Gastrointestinal Drugs Flashcards
Antacids Mechanism of Action
Promotes gastric mucosal defense mechanism
Mucus Secretion: Protective barrier against HCl
Bicarb: Helps buffer acidic properties of HCl
Prostaglandins: Prevent activation of Proton Pump, leads to decrease HCl Production
NOTE: Antacids don’t prevent overproduction of Acid, but they do neutralize acid once it is in the stomach
Antacid Drug Effects
Reduce pain associated with acid-related disorders
Antacids: Aluminum Salts
Carbonate, Hydroxide
Constipating Effects, used with magnesium to fight constipating effects.
Examples: Basaljel (carb) , Alternagel (hydroxid) , Maalox, Mylanta (both combo)
Antacids: Magnesium Salts
Carbonate, Hydroxide, oxide, trisilicate
Causes Diarrhea
Dangerous when used with Renal Failure
Example: Mag Hydroxide (MOM), Gaviscon, Combo: Maalox, Mylanta
Antacids: Calcium Salt
Carbonate, but there are many forms
Can cause Constipation, and may result in kidney stones
Extra source of Calcium
Example: Tums
Antacids: Sodium Bicarbonate
Very soluble
Buffers HCl
Quick onset, short duration
Causes metabolic alkalosis,** can cause problem inpatients with CHF, HTN, Renal insufficieny**
Antacids/Antiflatulents
Antiflatulents: used to relieve painful symptoms associated with gas.
OTC Drugs: Activated charcoal and Simethicone
Antacid Side Effects
Minimal
Aluminum/Calcium: Constipation
Magnesium: Diarrhea
Calcium Carbonate: Gas/belching
H2 Antagonists
Reduce acid secretion
Available OTC
Cimetidine/Tagamet
Famotidine/PEcid
Ranitidine/Zantac
H2 Antagonists: Mechanism of ACtion
Blocks Histamine (H2) at receptors of parietal cells which results in decreased production of HCl
H2 Antagonist Side Effects
Cimetidine: Impotence/Gynecomastia
Headache, lethargy, confusion, diarrhea, urticaria, swearing, flushing
H2 Antagonist Drug Interactions of Cimetidine/Tagamet
BInds with P450 in liver, results in inhibitied oxidation of drugs and increased level of drugs
All H2 antagonists inhibit absorption of drugs that require acidic GI for absorption
Smoking decreases the effectiveness of H2 Blockers (increases gastric acid production)
What is the action of the proton pump? Do H2 blockers and Antihistamines stop its action?
Parietal cells realese positive hydrogen during HCl production
They don’t stop the action.
Proton Pump Inhibitors: Mechanism of Action
Irreversible bind to H+/K+ ATPase enzyme
Causes achlorhydria: blocking of gastric acid secretion
PPI Drugs
“-prazole”
Prevacid, Prilosec, Nexium
Indications for PPIs
Gerd Maintenance therapy
Treatment of H. Pylori ulcers
erosive esophagitis
PPI Side Effects
Safe for short term
Protonix/Nexium parenteral administration
Can increase levels of diazepam/phenytoin, increased chance of bleeding with warfarin
Sucralfate/Carafate
Cryoprotective
used for stress ulcers, erosions
Don’t give with other medications
Misoprostol/Cytotec
Used for prevention of NSAID-Induced gastric Ulcers
Antidiarrheals: Adsorbents MOA
Coat walls of GI, bind to toxin and eliminate through stool
Pepto-Bismol, Activated Charcoal, Kaopectate
Antidiarrheals: Anticholinergics MOA
Decrease intestinal muscle tone and peristalsis
Donnatal/Atropine
Antidiarrheals: Intestinal Flora MOA
Lactobacillus: supplies missing bacterie to GI, suppress diarrhea causing bacteria
Lactinex
Antidiarrheals: Opiates MOA
Decrease bowel motility/relieve rectal spasms
Codeine, Lomotil, Imodium
Antidiarrheals
Side effects of Adsorbents
Increased bleeding time, constipation, dark stools, tinnitus, hearing loss
Antidiarrheals
Anticholinergics Side effects
urinary retention, impotense, headache, dizziness, confusion, dry skin, rash, blurred vision photophobia, Hypotension, hypertension, brady/tachycardia
Antidiarrheals
Opiates Side Effects
Drowsiness, sedation, dizziness, lethargy, N/V, bradycardia, palpitations, Hypotension
Laxatives
Bulk forming MOA and SE
High fiber, absorbs water, distends bowel
Metamucil
SE: Impaction/ fluid overload
Laxatives
Emollient MOA and SE
Stool softener/lubricant
more water/fat in stools
Colace/Surfak
Mineral oil
SE: Skin Rash, decreased vitamin absorption
Laxatives
Hyperosmotic MOA and SE
Increase fecal water content
bowel distention, increased peristalsis
GoLytely
Sorbitol
SE: Abdominal bloating, rectal irritation
Laxatives
Saline MOA and SE
increase osmotic pressure within intestinal tract, causes more water to enter intestines
Causes bowel distention, increased peristalsis, evacuation
Examples: Epsom salts, magnesium hydroixide, fleet enema
SE: magnesium toxicity, cramping, diarrhea, increased thirst
Laxatives
Stimulant MOA and SE
Increase peristalsis via nerve stim.
Castor oil, Senokot
SE: nutrient malabsorption, skin rashes, gastric irritation, rectal irritation
MOA of Antiemetic and Antinausea
Blocks vomiting pathway, blocks stimulus that induces vomiting
Antiemetics/antinausea
Anticholinergic MOA/Indications
bind to ACh receptors in inner ear, blocks nauseating stimuli to CTZ
Scopolamin, used for motion sickness
Antiemetics/antinausea
Antihistamine agents H1 blockers
inhibit ACh by binding to H1
Prevents stim in vestibular/reticular area
Benadryl, Phernergan
also for cough, allergies, sedation
Antiemetics/antinausea
Neuroleptics MOA
Block dopamine receptors on CTZ
Thorazine, Compazine
Also psychotic disorders, intractable hiccups
Antiemetics/antinausea
Prokinetic agents
Block dopamine in CTZ
stimulates peristalsis in GI
Reglan
Antiemetics/antinausea
Serotonin Blockers
Anzemet, Kytril, Zofran
Used for N/V in patients getting chemo, also postop N/V
Antiemetics/antinausea
THC MOA
Inhibits reticular formation, thalamus, cerebral cortex
Marinol
Used for N/V associated with chemo and anorexia with weight loss in AIDS patients
Antiemetics/antinausea SE
Varies, due to nonseletive blocking
Cause drowsiness
Antiemetics + alcohol = CNS Depression
