Drugs Acting on GIT PDF

Module 8 Drugs Acting on the Gastrointestinal System CHOLEN CALDITO, RN, MAN, LPT INSTRUCTOR Drugs and GI System GIT is basically a hollow, muscular tube that begins at the mouth and ends at the anus encompasses the pharynx, stomach, and the small and large intestines to digest and absor...

Module 8 Drugs Acting on the Gastrointestinal System CHOLEN CALDITO, RN, MAN, LPT INSTRUCTOR Drugs and GI System GIT is basically a hollow, muscular tube that begins at the mouth and ends at the anus encompasses the pharynx, stomach, and the small and large intestines to digest and absorb food and fluids and excrete metabolic wastes Lesson 1 Antiulcerant Drugs CHOLEN CALDITO, RN, MAN, LPT INSTRUCTOR Antacids group of inorganic chemicals that neutralize stomach acid OTC used alone or with combination with other drugs to treat peptic ulcers* include magnesium hydroxide, aluminum hydroxide, simethicone, magaldrate (aluminum- magnesium complex), calcium carbonate, sodium bicarbonate** Antacids Pharmacokinetics neutralize gastric acid* distributed throughout the GIT and are eliminated primarily in the feces Pharmacodynamics the acid-neutralizing action of antacids reduces the total amount in the GIT allowing peptic ulcers time to heal** Antacids Pharmacotherapeutics used alone or with other drugs to relieve pain and promote healing in PUD relieve symptoms of acid indigestion, heartburn, dyspepsia or GERD* Drug Interactions interfere with the absorption of oral drugs if given at the same time absorption of digoxin, iron salts, isoniazid, quinolones, and tetracyclines may be reduced if taken within 2 hours of antacids H2 Receptor Antagonists H2 blockers commonly prescribed include cimetidine, nizatidine, ranitidine and famotidine Pharmacokinetics cimetidine, nizatidine, and ranitidine are absorbed rapidly and completely from GIT famotidine is not absorbed completely food and antacids may reduce absorption distributed widely through the body, metabolized by the liver and excreted in the urine H2 Receptor Antagonists Pharmacodynamics block histamine from stimulating the acid-secreting parietal cells of the stomach blocking gastric acid secretions and promote healing of ulcer by eliminating its cause* Pharmacotherapeutics treatment of active duodenal ulcer or benign gastric ulcer treatment of pathologic GI hypersecretory* conditions such as Zollinger-Ellison Syndrome** reduce gastric acid production and prevent stress ulcers in severely ill patients and in those with reflux esophagitis or upper GI bleeding*** treatment of erosive gastroesophageal reflux* relief of symptoms of heartburn, acid indigestion, and sour stomach H2 Receptor Antagonists Drug Interactions antacids reduce the absorption of cimetidine, nizatidine, and famotidine cimetidine may increase the blood levels of oral anticoagulants, propranolol, benzodiazepines, TCAs, theophylline, procainamide, quinidine, lidocaine, phenytoin, calcium channel blockers, cyclosporine, carbamazepine and narcotic analgesics by reducing their metabolism in the liver and subsequent excretion cimetidine inhibits metabolism of ethyl alcohol in the stomach, resulting in higher blood alcohol levels H2 Receptor Antagonists Adverse Reactions headache, dizziness, malaise, muscle pain, nausea, diarrhea or constipation, rashes, itching, loss of sexual desire and impotence famotidine and nizatidine produce few adverse reactions with headache as the most common followed by constipation or diarrhea and rash Proton Pump Inhibitors disrupt the chemical binding in the stomach cells to reduce acid production, lessening irritation and allowing peptic ulcers to better heal* include rabeprazole, pantoprazole, omeprazole, lansoprazole, esomeprazole** Pharmacokinetics given orally in enteric-coated formulas to bypass the stomach because they’re highly acid labile when in small intestine, they are dissolved, and absorption is rapid highly protein-bound and are extensively metabolized by the liver to inactive compounds then eliminated in the urine Proton Pump Inhibitors Pharmacodynamics block the last step in the secretion of gastric acid by combining with hydrogen, potassium and adenosine triphosphate in the parietal cells of the stomach* Pharmacotherapeutics short term treatment of active gastric ulcers, active duodenal ulcers, erosive esophagitis, symptomatic GERD that is not responsive to other therapies, active peptic ulcers associated with H. pylori infection in combination with antibiotics, long term treatment of hypersecretory states such as Zollinger-Ellison syndrome Proton Pump Inhibitors Drug Interactions interfere with the metabolism of diazepam, phenytoin and warfarin causing increased half-lives and elevated plasma concentrations of these drugs Contraindications known allergy to the drug or its components caution in pregnant or lactating women* Side Effects and Adverse Reactions** CNS effects of dizziness and headache are common; GI effects include abdominal pain, diarrhea, nausea and vomiting, dry mouth and tongue atrophy; URT symptoms include cough, stuffy nose, hoarseness, and epistaxis Other Peptic Ulcer Drugs Sucralfate gastrointestinal protectant works locally in the stomach, rapidly reacting with hydrochloric acid to form a thick, paste-like substance that adheres to the gastric mucosa and especially to ulcers* also inhibits pepsin activity in gastric juices, preventing further breakdown of proteins in the stomach, including the protein wall of the stomach rapidly absorbed after oral administration, metabolized in the liver, and excreted in the feces; it crosses the placenta and may enter breast milk Other Peptic Ulcer Drugs Sucralfate should not be given to any person with known allergy to the drug or any of its components to prevent hypersensitivity reactions should not be given to individuals with renal failure or undergoing dialysis* caution in patients who are pregnant or lactating** adverse effects associated with this drug are primarily related to its GI effects such as constipation***, diarrhea, nausea, indigestion, gastric discomfort, and dry mouth; others include dizziness, sleepiness, vertigo, skin rash, and back pain if aluminum salts are combined with sucralfate, there is a risk of high aluminum levels and aluminum toxicity*; sucralfate decreased serum levels of phenytoin, fluoroquinolone or penicillin** Other Peptic Ulcer Drugs Misoprostol synthetic prostaglandin* inhibits gastric acid secretion and increases bicarbonate and mucus production in the stomach thus protecting the stomach lining primarily used to prevent NSAID-induced gastric ulcers in patients who are at risk for complications from a gastric ulcer** given orally; rapidly absorbed from the GIT, metabolized in the liver, and excreted in the urine; crosses placenta and enters breast milk Other Peptic Ulcer Drugs Misoprostol contraindicated to patients with allergy to any part of the drug contraindicated during pregnancy because it is an abortifacient caution should be used during lactation and in patients with hepatic or renal impairment* adverse effects associated with this drug are primarily related to its GI effects – nausea, diarrhea, abdominal pain, flatulence, vomiting, dyspepsia, and constipation; Genitourinary effects – which are related to the actions of prostaglandins on the uterus, include miscarriages, excessive bleeding, spotting, cramping, hypermenorrhea, dysmenorrhea, and other menstrual disorders Lesson 2 Laxatives CHOLEN CALDITO, RN, MAN, LPT INSTRUCTOR Chemical Stimulants directly stimulate the nerve plexus in the intestinal wall, causing increased movement and the stimulation of local reflexes include bisacodyl (Dulcolax), cascara, castor oil, and senna (Senokot) Pharmacokinetics most of these agents are minimally absorbed and exert their therapeutic effect directly in the GIT* castor oil has an onset of action of 2-6 hrs; 6-8 hrs (others)** Chemical Stimulants Pharmacotherapeutics castor oil is used when a thorough evacuation of the intestine is desired* bisacodyl acts in a similar manner but is somewhat milder in effect; can also be given in a water enema to stimulate the activity in lower GIT cascara is milder than castor oil and is often used when effects are needed overnight senna is available orally in tablet and syrup form and as a rectal suppository Chemical Stimulants Contraindications and Cautions allergy to any component of the drug* acute abdominal disorders (appendicitis, diverticulitis, and ulcerative colitis)** use with caution in patients with heart block, coronary artery disease, or debilitation*** use with caution in pregnancy and lactation* Adverse Effects GI effects such as diarrhea, abdominal cramping, and nausea (most common) CNS effects such as dizziness, headache, and weakness** sweating, palpitations, flushing and fainting*** cathartic dependence* Bulk Stimulants also known as mechanical stimulants rapid-acting, aggressive laxatives that cause the fecal matter to increase in bulk* include magnesium sulfate (Epsom salts), magnesium citrate (Citrate of Magnesia), magnesium hydroxide (Milk of Magnesia), lactulose (Constilac), polycarbophil (FiberCon), psyllium (Metamucil), polyethylene glycol (MiraLax), polyethylene glycol electrolyte solution (GoLYTELY), and sodium picosulfate with magnesium oxide (Prepopix) Bulk Stimulants Pharmacokinetics taken orally directly effective within the GIT and are not generally absorbed systemically rapidly acting, causing effects as they pass through the GIT Contraindications and Cautions allergy to the drug or any of its components acute abdominal disorders used with caution in heart block, CAD, debilitation, pregnancy and lactation polyethylene and glycol electrolyte solution should be used with caution in any patient with history of seizures* use with caution and take bulk laxatives with plenty of water** Bulk Stimulants Pharmacotherapeutics lactulose, a saltless osmotic laxative that pulls fluid out of the venous system and into the lumen of the small intestine magnesium citrate and hydroxide, milder and slower-acting laxatives and work by saline pull* magnesium sulfate, exerts a hypertonic pull against the mucosal wall** polycarbophil*, stimulates local activity; milder and less irritating than many other bulk stimulants polyethylene glycol and polyethylene glycol electrolyte solution, hypertonic fluids containing many electrolytes that pull fluid out of the intestinal wall to increase the bulk of intestinal contents psyllium, gelatin-bulk stimulant; similar to polycarbophil in action and effect sodium picosulfate with magnesium oxide provides a combination stimulant laxative with a bulk laxative*** Bulk Stimulants Adverse Effects GI effects such as diarrhea, abdominal cramping, and nausea CNS effects including dizziness, headache and weakness* sweating, palpitations, flushing, and fainting** Drug Interactions the administration of laxatives and other medications should be separated by at least 30 minutes* increased risk of neuromuscular blockade when using nondepolarizing neuromuscular junction blockers with magnesium salts** Lubricants make defecation easier without stimulating the movement of the GIT* include docusate (Colace), glycerin (Sani-Supp), and mineral oil Pharmacotherapeutics docusate has a detergent action on the surface of the intestinal bolus** glycerin is hyperosmolar laxative that is used in suppository form to gently evacuate the rectum without systemic effects higher in the GIT mineral oil is the oldest of these laxatives; not absorbed and forms a slippery coat on the contents of the intestinal tract* Lubricants Pharmacokinetics not absorbed systemically and are excreted in the feces docusate and mineral oil are given orally glycerin is available as a rectal suppository or as a liquid for rectal retention Contraindications and Cautions allergy to any component of the drug* acute abdominal disorders** used with caution in heart block, CAD, and debilitation* caution should be used during pregnancy and lactation** Lubricants Adverse Effects most common are GI effects such as diarrhea, abdominal cramping, and nausea leakage and staining may be a problem when mineral oil is used, and the stool cannot be retained by external sphincter CNS effects including dizziness, headache, and weakness are not uncommon* sweating, palpitations, flushing, and fainting have been reported after laxative use** Drug Interactions frequent use of mineral oil can interfere with the absorption of the fat-soluble vitamins A,D,E and K Lesson 3 Gastrointestinal Stimulants CHOLEN CALDITO, RN, MAN, LPT INSTRUCTOR Gastrointestinal Stimulants stimulate parasympathetic activity or make the GI tissues more sensitive to parasympathetic activity include dexpanthenol (Ilopan) and metoclopramide (Reglan) Pharmacotherapeutics increase GI secretions and motility on a general level throughout the tract* indicated when more rapid movement of GI contents is desirable dexpanthenol works by increasing acetylcholine levels and stimulating the parasympathetic system metoclopramide works by blocking dopamine receptors and making GI cells more sensitive to acetylcholine** Gastrointestinal Stimulants Pharmacokinetics dexpanthenol is given by IM and reaches peak levels within 4 hours metoclopramide is given orally or by IM or IV infusion and has a peak effect by all routes in 60-90 mins metabolized in the liver and excreted in the feces and urine metoclopramide crosses the placenta and enters breast milk dexpanthenol may cross the placenta and enter breast milk Contraindications and Cautions should not be used in patients with a history of allergy to any of these drugs or with GI obstruction or perforation* should be used with caution during pregnancy or lactation** Gastrointestinal Stimulants Adverse Effects most common effects include nausea, vomiting, diarrhea, intestinal spasm, and cramping others include declining blood pressure and heart rate, weakness and fatigue* Drug Interactions metoclopramide has been associated with decreased absorption of digoxin from the GIT** decreased immunosuppressive effects and increased toxicity of cyclosporine have occurred when combined with metoclopramide*** increased sedation can occur if either of these drugs is combined with alcohol or other CNS sedative drugs Lesson 4 Antidiarrheals CHOLEN CALDITO, RN, MAN, LPT INSTRUCTOR Antidiarrheals block stimulation of the GIT for symptomatic relief from diarrhea include bismuth subsalicylate, crofelemer, loperamide, opium derivatives Pharmacotherapeutics slow the motility of the GIT through direct action on the lining of the GIT to inhibit local reflexes (bismuth subsalicylate) through direct action on the muscles of the GIT to slow activity (loperamide), or through action on CNS centers that cause GI spasm and slowing (opium derivatives) indicated for the relief of symptoms of acute and chronic diarrhea, reduction of volume of discharge from ileostomies, and prevention and treatment of traveler’s diarrhea* Antidiarrheals Pharmacokinetics bismuth subsalicylate is absorbed from the GIT after oral administration, metabolized in the liver, and excreted in the urine; it crosses the placenta* loperamide is slowly absorbed after oral administration, metabolized in the liver, and excreted in the urine and feces; it may cross the placenta and enter breast milk opium derivative, a category C-III controlled substance, is readily absorbed after oral administration, metabolized in the liver, and excreted in the urine; crosses the placenta and enters breastmilk Crofelemer is minimally absorbed, and its half-life, metabolism, and excretion are unknown Antidiarrheals Contraindications and Cautions should not be given to anyone with known allergy to the drug or any of its components caution should be used in pregnancy and lactation* care should be taken in individuals with any history of GI obstruction and acute abdominal conditions** or diarrhea due to poisonings*** or with hepatic impairment* Adverse Effects constipation, distention, abdominal discomfort, nausea, vomiting, dry mouth, and toxic megacolon** others include fatigue, weakness, dizziness, and skin rash opium derivatives are also associated with light headedness, sedation, euphoria, hallucinations and respiratory depression***