GI Pharmacology I Flashcards
Which class of drugs are antacids, H2 receptor blockers and proton pump inhibitors?
Acid reducing agents
**mainly used for GERD**
Review the slide below on the location of gastric cells
Describe the mechanism of action of antacids
Antacids can have drug-drug interactions with what classes/types of drugs? (2)
What side effects arise from using antacids that contain calcium and magnesium?
MOA: literally just neutralize stomach acid. combo of Mg, Aluminum +/- Ca-carbonate
Antacids can have drug-drug interactions w/ drugs that depend on absoprtion of stomach acid to work, or drugs where functional groups may be chelated by cations
Side effects that arise from using antacids that contain calcium and magnesium:
Calcium can cause constipation
Magnesium causes diarrhea
**FA:
Aluminun hydroxide - CHOPS - constipation, hypophosphatemia, osteodystrophy, proximal ms weakness, seizures
Calcium carbonate - hypercalcemia, rebound increase in acid - chelates other drugs
Mg hydroxide - diarrhea, hyporeflexia, hypotension, cardiac arrest
Describe the mechanism of action of histamine receptor blockers
Reversible block of histamine receptors >> decreased H+ secretion by parietal cells
**H2 receptors allow for activation of Gs >> increased cAMP >> used for energy for H/K ATPase >> increased H+
**used for occasional GERD/heartburn, anticipatory heartburn
Review the slide below on the generation of acid in pariteal cells
What are the H2 receptor blocker drugs? (4)
-drugs that end in dine
Cimetidine - potent inhibitor of CYP450, also has anti-androgenic effects (low libido, gynecomastia, prolactin release, impotence); crosses blood-brain barrier + placenta; decreased creatinine excretion
Ranitidine - decreased creatinine excretion
Famotidine
Nizatidine
Describe the mechanism of action of proton pump inhibitors
MOA: irreversibly inhibit H/K ATPase >> no acid secretion
Which drugs are in the class of proton pump inhibitors? (5)
Omeprazole
Esomeprazole
Lansoprazole
Pantoprazole
Dexlansoprazole
*drug drug interactions, decreased Ca2+ absorption, decreased serum Mg2+, increased risk of C. diff, pneumpnia, acute interstitial nephritis*
*Omeprazole + esomeprazole – metabolized by CYP2C19 – decrease availability of clopidogrel*
___ are a class of drugs used to protect the gastric or duodenal mucosa from effects of acid
Mucosal protectants are a class of drugs used to protect the gastric or duodenal mucosa from effects of acid
**mainly used to treat gastric and peptic ulcers**
Which drugs are mucosal protectants? (3)
Coating agents - sucralfate
Bismuth subsalicylate
Prostaglandin analogs
Describe the mechanism of action of coating agents
Which drug is in this class?
Sucralfate
Forms a paste-like coating that protects gastric lining from acid, pepsin, bile salts
*careful in folks w/ diabetes - hyperglycema; folks w/ renal impairment - aluminum-induced damage
*only oral or NG tube; take other meds after 2 hours b/c this blocks absorption of things*
Describe the mechanism of action of bismuth subsalicylate (aka pepto bismol)
Bismuth is alo used in quadruple therapy for gastritis induced by what bacteria? (1)
MOA: Binds to the base of the ulcer and forms a paste-like coating >> releases HCO3- >> re-establish pH gradient (antisecretory, antimicrobial, anti-inflammatory)
Bismuth is alo used in quadruple therapy for gastritis induced by H. pylori
**salicylate - anti-secretory, anti-inflammatory; bismuth - anti-microbial**
*overuse in humans/cats - salicylate poisoning; causes Reye syndrome in babies b/c its an aspirin analogue, Bismuth also causes black stool*
What is the function of prostaglandins in the GI tract? (2)
Describe the MOA of prostaglandin analogs
Which drugs are in this class? (1)
Why would you use this drug w/ NSAIDs?
Normally, prostaglandins inhibit acid secretion and stimulate secretion of bicarbonate+ mucus
Prostaglandin analogs do what prostaglandins do normally
Misoprostol
Apparently you would give Misoprostol w/
NSAIDs because they’re COX inhibitors (in this case COX2) and inhibit prostaglandins for anti-inflammatory effects
They inhibit COX 2, which doesn’t have effects on prostaglandins in the stomach, so you can use those COX2 inh’s for anti-inflammatory effects everywhere else, and still use this Misoprostol in the stomach
Which drugs are pro-motility agents (6) and what are they used to treat?
Drugs considered pro-motility agents:
Dopamine antagonist
Cholinomimetics
GABA(b) antagonists
GC activators
Cl channel activator
Motilin agonist
Used to treat gastroparesis >> delayed gastric emptying not due to mechanical obstruction
*pts present w/ nausea, vomiting, belching, bloating, satiety, upper abdominal pain*
Describe the mechanism of action of dopamine antagonists
Name the drug that is in this class (hint: me-‘ticklo’)
MOA: Blocks D2 receptor - increases response of ACh to upper GI tract ms >> increased resting tone, motility, promotes gastric emptying, LES tone; doeesn’t affect gastric/biliary/pancreatic secretions
Drug in this class: metoclopramide (me’ticklo’promide)
(Metoclopramide dumped dopamine and now she’s well rested, motile and empties better! Still isn’t secreting tho)
**SEs:
tardive dyskinesia, increased parkinsonian effects, restlessness, fatigue, drowsiness, depression, diarrhea (anti-emetic)
DDIs: digoxin + diabetic drugs
DO NOT USE in pts w/ Parkinson disease, diabetics, small bowel obstruction
Describe the mechanism of action of cholinomimetic drugs
Name the drugs in this class (2)
Cholinomimetics block acetylcholinesterase >> increased ACh at neuromuscular junction >> directly affects skeletal muscle, mayble also smooth ms and autonomic ganglin/CNS cells
Side effects:
braycardia, cholinergic crisis (very wet - lacrimaton, blurry vision, diarrhea etc)
Drugs in this class: Neostigmine, Bethanecol
Describe the mechanism of action of GABA(b) agonists in the GI system
Which drug is in this class (1)?
MOA: don’t know; has inhibitory effect on transient LES relaxation
Drug in this class: baclofen - muscle relaxer/antispasmotic; oral and intrathecal only
SE: nausea, vomiting, drowsiness, hypotonia
Describe the MOA of motilin agonists
Which drug is this class? (hint: its an antibiotic)
MOA: induces high amplitude gastric propulsive contractions
SE: QT prolongation
Drug in this class: erythromycin
Review the slide below on the location of receptors incholved in vomiting (in brain) and other GI things
Note that NK1 receptors occur wherever serotonin receptors are as well, but you can have serotonin receptors separate from NK1 receptors
**note the receptors in each ctr of the brain**
Describe the MOA of serotonin antagonists (2)
Name the drugs in this class (3)
MOA: peripheral effects: block serotonin receptors on vagal nerve terminals; central: block chemoreceptors in trigger zone/vomiting ctr
drugs in this class: - end in setron
Odansetron (most common)
Granisetron
Palonosetron
SE: QT prolongation
Describe the MOA of anticholinergics (2) and antihistamines
Anticholinergics: block ACh activity @ parasympathetic receptors in sm ms, secretory glands, CNS; antagonize histamine + serotonin
Antihistamines: competitively inhibit H1 receptor (anti-cholinergic + sedative effects)
**both used for motion sickness
Which drug are anticholinergics (1), antihistamines? (4)?
Anticholinergices: scopalamine
Antihistamines: -ines and an outlier:
Meclizine
Diphenhydramine
Hydroxyzine
Dimenhydrate (outlier)
*note the effects on the slide*
Describe the MOA of Dopamine antagonists
Which drugs are in this class? (2)
MOA: block postsynpatic D1 and D2 receptors in different places so there are varying effects
chemoreceptor trigger zone: decrease hypothalamic, hypophyseal hormone release
reticular activating system: effects on basal metabolism, temp, wakefulness, vasomotor tone, emesis
SE: QT prolongation, extrapyramidal effects
Drugs in this class: prochlorperazine, promethazine
Describe the mechanism of action of cannabinoids
What drug is in this class (1)
MOA: block CB1/CB2 receptors;
CB1 block effects: increased appetite, decrease nausea
Drug in this class: Marinol (delta-9-tetrahydrocannabinol)
Describe the mechanism of action of neurokinin antagonists
Which drugs are in this class? (2)
Neurokinin antagonists MOA: block NK1 receptors in brain (aka Substance P antagonists)
drugs in this class: Aprepitant, fosaprepitant
**used for chemotherapy-incuded vomiting and nausea; in combo w/ steroids + serotoning receptor antagonists**
*careful in folks w/ liver disease*
