Week 6 GI Flashcards by Susan French

Emesis is controlled by the vomiting centre, also known as the:

Central Pattern Generator (CPG)

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Where is the Chemo Receptor Trigger Zone located? (CTZ)

Dorsal surface of the medulla oblongata

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Where does the CTZ (chemo receptor trigger zone) receive input from?

Blood bound drugs and hormones

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What causes blood bound drugs and hormones to stimulate the CTZ (chemoreceptor trigger zone)? (4)

Drugs
Toxins
Chemo
Hypoxia

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What is the medulla oblongata?

Continuation of the spinal cord into the skull
Lowest part of the brain stem
Contains control centres for heart, lungs and CTZ

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What are of the brain is responsible for motion sickness?

Vestibular apparatus

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What area of the brain is responsible for vomiting r/t psychiatric disorders, stress, anxiety, anticipation?

Cerebral Cortex

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What stimulates the visceral afferent nerves in the GI tract to send signals to the vomiting centre? (3)

Distention
Chemo
Radiation

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in the medulla oblongata of the brainstem
has permeable capillaries and sensory neurons
detects circulating chemical messengers in blood and transduces them into neural signals and networks
sensory transducer = integrates blood-to-brain autonomic functions
detection of circulating hormones involved in vomiting, thirst, hunger, and blood pressure control

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Neurotransmitters responsible for N and V are located in? 3()

The vomiting centre
CTZ
GI tract

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The CTZ is composed of?

AP (area postrema)

NTS (nulceus tractus soliatarius)

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What to do 1st to tx Nausea and Vomiting? (4)

1-identify CAUSE
2-identify PATHWAY
3- what neurotransmitter involved? what will act on this?
4- what worked in the past?

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Muscarinic receptors

acetylcholine activates muscarinic receptors, allowing for a parasympathetic reaction in any organs and tissues where the receptor is expressed (parasympathetic, except for sweat glands= sympathetic)

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extrapyramidal sx

Dystonia (continuous spasms, muscle contractions)
Akinesia (motor restlessness)
Parkinsonian sx (rigidity, bradykinesia)
Tremor, tardive dyskinesia

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Drug that can induce heart arrhythmias and cardiac arrest (esp in pt over 60 or dose > 30mg od)

Domperidone

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Which antiemetic drugs have significant anticholinergic effects?

Prochlorperazine

Promethazine

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Drug for motion sickness that causes significant dry mouth?

Scopolamine

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What drug should be given pre- nausea?

Ondansetron
(serotonin 5- HT3 antagonists)

** take too long to work

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Individual factors affecting emetogenic potential of chemo drugs:

Hx of motion sickness
> 50 years old
Female
Anxiety
Absence of heavy alcohol use
Poor performance status

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Things that can effect emetogenic potential:

Infusion time (longer time= less nausea)
Dose (higher dose= worse)
Number of drugs

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Chemo drug with very high emetogenic potential?

Cisplatin > 50mg

Best antiemetics for CINV:

Type 5 – HT3 (serotonin) receptor antagonists
Neurokinin – 1 receptor antagonists
Glucocorticoids

When does delayed emesis occur after chemo?

> 24 hours

usually with Cisplatin

Aprepitant is a?

Dose?

NK1-R receptor antagonist

80 mg po daily on day 2 and 3
Side effect: fatigue

First choice for DELAYED CINV?

Dexamethasone | 4-8 mg PO BID

Side effects of dexamethasone?

Agitation Insomnia Hyperglycemia

How long should PPIs take to be effective?

4-8 weeks

Red flag sx for GERD needing endoscopy followup urgently

``` Vomiting bleeding abdominal mass unexplained weight loss bleeding choking dysphagia ```

Goals of GERD therapy? (5)

``` reduce/eliminate sx heal esophageal mucosa prevent recurrence prevent complications identify triggers ```

What are some medications that may help with GERD but have side effects that limit their use?

Metoclopromide Domperidone Baclofen (increases LES tone)

Why should tablet formation of bismuth subsalicylates be avoided with concurrent h. pylori therapy?

Contains calcium bicarbonate and decreases effectiveness of tetracycline abx

5 causes of GERD?

``` LES pressure changes impaired esophageal clearance delayed gastric emptying hiatus hernia lifestyle/ diet ```

Tx goals for GERD

- Reduce/eliminate sx - Heal esphageal mucosa - Prevent recurrence - Prevent complications - Identify triggers

Causes of peptic ulcer disease?

- - ZES - - H Pylori - - NSAIDS - - Smoking - - Alcohol - - Ischemia - - Bile acids - -stress (non-ulcer dyspepsia) - - genetics

Duodenal ulcers are sometimes relieved by?

Eating (food in stomach)

Gastric ulcers are sometimes releived by?

Not eating (acid is then secreted in duodenum instead)

Which NSAIDS are the highest and lowest risks?

Highest= Piroxicam, indomethacin, ketoralac Lowest risk= low dose ibuprofen

When are H2RAs NOT recommended?

H2RA are not recommended for use in erosive esophagitis, H. | pylori related ulcers or NSAID induced ulcers

Which PPI is the most expensive with possilble increase side effects?

Dexlansoprazole

Dexlansoprazole causes...

Increased risk of adverse events • Increased risk of nonfatal serious events • Increased risk of cardiovascular events in Dex 30 • Increased risk of injury-related adverse events

In which conditions is BID dosing of PPIs recommended in primary care?

gastric acid hypersecretory conditions H. pylori eradication therapy

Examples of hyergastrinemia states?

Gastric outlet obstruction Gastric dysmotility states ZES (Zollinger-Ellison Syndrome)

Why is BID dosing of PPI not recommended?

Hasn't demonstrated consistent clinical benefit.

Drugs approved for 8 week tx to heal errosive esophagitis?

dexlansoprazole 60mg | esomeprazole 40mg

PPI not working try?

Changing to different PPI or change to BID (try to taper down after effective)

BID PPI may be considered in the following pts? (2)

- Patients with severe sx despite standard OD PPI dosing | - Severe esophagitis (confirmed by endoscopy)

Which PPI has the most CYP450 drug interactions?

Omeprazole Pantoprazole = the least

Meds used to tx TB

Rifampin (plus) isoniazid ethambutol pyrazinamide

Risk associated with statin therapy? (2)

Rhabdomyolysis | myopathy

Ways to prevent rhabdomyolysis and myopathy from statin tx?

Avoid adding cytochrome P450 3A4 inhibitors to statins metabolized by CYP3A4 (atorvastatin, lovastatin, simvastatin) Interupt statin tx for short period when interacting drug required (i.e. macrolide) Reduce statin dosage if interacting drug needed (i.e. Simvastatin 20mg with amiodarone). Switch to statin with lower pharmakokinetic interactions (Pravastatin) Watch for muscle related sx (muscle pain, weakness, dark urine) Avoid combos (i.e. fibrate with statin)

True or False: Fibrates WITH statins reduce risk of CHD events?

False

Classic triad for rhabdomyolysis?

myalgia, weakness, and tea-colored urine