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Flashcards in GI DISEASES Deck (65)
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1

ANTACID MECHANISM

weak bases that react with gastric HCl to form salt and water. The end result is an INCREASED pH. Provide QUICK RELIEF OF SYMPTOMS

2

COMMONLY USED ANTACIDS

1) MAGNESIUM HYDROXIDE (Milk of Magnesia)

2) ALUMINUM HYDROXIDE

3) CALCIUM CARBONATE (TUMS)

3

ADVERSE EFFECT of

1) MAGNESIUM HYDROXIDE

2) ALUMINUM HYDROXIDE

3) CALCIUM CARBONATE (TUMS)

1) Magnesium hydroxide produces Mg salt, which is very poorly absorbed and causes DIARRHEA

2) ALUMINUM HYDROXIDE: reacts with HCl to form Aluminum chloride, which is insolube and causes CONSTIPATION + HYPOPHOSPHATEMIA

3) CALCIUM CARBONATE: hypercalcemia, nephrolithiasis, and constipation (fecal compaction) -

NOTE FOR ALL 3: note that Ca, Mg, and Al can all CHELATE TETRACYCLINE

4

FACTORS that ENHANCE GASTIC ACID SECRETION

3 AGONISTS:

1) HISTAMINE

2) ACETYLCHOLINE

3) GASTRIN 

-the final pathway of these compounds is activation of the H+/K+ ATPase pump

 

5

H2 RECEPTOR BLOCKERS

Names + function

1st Gen: CIMETIDINE =

--> shorter acting and inhibit CYP450 

2nd Gen: = 

--> longer acting and do not inhibit CYP450

--> anything that ends in "TIDINE" that's not Lora Fux

1) Famotidine

2) Ranitidine

3) Famotidine

4) Nizatidine

FUNCTION: blocks the Gs mediated increase in cAMP that activates the H+/K+ pump

--> are capable of decreasing nearly 60-90% of basal secretion of gastric acid following a single dose 

6

INDICATION for ANTACIDS

1) GERD

2) GASTRITIS

3) PUD

-provide quick releif for these symptoms 

7

Drug used to treat ACUTE STRESS ULCERS (associated with major trauma and in high-risk patients in intensive car units)

H2 BLOCKERS --> are usually given IV injection

8

Drus used PREOPERATIVELY to PREVENT ASPIRATION PNEUMONIA

H2 blocker

9

ADVERSE EFFECTS of H2 BLOCKERS

-H2 second gen: normally all tolerated well 

H2 blocker: first gen = CIMETIDINE: presents unwanted endocrinal adverse effects including

1) GYNECOMASTIA, ("Ci-me-tiddies")

2) ELEVATED SERUM PROLACTIN LEVELS,

3) CONFUSION in ELDERLY

Big tittied confused lady at dinner that's lactating

CIMETIDINE is also a STRONG INHIBITOR of cytochrome P450

10

PROTON PUMP INHIBITORS (names)

1) OMEPRAZOLE

2) LANSOPRAZOLE

3) PANTOPRAZOLE

4) ESOMEPRAZOLE

5) RABEPRAZOLE

11

PPI MECHANISM OF ACTION

-is a PRODRUG that after transporation into the parietal cell canaliculus, is converted to the active form, which reacts with a CYSTEINE RESIDUE of the H+/K+ ATPase, forming a stable COVALENT BOND leading to IRREVERSIBLE INACTIVATION OF ENZYME

12

PPI INDICATIONS

1) GERD

2) DUODENAL/GASTRIC ULCERS

3) MEN-1/ZOLLINGER-ELLISON SYNDROME

4) Contribute in combo with antibotics to eradicate H. Pylori

5) NSAID INDUCED ULCERS --> they support platelet aggregation and maintain clot integrity --> used in hemorrhagic ulcers

13

PPI SIDE EFFECTS

-are well tolerated, but can produce nausea/diarrhea

-long term administration of Omeprazole, in ANIMALS, is associated with gastric carcinoid tumors (not seen in humans) 

-Omeprazole INHIBITS the metabolism of warfarin, clopidogrel, phenytoin, diazepam, and cyclosporin

-reports of small increase in resp and GI infections; decrease in serum Mg2+ and Hip fractures with long term use of PPI 

-rarely pancreatiits, hepatotoxicity, and interstitial nephritis 

-prolonged therapeutic use of PPI + H2 blockers may DECREASE BIOAVAILABILITY of

1) VITAMIN

2) DIGOXIN

3) KETOCONAZOLE 

this is because the acid is required for their absorption 

14

ANTIMICROBIALS used for H. Pylori eradication

1) CLARITHROMYCIN (crows in sketchy

2) AMOXICILLIN (amo box in sketchy) 

3) METRONIDAZOLE

4) TERACYCLINE 

 

-to document infection with H. Pylori --> do

1) endoscopic biopsy of the ulcer margin,

2) serolgic tests OR

3) Urea breath tests: 

-eradication of H. pylori results in rapid healing of active peptic ulcers and low recurrence rates  

15

UREASE BREATH BEST

-used to diagnose Helicobacter Pylori infection 

1. Subjects are given urea labelled with 13C orally

2. H. pylori produces UREASE, which hydrolyses the labelled urea to 13CO2 and ammonia

3. 13CO2 is dissolved in the blood and transported to the lungs

4. Exhaled 13CO2 is analyzed --> the presence of H. pylori results in an increase in the ratio of 13CO2: 12CO2 in expired breath 

16

FIRST + SECOND LINE REGIMEN for eradication of H. Pylori

FIRST LINE: TRIPLE THERAPY, regimen for at least 4 WEEKS

1) 2 ANTIBIOTICS

2) PPI

-clathithromycin + amoxicillin, or clarithromycin + metronidazole both = 70=85% eradication rate

SECOND LINE THERAPY: QUADRUPLE THERAPY for 4 weeks

1) BISMUTH (a mucosal protective agent)

2) 2 ABX (Metro + tetracycline) 

3) PPI OR RANITIDINE

-second line therapy has a 75-90% eradication rate 

17

MUCOSAL PROTECTIVE AGENTS

1) SUCRALFATE

2) BISMUTH SUBSALICYLATE

3) MISOPROSTOL

 

"Sugar Latte's By Mouth and Miso Soup" all help with mucosal protection

18

SUCRALFATE MOA

"sugar-late" --> binds all the shitty girls = the necrotic tissue --> needs to be ACIDIC (hot) or else they won't like them (ie can't be given with an H2 blocker or PPI)

is a mucosal protecting agent that undergoes polymerization and selective binding to NECROTIC TISUE where it acts as a barrier to acid 

-it also stimulates PROSTAGLANDIN SYNTHESIS 

Note: sucralfate is INEFFECTIVE with action of H2 receptor blockers or PPI 

--> it requires acidic pH to be activated therefore it should NOT be administered simultaneously with H2 blockers, PPI, or other antacids 

19

BISMUTH THERAPEUTIC ACTIONS

-appears to have some antimicrobial effect on H Pylori

--> when it is admisisterd along with metronidazole and tetracycline, ulcer healing rate increases to 90% 

20

MISOPROSTOL 

MISO SOUP of PROSTaglandins for Every1

--> AEs include DIARRHEA + ABORTIONS --> soup makes everything come out AND irritates bowel!!!

-a muucosal protective agent that is a PROSTAGLANDIN E1 ANALOGUE that 

1) DECREASES ACID SECRETION

2) STIMULATES MUCIN + BICARB PRODUCTION

Clinical Uses: approved for PREVENTION OF GASTRIC ULCERS induced by NSAIDS, but it is LESS EFFECTIVE than H2 blockers or PPI in acute cases 

ADVERSE EFFECTS: 

1) DIARRHEA in up to 30% of patients

2) ABORTIONS --> d/t induction of uterine contractions during pregnancy, therefore it is contraindicated in pregnancy

3) Exacerbations of inflammatory bowel disease 

21

GERD TREATMENT

NON-PHARMACOLOGICAL: 

-small meals, weigh loss, avoid bed-time acid rich drinks, elevate head of the bed to 6-8 inches and lifestyle modifications (smoking, alcohol) 

DRUGS: 

1) PPI +/- H2 blocker

22

PROKINETIC DRUGS USED IN GI DISORDERS

1) NEOSTIGMINE/BETHANECHOL 

2) METOCLOPRAMIDE 

3) CISAPRIDE

4) ERYTHROMYCIN

23

METOCLOPRAMIDE

"Metro-cop Ride" --> Serotonin3 and Dopamine receptor blocker (blocks the good things b/c is a cop), but allows the "4" to be an agonist 

AE: they always PARK, SLEEP, and POOP in the wrong places (parkinsons, sedation, and diarrhea all d/t dopamine

-is a PROKINETIC DRUG that performs as a 5-HT3 and D2 receptor blocker

-The prokinetic activity of metoclopramide is mediated by muscarinic activity via 5-HT4 receptor agonist activity.

--> It accelerates gastric emptying and intestinal motility.

USES: 

1) DIABETIC + POST-OP GASTROPARESIS

2) ANTIEMETIC (reduces nausea and vomiting associated with chemo agents)

3) RELIEF OF SX OF GERD

-At HIGHER DOSES, 5-HT3 antagonist activity may also contribute to the anti-emetic effect.

ADVERSE EFFECTS: are d/t ANTI-DOPAMINERGIC effects = sedation, diarrhea, and Parkinsonian effects which limit its high-doses and long-term use

24

CISAPRIDE

"CIS PRIDE" --> like metro cop ride but is the CIS, so can drive fast (4 wheels for HT4 agonist) --> stimulates ACh secretion etc... but because CIS agents work so hard, their adverse effect = arrhythmia 

-5-HT4 AGONIST --> stimulates ACh secretion 

USES:

1) GASTROPARESIS

2) GERD

3) CONSTIPITION 

AEs: ARRYTHMIAS

25

NEOSTIGMINE

-is a CHOLINOMIMETIC 

USES:

1) COLONIC PSEUDO-OBSTRUCTION in hospitalized patients

26

BETHANECHOL

-a CHOLINOMIMETIC

-is resistant to cholinesterdase, has a long duration of action

USES:

1) POST-OP BOWEL + BLADDER atony

27

ERYTHROMYCIN

-is a MACROLIDE antibiotic that acts as a PROKINETIC AGENT 

--> is a MOTLIN RECEPTOR AGONIST

USES:

1) GASTRIC EMPTYING before upper GI endoscopic procedures

Tolerance may develop in gastroparesis

 

28

ANTIEMETIC AGENTS

a) 5-HT3 inhibitors – Ondansetron (Zofran)

b) H1 antihistamines & antimuscarinics

Diphenhydramine & Scopolamine
c) Corticosteroids – Dexamethasone
d) NK1–receptor blocker – Aprepitant
e) D2 Receptor antagonist – Prochlorperazine f) Benzamide – Metoclopramide
g) Marijuana – Dronabinol (Marinol)

29

ONDANSETRON

"little chemo girl on the "jumbo-tron" dancing... dancing on 2 legs and has 1 arm up = serotonin 3 receptor

5-HT3 INHIBITOR/ANTAGONIST in the GUT + CNS

USES:

1) CHEMOTHERAPY INDUCED moderate-severe emesis or post-op nausea/vomiting 

-usually given IV, for prophylaxis given orally 

Note: CORTICOSTEROIDS can be combined with ondansetron to provide a GREATER ANTI-EMETIC EFFECT

30

DIPHENHYDRAMINE

CYCLIZINE

MECLIZINE

H1 ANTIHISTAMINES

-are moderately effective in motion sickness + chemotherapy induced nausea/vomiting