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Flashcards in Motility d/o Deck (58):
1

What are prokinetics

Drugs that selectively stimulate gut motor function

2

Explain the enteric nervous system

Serotonin is released from EC cells in gut
Distention stimulates intrinsic primary and extrinsic primary afferent neurons
Submucosal IPAN activate enteric neurons responsible for peristalsis and secretory reflex
5HT4 receptors release ACh and promote reflex activity

3

What drugs stimulate GI motility (prokinetics)

Cholinomimetics
Metoclopramide, Domperidone
Macrolides

4

What are the cholinomimetic agents

Bethanecol: stimulates M3 receptors on muscle and myenteric plexus. Tx GERD and gastroparesis
Neostigmine:ACh inhibitor, enhances gastric, small intestine, and colonic emptying

5

What are ADE of cholinomimetics

excess salivation
nausea
vomiting
diarrhea
bradycardia
(cholinergics; SLUDGE)

6

Cholinomimetics can be used for

GERD: used w/ anti-secretory agents if w/ regurg
Impaired gastric emptying: post-op, diabetic gastroparesis, promote advancement of NG tube
NUD: Sx improvement
Prevent vomiting: metoclopramide

7

What id Domperidone

Dopamine antagonist/cholinomimetic used in Canada (not FDA approved in US) to promote postpartum lactation

8

What is Metoclopramide

Dopamine antagonist with prokinetic mechanisms
Inhibit cholinergic smooth muscle stimulation
Increase esophageal peristaltic amplitude
Increase LES pressure
Enhance gastric emptying
-no effect on small or large intestine

9

How does metoclopramide help nausea and emesis

Blocks D2 receptor in the chemoreceptor trigger zone of the medulla

10

ADE of metoclopramide are

CNS: restless, drowsy, insomnia, anxiety, agitation
EPS: dystonia, akathisia, parkinsonian features
Tardive dyskinesia
Elevated PRL: galactorrhea, gynecomastia, impotence, menstrual disorders

11

How does erythromycin (macrolide) affect motility

Directly stimulate motilin receptors on GI smooth muscle
Benefits gastroparesis but tolerance develops fast
Can also be used for an upper GI bleed to empty stomach of blood prior to EGD

12

What meds have an ADE of constipation

Analgesics
Antihistamines, antiparkinsons, phenothiazine, TCA
Antacids w/ calcium carbonate or aluminum hydroxide
Barium sulfate
CCB
Clonidine
Diuretics
NSAIDs

13

Intermittent constipation is best prevented with

high fiber diet
adequate fluid intake
regular exercise
going to the bathroom when you need to

14

If you do not have a specific Dx (and Tx) how do you treat constipation

Diet mod (increase fiber)
Add osmotic laxative (PEG) 2-4 wks
Add stimulant laxative
Lubiprostone
Linaclotide
Opioid antagonists if opioid induced

15

What are some laxatives you can use

Bulk forming
Stool surfactant agents (softeners)
Osmotic laxative: PEG
Stimulants: senna, cascara, bisacodyl
Cl channel activator: Lubiprostone
Guanylate cyclase C agonist: Linaclotide
Serotonin agonist: Tegaserod

16

List agents that soften stool in 1-3 days

Osmotic laxatives: psyllium, polycarbophi, methylcellulose
Emollients: Docusate
PEG: Lactulose, sorbitol

17

List agents that cause soft semi-fluid stool evac in 6-12 hours

Bisacodyl
Senna
Mag sulfate

18

List agents that cause watery evacuation in 1-6 hours

Mag citrate

19

What are bulk forming laxatives

Indigestable hydrophilic colloids that absorb water and cause a bulky, emollient gel that distends the colon and promotes peristalsis
Natural: Psyllium, Methylcellulose (bloating and gas)
Synthetic: polycarbophil

20

What are stool surfactant agents

Soften stool material by mixing aqueous and fatty materials within intestine
Docusate (oral or enema)
Mineral oil (clear viscous oil that lubricates stool but retards water absorption)

21

What is mineral oil used for

to prevent fecal impaction in young kids and debilitated adults
CAUTION: aspiration can lead to lipid pneumonitis
If used long term, can impair A, D, E, K absorption

22

What are osmotic laxatives

Soluble but not absorbable compounds resulting in increased stool liquidity
Colon normally can't concentrate or dilute fecal fluid bc fecal water is isotonic

23

What are non-absorbable sugars or salts

Mag hydroxide (milk of magnesia)-osmotic laxative to Tx acute constipation and prevent chronic
Sorbitol, Lactulose: prevent or treat chronic constipation. sugars are metabolized by colon bacteria and produce flatus and cramps

24

Use Milk of magnesia cautiously long term in

pts with renal insufficiency, risk of hypermagnesemia

25

What are purgatives

Cause rapid water movement into distal small bowel and colon
Mag citrate and Sodium phosphate: empty bowel in 1-3 hours. Stay hydrated!

26

What are some ADE of sodium phosphate

Hyperphosphatemia, Hypernatremia
Hypokalemia, Hyocalcemia
-These can cause arrhythmias or acute renal failure (calcium phonphate deposits in the renal tubules

27

Who should you NOT use sodium phosphate in

Elderly
Renal insufficiency
Cardiac disease
Unable to maintain adequate hydration during bowel prep

28

What is PEG (polyethylene Glycol)

Balanced, isotonic sln made of non-absorbable sugar (PEG) with sodium sulfate/chloride/bicarb, or potassium chloride
Designed so NO significant intravascular fluid or electrolyte shifts occur= Safe for all patients! No cramps or gas!

29

What can PEG be used for

Bowel prep: ingest rapidly (2-4L over 2-4 hours)
Prevent chronic constipation: mix smaller doses w/ water or juice

30

What are cathartics

Stimulant laxatives that induce BM by directly stimulating enteric nervous system, colon electrolyte & fluid secretion

31

Who are cathartics good for

Long term treatment is neurologically impaired, and bed bound patients in long term care facilities

32

Can laxatives be used long term

Long term use is controversial; new studies say it's ok because it is nerve damage that causes constipation, not using laxatives
BUT, if used long term, still need to monitor ADE

33

What are Anthraquinone derivatives

Aloe, Senna, Cascara (natral plants)
They are poorly absorbed, undergo hydrolysis in the colon and produce BM in 6-12 hours (PO) or in 2 hours (per rectum)

34

Chronic use of anthraquinones causes

brown pigmentation of the colon (melanosis coli)
They may be carcinogenic, but no studies prove relation to CRC

35

Senna is used frequently in those that

Have opioid induced constipation

36

What is Bisacodyl (ducolax)

Diphenylmethane derivative to treat chronic constipation
Used with PEG solutions as bowel prep prior to colonoscopy
Induces BM in 6-10 hours (PO) or 30-60 min (per rectum)
Safe for short and long term use bc of minimal systemic absorption

37

How do opioids cause constipation

They decrease intestinal motility leading to prolonged transit time and increased absorption of fecal water

38

What are the two selective agents of the mu-opioid receptor

Methylnaltrexone bromide
Alvimopan and Naloxegol
-They do not cross the BBB
-Inhibit peripheral mu receptors w/o impacting analgesic effects w/in the CNS

39

What are the agents used in opioid induced constipation

Methylnaltrexone: approved for those receiving palliative care for advanced illness.
Alvimopan: short term use in post-op ileus in hospitalized pts s/p bowel resection. 7 days max.
Naloxegol: any opioid induced constipation

40

ADE of mu receptor antagonists are

Methylnaltrecone: Adjust if CrCl <30
Alvimpoan: cardiovascular toxicity
Naloxegol: Adjust dose if CrCl <60. Avoid if w/ hepatic impairment. CI if w/ GI obstruction

41

Treatment goals when treating diarrhea

Manage diet
Prevent excess whater, electrolyte, and acid base disturbances
Provide Sx relief
Treat curab;e causes
Manage secondary disorders

42

Define fever levels

PO: 100.4
Axillary: 1 degree lower
Rectal: 1 degree higher

43

What are key points that spark clinical controversy in regards to diarrhea

Most recommend no solid food or dairy for 24 hours if w/ acute diarrhea
But withholding food is not appropriate in pts / no signs of severe dehydration
Osmotic diarrhea, food may control problem
If it is secretory, diarrhea will persist
If w/ N/V, eat low residue diet for 24 hours. if vomiting persists and not controlled w/ antiemetics, NPO

44

What is in oral rehydration solutions

Carbs
Calories
Na, K, Cl, citrate, bicarb
*Listen to slide 34?

45

What are some antidiarrheals

Antimotility: opioid agonists
Adsorbents: Kaolin pectin, polycrbophil, attapulgite
Antisecretory: colloidal bismuth, bile salt binding resins, octreotide
Bacterial replacement and enzymes

46

Who should NOT use antidiarrheals

Bloody diarrhea
High fever
Systemic toxicity
-risk of worsening underlying condition
-d/c in pts who's diarrhea is worsening despite therapy

47

How do opioid agonists act as antidiarrheals

Increase colonic phasic segmentation activity by inhibiting presynaptic cholinergic nerves in myenteric plexus= increased fecal colonic transit time and fecal water absorption

48

What are the opioid agonist antidiarrheals

Loperamide: does not cross BBB. Not an analgesic, no addiction potential. No tolerance reported (non-Rx)
Diphenopxylate: Rx. No analgesics in regular dose. High dose has CNS ADE. Prolonged use can lead to dependence. Some formulations have atropine in them to discourage overuse. (atropine also an anticholinergic)

49

What do adsorbent antidiarrheals do

Adsorb nutrients, toxins, drugs, and digestive juices. like sponges

50

Colloidal bismuth compounds are

Mucosally protective

51

Who are bile acid binding resins used for

They are normally absorbed in the terminal ileum
In those w/ terminal ileum d/o (crohn's), they have malabsorption of bile salts= colonic secretory diarrhea

52

What are the bile acid binding resins

Cholestyramine, colestipol, colesevelam: decrease diarrhea 2/2 excess fecal bile acids

53

ADE of bile acid binding resins are

Bloating
flatulence
constipation
fecal impaction
Fat malabsorption if they already have low circulating bile acids

54

Do bile acid binding resins interact with other drugs

cholestyramine and colestipol bind a few drugs and reduce their absorption. Wait 2 hours to admin other drugs
colesevelam does not

55

What is octreotide

Somatostatin;
Inhibits secretion of hormones and transmitters (gastrin, CCK, glucagon, GH, insulin, secretin, 5HT)
Reduce intestinal and pancreatic fluid secretion
Slow GI motility and inhibit gallbladder contraction
Reduce portal and splanchnic blood flow
Inhibit secretion of other ant pit hormones

56

Octreotide's usefulness is limited by

it's short half life (3 minutes) when given IV

57

Octreotide is used clinically for

Inhibiting endocrine tumor effects (secretory diarrhea, flushing, and wheezing 2/2 carcinoid or VIPoma)
Other causes of diarrhea (low dose stimulates motility but high dose inhibits): Vagotomy, dumping syndrome, short bowel syndrome, AIDS
-also: inhibit pancreatic secretion value in patients w/ pancreatic fistula, Tx pit tumors and GI bleeding

58

ADE of octreotide are

Steatorrhea
Nausea, abdominal pain, flatulence, diarrhea
Altered fat absorption (inhibits gallbladder contractility)
Hyperglycemia (sometimes hypo-)
Hypothyroid w/ prolonged use Bradycardia