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73 Cards in this Set
- Front
- Back
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Major physiologic process that occur in the GIT |
Secretion Digestion Absorption |
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Includes the transport of fluid, electrolytes, peptides and proteins into the lumen of the alimentary canal |
Secretion |
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Involved in the digestion of carbs and proteins |
Enzymes in saliva and pancreatic secretions |
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Protect the linings of the lumen of the GIT |
Mucus |
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Breakdown of food constituents into smaller structures in preparation for absorption |
Digestion |
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Fiid constituents are mostly absorbed in the? |
Proximal area (duodenum) of the small intestine |
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Entry of constituents from the lumen of the gut into the body |
Absorption |
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Net result of both lumen-to-blood and blood-to-lumen transport movements |
Absorption |
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Drugs administered orally pass through various parts of the enteral canal including: Residues eventually exit the body through the: |
1. Esophagus Oral cavity Various parts of GIT 2. Anus |
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Total transit time including gastric emptying, small intestinal transit and colonic transit |
0.4 to 5 days |
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Most important site of drug absorption |
Small intestine |
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Small intestine transit time |
3-4 hrs |
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Normally filled with digestive juices and liquids, keeping the lumen contents fluid |
Small intestine |
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Fluid in the colon |
Reabsorbed |
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Luminal content in the colon |
Either semisolid or solid, making further drug dissolution erratic and difficult |
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Less favorable environment for drug absorption |
Lack of the solubilizing effect of the chime and digestive fluid |
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Normal physiologic processes of the alimentary canal may be affected by: |
Diet Contents of the GIT hormones Visceral nervous system (movement of the intestine, stomach, etc) Disease ( diarrhea, inflammatory bowel disease) Drugs (anticholinergics) |
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Drugs given by the enteral route for systemic absorption may be affected by the: |
Anatomy Physiologic functions Contents of the alimentary canal |
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Properties of the drug that will affect its own absorption from the alimentary canal |
Physical Chemical Pharmacologic |
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Reasons why GIT offers an efficient absorption system |
1. Copious blood supply 2. Entire length of GIT is lined with mucous membrane 3. There are around 8-10 L of fluid/day produced by or secreted into the GIT; and 1-2 L come from the food and fluid intake 4. GIT is perfused by capillary network that allows efficient absorption and distribution of nutrients and drugs |
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Rich in blood vessels and will facilitate absorption of drug |
Mucous membrane |
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High mw polysaccharide that may bind drugs |
Mucin |
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Secretes mucin |
Mucous membrane |
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pH 7 |
Oral cavity Ileum Rectum |
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pH 2-6, 1.5-2 |
Stomach |
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pH 6-6.5 |
Duodenum |
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pH 5.5-7 |
Colon |
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Has an average length of 15-20 cm |
Oral cavity |
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Main secretion is saliva (1,500 ml/day) |
Oral cavity |
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Salivary amylase and can digest starches |
Ptyalin |
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Glycoprotein that may interact with drugs |
Mucin |
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Villi is absent |
Oral cavity |
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Basic drugs are solubilized rapidly by? |
Stomach acid |
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Control ng food para di bumagsak |
Pyloric sphincter |
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Presence of bicarbonate |
Duodenum |
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Trypsin, chymotrypsin & carboxypeptidase ➡ proteins to amino acids |
Duodenum |
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Amylase ➡ CHO |
duodenum |
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Pancreatic lipase ➡ fats to fatty acids |
Duodenum |
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Complex fluid medium helps dissolve drugs with limited aqueous solubility |
Duodenum |
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Ester prodrug are hydrolyzed |
Duodenum |
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Protein drugs are unstable due to proteolytic enzymes |
Duodenum |
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Acid drugs will dissolve due to bicarbonate secretion |
Ileum |
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Fats and hydrophobic drugs are dissolved by bile secretion |
Ileum |
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Lack microvilli |
Colon |
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Very limited drug absorption due toviscous and semisolid nature of lumen contents |
Colon |
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Mucin as lubricant and protectant |
Colon |
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Theophylline and metoprolol are absorbed |
Colon |
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Absorbed at this region are good candidates for sustained release dosage forms |
Colon |
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Aerobic and anaerobic microorganisms which metabolizes drugs (L-dopa and lactulose) |
Colon |
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Avoid 1st pass effect |
Middle and inferior hemorrhoidal vein |
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Superior, middle, inferior hemorrhoidal vein |
Rectum |
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Factors that can affect the transit time of drugs in the GI tract |
Pharmacologic properties of the drug Type of dosage form (physiochemical) Physiologic factors |
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Alternating cycles of propulsive movement that empties the upper GI tract to the cecum |
Migrating motor complex (mmc) |
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Functions of gastric motility |
1. Allow the stomach tos erve as a reservoir for the large volume of food that may be ingested at a single meal 2. To fragment food into smaller particles ro mix chyme with gastric secretion so that digestion can begin 3. Empty gastric contents into the duodenum at a controlled rate (gastric emptying time) |
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Factors that affect gastric emptying |
Volume Fatty acids Triglycerides Carbs Amino acids, proteins Osmotic pressure Physical state or gastric contents Acids Alkali Drugs Body position Viscosity Emotional states Bile salts Exercise Disease states |
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SITT fasted state |
4-8 hrs |
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SITT fed state |
8-12 hrs |
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Mouth-to-anus transit time |
53.3 hrs |
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Mean colon transit time |
35 hrs |
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Important in carrying the drug into systemic circulation |
Perfusion of GI tract |
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Receives about 28% of the cardiac output and is increased after meals |
Splanchnic circulation |
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Many poorly water soluble drugs are soluble in oil and lipids which may dissove in: |
Chylomicrons |
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Some drigs can be absorbed in lymphatic circulation and bypass first pass effect |
Perfusion of GI tract |
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Effect of food in GI drug absorption |
Delay in gastric emptying Stimulation of bile flow Change in pH of the GI tract An increase in the splanchnic blood flow Change in the luminal metabolism of drug substance Physical or chemical interaction of the meal with the drug product |
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Reduced absorption with food |
Tetracycline Penicillin G Isoniazid Amoxicillin Aspirin Rifampicin Furosemide Phenacitin |
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Delayed absorption with food |
Aspiri Acetaminophen Nitrofurantoin Digoxin Sulfisoxazole Cephradine Cefaclor Sulfadiazine |
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Increased absorption with food |
Dicoumarol Griseofulvin Phenytoin Metoprolol Oxazepam Propranolol Hydralazine |
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Not affected with food |
Theophylline Prednisolone Chkorpropramide Metronidazole PTU |
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Timing of drug intake in relation to food |
Therapeutic goal Physiochemical properties of the drug Dosage form Character of drug Drug interaction/ incompatibilities |
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Double peak phenomenon |
Usually seen in administered single dose of fasted patients Variability of stomach emptying Variability of intestinal motility Presence of food Enterohepatic recycling Failure of a tablet dosage form |
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1st peak |
Stomach release to intestine |
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Pagbaba |
Delayed gastric emptying time |
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2nd peak |
Stomach empty into intestine |
