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N550 Pharm > GI, diuretics > Flashcards

GI, diuretics Flashcards

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1
Q

What is histamine

A

Naturally occurring endogenous amine, synthesized in tissues (decarboxylation of histadine)
Stored in vesicles of mast cells (skin, lung, gastric mucosa) and basophils
Released in response to antigen-antibody reaction

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2
Q

What does histamine regulate?

A

Regulates gastric acid secretion
Regulations neurotransmission (doesn’t easily cross BBB, no CNS effect)
Receptors H1, H2, H3

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3
Q

Do H1 and H2 antagonist inhibit the release of histamine or block the response to histamine?

A

Block the RESPONSE to histamine

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4
Q

What are the effects of activating H1?

A

Bronchoconstriction (asthma/bronchitis: inc airway resistance)
Vasodilation
Inc capillary permeability
Peripheral nerve sensitization (itching, pain, sneezing)
Heart: found in AV node, slow HR conduction

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5
Q

What are the effects of H2?

A

Found in gastric parietal cells, cardiac muscle, and mast cells
Inc HR and contractility
Vasodilate (offsets H1 constriction)
Bronchodilate
Stomach: activate cAMP, activate proton pump of parietal cells to secrete H ions, gastric acid secretion ->PUD, GERD

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6
Q

What are the effects of H3?

A

Heart and presynaptic postganglionic SNS fibers
Stimulation causes inhibition of synthesis and release of histamine
Activity impaired by H2 antagonists, avoid rapid administration, esp with a histamine releaser

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7
Q

H1 receptor antagonists first vs. second generation? What effects do they have? How are they bound? List examples of each.

A

First: sedation, activate muscarinic, serotonin and alpha receptors, lipophilic, neutral at physiologic pH, ex: diphenhydramine, hydroxyzine, chorpheniramine, promethazine, doxepin
Second: non-drowsy, decreases CNS toxicity, albumin binding, ionized at physiologic pH, ex: loratidine (claritin D), desloratidine, acrivastine, fexofenadine (allegra)

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8
Q

H1 receptor antagonist uses?

A

Rhinitis, conjunctivitis, urticaria, pruritis
(not effective for systemic anaphylaxis or asthma)
Motion sickness, chemotherapy-related N/V
Insomnia

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9
Q

H1 antagonist pharmacokinetics?

A

Excellent absorption
Protein binding up to 99%
Hepatically metabolized by CP450
E1/2t is variable (chlorpheniramine is over 24 hours, acrivastine is 2 hours)

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10
Q

H1 antagonist adverse effects?

A

CNS toxicity, sedative effects
Cardiac toxicity, QT prolongation
Anticholinergic effects, pupillary dilatation, dry eyes, dry mouth, urinary hesitancy

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11
Q

H1 antagonist vs. H2 antagonist uses?

A

H1 blocker for allergic rhinitis

H2 blocker to inhibit acid of gastric fluid secretion, used for duodenal ulcer disease, GERD, chemoprophylaxis

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12
Q

H2 antagonists MOA?

A

Competitive antagonism of H2 receptors by decreasing intracellular cAMP (and dec the secretion of H ions) to suppress gastric acid secretion by parietal cells
(NO effect on lower esophageal sphincter tone, gastric emptying, pH, or volume)

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13
Q

List some H2 antagonists.

A

Cimetidine (tagamet)- least potent 300mg
Nizatidine (don’t use on renal failure pts)
Ranitidine (Zantac) 150mg po/ 50mg IV
Famotidine (pepsid)- most potent 20-40mg

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14
Q

H2 antagonist pharmacokinetics?

A

Rapid absorption oral, first pass hepatic metabolism
Low protein binding, crosses BBB
Elimination 1/2t 1.5-4h
Nizatidine renal excretion
Hepatic metabolism by cimetidine, ranitidine, and famotidine

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15
Q

Rapid IV administration of cimetidine/ranitidine may cause what? So give these over 15-30 min
Also, give famotidine over 2 min

A

Bradycardia or hypotension

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16
Q

H2 antagonist adverse effects?

A

Cimetidine slows metabolism of lidocaine and dec metabolism of drugs that undergo extensive hepatic extraction (propranolol, diazepam) due to inducing P450
Transient elevation in LFTs

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17
Q

3 factors in PUD development?

A

Bacterial infection of H pylori
NSAID use
Smoking

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18
Q

3 goals of therapy for PUD

A

Reduce gastric acidity
Enhance mucosal defenses
Eliminate H pylori

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19
Q

What drugs inhibit acid secretion?

A

H2 antagonists
PPIs
Anticholinergics

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20
Q

What drugs neutralize gastric acid?

A

Antacids

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21
Q

What drugs protect gastric mucosa?

A

Sucralfate
Colloidal bismuth
Prostaglandins

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22
Q

What drugs eradicate H pylori?

A

Antibiotics

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23
Q

How do PPIs work?

A

Block K-H-ATPase (proton pump) which stops acid release

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24
Q

List PPIs.

A 
Lasoprazole
Pantoprazole (protonix)
Esomeprazole (nexium)
Omeprazole (prilosec)
Rabeprazole
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25
PPI pharmacokinetics?
Rapid absorption, short half-life Prodrug converted to active drug in parietal cell Hepatic metabolism by CYP2C193A4 Cross placenta
26
PPI adverse effects?
Headaches GI disturbance, nausea Enteric infections
27
PPI uses?
PUD with H pylori Hemorrhagic ulcers PUD in patient who requires NSAID use
28
Anticholinergics work on what?
Muscarinic Ach receptor antagonist Decreases acid secretion Less effective than H2 antagonists and PPIs
29
Anticholinergic adverse effects?
Dry mouth, constipation, blurred vision, cardiac arrhythmia, urinary retention
30
How does sucralfate work?
Complex salt of sucrose sulfate and aluminum hydroxide, forms a viscous gel that sticks to areas of ulceration Protects ulcerated tissue from aggressive factors such as pepsin, acid, and bile salts DOESN'T alter gastric pH, good for symptom relief
31
Sucralfate adverse effects?
Constipation | Little systemic absorption (it binds to other drugs)
32
How does colloidal bismuth work?
It is a coating agent used in PUD Protects mucosa from acid and pepsin degradation (barrier formation and stimulation of mucosal bicarb and PGE2) Impede growth of H. Pylori
33
What is Misoprostol? AE?
A prostaglandin analoague Prevents NSAID-induced ulcers AE: abdominal discomfort, diarrhea CI in pregnancy
34
What would triple therapy of H Pylori include? Quadruple therapy?
Triple: Amoxicillin, clarithromycin, PPI Quad: Tetracycline, metronidazole, PPI, bismuth
35
Antacids
Neutralize or remove acid from gastric content Aluminum, calcium, magnesium salts INC gastric pH over 5 (from 2.5) Not first line for ulcers but inc rate of ulcer healing and pain relief
36
List some antacids. What are side effects?
``` Aluminum hydroxide Magnesium hydroxide Sodium bicarb (caution in cardiac pt) Calcium carbonate (tums) Side effects: constipation, diarrhea, electrolyte abnormalities ```
37
What does sodium citrate (bicitra) do?
It is a preoperative nonparticulate (clear) antacid therapy, causes less of a foreign body reaction if aspirated Rapid onset, give 15-30 min prep, 15-30mL, pH of 8.4, unpleasant taste
38
Prokinetic drugs: what do they do?
Increase lower esophageal sphincter tone Accelerate rate of gastric emptying Enhance peristalsis
39
What is metoclopramide (reglan)?
Dopamine antagonist, kinetic only Gastric pH unchanged Cholinergic stimulation of GI tract: increase LES tone, increase gastric/small bowel motility, relaxation of pylorus and duodenum
40
Interactions with metoclopraminde?
Post-synaptic release of Ach GI actions opposed by atropine and glycopyrrolate Dopamine receptor antagonism May inhibit plasma cholinesterase
41
Metoclopramide pharmacokinetics?
Rapidly absorbed PO Peak plasma concentration 40-120 min E1/2t 2-4h Renal excretion, 40% unchanged drug
42
Metoclopramide uses?
Decrease gastric fluid volume Antiemetic Treatment of gastroparesis Symptom treatment of GERD
43
Metoclopramide dose?
10-20 mg IV over 3-5 min 15-30 min prior to induction Child/mom dose: 0.15 mg/kg Diabetic gastroparesis (full stomach) dose: 10 mg IV
44
Metoclopramide side effects?
CNS effects Extrapyramidal effects Stimulate prolactin secretion Anti-emetic Abdominal cramping (with rapid administration, push in 3-5 min) Cardiac dysrhythmias, sedation, dry mouth
45
Metoclopramide contraindications?
BOWEL OBSTRUCTION Parkinsons Seizure disorder Phenothiazines (these also create extra-pyramidal effects)
46
Serotonin (5HT): what is is synthesized from? Where is it located intrinsically?
5HT is synthesized from tryptophan Important as a neurotransmitter with pain/nausea impulses 90% in the enterochromaffin cells (gut) 10% in CNS and platelets
47
Where can 5HT3 antagonists work? What are they used for?
Antagonism at peripheral (vagal afferents in GI) and central (CRTZ) receptors Used as an antiemetic for postop N/V, chemotherapy, hyperemesis gravidarum
48
Name some 5HT3 antagonists and dosages
Ondansetron 4-8mg IV (Peds 0.05-0.15 mg/kg IV up to 4 mg) Granisetron 0.01-0.04 mg/kg Dolasetron 12.5 mg IV Tropisetron
49
Side effects of 5HT3 antagonists
Headache with rapid IV administration (ondansetron) Cardiac dysrhythmias- rare Rely on liver metabolism (reduce dosage appropriately in liver disease)
50
Dexamethasone used for PONV prevention, what is the dosage?
Steroid | 4-10mg IV
51
Name a couple phenthiazines. What are they used for?
Prochlorperazine (compazine) Promethazine (phenergan) Exerts anti-emetic effects by interaction with dopaminergic receptors in CRTZ
52
Phenergan taken off the market for what?
Neurolept malignant syndrome 24-48 h after dose Presentation: tachy, cardiac dysrhythmias, alterations in BP, presents like MH (distinguish by effect of NDMRs which produce flaccid paralysis in NMS but not in MH) Treat with amantadine and dantrolene
53
Droperidol
Inhibits dopaminergic receptors in CRTZ, for PONV, decrease BP, peripheral alpha blockade, EPS, akathesia, dysphoria, neurolept anesthesia Black box for QT prolongation and torsades de pointe
54
Thiazides: what does it work on, what does it do? K wasting/sparing? Prototype: HCTZ (hydrochlorothiazide)
Works on the distal convoluted tubule Impairs Na and Cl reabsorption Peripheral vasodilation (anti-HTN) K wasting
55
Thiazides anesthesia concerns?
Hypokalemia, hypochloremia, hypomagnesemia Muscle weakness potentiates muscle relaxants Nephropathy Inc risk of dig toxicity Fluid volume status
56
Loop diuretics: where do they work?
Act on ascending loop of henle, inhibits passive transport of Na/K/Cl from lumen Prototype: Furosemide
57
Loop diuretic side effects?
Hypokalemia, hypochloremia Presynaptic effect potentiates NDMRs Enhances possibility of nephrotoxicity when administered with aminoglycosides and cephalosporins (ABX) Dec renal clearance of lithium Cross reactivity with sulfonamide allergy
58
Furosemide dose? Pharmacokinetics?
0.1-1 mg/kg Extensive protein binding Excreted by glomerular filtration and renal tubular secretion
59
Furosemide uses?
Mobilization of edema fluid- peripheral vasodilation precedes onset of diuresis Reduction of ICP, dec venous return Used for hypercalcemia/ parathyroid syndrome and oliguria
60
Osmotic diuretic
Mannitol is the prototype (must give IV) Cleared from plasma by glomerular filtration, increases renal tubular fluid osmolarity and plasma osmolarity Draws fluid from IC to EC space, inc intravascular volume (problem with poor LV function/pulmonary edema)
61
Osmotic diuretic clearance
``` 100% by GF None reabsorbed (so don't use in renal failure) ```
62
Mannitol uses?
Differential diagnosis of oliguria Prophylaxis for ARF Reduces ICP Reduces IOP
63
Mannitol dose? Anesthesia concerns?
0.25-1 g/kg IV Works in 10-15 min, lasts 2 hours Anesthesia concerns: pulmonary edema, hypovolemia, electrolyte changes
64
Which diuretics are potassium sparing?
``` Epithelial sodium channel blockers (triamterene) Aldosterone antagonists (spironolactone) ```
65
How does triamterene work?
Works on the collecting duct Non-competitive antagonism of aldosterone, Na channel blockade Can cause hyperkalemia
66
How does spironolactone work?
Competitive aldosterone antagonist (blocks aldosterone from reabsorbing Na and water and secretion of potassium)
67
Spironolactone uses?
K sparing Treats heart failure, ascites, low-renin HTN, hypokalemia, Conn's syndrome It is a weak diuretic, usually combined with other diuretics
68
Carbonic anhydrase inhibitor: what does it do?
Prototype: acetazolamide (diamox) Uses: glaucoma, altitude sickness, ICP Blocks carbonic anhydrase, inc amounts of bicarb, Na, and water in the urine (Carbonic anhydrase catalyzes H and bicarb released from CO2 and water. H is then excreted in exchange for Na on the renal luminal membrane and bicarb is reabsorbed with Na)

N550 Pharm (14 decks)

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