Exam 2 GI drugs Flashcards
Misoprostol (Cytotec): Class, use, SE
PGE1 analogue
Prevents/reduces NSAID induced damage
Nausea, diarrhea, HA dizzy
- do not use in preg (induce abortion)
MOA, PK, use of PPI “prazole”
Pro drugs activated in parietal cell to sulfenamide
1x/d dosing on empty stomach, eat 30 min later
irreversible block of acid formation (takes 2-5 d)
long lasting effect (1-2 d to replace pump)
SE of PPI “prazoles”
Nausea, diarrhea, colic
OP (decrease Ca abs), Decrease Mg abs (cramps)
HA, dizzy, sleepiness, increased LFT uncommon
Skin rash, bacterial overgrowth possible
Omeprazole may inhibit CYP2C19 (phenytoin, warfarin, diazepam, clopidogrel)
PPI: Use
Ulcers unresponsive to H2 blockers 4 wk to heal duodenal ulcer, 8 wk gastric DOC GERD Pt on NSAIDS ZES
Sodium Bicarb: Class, use
Acid Neutralizing agent (GI)
Inorganic base neutralizes acid by binding to HCl
Temporary fix for heartburn, gastritis; adjunct to other drugs bc rapid acting
Calcium Carbonate (tums): Class, use
Acid Neutralizing (GI)
Inorganic base neutralizes acid by binding to HCl
Temporary fix for heartburn, gastritis; adjunct to other drugs bc rapid acting
MgOH/AlOH (Maalox, Gaviscon): Class, use
Acid Neutralizing (GI)
Inorganic base neutralizes acid by binding to HCl
Temporary fix for hearburn, gastritis; adjunct to other drugs bc rapid acting
PK H2 blockers “tidines”
Oral, half life 12 hr
Liver metab, kidney excretion
Most effective at night
SE of H2 blockers “tidines”
Few (worse in elderly)
HA, dizziness, nausea, rash itch
Cimetidine: anti testosterone (gynecomastia, loss libido, impotence); also inhibits metab of drugs meta by CYP3A4 (warfarin, phenytoin, theophylline, digoxin
What drugs are metab by CYP3A4
Warfarin, phenytoin, theophylline, digoxin
“tidines”: Class, use
H2 blockers
Decrease GI acid formation through H2 receptor blockade (now OTC)
Used to treat/prevent ulcers (stress/NSAID induced), pre anesthesia, GERD adjunts, with H1 antagonists for severe allergic rxn
What is Sucralfate (Carafate)
Cytoprotective Agent,
Take on empty stomach
Polymerizes to provide protective barrier cells in ulcer base; rarely used
Has aluminum – constipation; upset stomach and drug interactions
Tx of H pylori and Ulcers
Block acid and kill bactera: Pepto Bismol, Metro, Clarithromycin, tetracycline, amoxicillin, H2 blocker
What are the prokinetic agents
Metoclopramide (D2 antagonist that increases ACh release, antiemetic – SE cramping, diarrhea, tardive dyskinesia, infant methemoglobinemia, don’t use if pregnant)
Bethanechol (M agonist – diarrhea, cramps)
Erythromycin (used in diabetic gastroparesis)
Sx and tx of IBS
Abd pain, bloating, gas, constipation/diarrhea
Visceral hyperalgesia
Tx: diet, drugs, reduced stress
Glycopyrrolate, dicyclomine, TCAs (M antagonists, antispasmodic, TCA for chronic pain)
Drugs for treating IBS
Glycopyrrolate, dicyclomine (both antispasmodics aka antiM drugs), TCAs (good for chronic pain)
Pathophysiology of IBS
Stimulation of 5-HT4 receptors on nerve terminal increases ACh release, increases peristalsis
Release of 5-HT from Enterochromaffin cells stimulates 5HT3 receptors
Sends pain signal to CNS
Alosetron (Lotronex) class, MOA and use
Serotonin 5HT3 receptor antagonist
IBS with severe diarrhea in women
Constipation most common SE
SE can be severe – GI obstruction, perforation
Many contraindications, risk benefit statement req
Tegaserod (zelnorm) class, MOA, details
5-HT4 partial agonist, off market bc cardiac risk
Targets for vestibular system
H1 and M1 receptor
Targets for CTZ
Chemoreceptors, D2 receptor, NK receptor, 5 HT3 receptor
Targets for GI tract and heart
Mechanoreceptors, chemoreceptors, 5 HT3 receptors
“setrons” class MOA, use
Serotonin 5HT3 antagonists
Tx N/V induced by chemo, radiation, gastric dz
NOT for motion sickness
SE: HA, constipation, dizziness
Prochlorperazine (Compazine), Promethazine (Phenergan): Class, MOA, Use, SE
Antinausea/antiemetics
Block DA, M and Histamine recpetors
Use: post op, gastroeneteritis, chemo, motion sickness (DOC motion sickness is dimenhydrinate and scopolamine)
SE: sedation
Dranbinol (Marinol) /Medical marijuana/Nabilone: Class, MOA, use, SE
THC cannabinoid used for chemo induced N/V
Stimulates appetite
DOC motion sickness
Scopolamine, dimenhydrinate (Dramamine)
What influences bowel function: peristalsis/motility
Increased by PNS, decreased somewhat by SNS
Decreased by opioids (CNS and PNS effects)
Describe function of the bowel
8-9 L H2O/d enters, most reabs - only 100 mL in feces
Abs of water, electrolyes
Secretion water &electrolyes
Abs of CHO, PRO, minerals and nutrients (via transporters)
Define normal bowel freq vs constipation
Normal is >3x/wk
25% people think they are constipated (due to decreased freq, difficulty initiating, feces too firm, incomplete emptying) but 1/3 who use laxatives are not actually constipated
Chronic use of laxatives causes problems
How do Laxatives work
Increase GI motility, prevent reab of water/electrolyte
Enhance secretion of water/electrolytes
Dissolve or lubricate feces
What are the types of laxatives and their intensity
Bulk forming: mild Osmotic: INTENSE, cathartic Mucosal agents: irritant Lubricating Stool softeners
What are the bulk forming laxatives and SE/recommendations
Fiber: dietary, methylcellulose (Citrucel), Psyllium (Metamucil), Polycarbophil *High fiber diet best SE: bloating, flatulence common Rec: plenty of water *Some may later abs of drugs
What are the Osmotic Laxatives
MgOH (milk of magnesia) (also stimulates GI tract, increases peristalsis)
Sodium salts: oral or enema (fleet)
Sorbitol, mannitol, sucralose (also used as sweeteners)
Lactulose (chronolac): used in cirrhossis and liver dz to decrease NH4, causes gas
Polyethelene glycol (Colyte, miralax): prep colonoscopy, miralax OTC for constipation
Drink lots of water!!!!
How do mucosal agents work? Class?
Laxatives Stimulate peristalsis Enhance secretion/inhibit absorption H2O Mild: Bisacodyl, Senna (Senokot) Intense: Castor oil (requires bile, stimulates uterus so do not use if preg; used for surery, dx)
Bisacodyl, Senna (senokot) class, MOA
Mild mucosal agent/laxative
Stimulate peristalsis, enhance secretion/inhibit abs H2O
Bisacodyl: class, MOA, use
Mucosal agent (laxative) Stimulates peristalsis, enhances secretion, inhibits absorption of H2O
Castor oil: class, MOA, use
Mucosal agent (intense)
Requires bile, stimulates uterus (CI in preg)
Used for surgery, diagnostic (colonoscopy)
Don’t use if pt has gallbladder or bile problem
Lubricants/softeners: MOA, use, effectiveness
Increase bulk
Soften and lubricate stool
Not very effective
Mineral oil, Docusate (emulsifies), Glycerin (lubricate)
Mineral Oil: class, MOA, use, SE
Lubricant/softener
Increases bulk, softens and lubricates stool
Can decrease abs of Fat soluble vitamins (A, D, E, K)
If inhaled into lungs, can cause lipoid pneumonia
Can cause leaking – stains clothing and furniture
Docusate sodium (Colace, Doxinate): class, MOA, use, SE
Most effective of the lubricant/softener class Emulsifies, softens colonic contents and may increase water abs
Glycerin: class, MOA, use
Lubricant/softener (laxative)
Suppositories that help lubricate distal end of bowel
How effective are lubricants/softeners
Not very effective
Lubiprostone (amitiza): MOA, use, SE
Laxative
PGE1 analogue, activates ClC2Cl channels in luminal cells to increase fluid secretion
Softer stool, better motility, less constipation
NO effect on electrolytes, no laxative dependence, not absorbed systemically
SE: N, D, HA
Uses of Laxatives?
Reduce straining, maintain soft stools
Empty bowel for dx or surgical procedures
Decrease Bowel tone
Geriatrics, pregnancy
Get rid of pathogens/toxins
Constipation (cause may include opioids) – manage with diet, water consumption, exercise
Contraindications for laxative use
N/V, cramps
Undx abdominal pain
Appendicitis
Obstruction
Overuse of laxatives…
Occasional = ok Chronic = adverse effects incl dependence, electrolyte/fluid imbalance, spastic colitis, Ulcerative colitis (UC)
Pathophysiology and risks of Diarrhea. Causes?
Fluid > capacity to absorb
Frequent, loose watery stools
Dehydration/electrolye imbalance
Causes: Pathogens, IBS, inflammation, Malabs, laxatives, thyroid dz, drugs
How do antidiarrheal drugs work
Absorb excess water (fiber, Aluminum salts)
Inhibit secretion
Decrease motility (opioids, anticholinergics)
*note: fiber good for both constipation and diarrhea
*note: opioids very effective
Adsorbents: MOA, use, effectiveness
Absorb water, form gel like mass
Bulk forming agents (man are also laxatives)
May benefit watery diarrhea by increasing bulk
Dietary approach: bananas, applesauce, rice
NOT very effective
Loperamide (Imodium): class, MOA
Anti diarrheal opioid
Does not enter CNS, low abuse potential
May cause abdominal pain, constipation
Diphenoxylate/atropine (Lomotil): class, MOA, SE
Antidiarrheal
Opioid with atropine reduces abuse potential, increases effectiveness (OD = sx atropine poisoning)
Anticholinergic SE: red as a beet, blind as a bad, dry as a bone, mad as a hatter
When should you not use opioids to treat Diarrhea
Infections (will decrease expulsion of pathogens)
UC (toxic megacolon risk)
Recovering drug addicts (some abuse potential – diphenoxylate)
Bismuth subsalicylate (pepto bismol): class, MOA, use, SE
Anti-diarrheal for “Travellers diarrhea” Absorbs water and pathogens Salicylate = anti inflam SE: black tongue, mouth and stool CI: ASA allergy, kids (Reyes), asthmatics (asa asthma)
Simethicone (Gas-X): class, MOA, use
Antiflatulent that coats and dissipates gas to make it pass less noticeably; decreases bloating
Sulfasalazine (azulfidine): MOA, use, SE
Anti inflam 5 aminosalicylic acid + sulfapyridine
Activated by bacteria in GI tract
Tx: IBD (UC and crohns)
SE: allergic rxn possible (salicylate)
Avoid in children bc risk of Reyes syndrome
