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Pharmacology-RALI > Gastrointestinal protectants/prokinetics/antiemetics > Flashcards

Gastrointestinal protectants/prokinetics/antiemetics Flashcards

1
Q

Ranitidine

A
  • Gastric acid reducer
  • MOA: H2RA
  • Has prokinetic effect
  • Gan be given with food (does not effect absorption)
  • Sunstantial first-pass hepatic metabolism
  • Metabolized by the liver
  • Has much less effect on hepatic P-450 then cimetidine

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2
Q

H2RA

A
  • Block histamine receptor on the gastric parietal cell
  • Competative inhibitors of gastric acid secretion (which means they do not decrease gastric acid secretion as well as PPIs)
  • Maximal effect of decreasing gastric acid secretion occurs almost immediately
  • Some prokinetic activity via antiacetylcholinesterase activity (Nizatidine and ranitidine)

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3
Q

Potency order of H2RA

A

Most potent- famotidine

Intermediate potency- nizatidine

Least potent- Cimetidine and ranitidine

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4
Q

Cimetidine

A
  • Gastric acid reducer
  • MOA: H2RA
  • Absorption delayed with food adminstration (unlike others)
  • Metabolized extensively by the liver with extensive first-pass metabolism
  • Marked inhibition of hepatic P-450 enzymes and has been used to decrease severity of acetaminophen toxicity
  • Cimetidine decrease hepatic blood flow by 20%

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5
Q

Which two H2RAs have prokinetic effects?

A

Ranitidine

Nizatidine

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6
Q

Famotidine

A
  • Gastric acid reducer
  • MOA: H2RA
  • Most potent H2RA
  • Longest duration of action of H2RA
  • Gan be given with food (does not effect absorption)
  • Sunstantial first-pass hepatic metabolism
  • Least bioavailable orally (of the H2RAs)
  • Not metabolized by liver (excreted unchanged in urine)

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7
Q

Nizatidine

A

Gastric acid reducer

  • MOA: H2RA
  • Has prokinetic effect
  • Gan be given with food (does not effect absorption)
  • NO first-pass hepatic metabolism
  • Not metabolized by the liver (excreted unchanged in urine)
  • No effect on hepatic P-450

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8
Q

New H2RA- Lafutidine

A
  • additional MOA (NO mediated and histamine independent mechanism)
  • Mucus protective action via capsaicin-sensative sensory nerves

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9
Q

PPI MAO (specifically omeprazole)

A
  • Irreversibly inhibit hydrogen-potasssium ATP on the luminal side of the parietal cell, thus stopping secretion of hydrogen ions into the gastric lumen
  • Omeprazole (a prodrug) susceptible to destruction by gastric acid (so adminsitered in enteric-coated granules which are absorbed in the duodenum)
  • Absorption decreased by food (best to give 1 hour before meal because there is maximal acidity in the parietal cells and thus increase the amount of omeprazole sequestered there).
  • First pass hepatic metabolism and the rest is selectively sequestered in the acidic environment of the parietal cells where it is transformed into the active drug.
  • Takes 2-5 days before maximal acid suppression
  • More effective than H2RAs
  • Inhibit hepatic P-450 enzymes

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10
Q

Sucralfate

A
  • The octasulfate of sucrose combined with aluminum hydroxide
  • Locally acting drug
  • Binds tightly to epithelial cells in the acidic environment of the stomach (especially to the base of erosions or ulcers) and remains for 6 hours (give before antiacid therapy for maximal effect)
  • Protects and stimulates local production of prostaglandins and binding to epidermal growth factor (favors mucosal repair)
  • SE- consitpation
  • Absorbs other drugs
  • Do not give with enteral feeding because it may bind the fat soluable vitamins

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11
Q

Misoprostol

A
  • Prostoglandin E1 analog
  • Antiacid (>)and mucosal protective properties (stimulates secretion of the mucus and bicarbonate and increases gastric mucosal blood flow)
  • Acts directly on parietal cells to inhibit both nocturnal acid secreation and secretion in response to food, pentagastrin and histamine.
  • Rapidly absorbed, first-pass metabolism (liver becomes active form)
  • Short half live, dose frequenty (q8-12hr)
  • SE: diarrhea (due to increased colonic motility), uterine contraction (abortion in pregnant females)

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12
Q

Antiacids

A
  • Numerous durgs PO to neutralize gastric acid
  • Dont prevent or treat GUE due to short half life compared to H2RA and PPI
  • Can delay or prevent absorption of other drugs

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13
Q

GI protects drug chart

A
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14
Q

Maropitant

A
  • Antiemetic
  • Neurokinin-1 Receptor Antagonist (NK-1), which blocks the action of substance P in the CNS as well as at peripheral NK-1 receptors in the GIT
  • SE- bone marrow hypoplasia when adminsitered to puppies
  • First-pass metabolism (higher bioavailability when given SQ/IV then PO)
  • Other possible effects include- antiinflamamtory, neuroproectant, hepatoprotectant, antitumor.
  • Will decrease visceral pain and reduce MAC during anesthesia (IV)

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15
Q

Ondansetron (+ granisetron, dolasetron)

A
  • Antiemetic
  • 5-HT3 Receptor Antagonists, competatively blocks seratonin (5-HT3) receptors which are both found peripherally (intestinal vagal afferent input- many in the GIT) and centrally (in the CRTZ) and meduallary vomiting center (MVC)
  • Metabolized by the liver [Dolansetron is metabolized to the active form (hydrodolasetron) by ubiquitous carbonyl reductase
  • Eleminated by hepatic P-450, then in urine and bile
  • Ondansetron will decrease the efficacy of tramadol

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16
Q

Metoclopramide

A
  • Antiemetic/Prokinetic
  • MOA: antidopaminergic activity and blocks 5-HT3 receptros = blocker of CRTZ (less effective in cats due to the dopamine receptors portion of action).
  • Prokinetic activity increases gastric emptying and decrease gastroesophageal reflux
  • Prokinetic effects may also be because of incresed sensitivity of the smooth muscle in the small intestins to the effects of acetylcholine
  • Better as CRI, light sensative
  • Excerted by kidneys

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17
Q

Promazine Derivatives

(Chlorpromazine, Prochlorperazine, Acepromazine)

A
  • Antiemitic
  • MAO- broad spectrum, centrally acting antiemtics (effective against all but inner ear disease). Antidopaminergic and antihistamine effects that block the CRTZ (MVC at higher doses). Aslo have anticholinergic, antispasmodic and alpha-adrenergic blocking effects
  • SE: vasodilation/hypotension (due to the aplpha-adrenergic blockage), may also increace CVP and change heart rate +/- arrythmias (dog)
  • Metabolized by liver (can cause CNS side effects if hepatic insufficiency- especially with PSS)

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18
Q

Anticholinergic Agents

(Aminopentamide)

A
  • Antiemetic
  • MOA: anticholinergic- there are cholinergic recptors in the brain involved in the vomiting center and in the upper GIT via the vagus nerve (muscarinic receptors)
  • Less effective then metoclopramide and far inferior than 5-HT3 and NK-1 antagonists

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19
Q

Trimethobenzamide

A
  • Antiemetic
  • MOA: antidopamiinergic properties
  • Weak antiemetic in dogs

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20
Q

Steroids as antiemetics?

A
  • Often used in human chemo patients
  • May have some effect- think of the IBD cat

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21
Q

Other (less common) antiemetics?

A

1) Megestrol acetate
2) Gabapentin
3) Propofol
4) Acupuncture

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22
Q

Peripherally acting antiemetics

A
  • Soothe inflammed mucosal lesions - ex- bismuth subsalicylate or barium sulfate
  • decrease dyspepsia (or indigestion)- ex) antacid or gastric acid reducing drugs

Overall much less effective

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23
Q

Cisapride

A
  • Prokinetic
  • MOA: 5-HT4 serotonergic agonist (the most effective prokinetic class in vetmed) to increase gastric emptying and to increase gastroesophageal sphincter pressure (it is ineffective on striated muscle), also increase small intestinal motility
  • Tx: GE reflux, decreased gastric emptying, chronic constipation
  • Well absorbed, first-pass metabolism via liver

Japan (Mosapride)- can go IV, less colon effects

Europe (Tegaserod) - increases colonic motility

Europe (Prucalopride)- increases colonic and gastric motility

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24
Q

Cholinomimetic Drugs

(Bethanechol, ranitidine, nizatidine)

A

-Prokinetic, specifically colon

Bethanechol- binds muscarinic receptors to effect receptors throughout the GIT

Ranitidine/Nizatidine- inhibit acetylcholinesterace, better at gastric then colonic motility

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25
Q

Erythromycin

A
  • Prokinetic, AB
  • MOA: stimulates motilin receptors to promote GI motility, also increases lower esophageal sphincter pressure and increases large and small intestinal peristalsis

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26
Q

Antiemetic Chart

A

Pharmacology-RALI (10 decks)

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