Lecture 12. Gastrointestinal Agents Chapters 41 & 42. GI Agents. GI tract = Oral cavity of mouth, esophagus, stomach, sm. intestine (duodenum, jejunum, ilium), lg. intestine (cecum, colon, rectum), & anus
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Lecture 12 Gastrointestinal Agents Chapters 41 & 42
GI Agents • GI tract = Oral cavity of mouth, esophagus, stomach, sm. intestine (duodenum, jejunum, ilium), lg. intestine (cecum, colon, rectum), & anus • Accessory organs contributing to the digestive process = Salivary glands, pancreas, gallbladder, liver • Main function = Digestion of food particles & absorption of digestive contents (nutrients, electrolytes, minerals, & fluids) - into circulatory system for cellular use • Undigested material passes through the lower intestinal tract w/ aid of peristalsis to rectum & anus - excreted as feces or stool
GI AgentsVomiting - Antiemetics • Vomiting = the expulsion of gastric contents Before treating, the cause of the vomiting needs to be identified • Causes are many: motion sickness, viral & bacterial infection, food intolerance, surgery, PG, pain, shock, effects of some drugs, radiation, & disturbances of the middle ear affection equilibrium. • Antiemetics can mask the cause & should not be used until cause is determined, unless vomiting is severe enough to cause dehydration & electrolyte imbalance
GI AgentsVomiting - Antiemetics • Two major cerebral centers are the chemoreceptor trigger zone (CTZ), which lies near the medulla, & the vomiting center, in the medulla - both cause vomiting when stimulated • The CTZ receives most of the impulses from drugs, toxins, and the vestibular center. The neurotransmitter dopamine stimulates the CTZ, which stimulates the vomiting center, when triggered, motor neuron responds contraction of diaphragm, anterior abdominal muscles, & the stomach. the glottis closes, the abdominal wall moves, upward & vomiting occurs.
GI AgentsAntiemetics • Nonpharm Rx= weak tea, flattened carbonated drinks, Gatorade & pedialyte (children), crackers dried toast • Nonprescription antiemetics = used to prevent motion sickness - minimal effect on severe vomiting from anticancer agents, radiation, and toxins. - take 30 min. before traveling • Dimenhydrinate (dramamine), meclizine HCL (Antivert), diphenhydramine HCL (Benadryl) - SE = drowsiness, dryness of mouth, constipation
GI Agents-Antiemetics • bismuth subsalicylate (Pepto-Bismol) - act directly on gastric mucosa to suppress vomiting - liquid & chewable – taken for gastric discomfort & diarrhea • Phosphorated carbohydrate (Emetrol) Hyperosmolar carbohydrate decreases N&V by changing the gastric pH • Antiemetics were used in the 1st trimester of PG , but no more due to poss. harm to fetus. Non – pharm methods should be used & OTC antiemetics avoided unless N & V become life threatening to mom & baby. Then use Tigan given.
GI AgentsAntiemetics • Prescription Antiemetics - eight categories: 1 & 2. Antihistamines & Anticholinergics - Hydroxyzine (Vistaril, Atarax), Promethazine (Phenergan), Scopolamine (Transderm Scop) - Act primarily on the vomiting center, dec. stimulation of CTZ - SE = drowsiness, dry mouth, blurred vision (pupil dilation), tachycardia (anticholinergics), constipation - Do not use in clients w/ glaucoma d/t dilation of pupils
GI Agents - Antiemetics 3. Dopamine antagonists - blocks dopamine-2 receptors in the CTZ. SE = Extrapyramidal symptoms (tremors, mask face, rigidity, shuffling gait) • Phenothiazine - largest group of drugs used for N & V Chlorpromazine (Thorazine), prochlorperazine edisylate (Compazine) - most frequently prescribed, perphenazine (Trilafon) - frequently used w/ anticancer therapy - Action - inhibits dopamine in the CTZ thus dec. CTZ stimulation of the vomiting center - Use - severe N & V from sugery, anesthetics, chemo & radiation sickness - SE = dry mouth, drowsiness, EPS, dizziness, hypotension
GI Agents - Antiemetics Perphenazine (Trilafon) used with anti cancer therapy, inhibits dopamine in the CTZ decreasing CTZ stimulation vomiting center, also an antipsychotic Onset 2 – 6 h, duration 6-12 h Interactions: Taken with ETOH, antihypertensive agents, and nitrates, hypotension can result CNS depression when taken with ETOH, narcotics, sedative- hypnotics and general anesthetics SE: moderate sedation hypotension, EPS ( parkinsonism) CNS effects (restlessness, weakness, dystonic reactions, agitation), and mild anticholinergic s/s (dose lower as antiemetic than antipsychotic, so SE not as severe.
GI AgentsAntiemetics • Butyrophenones - Haloperidol (Haldol), droperidol (Inapsine) - block dopamine-2 receptors in the CTZ - Use - Rx of post-op N & V & emesis associated w/ toxins, chemo & radiation therapy - SE - EPS if used over extended time, hypotension • Metoclopramide - metoclopramide (Reglan) - blocks dopamine & serotonin receptors in the CTZ - Use = post-op emesis, chemo & radiation therapy - SE = sedation & diarrhea w/ high doses
GI AgentsAntiemetics 4. Benzodiazepines - Lorazepam (Ativan) - for N & V d/t chemo - May be given w/ an antiemetic such as metoclopramide (Reglan) 5. Serotonin Antagonists - ondansetron (Zofran), granisetron (Kytril) - - Action - suppress N & V by blocking the serotonin receptors in the CTZ & afferent vagal nerve terminals in upper GI tract - Do not cause EPS symptoms - Use - chemo induce emesis - PO & IV - SE - headache, diarrhea, dizziness, fatigue
GI Agents - Antiemetics 6. Glucocorticoids - Dexamethasone (Decadron), methylprednisolone (Solu-Medrol) - effective w/ chemo treatment in suppressing emesis - given IV 7. Cannabinoids - active ingredient in marijuana - approved for clinical use since 1985 to alleviate N & V from cancer treatments - dronabinol (Marinol), nabilone (Cesamet) - for clients unable to use or respond to other antiemetics - SE = mood changes, euphoria, drowsiness, nightmares, dry mouth, confusion, HA, depersonalization, nightmares, incoordination, memory lapse, orthostasis, hypertension & tachycardia
GI AgentsAntiemetics/Emetics 8. Miscellaneous - Benzquinamide HCL (Emete-Con), diphenidol (Vontrol), trimethobenzamide (Tigan) - suppress the impulses to the CTZ, Vontrol also prevents vertigo by inhibiting impulses to the vestibular area - labeled misc. because they don’t act strictly as antihistamines, anticholinergics, or phenothiazides - SE = drowsiness, anticholinergic symptoms, CNS stimulation, EPS
GI Agents - Emetics • Emetics - for when an individual has consumed certain toxic substances and must be expelled before absorption -- Don’t induce vomiting if caustic substances have been ingested, ammonia, chlorine bleach, lye, toilet cleaners, or battery acid.Activated charcoal is given when emesis is CI • Ipecac - stimulates the CTZ in the medulla & acts directly on the gastric mucosa - take w/ water (not milk or carbonation) - onset in 15 to 30 min. Repeat tx if needed. Toxic if absorbed give charcoal. - s/s toxicity hypotension, tachycardia, chest pain – SE: diarrhea, sedation, lethargy • Apomorphine is a morphine derive emetic, SQ/IM, Onset 15 min
GI Agents - Antidiarrheals • Diarrhea = frequent liquid stool d/t an intestinal disorder - causes: foods, fecal impaction, bacteria, virus, drug rxn, laxative abuse, malabsorption syndrome, stress, bowel tumor, inflammatory bowel disease - can be mild to severe - ID underlying causes first - can cause minor or severe dehydration & electrolyte imbalance - can be life threatening to the young & elderly • Nonpharm Rx = clear liquids & oral soln’s (gatorade, pedialyte), IV electrolyte soln’s….. (BRAT diet)
GI Agents - Antidiarrheals • Used to decrease hypermotility (inc. peristalsis cause of diarrhea - needs to be corrected) Do not use longer that 2 days & not use with fever. Underlying cause must be found. (Ex. E. Coli) • 4 categories (Opiates, opiate related agents, adsorbents antidiarrheal combos) • Opiates - decrease intestinal motility thus dec. peristalsis tincture of opium, paregoric, codeine - in combo w/ other agents SE = CNS depression ( taken with ETOH, sedatives or tranqs), constipation Duration = 2 hrs. • Opiate-Related Agents - Diphenoxylate (Lomotil), loperamide (Imodium) - synthetic drugs chemically related to meperidine - Action - decrease intestinal motility - “travelers diarrhea” - SE = N & V, drowsiness, abd. Distention
GI Agents - Antidiarrheals • Imodium works against diarrhea longer than similar dose of Lomotil Lomotil is approx 50% atropine (to discourage abuse), Action time of 45 – 60 mins. Duration – 3-4 hrs. • - CI in hepatic diesease, glaucoma - SE= many due to atropine dry mouth, urinary retention, dec secretions. • Adsorbents - coat the wall of the GI tract and adsorbing the bacteria or toxins causing diarrhea (Substance takes in toxin) • - Kaopectate (kaolin & pectin) OTC • - Pepto-Bismol adsorbs bacterial toxin & for GI discomfort, OTC Miscellaneous: Furazolidone & Lactobacillus acidophilus
GI AgentsConstipation • Constipation - accumulation of hard fecal material in the large intestine - a major problem of the elderly - Causes - poor H2O intake & poor dietary habits, ignoring the urge, fecal impaction, bowel obstruction, chronic laxative use, neurologic disorders (paraplegia), lack of exercise, selected drugs (anticholinergics, narcotics & certain antacids) • Nonpharm Rx = diet that contains fiber, water, exercise, routine bowel habits (normal can be 1-3/day or 3/wk – varies from person to person) The freq. is secondary to consistency – feces hard & dry
GI Agents - Constipation • Pharmacologic measures laxatives & cathartics • - Laxatives – inc. peristalsis , promote soft stool • - cathartics - result in soft to watery stool with some cramping • Use painful elimination due to episiotomy, hemorrhoiods & anorectal leisions; cardiovascular disease, prior to surg. or tests • Laxative abuse from chronic use a problem, esp. with elderly – client teaching • Laxatives should be avoided if there is any question of pts. having an intestinal obstruction, severe abd. pain, symptoms of appendicitis, ulcerative colitis, or diverticulitis
GI Agents -Laxatives • Osmotic Laxatives (Hyperosmolar laxatives) - include salts or saline products, lactulose, & glycerine Lactulose (Cephulac), Magnesium hydroxide (MOM), sodium biphosphate (Fleet Phospho-Soda), Fleet enema • Action – These poorly absorbed salts osmotic action draws water into the intestine, inc. H20 causes fecal mass to soften and swell stretches intestine & stimulate peristalses. • Saline preps contains NA+, Mg+, a small amt. may be systemically absorbed so CI in poor renal function
GI Agents - Laxatives • Osmotic laxatives contain 3 electrolytes (NA+, MG+, K+) Used in bowel prep for dx & surg. procedures • Polyethylene glycol (PEG) or (GoLytely) – non absorbable osmotic substance, so can be used by clients with renal impair or cardiac probs, PO 3 to 4 liters over 3 hours for bowel prep. • Lactulose (saline lax) draws H2O into the intestines - SE = flatulence, diarrhea, abd. cramping, N & V • CI: Clients w/ CHF, w/ renal insufficiency should avoid magnesium salts, in some laxatives (Milk of Mag) • Electrolytes should be monitored.
GI AgentsLaxatives • Stimulant (Contact) Laxatives - Increase peristalsis by irritating sensory nerve endings in the intestinal mucosa phenolphytalein (Ex-Lax), biscadyl (Dulcolax), senna (Senokot), castor oil (purgative) - Biscadyl & phenolpythalein are two of the most frequently used & abused laxatives - OTC - Castor Oil = harsh laxative that acts on the small bowel & produces a watery stool - SE = Nausea, abd. cramps, weakness, Fluid & electrolyte imbalances w/ chronic use
GI Agents - Laxatives • Bulk-Forming Laxatives - Calcium polycarbophil (FiberCon), methylcellulose (Citrucel), psyllium hydrophilic mucilloid (Metamucil) - Natural fibrous substances that promote lg. soft stools by absorbing water into the intestine - inc. fecal bulk & peristalsis - Does not cause laxative dependence & may be used by clients w/ diverticulosis, irritable bowel syndrome & ileostomy & colostomy - Powders mixed w/ H2O or juice, drink immediately, followed by a full glass
GI Agents - Laxatives • Emollients (Surfactants) - Docusate calcium (Surfak), docusate potassium (Dialose), docusate sodium (Colace), docusate sodium w/ casanthranol (Peri-Colace) - Stool softeners (surface acting drugs) and lubricants used to prevent constipation - dec. straining during defecation - Action - lowers surface tension & promotes H2O accumulation in the intestine and stool - Use - after an MI, post-op - SE - N & V, diarrhea, cramping
GI AgentsAntiulcer Drugs • Peptic Ulcer - a broad term for an ulcer occurring in the esophagus, stomach, or duodenum w/in the upper GI tract (esophageal, gastric & duodenal ulcers). • Ulcers develop when there is an imbalance between mucosal defensive factors & aggressive factors. Maj. defensive factors are mucus & bicarb. (Keep stomach & duodenun from self–digestion) Major aggressive - H. pylori, NSAID, gastric acid, & pepsin • Duodenal ulcers 10X more frequent than gastric, esophageal • Release of hydrochloric acid (HCL) from the parietal cells of the stomach influenced by histamine, gastrin & acetylcholine - Peptic ulcers caused by hypersecretion of HCL & pepsin, erode the GI mucosal lining
GI AgentsAntiulcer Drugs • Gastric secretions of the stomach strive to keep a pH of 2 to 5 Pepsin-a digestive enzyme is activated at a pH of 2, the acid-pepsin complex of gastric secretions can cause mucosal damage - If the pH inc. to 5 - the activity of pepsin declines • Gastric Mucusal Barrier (GMB) - thick, viscous, mucous material that provides a barrier between the mucosal lining & the acidic gastric secretions - defense against corrosive substances, maintains integrity of the gastric mucosal lining
GI Agents - Antiulcer Drugs • Two sphincter muscles: - Cardiac - located at the upper portion of the stomach - prevents reflux of acid into the esophagus - pyloric - located at the lower portion of the stomach - prevents reflux of acid into the duodenum * Esophageal ulcers reflux of acidic gastric secretion into the esophagus d/t a defective or incompetent cardiac sphincter * Duodenal ulcers hypersecretion of acid from the stomach that passes to the duodenum * Gastric ulcer breakdown of GMB (gastric mucosal barrier)
GI Agents - Antiulcer Drugs • Predisposing factors - mechanical disturbances, genetic, bacterial organisms, environmental, drugs - Nurse needs to help identify & teach ways to avoid • Symptoms = gnawing, aching pain - gastric = 30 min. – 1 1/2 h after eating - duodenal - 2 - 3 h after eating • Stress ulcer usually follows a critical situation - trauma, major surgery - prophylactic use of antiulcer drugs dec. the incidence of stress ulcers
GI Agents - Antiulcer Drugs • Helicobacter pylori (H. pylori) - a gram (-) bacillus linked w/ the development of peptic ulcer - H. pylori known to cause gastritis, gastric ulcer & duodenal ulcer –When a peptic ulcer recurs after anti-ulcer tx and it’s not caused by NSAIDS such as ASA or Ibuprofen client should be tested for H. pylori - A noninvasive breath test is used or serology to check for antibodies of H. pylori
GI Agents – Antiulcer Before the breath test an endoscopy & bx. Needed both to detect H. pylori. Meretek UBT is a breath test. Pt. Drinks a liquid containing 13 C urea & then breaths into a container. If Hpylori is present the bacteria releases 13CO2. 90 – 95% effective - Various protocols for treatment - dual, triple, or quadruple drug therapy program using various antibacterial agents & antiulcer drugs - the combo of drugs differs for each client, depends on the sensitivity of the bacteria, H pylori is readily resistant to drugs. Rx for 7 to 14 days
GI Agents - Antiulcer Drugs • Gastroesophageal reflux Disease (GERD) - 40 to 45% of adults have heartburn in many cases d/t GERD - Inflammation of the esophageal mucosa caused by reflux of gastric acid content into the lower esophageal sphincter - Rx similar to treatment of peptic ulcers - the use of common antiulcer drugs to neutralize gastric contents & reduce acid secretion - A chronic disorder requiring continuous management & education
GI AgentsAntiulcer Drugs • Nonpharm Rx = avoiding smoking & ETOH can dec. gastric secretions, wt. loss (obesity enhances GERD), avoid hot, spicy, greasy foods, Take NSAIDs w/food, do not eat before bedtime • Pharmacologic Rx = there are 8 groups of antiulcer agents 1. Tranquilizers - minimal effect in preventing & treating ulcers. Reduce vagal stimulation & dec. anxiety Librax - combo of anxiolytic chlordiazepoxide (Librium) & the anticholinergic clidinium (Quarzan) used in the treatment of ulcers
GI AgentsAntiulcer Drugs 2. Anticholinergics - Not used as much w/ the newer drugs on board. Relieve pain by dec. GI motility & secretion 3. Antacids - Promote ulcer healing by neutralizing HCL & reducing pepsin activity; they do not coat the ulcer, Two types: Systemic or non systemic Calcium carbonate (Tums)- Systemically absorbed antacid - neutralizes acid, however, 1/3 to 1/2 of drug systemically absorbed & causes acid rebound. Hypercalcemia can result from excess use Sodium bicarb.- systemically absorbed many SE = hypernatremia, water retention are a few
GI AgentsAntiulcer Drugs • Nonsystemic antacids composed of alkaline salts - aluminum (aluminum hydroxide - Amphojel) and magnesium (magnesium hydroxide - Maalox, Mylanta) - The combo of magnesium & aluminum neutralizes gastric acid w/o causing constipation or severe diarrhea - aluminum itself causes constipation & magnesium alone can cause diarrhea - Ideal dosing is 1 and 3 h after meals
GI AgentsAntiulcer Drugs 4. Histamine -2 Blockers (H2) or histamine-2 receptor antagonists - most popular drugs used to treat ulcers - Action - Block the H2 receptors of the parietal cells in the stomach, thus reducing gastric acid secretion & concentration to promote healing Cimetidine (Tagamet), Famotidine (Pepcid), Nizatidine (Axid), ranitidine (Zantac) - Tagamet = first H2 blocker - Need good kidney function, 50-80% of drug excreted unchanged in the urine do not give w/ antacids - dec. effectiveness of drug
GI Agents - Antiulcer Drugs - Zantac, Pepid, & Axid = more potent – in addition to blocking of gastric secretion they also promote healing of the ulcer by eliminating its cause. - Duration of action longer & fewer side effects - Use - to treat gastric & duodenal ulcers & can be used prophylactically also useful in relieving symptoms of reflux esophagitis, preventing stress ulcers post-op - SE = headaches, dizziness, constipation, rash - DI = many w/ cimetidine - check carefully
GI AgentsAntiulcer Drugs 5. Proton Pump Inhibitors (gastric acid secretion inhibitors, gastric acid pump inhibitors (PPIs) - suppress gastric acid secretion by inhibiting the hydrogen / potassium ATP-ase enzyme system located in the gastric parietal cells, they tend to inhibit gastric acid secretion up to 90% greater than the H2 blockers - these agents block the final step of acid production Omeprazole (Prilosec), lansoprazole (Prevacid) - Used for Rx of peptic ulcers & GERD - highly protein-bound SE = headache, dizziness, diarrhea, abd. pain, rash * Monitor liver enzymes
GI AgentsAntiulcer Drugs 6. Pepsin Inhibitor - Sucralfate (Carafate) - a mucosal protective drug. Nonabsorbable & combines w/ protein to form a viscous substance that covers the ulcer and protects it from acid & pepsin - does not neutralize acid or dec. acid secretions - SE - few because not systemically absorbed, but may cause nausea & constipation 7. Prostaglandin analogue antiulcer drug - Misoprostol (Cytotec) - New for prevention & Rx of peptic ulcers
GI Agents - Antiulcer Drugs - Action - It appears to suppress gastric acid secretion & inc. cytoprotective mucus in the GI tract. Causes a mod. dec. in pepsin secretion - Use - gastric distress from taking NSAIDs, ASA & indomethacin that are prescribed for long-term therapy - CI - during pregnancy & for women of child bearing yrs. 8. GI stimulants - Cisapride (Propulsid) - increases gastric emptying time preventing acid reflux - used for nocturnal heartburn & GERD CI - cardiac dysrhythmias, heat disease, CHF - an ECG should be done before & during therapy, renal & resp. failure