Pharmacology of Lower GI tract

What is emesis?

Appropriate or inappropriate gastric emptying, stimulated by toxins (bacterial poisons/alcohol/drugs), motion, smell, pregnancy, migrane etc

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What are the 5 main anti-emetic drugs?

H1-receptor antagonists (motion sickness), anti-muscarinic agents (motion, stomach irritation), dopamine antagonists (effect against cancer drugs), 5-hydroxytryptamine antagonists (effect against cancer drugs, post-op nausea & vomiting) & steroids

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What causes diarrhoea?

Often bacterial or viral infection: rotavirus damages small bowel villi, invasive bacteria damage epithelium (cytotoxins damage mucosa), adhesive enterotoxigenic bacteria adhere to brush border. Increase cAMP -> Na/Cl secretion followed by water

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What type & how do drugs cause diarrhoea?

Antibiotics (superinfection): broad spec antibiotics alter/kill lower GI flora, less healthy bacteria to compete with pathogenic bacteria. Orlistat -> steatorrhoea. Misoprostal (PPIs)

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What is the treatment for diarrhoea?

Oral rehydration therapy e.g. dioralyte. Isotonic to replace lost electrolytes as well as H20, glucose allows reabsorption of Na via a symporter follower by water (reverses secretory diarrhoea)

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What other treatments may to used to help rehydration therapy?

Probiotics: decrease antibiotic & C. difficile associated diarrohea. Antimotility agents: opiods/loperamide, decrease tone & peristaltic movements, inhibits ACh release, promotes H20 reabsorption. Antimuscarinic agents: blocks ACh action

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What are the treatment options for constipation?

Balanced diet with roughage & increased fluid. Osmotic laxaties e.g. lactulose, converted by bacteria, raises fluid volume osmotically, increases bulk of stools. Others: Macrogols/Magnesium/Bulking agents/Stilmulant laxatives/Prucalopride

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What is IBS? What are the symptoms?

Irritable bowel syndrom. ABC symptoms: Abdominal pain/discomfort. Bloating relieved by defecation. Change in bowel habit - episodes of diarrhoea and/or constipation

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What is the treatment for IBS?

Depends on presenting symptom (lactulose or loperamide). Anitspasmodic agents: antimuscarinics inihibit parasympathetic activity, phosphodiesterase & mebeverine (direct relaxant of smooth muscle). Amitriptyline: pain relief, antimuscarinic effects

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What is inflammatory bowel disease (IBD)?

Chronic inflammation with pain & bloody diarrhoea. Chron's disease: mouth -> anus, widespread deep inflammation. Ulcerative colitis: rectum -> colon, superficial inflammation

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What is the treatment for IBD?

Anti-inflammatories & imunosuppressants (corticosteroids)

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Pharmacology of Lower GI tract

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