GIT DRUGS.pptx to understand the actions

GI drugs

1. Gastro Intestinal DRUGS

2. CONSTIPATION VS DYSCHEZIA Constipation means delayed passage of faeces through the intestine with defaecation process some remaining normal. Evacuation is often associated with straining and is usually incomplete. Dyschezia means derangement of defaecation process which may result due to pain arising from used haemorrhoids or fissure, sudden cessation of a habitual use of a purgative. * Purgative vicious cycle

3. Purgatives BULK FORMIN PURGATIVE Wheat bran, Psyllium husk, Ispaghula husk. Semisynthetic cellulose such as carboxy- methyline purgative These are luminally active, hydrophilic, indigestible vegetable fibres . They stimulate peristalsis and defaecation reflexes by increasing faecal bulk due to their water absorbing and retaining capacity.

4. Osmotic Purgatives Saline purgatives : Magnesium sulphate, Magnesium hydroxide (milk of magnesia), Sodium sulphate and Sodium phosphate; Saline purgatives are soluble inorganic salts which increase the faecal bulk by retaining water by osmotic effect, thus increasing peristalsis in- directly.. Electrolyte osmotic purgative Osmotic purgatives lead to watery evacuation; Polyethylene glycol ,Lactulose (10 g/15 ml), Sorbitol. Site and Mode of Action: All of them act on small as well as large intestine. They lead to watery evacuation by virtue of their high osmotic nature.

5. Lubricant Purgative Liquid paraffin Faecal lubricant stool softener. 15-30 ml at bedtime. 1-3 days.

6. Irritant Purgative Anthraquinone group: Senna, It Cascara and Aloe: (B) Organic irritants: Phenolphthalein, Bisacodyl (and its suppository); Sodium picosulfate ; (C) Oils: Castor oil. Irritant purgatives provide soft semifluid stools. MOA Stimulate peristalsis by irritant action on intestinal mucosa. They also stimulate colonic electrolyte and fluid secretion by altering the absorptive and secretory r activity of the mucosal cells. Aloe, senna and cascard occur naturally in plants. Senna is most commonly used. These plant purgatives contain anthraquinon glycosides. On reaching the colon, the bacteri degrade them to the active principle " anthrol "- stimulates small intestine. S/e melanosis coli.

7. Diarrhoea Diarrhoea is an abnormal and the decreased ability of intestine to absorb water from the stool are the major factors in the causation of diarrhoea . For the symptomatic relief of non- specific diarrhoeas , the following category of drugs can be used:

8. Opiod agonists Loperamide, diphenoxylate, difenoxin (an active metabolite of diphenoxylate) and racecadotril . Act on u receptors- decrease motility Act on $ receptor –decrease secretion

9. Anti - cholinergics Hyoscyamine Dicyclomne Decrease bowel motility Increase fluid absorption, Decrease abdominal cramps.

10. Bismuth salicylate Bismuth subsalicylate reduces stool frequency and liquidity in acute diarrhoea due to inhibition of PG synthesis and CI secretion by its salicylate counterpart. Bismuth has some antimicrobial effects, binds to enterotoxins and also provides protective coating over inflammed gastric mucosa. It is now rarely used because the doses required for relief are large and need to be administered frequently. subsalicylate causes blackening of stool (mistaken for melaena) and darkening of tongue because of a reaction between bismuth and the sulfide (produced by bacteria) to form a black bismuth sulfide.

11. Octeotride Lanreotide Seglitide Vapreotide Telotristat ethyl Lactobacillus sporogens should be used to replace normal bnacterial flora.

12. Anti ulcer Drugs

13. Histamine-2 receptor antagonists : Mechanism of action —  istamine H-2 receptor blockers stop the action of histamine on the gastric parietal cells, inhibiting the secretion of gastric acid. These drugs are less effective than the proton pump inhibitors, but may achieve a 75-79% reduction in acid secretion.  cimetidine, Rantidine famotidine nizatidine Roxatidine loxat idine S/e cimetidine- impotence,gynomestia,enzyme inhibtor Secreted in breast milk,to be avoided in pregnancy.

14. The  proton pump inhibitors  block the secretion of gastric acid by the gastric parietal cells. The extent of inhibition of acid secretion is dose related. In some cases, gastric acid secretion is completely blocked for over 24 hours on a single dose. Eg :-Omeprazole is a prototype while esomeprazole, lansoprazole, Dexlansoprazole , pantoprazole , rabeprazole were introduced later. . New drug-Tenatoprazole New class of drugs -Potassium Competitive Acid Pump blockers

15. Sucralfate and Colloidal bismuth subcitrate Aluminium salt of sulfated sucrose. Both do not inhibit gastric acid, but rather, reacts with existing stomach acid to form a thick coating that covers the surface of an ulcer, protecting the open area from further damage. Also stimulate mucus and bicarbonate secretion. Bismuth also has addition antimicrobial property. Not to be given with PPIs Works for 6 hrs (so 1gm QID) and (120 gQID ) Binds to phosphate ions so hypophosphatemia Other uses :. Its gel is used for burn dressing and bed sores. In slightly higher doses it may be used to prevent phosphate stones in kidney. Its preparations with surface local anaesthetic are also available.

16. H pylori 50% cases of H. pylori.. It has become widely accepted as a cause of chronic atrophic gastritis. H. pylori is also a risk factor for gastric adenocarcinoma and to some This bacterium, is able to survive in the acidic gastric environment by its ability to produce urease, which hydrolyses urea into ammonia. Ammonia neutralises gastric HCI to create a neutral protective cloud over the bacteria., disturbs the normal negative feedback mechanisms which cause more secretion of gastric acid through release of more gastrin in response to food. H. pylori also produces various other proteolytic enzymes such as proteases and lipases which further degrade the important mucosal barrier

17. H pylori regimen

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