enteric coated to dissolve in small intestine and produces stimulating effect on colon. Can irritate stomach hence enteric coated. Evacuation 6-12 hours after oral and 15-60 mins supp

  6. Types of Bulk Stimulants • Magnesium sulfate (Epsom Salts) • Magnesium citrate (Citrate of Magnesia) • Magnesium hydroxide (Milk of Magnesia) • Lactulose (Chronulac) • Polycarbophil (FiberCon) • Psyllium (Metamucil)

  7. Types of Lubricating Laxatives • Docusate, liquid paraffin. • Has a detergent action on the surface of the intestinal bolus, making a softer stool • Glycerin (Sani-Supp) • Hyperosmolar laxative used to gently evacuate the rectum without systemic effects higher in the GI tract • Mineral oil (Agoral Plain) • Forms a slippery coat on the contents of the intestinal tract

  8. Indications for the Use of Laxatives • Short-term relief of constipation • Prevent straining when it is clinically undesirable • Evacuate the bowel for diagnostic procedures • Remove ingested poisons from the lower GI tract • As an adjunct in athelmintic therapy ( T of worms)

  9. Focus on the Prototype Chemical Stimulant: Castor Oil • Indications:Evacuate the bowel for diagnostic procedures; remove ingested poisons from the lower GI tract; adjunct in anthelmintic therapy • Actions:Directly stimulates the nerve plexus in the intestinal wall, causing increased movement and the stimulation of local reflexes • Pharmacokinetics:Not absorbed systemically • Not absorbed systemically

  10. Focus on the Prototype Bulk Laxative: Magnesium Citrate • Indications:Short-term relief of constipation; prevent straining; evacuate the bowel for diagnostic procedures; remove ingested poisons; adjunct in anthelmintic therapy • Actions:Increases motility of the GI tract by increasing the fluid in intestinal contents; enlarges bulk; stimulates local stretch receptors; activates local activity • Pharmacokinetics:Not absorbed systemically Not absorbed systemically

  11. Focus on the Prototype Lubricant: Mineral Oil • Indications:Short-term relief of constipation; prevent straining; remove ingested poisons; an adjunct in anthelmintic (treatment of worms) therapy • Actions:Forms a slippery coat on the contents of the intestinal tract; less water is absorbed out of the bolus; bolus is less likely to become hard or impacted • Pharmacokinetics:Not absorbed systemically • Not absorbed systemically

  12. Types of Gastrointestinal Stimulants • Dexpanthenol (Ilopan) • Increases acetylcholine levels and stimulates the parasympathetic system • Metoclopramide (Reglan) • Blocks dopamine receptors and makes the GI cells more sensitive to acetylcholine • Leads to increased GI activity and rapid movement of food through the upper GI tract

  13. Focus on the GI Stimulant Prototype: Metoclopramide • Indications:Acute and chronic diabetic gastroparesis; gastroesophageal reflux disorder; postoperative nausea and vomiting; small bowel intubation; gastric emptying; intestinal transit of barium • Actions:Stimulates movement of the upper GI tract without stimulating gastric, pancreatic, or biliary secretions; sensitizes tissues to acetylcholine effects • Routes: Oral, IM, IV • metabolized in the liver; excreted in urine

  14. Types of Antidiarrheal Drugs • Bismuth subsalicylate (Pepto-Bismol): Coats the lining of the GI tract and soothes irritation stimulating local reflexes to cause excessive GI activity and diarrhea • Loperamide (Imodium): Has a direct effect on the muscle layers of the GI tract; slows peristalsis and allows increased time for absorption of fluid and electrolytes • Opium derivatives (paregoric): Stimulates spasm within the GI tract, stops peristalsis and diarrhea

  15. Functions of Antidiarrheal Drugs • Soothe irritation to the intestinal wall • Block GI muscle activity to decrease movement • Affect CNS activity to cause GI spasm and stop movement • Relief of symptoms and fluid and electrolyte loss • Many OTC antidiarrhoeal drugs, contain limited amounts of opiods (codeine, loperamide) aluminium hydroxide, kaolin and pectin (hyoscineand atropine)

  16. Antidiarrhoeals • Precautions • Care should be taken when using antidiarrhoelsa if the cause of the diarrhoea is bacterial as this allows the bacterial toxin to rmain in the body. • Constipation can result from excess use

  17. Adsorbents • Act by coating the intestinal mucosa, absorbing the bactreria or toxins causing the diarrhoea and passing them out with the stools • Examples include aluminium hydroxide (Kaomagna) and kaolin and pectin (Kaopectate) • General initial higher dose then lower after each bowel movement • Caution if other meds given concurrently, they can bind the other drugs

  18. Opiod Antidiarrhoeals • Loperamide are OTC opiods that activate opiod receptors in the gut wall, resulting in a reduction in secretions and inhibiton of propulsive movements in the gut. • This slows the passage of intestinal contents and allows reabsorption of water and electrolytes, reducing stool frequency • Indicated for short term treatment • Lomotil can produce adverse reactions of dizziness, dry mouth and blurred vision

  19. Inflammatory Bowel Disease • Includes ulcerative colitis and crohns disease • Includes drug therapy, dietary and lifestyle factors • Current therapy corticosteroids and sulphazine,mesalazine and olsalazine and immunosupressants such as cyclosporin and methotraxate • Infliximab a new humanised antibody that targets tumour necrossis factor alpha, for crohns disease

  20. Aminosalicylates • Sulphasalazine • Consists of sulphonamide antibiotic, sulphapyridine, linked to the anti inflammatory salicylate,mesalazine. • Poorly absorbed and in the colon is split by bacteria into sulphapyridine and mesalazine which is the active component effective in the treatment of IBD

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