GI Medications Flashcards by Kelly K

What are patient factors that relate to PONV?

women
non-smokers
hx motion sickness
hx PONV

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What are surgical factors that relate to PONV?

length of surgery
laparotomies & laparoscopies
gynecologic
ENT
breast
orthopedic

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What are anesthesia factors that relate to PONV?

inhalation agents
nitrous oxide
neostigmine
narcotics
etomidate

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Where is the vomiting center located?

medulla oblongata

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How does the vomiting center work?

efferent pathways > vagal sympathetic and parasympathetic chains > motor response

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Where are signals transmitted from?

chemoreceptor trigger zone
vestibular apparatus
thalamus and cerebral cortex
neurons in GI tract

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What are the neurotransmitters and corresponding receptors that are involved with PONV?

dopamine: dopamine receptors
serotonin: 5HT3 receptors
acetylcholine: muscarinic receptors
histamine: histamine receptors
substance P: neurokinin receptors

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What anticholinergics are used to treat PONV?

scopolamine
atropine
hyosine

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What benzamides are used to treat PONV?

metoclopramide

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What benzodiazepines are used to treat PONV?

midazolam

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What butrophenones are used to treat PONV?

droperidol
haloperidol

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What cannabinoids are used to treat PONV?

dronabinol
nabilone

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What glucocorticoids are used to treat PONV?

dexamethasone

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What 5HT3 antagonists are used to treat PONV?

ondansetron
dolasetron
granisetron
palonosetron
ramosetron
tropisetron

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What neurokinin-1 antagonsists are used to treat PONV?

aprepitant
fosprepitant

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What phenothiazines are used to treat PONV?

promethazine, prochoperazine, chlorpromazine

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What is the mechanism of action of Scopolamine?

thought to block transmission from vestibular apparatus to medulla

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What is the dose of Scopolamine?

5 mcg/hr for 72 hours
*best if given 4 hours before stimulus

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What is Scopolamine used to treat?

motion sickness
PONV from middle ear surgery
N/V from PCA or epidural morphine

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What are the side effects of Scopolamine?

visual disturbances
*dilated pupils

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What is the mechanism of action of Metoclopramide?

stimulate the GI tract via CHOLINERGIC mechanism and ANIT-DOPAMINERGIC effect

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What patients do we use caution with Metoclopramide?

RLS
Parkinson’s
*due to anti-dopamine effects

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What is the mechanism of action of Midazolam?

thought to decrease the stimulation and release of dopamine in the CRTZ

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When should Midazolam be given if using to treat PONV?

at the end of the case

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What is the mechanism of action of Droperidol?

competitive dopamine antagonist

What are the receptor and ligands for Droperidol?

receptor: D1 ligands: dopamine & GABA

What is the dose of Droperidol?

0.625 mg (initial) 1.25 mg (rescue)

What patients do we use caution with Droperidol?

RLS Parkinson's *due to anti-dopamine effects

What is a critical side effect of Droperidol?

QT prolongation *seen in high doses

What is the mechanism of action of Dexamethasone?

inhibits prostaglandin release and controls endorphin release

What is the dose of Dexamethasone?

4 mg

What patients do we use caution with Dexamethasone?

diabetic patients and obese *due to potential hyperglycemia

What kind of receptor is a 5HT3?

ligand-gated ion channel (Na & K) inotropic excitatory

What other body functions does serotonin affect?

mood, cognition, sleep

What other effects does serotonin have?

addiction aggression vasoconstriction increased intestinal motility learning and memory consolidation

What are 5HT3 antagonists used to treat?

PONV N/V due to chemotherapy *does not work for motion sickness, no 5HT3 receptors in the vestibular apparatus

What is the dose of Ondansetron?

4 mg

What is the onset of Ondansetron?

30-60 minutes

What are the side effects of Ondansetron?

headache QT prolongation diarrhea

Why does Ondansetron have very few CNS effects?

does not cross BBB

What is Tropisetron used to treat?

symptoms of carcinoid syndrome

What is the dose and duration of Granisetron?

dose: 0.1 mg duration: 24 hours

What is special about Dolasetron?

has an active metabolite

What is Substance P?

primary neurotransmitter produced by pain/temperature afferent peripheral neurons

What is the mechanism of action of Aprepitant?

competitive antagonist at NK1 receptors

What is Aprepitant used to treat?

N/V due to chemotherapy

What is a critical side effect of Aprepitant?

can inhibit steroidal birth control for 7-10 days

What is the mechanism of action of Promethazine?

antagonizes H1 (histamine) and M1 (acetylcholine) receptors

Where are H1 receptors located?

vascular smooth muscle bronchial smooth muscle CNS

What are some H1 receptor antagonists?

Diphenhydramine (Benadryl) Dimenhydrinate (Dramamine) Loratadine (Claritin) Hydroxyzine (Atarax) Promethazine (Phenergan)

Where are H2 receptors located?

stomach

What are some H2 receptor antagonists?

famotidine

Where are H3 receptors located?

presynaptic nerve terminals *reduces further histamine release

What is the mechanism of action of H1 antagonists?

competitively blocks H1 receptors

What is the dose of Diphenhydramine?

25-50 mg

What is the onset and duration of Diphenhydramine?

onset: 3 minutes duration: 1-7 hours

What receptors does Dymenhydrinate block?

H1 & M1 (vestibular apparatus) *effective against motion sickness and as a sleep aid

What is a critical side effect of Promethazine?

orthostatic hypotension *adrenoceptor blocking action potentiates anesthetic sedative effects

What are H1 receptor antagonists used to treat?

allergic reactions motion sickness N/V of pregnancy (Promethazine)

What patients are at increased risk of aspiration?

pregnant women diabetics mask induction (no protected airway) emergency cases

What is the mechanism of action of antacids?

removes H+ ions neutralize gastric pH

What is the duration of action of antacids?

about 30 minutes

What are side effects of antacids?

increase gastric volume change the metabolism of other drugs

What antacid is used prior to cesarean sections? What is the dose and when is it given?

Bicrita 15-30 mL immediately before induction

What are some H2 receptor antagonists?

Cimetidine (Tagamet) Ranitidine (Zantac) Famotidine (Pepcid) Nizatidine (Axid)

What is the mechanism of action of H2 antagonists?

selectively and reversibly block histamine at H2 receptors

What are H2 antagonists used to treat?

peptic duodenal ulcer gastric ulcer erosive esophagitis hypersecretory conditions

What are critical side effects of Cimetidine?

*CNS dysfunction in elderly (slurred speech, delirium, confusional states) *liver toxicity

Do H2 antagonists cross the placenta and enter breastmilk?

Yes! *can affect the baby

What drugs when given with Cimetidine can lead to toxicity due to a decrease in hepatic blood flow and inhibition of the P450 system?

Warfarin Dilantin Propranolol Metoprolol Labetalol Quinidine Caffeine Lidocaine Theophylline Alprazolam Diazepam Flurazepam Triazolam Carbamazepine Ethanol Tricyclic antidepressants Calcium channel blockers

What are some proton pump inhibitors?

Omeprazole Pantoprazole Esomerprazole Lansoprazole

What is the effect of proton pump inhibitors?

increase gastric fluid pH decrease gastric fluid volume

What type of drug is Omeprazole?

prodrug *becomes PPI after metabolism

What is the onset of Omeprazole and when is it best taken in regards to surgery?

couple of days night before surgery

Does Omeprazole cross the BBB?

Yes! Can cause headaches, agitation, confusion

What is Omeprazole specifically used to treat?

Zollinger-Ellison syndrome

What is the mechanism of action of Metoclopramide?

cholinergic stimulation & dopamine antagonism increasing lower esophageal sphincter tone, enhancing peristaltic contractions, accelerating the rate of gastric emptying

Does Metoclopramide cross the BBB?

Yes! also affects CRTZ

What is the dose of Metoclopramide?

10-30 mg

What patients do we use caution with Metoclopramide?

RLS Parkinson's patients on MAOI or tricyclic antidepressants GI surgery patients taking phenothiazines or butrophenones (r/t dopamine)

Does Metoclopramide change gastric pH?

No!

What is Metoclopramide used to treat?

diabetic gastroparesis antiemetic GERD enteral feeding assist in chronically ill

What are the side effects of Metoclopramide?

placental transfer abdominal cramping extrapyramidal effects (anti-cholinergic) prolonged succinylcholine effect (inhibits plasmaesterase synthesis)

What are anticholinergic side effects?

red as a beet (flushed skin) dry as a bone (dry eyes, mouth, & skin) blind as a bat (dilated pupils, blurry vision) mad as a hatter (confusion, agitation) hot as a hare (overheating) full as a flask (urinary retention)