Presentation on theme: "Drugs Affecting the digestive system"— Presentation transcript:
1Drugs Affecting the digestive system Chapters 56, 59, 62By Sandy Kaminski
2Chapter 56: Physiology of the Digestive System The organs of the digestive systemOral cavityEsophagusStomachSmall intestineLarge intestinePancreasGallbladderLiver
3The Main Function of the GI System To provide the body with fluids, nutrients, and electrolytes in forms that can be used at the cellular level.The system also disposes of waste products that result from the digestive process.SalivaGastric Juicesmucusdigestive enzymeshydrochloric acidElectrolytesPancreatic juicesamylaselipasetrypsin and chymotrypsinBile
4Effects of Drugs on the Digestive System To relieve symptoms and disorders of the digestive systemTo alter the digestive system secretion, absorption, or motilityDrugs used may also cause digestive symptomsie, nausea, vomiting, constipation, diarrhea, abdominal pain
5Questions: The major digestive enzyme in gastric juice is pancreatase. The parasympathetic nervous system increases motility and secretions.Blood flow increases during digestion, absorption, and parasympathetic stimulationF. The major digestive enzyme in gastric juice is pepsin, a proteolytic enzyme.T
6QuestionsThe sympathetic nervous system (fight or flight) increase gastric motility and secretions.The GI secretions can break down medications so they can be absorbed or they may destroy the medications.FT
7Chapter 59: Drugs Used for Peptic Ulcer (PUD) and Acid Reflux Disorders (GERD) H.Pylori Agents (Antibiotics)AntacidsProton-pump Inhibitors
8Peptic Ulcer Disease (PUD) Attributed to an imbalance between cell-destructive and cell-protective effectsSuch asgastric acidPepsinH. pylori infectionNSAIDsStressCigarette smokingPUD is ulcer formation in theEsophagusStomachDuodenumareas of the GI mucosathat are exposed to gastric acid and pepsin
9PUD Gastric Acid Pepsin Proton-pump system secreted by parietal cells in the mucosa of the stomach antrum, near the pylorusDissolve foodAct as a bactericideConvert pepsinogen to pepsinPepsinA proteolytic enzyme that helps digest protein but can also digest the stomach wallProton-pump systemcatalyzes the production of gastric acid and acts as a gastric acid (proton) pump to move gastric acid from parietal cells in the mucosal lining of the stomach into the stomach lumen.
10PUD Helicobacter pylori (H. pylori) Cell-protective effects Bacterium found in GI tract of 75% in those with gastric ulcers and more than 90% in those with duodenal ulcersIt colonizes the mucus-secreting epithelial cells of the stomach mucosa and is thought to produce gastritis and ulceration by impairing mucosal function.Antibiotics are used to eradicate H. pyloriamoxicillin, clarithromycin, metronidazole, tetracyclineCell-protective effectssecretion of mucus and bicarbonatedilution of gastric acid by food and secretionsprevention of diffusion of hydrochloric acid from the stomach lumen back into the gastric mucosal liningthe presence of prostaglandin Ealkalinization of gastric secretions by pancreatic juices and bile
11Gastroesophageal Reflux Disease (GERD) Most common disorder of the esophagusRegurgitation of gastric contents (gastric acid and pepsin) into esophagusMain cause is incompetent lower esophageal sphincter (LES)Main symptoms – heartburn and pain on swallowing
12Risk factors that contribute to impaired contraction of the LES include foods (eg, fats, chocolate)ﬂuids (eg, alcohol, caffeinated beverages)medications (eg, estrogens, progesterone, beta-agonists, anti-cholinergics, calcium channel blockers, narcotics, nitrates)gastric distensioncigarette smokingrecumbent postureObesityPregnancy
13What can PUD and GERD lead to? BleedingPerforationObstructionsGERDBarrett’s esophagusTissue lining changes and resembles that of instestine30 to 125 times more likely to develop esophageal cancerEsophageal cancerLaryngeal cancerErosive esophagitisEsophageal strictures
14Antacids Alkaline substances that neutralize acids Raising the pH to approximately 3.5 neutralizes more than 90% of gastric acid and iinhibits conversion of pepsinogen to pepsinCommonly used antacids are aluminum, magnesium, and calcium compoundsUsed to treat PUD, GERD, esophagitis, heartburn, gastritis, GI bleeding, stress ulcers
15Antacids: Drug Interactions Most often they decrease the absorption of other medications by the process of chelationChelationChemical binding, or inactivation, of another drugProduces insoluble complexesResult: reduced drug absorptionalso affect the absorption of some nutrients.Dietary folate, Fe, Ca, and Vit B12 are better absorbed in acidic environment and therefore deficiencies may occur.
16Antacids: Nursing Implications Assess for allergiesPreexisting conditions that may restrict the use of antacids includeElectrolyte imbalancesRenal diseaseDMPregnancyGI obstructionHF
17Histamine2 Receptor Antagonists (H2RAs) Histamine causes strong stimulation of gastric acid secretionH2RAs inhibit both basal secretion of gastric acid and secretion stimulated by histamine, acetylcholine, and gastrinDecrease amount, acidity, and pepsin content of gastric juicesCimetidine, ranitidine (Zantac), famotidine are available H2RAsAdjunct therapy in control of upper GI bleedingEspecially in relation to acute stress ulcersAdverse effects are rare and usually mild
18H2 Antagonists: Nursing Implications Assess for allergies and impaired renal or liver functionDose must be reduced in renal impairmentUse with caution in clients who are confused, disoriented, or elderlyTake 1 hour before or after antacidsAvailable in both OTC and Rx preparationsFor intravenous dosesfollow administration guidelines
19Proton Pump Inhibitors (PPIs) Strong inhibitors of gastric acid secretionBind irreversibly to the gastrin proton pump to prevent release of gastric acid from parietal cells thereby blocking final step of acid productionSuppress gastric acid secretion from parietal cells in response to all primary stimuli (histamine, gastrin, and acetylcholine)Available preparations:Omeprazole, esomeprazole, lansoprazole, pantoprazole, and rabeprazole
20Proton Pump Inhibitors: Nursing Implications Assess for allergies and history of liver diseasePantoprazole is available for parenteral administration, and can be used for clients who are unable to take oral medicationsSafe for short-term therapyUse cautiously in those with severe liver impairmentLansoprazole and rabeprazole
21Helicobacter Pylori Agents Recommended treatment includesTwo or three antimicrobialsAmoxicillin, clarithromycin, metronidazole, tetracyclineSingle agent not used b/c of concern about emergence of drug-resistant H. pyloriPPI or H2RAPPI = proton-pump inhibitorH2RA = Histamine 2 Receptor AntagonistsAccelerates symptom relief and healing of the ulcerRemember: Bacterium found in GI tract of 75% in those with gastric ulcers and more than 90% in those with duodenal ulcersIt colonizes the mucus-secreting epithelial cells of the stomach mucosa and is thought to produce gastritis and ulceration by impairing mucosal function.Antibiotics are used to eradicate H. pyloriamoxicillin, clarithromycin, metronidazole, tetracycline
22Questions: T F - lower esophageal sphincter Risk factors for PUD include stress, NSAID ingestion, Helicobacter pylori infection, and cigarette smoking.Prostaglandin E and mucus are cell-protecting effects that protect the wall from injury.GERD is thought to be the result of an incompetent upper esophageal sphincter.TF - lower esophageal sphincter
24DefinitionsNausea: unpleasant sensation of abd discomfort accompanied by a desire to vomit. May occur without vomiting.Vomiting: expulsion of stomach contents through the mouth, May occur without prior nausea.Occurs when the vomiting centre (VC) or chemoreceptor trigger zone (CTZ) are stimulated
25Causes of N/V in hospital Gastrointestinal disordersincluding infection or inflammation in the GI tract, liver, gall-bladder, or pancreasimpaired GI motility and muscle tone (eg, gastroparesis)overeating or ingestion of foods or fluids that irritate the GI mucosaCardiovascular, infectious, neurologic, or metabolic disordersDrug therapyPain and other noxious stimuliEmotional disturbances; physical or mental stressRadiation therapyMotion sicknessPost-operative status
26Mechanism of Action of Anti-Emetics blocking one of the vomiting pathways, thus blocking the stimulus that induces vomitingseveral different therapeutic classiﬁcationsanti-cholinergicanti-dopaminergicanti-histaminicanti- serotonergic effectsmore effective in prophylaxis than treatmentEg. Administering Morphine IV with Gravol IVEg. Taking anti-motion meds 30 minutes prior to getting on the boat!!
27Where anti-nauseants exert their affects. Labyrinths is the intricate passages of the inner ear.
29Classifications of Anti-emetics – all lumped into anti-cholinergics / anti-dopminergics/ anti-histaminic/anti-serononergic1. PhenothiazinesBlock dopamine from receptor sites in brain and CTZ(chemoreceptor trigger zone)chlorpromazine (Largactil) is the prototypeprochlorperazine (Stemetil)CNS depressant – therefore causes sedationEffective for n/v induced by drugs and radiation therapyNot effective for motion sickness2. Anti-histaminesblock action of acetylcholine in brain (anti-cholinergic effects)Dimenhydrinate (Gravol) and meclizine (Bonamine)effective in treating motion sickness
30Classifications of Anti-emetics – all lumped into anti-cholinergics / anti-dopminergics / anti-histaminic / anti-serononergic3. CorticosteriodsBlock prostaglandin activity in the cerebral cortexDexamethasone (Decadron)Commonly used in the management of chemotherapy-induced emesis and intra-operativelyCauses euphoria, insomnia4. BenzodiazapinesProduce relaxation and inhibit cerebral cortex input to vomiting centerlorazepam (Ativan)Anticipatory chemotherapy induced n/v
316. 5-Hydroxytryptamine 3 (5-HT3 or Serotonin Receptor Antagonists) Classifications of Anti-emetics – all lumped into anti-cholinergics / anti-dopminergics/ anti-histaminic/anti-serononergic5. Prokinetic AgentsIncrease the release of Ach from the GI tractmetoclopramide (Maxeran)Increases GI motilityUsed in gastroparesis (gastric retention of foods)May increase the effects of alcohol6. 5-Hydroxytryptamine 3 (5-HT3 or Serotonin Receptor Antagonists)Antagonize serotonin receptorsondansetron (Zofran)Moderate to severe n/v (cancer therapy, post-op)May cause diarrhea, headache, muscle aches, elevated liver enzymes
32What’s important for me to know about anti-emetics? Drug selection, dose and route depend on the cause of the nausea/vomitingMost adverse affects are sedation, drowsiness, dry mouth, diarrhea or constipation, and headacheMulti-drug regimens may be used to treat n/vUse in special populations should be consideredEg. Older adults – increased sedative effectsEg. Scopolamine not recommended in pediatric populationEg. Metoclopramide doses should be reduced in renal failure patients
33What’s important for me to know about anti-emetics? Antiemetics have anticholinergic, antidopaminergic, antihistaminic, or antiserotonergic effects. Most exert an effect on the vomiting center, CTZ, cerebral cortex, vestibular apparatus, or a combination of these areasPretreatment is usually most effective5-HT3 receptor antagonists like ondansetron are usually considered the most effective antiemetics.
34Question – T or FThe benzodiazapine antianxiety drugs are used as anti-emetics in multidrug regimens to prevent nausea and vomiting associated with chemotherapy.True!