Pharm: Anti-emetics

Question 1

Best question to ask any woman of child bearing age that presents with nausea.

Answer 1

Time of last menses

Question 2

What are the 3 phases of emesis?

Answer 2

1. Pre-ejection (gastric relaxation, retroperistalsis)
2. Retching (rhythmic respiratory action w/ abdominal contraction)
3. Ejection (contraction of upper abdominal muscles and relaxation of UES)

Question 3

Where is the vomiting center?

Answer 3

Chemoreceptor Trigger Zone (CTZ) in the area postrema

Question 4

Where does the vomiting center send efferent signals?

Answer 4

Medulla

-medulla then sends the necessary efferents elsewhere

Question 5

Atropine

Answer 5

MOA: strong muscarinic and cholinergic antagonist

Ends up being used more as a poison than therapy, causes Cardiovascular collapse and respiratory failure

Question 6

Scopolamine

Answer 6

MOA: M1 muscarinic antagonist

Uses: prophylaxis for motion sickness

Contraindicated: in patients w/ glaucoma

Question 7

Meclizine

Answer 7

MOA: H1 antagonist

Uses: motion sickness

Question 8

Where are most of the muscarinic and H1 receptors located that allow these drugs to treat motion sickness?

Answer 8

Vestibular apparatus.

Question 9

Prochlorperazine

Answer 9

MOA: D2 antagonist

Uses: N/V associated with chemotherapy and migraines

Adverse Effects: excess Prolactin (MAIN), parkinsonism, Tardive Dyskinesia, dementia

Question 10

Droperidol

Answer 10

MOA: D2 antagonist

Uses: major tranquilizer with antiemetic properties

Not used anymore

Question 11

Haloperidol

Answer 11

MOA: D2 antagonist

Uses: major tranquilizer with antiemetic properties

Not used anymore

Question 12

Metoclopramide

Answer 12

MOA: increases ACh receptor sensitivity to enhance gastric motility and increase emptying

Uses: Nausea in pregnancy, gastroparesis

Adverse Effects: Tardive Dyskinesia

Question 13

Where are most of the D2 receptors that allows the anti-emetics to work?

Answer 13

Area postrema, pharynx, GI tract

Question 14

Ondasetron

Answer 14

MOA: 5-HT3 antagonist

Uses: emesis in chemotherapy, radiation, pregnancy

Adverse Effects: high dose leads to QT prolongation

Question 15

How do 5-HT3 antagonists prevent N/V?

Answer 15

5-HT3 is a receptor that inhibits secretion and motility in the GI tract. These drugs encourage digestions to prevent vomiting. Over activation of these receptors also send signals that excite the vomiting center.

Question 16

Aprepitant

Answer 16

MOA: Neurokinin 1 antagonist

Uses: oral dose to prevent N/V in chemotherapy

Question 17

Fosaprepitant

Answer 17

MOA: Neurokinin 1 antagonist

Uses: IV dose to prevent N/V in chemotherapy

Question 18

Bethanechol

Answer 18

MOA: muscarinic agonist

Uses: urinary retention, rarely used in GI for motility

Adverse Effects: may induce respiratory constriction in pts. with asthma

Question 19

Neostigmine

Answer 19

MOA: AChase inhibitor

Uses: Olgivie Syndrome (pseudo-obstruction in colon), paralytic ileus

Adverse Effects: cholinergic effects

Question 20

Physostigmine

Answer 20

MOA: AChase inhibitor

Uses: Olgivie Syndrome (pseudo-obstruction in colon), paralytic ileus

Adverse Effects: cholinergic effects

Question 21

Erythromycin (GI use)

Answer 21

MOA: stimulates motilin release from M cells

Uses: diabetic gastroparesis, upper GI bleeds

Question 22

Dexamethasone

Answer 22

MOA: glucocorticoid

Uses: anti-emetic in cancer hospice settings

Question 23

Dronabinol

Answer 23

MOA: cannabinoid receptor agonist

Uses: anti-emetic

Question 24

Midazolam, Lorazepam

Answer 24

MOA: binds and enhances GABA receptors

Uses: nausea

Adverse Effects: sedation and resp. depression