Drugs Affecting the GI System

Drugs Affecting the GI System I. GI Overview A. Special medical focus 1. Children—weight/height/age dictate dosaging 2. Pregnancy—risk vs. benefit is primary question with medication 3. Elderly—many have multiple Dx‟s, multiple meds, greater CNS risks (falls, dizziness) B. Patient teaching 1. Medication regimen 2. S/E that are reportable…? 3. Dietary/drug interactionsavoid self-medicating 4. Promotion of bowel elimination a. Fiber b. Water c. Exercise 5. Avoiding gastric irritants: a. Alcohol b. Smoking c. Caffeine d. NSAIDS C. Gastric secretions 1. Mucus— a. mucus-producing cells b. rich in bicarbonate—protects stomach lining from acid 2. Pepsinogen—chief cells—pepsinogenpepsin (enzyme) 3. Hydrochloric acid 4. Intrinsic factor 5. Gastrin— a. gastrin producing cells b. gastrin stimulates parietal cells c. HCL acid & intrinsic factor 6. Serotonin 7. Hormonal products 8. Histamine—enterochromaffin-like (ECL) cells (stimulates parietal cells to produce HCL) 9. D-cells-somastatin (inhibit HCL production) D. Digestion/Gastric Secretions Review 1. Gastrin  HCl and pepsinogen a. Sight, smell, taste  vagus nerve b. Distention of stomach (release of gastrin) c. Partially digested protein or caffeine 2. Food in stomach  histamine release 3. Initially—chyme entering duodenum  gastrin, then fats, in duodenum  release inhibitory hormones 4. 2 hours for stomach to empty 5. Fats are the last to leave stomach 6. 24-hour period = 1 ½ -3 L gastric secretions (leads easily to dehydration) 7. Normal pH of stomach is 1-2 (VERY acidic environment) 8. Chyme: fats slow stomach emptying, mixes with alkaline juices in duodenum to neutralize acids 9. Pancreatic juice—enzymes break down nutrients a. Amylase—carbohydrate

b. Lipase—fats c. Protease—proteins 10. Liver—bile a. Bile salts emulsify fats— b. Improve digestion c. Helps w/ breakdown II. Antiulcer Drugs A. Antacids 1. Neutralize gastric acid  a. Increasing pH in GI tract b. Reducing pepsin activity 2. ALAKALINES: Relieve symptoms but don‟t treat problem itself 3. Excreted in feces (some in urine & breast milk) 4. Brand names: AMPHOGEL, MAALOX, MYLANTA, MOM a. Tums, Rolaids, Alka-Seltzer b. Absorbed (systemic) and can have REBOUND effect (esp. Tums) so not given in hospital Generic Brand GI Effect Caution/Use Magnesium MOM Diarrhea Excreted in urine, breast milk Hydroxide Aluminum Magnesium Maalox, Balanced Mylanta Aluminum Hydroxide Amphojel Constipating Binds dietary phosphate; Renal pts careful: high doses, multiple over time; encephalopathy (confusion) possible 5. Indications: a. Indigestion b. Heartburn--*rule out cardiac c. GERD—gastro esophageal reflux disease d. PUD e. hyperPHOSPHATemia 6. Drug interactions: a. decrease absorption of quinolones, iron, isoniazid, phenytoin, and digoxin (ADMINISTER 2 HOURS APART) b. Causes premature dissolution of enteric-coated tablets (ADMINISTER 1 HOUR APART)—can be caustic: raising the pH of the stomach environment will start these medications absorbing prematurely in the stomach rather than the intestines 7. Assess: electrolyte imbalances, changes in elimination 8. Teach: a. Take 1-3 hours after meals (when SYMPTOMS ARE HAPPENING) b. Shake suspension well c. Drink water after chewing (4oz H20) d. Give 1 hour apart from enteric coated tablets e. For Heart failure or HTN pts, check sodium content (can be high in Na) B. H2 Receptor Antagonist 1. Developed in „70s and stopped people dying from bleeding ulcers 2. Inhibits gastric acid secretion by inhibiting the action of histamine at histamine 2 (H2) receptors in gastric parietal cells (not as much acid produced as normally would be)

a. Cimetidine (Tagamet) NOT AS GOOD AS OTHERS!!

i. S/E: Hallucination, anxiety, disorientation ii. CAUTION with elderly because of neuro effects iii. Many drugs interact and cause toxicity iv. Rapid infusion = arrhythmias o NO IV push o 1 hour at least to administer
b. Famotidine (Pepcid) i. Long term use can lead to thrombocytopenia (rare) ii. IV push 2-5 minutes iii. Evaluate cardiac reaction c. Ranitidine (Zantac) i. Mg and Al antacids may interfere w/absorption ii. IV push 2-5 minutes iii. Evaluate cardiac reaction 3. Indications: a. UGIB b. GERD

c. Zollinger-Ellison Syndrome (ZES)
i. Rare

ii. Diagnosed easily (pt has tumors in pancreas/small intestine constantly secreting gastrin which stimulates HCl production  ulcers form)
d. PUD 4. Caution: a. Elderly b. Impaired renal and hepatic function c. Pregnancy/lactation 5. S/E: (don‟t stop med) a. HA (most common) b. Dizziness c. Confusion d. Mild diarrhea e. Rash 6. Nursing Considerations for H2 Receptor Antagonist a. Baseline hepatic/renal function b. Monitor: serum AST/ALT levels, BUN/CR, mental status of elderly c. Teach: i. Not to take with antacids which interfere with action of histamine blockers ii. Avoid tasks that require alertness iii. Avoid smoking, ASA, caffeine, alcohol (GI stimulants work against med.) iv. Report HA, persistence of GI symptoms (is medication working?)

C. Proton Pump Inhibitors (PPIs) 1. Better than H2 blockers
2. Blocks gastric acid secretions by inhibiting enzyme system (H+/K+ ATPase), proton pump, in gastric parietal cells a. Works DIRECTLY on parietal cells b. Targets ATPase, the last step of the process, so acid is not released

3. Brand names: PREVACID, PROTONIX, PRIOLOSEC, NEXIUM, ACIPHEX
4. Indications: a. PUD—peptic ulcer disease b. GERD c. ZES d. Esophagitis e. H. pylori infection f. NSAID related ulcers 5. Caution: a. Liver pts b. Pregnant/lactating women 6. S/E: a. Abd pain b. N/V c. Diarrhea d. Long-term: i. Hypomagnesaemia—reversible once med stopped ii. Hip fractures iii. PPI‟s possibly increase c. diff risk (increase pH, increases chance) 7. Nursing Considerations: a. Assess therapeutic response o With existing condition, it‟s important to “get on board” early with treatment b. Monitor lab values c. Pt. teaching: i. Take on empty stomach o Not as important if given prophylactically ii. Do not crush or chew tablets d. Drug interactions (interferes with absorption of): i. Ampicillin ii. Digoxin iii. Phenytoin iv. Warfarin v. Sucralfate (GI drug)

D. Prostaglandin Analog
1. 2. 3. 4. Prophylactic for pts on long-term NSAID Tx Decreases gastric acid secretion and increases mucus and bicarbonate production Drug e.g.: MISOPROSTOL (CYTOTEC) Contraindicated: BLACK BOX warning

a. Pregnancy: Pregnancy X!!!! Not given to anyone even thinking of ever getting pregnant
b. Lactation E. Pepsin Inhibitor 1. Protects damaged gastric mucosa by forming an adhesive barrier at ulcer site a. Mucosa not there body‟s protein is exposed b. Muscle, blood, tissues all in danger 2. BINDS w/PROTEIN 3. Drug e.g.: SUCRALFATE (CARAFATE) 4. Major S/E: a. constipation (eliminated whole by GI tract)

b. may decrease absorption of H2 blockers, digoxin, phenytoin, tetracyclines, theophyline, warfarin i. give at least 2 hours apart ii. PPI‟s 30 minutes apart c. Made less effective by antacids i. Give 30 minutes apart ii. 1 hour before meals and HS

5. TIME LINE: a. PEPSIN INHIBITOR (e.g., Carafate) 1 hour before meal  b. PPI (e.g. Prilosec/Protonix) ½ hour before meal  c. MEAL  ANTACID 1-3 hours after meal F. H. pylori Therapy 1. H. pylori leading cause of ulcers (also: NSAIDS, ZES)
2. Unsanitary H20 (esp. in undeveloped countries)

3. PPI + 2 abx a. Bismuth b. Antibiotics i. Metronidazole (Flagyl)—some H. pylori strains resistant, though ii. Clarithromycin (Biaxin)—some H. pylori strains resistant iii. Amoxicillin iv. Tetracyclines c. Prevpac (Prevacid, Biaxin, Amoxicillin) packaged as 2x day x14 days tx 4. PPI + 2 abx + bisumth (if PPI + 2 abx doesn’t work)
III. Nausea/Vomiting A. Causes: 1. Motion 6. Pregnancy 7. Gastric sickness (use nonmucosal 2. Infection pharm tx if irritation 3. Pain possible) 8. Radiation 4. Drugs 9. Chemothera 5. Shock py B. Vomiting 1. Cerebral centers: a. Chemoreceptor Trigger Zone (CTZ) receives impulses from drugs, toxins and vestibular center in ear b. Vomiting center (medulla)—impulses from CTZ, senses (odor, sight, taste) and gastric disturbances c. Vestibular center (inner ear) i. Histamine 1 ii. Acetylcholine d. CTZ and vomiting center i. Serotonin ii. Dopamine 2. Antiemetics—Antihistamines & Anticholinergics a. Reduce motion sickness by inhibiting impulses from inner ear to the vestibular pathway i. Impulses don‟t make it to CTZ

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ii. Must be treated BEFORE it happens or can‟t be treated b. Non-prescription antihistamines—meclizine (ANTIVERT), Dramamine i. Prevention of motion sickness ii. Take 1 hour before travel iii. Caution: contraindicated for glaucoma: pressure can build up c. Anticholinergic i. Transderm Scop??? ii. Apply 4 hours in advance: lasts 3 days iii. S/E: (smooth involuntary muscle affected) o Dry mouth o Urinary retention o Blurred vision Antiemetics—Dopamine Antagonists a. Blocks dopamine receptors in brain i. Reglan increases gastric emptying and LES tone b. Brand names: COMPAZINE, PHENERGAN, REGLAN, THORAZINE c. Interactions: alter absorption of other drugs d/t changes in GI motility (e.g., Reglan) d. S/E: i. Sedation ii. Severe hypotension iii. Extrapyramidal symptoms (EPS) iv. Anticholinergic effects—VERY concerning S/E‟s: may not be reversible; stop med immediately e. Phenothiazine (anti-psychotic) i. Originally anti-psychotics, but in SMALLER DOSE: anti-emetic ii. Compazine: N/V (severe, post-op, chemo induced) iii. Thorazine: Nausea, intractable hiccups f. Prescription antihistamine: i. Phenergan: N/V (severe, post-op, chemo induced, motion sickness); sedative effect g. Prokinetic i. Reglan: N/V (anesthesia, pregnancy), diabetic gastroparesis—helps diabetics have improved elimination Antiemetic-Serotonin Antagonist a. Blocks 5-HT3 (serotonin) receptors in vomiting center and vagal nerve terminals in GI tract b. Brand names: ZOFRAN, KYTRIL, ANZEMET c. Indications: Chemotherapy, radiation, pre/post-anesthesia, severe N/V, pregnancy d. Common S/E: HA, dizziness, fatigue, constipation, diarrhea e. *Much less severe S/E‟s than dopamine antagonists Emetics—Ipecac Syrup (OTC) a. No longer recommended by AAPCC b. Drugs that act on CTZ to induce vomiting c. Used for acute poisoning by non-caustic agents, non-petroleum agents d. Alternatives: activated charcoal, antidotes, gastric lavage e. S/E: cardiotoxicity (hypotension, tachycardia, CP) Adsorbent—Activated charcoal a. Attracts and binds to toxins in GI tract, preventing absorption b. Not absorbed  excreted whole

c. Contraindicated: mineral acids, iron alkalines, cyanide, ethanol, methanol, organic solvents (dialysis may be required) d. S/E: black stool, constipation (because it is eliminated whole…) e. Interferes with absorption of oral meds IV. Constipation A. Causes: 1. Inadequate fluid intake 2. Poor dietary habits 3. Inactivity/bed rest 4. Ignoring urge to defecate 5. Laxative dependence 6. Neurological d/o 7. Effect of other drugs B. Laxatives/cathartics 1. Constipation—prevention, treatment 2. Prep for surgical, radiologic and endoscopic procedures C. Contraindications 1. Persistent or severe abd pain of unknown cause 2. Especially pain accompanied by fever a. Appendicitis, intestinal obstruction, fecal impaction b. Ulcerative colitis, diverticulitis D. Osmotic (saline) laxatives 1. Draws water into bowel, increasing the bulk of intestinal contents and stimulating peristalsis 2. Monitor for dehydration and electrolyte imbalances 3. Drug e.g.: MG CITRATE, MOM, PHOSPHO-SODA, GO-LYTELY (no net exchange ions so not an F/E issue with this med), MIRALAX, FLEET‟S ENEMA 4. S/E: cramps, distention, flatulence, and belching E. Hyper-osmotic laxative 1. Increase water content of stools and soften stools 2. Drug e.g.: LACTULOSE 3. Titrate to 3-4 BMs/day 4. Adjunctive tx for hepatic encephalopathy a. Ammonia builds up in blood b. Leads to coma or neuro issues c. Liver cleans blood, breaks down ammonia 5. Caution to diabetics—synthetic sugar F. Stimulant laxatives 1. Stimulate peristalsis and inhibit electrolyte and water reabsorption from intestine 2. Drug e.g.: SENNA (EXLAX, SENOKOT), BISACODYL (DULCOLAX, CORRECTOL), CASTER OIL 3. Risk: dependence, decreased colonic motility G. Bulk forming laxatives 1. Increases water content of stools, forming a viscous solution that promotes peristalsis and improves transit time 2. Manage chronic watery diarrhea 3. METHYLCELLULOSE (CITRUCEL), PSYLLIUM (METAMUCIL), POLYCARBOPHIL (FIBERCON) 4. Adverse reaction: esophageal or intestinal obstruction H. Emollients (stool softeners) 1. Allows more fluid to penetrate feces 2. Docusate sodium (Colace)

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3. Indications: post MI, poste rectal surgery (no straining, no suture rupture) I. Lubricant laxatives 1. Increase water retention in stools 2. Prevent water absorption from stools 3. Lubricate and soften intestinal contents 4. E.g.: MINERAL OIL 5. Adverse reaction: lipid pneumonia and nutritional deficiencies—interferes with oilbased vitamins (K, etc.) J. Nursing Responsibilities 1. Assess: a. Abd pain, distention, N/V, frank or occult bleeding, bowel sounds, freq./characteristics stool b. Monitor electrolyte imbalances 2. Teach: a. Short term use b. Risk of dependence/loss of colonic motility c. Dietary fiber, fluids and exercise Diarrhea A. Causes: 1. Foods—spoiled or spic 2. Bacteria—E. coli, Salmonella 3. Toxins 4. Fecal impaction 5. Drug reactions 6. Laxative abuse 7. Malabsorption syndrome 8. Stress, anxiety 9. Intestinal tumor 10. IBD—Crohn‟s; UC B. Antidiarrheal 1. Decrease hypermotility—slow GI tract to allow stool to get more firm 2. Short term treatment (2 days) 3. Need to find underlying cause—DIARRHEA IS A SYMPTOM a. Opiates, opiate-related agents b. Adsorbents c. Somatostatin analog
C. Antidiarrheal--Opiate/opiate related 1. DIPHENOXYLATE (LOMOTIL)  Traveler‟s Diarrhea, contains atropine a. Contraindicated for children < 2, lactating mothers, liver failure, glaucoma (atropine element) b. CNS & resp depression 2. LOPERAMIDE (IMODIUM)  chronic non-specific, OTC (NOT for UC) D. Antidiarrheal—Adsorbents 1. Reduce fluid content in stool, absorb toxin/bacterial 2. Drug e.g.: BISMUTH SUBSALICYLATE (PEPTO-BISMOL, KAOPECTATE) 3. Indication: prevention/treatment of Traveler‟s Diarrhea, indigestion a. Temporary darkening of tongue and stools b. Reye‟s syndrome, salicylism (ringing in ears) E. Antidiarrheal—Somatostatin Analog (somatostatin “imitator”) 1. Inhibits production of gastric secretions and intestinal fluids, decreases smooth muscle contractility 2. OCTREOTIDE (SANDOSTATIN) 3. Indication: severe diarrhea d/t metastic cancer 4. S/E: gall bladder abnormalities, hypo-/hyperglycemia (hyper more common), hypothyroidism, bradycardia