L22- GIT Drugs I (anti-emetics)

Question 1

list the many anti-emetic drug categories

Answer 1

• H1 antagonist
• D2 antagonist
• antimuscarinics
• 5HT-3 antagonists
• NK1 antagonists
• corticosteroids
• benzodiazepines
• cannabinoids

Question 2

list the H1 antagonists + indications

Answer 2

diphenydramine
meclizine
cyclizine

motion sickness, postoperative emesis

Question 3

describe MOA of H1 antagonist + indications

Answer 3

• blocks signals from vestibular afferents as well as from brainstem
• motion sickness, postoperative emesis

Question 4

list the D2 antagonists + indication

Answer 4

• promethazine
• droperidol

-motion sickness
(no CINV uses)

Question 5

D2 antagonist MOA and AEs

Answer 5

MOA: antagonism at CTZ (chemoreceptor trigger zone)

AE: extrapyramidal effects

Question 6

(1) is the main antimuscarinic used as an anti-emetic in (2) situations.

Answer 6

1- scopolamine

2- motion sickness, some postoperative n/v

(not first line choice for CINV)

Question 7

CINV =

Answer 7

chemotherapy induced nausea and vomiting

Question 8

CINV:

• (1) is the most associated drug
• (2) first phase
• (3) second phase

Answer 8

1- cisplatin

2- Acute: w/in 24hrs, universally experienced by patients

3- Delayed phase (days 2-5), only affects some patients

Question 9

list the 5-HT3 antagonists

Answer 9

ondansetron (prototype)

granisetron

Question 10

list the target sites for 5-HT3 antagonists

Answer 10

• vagal afferents
• STN
• CTZ
• AP

Question 11

list the uses of 5-HT3 as anti-emetic (include AEs)

Answer 11

• prophylaxis against acute CINV (drug of choice)
• hyperemesis gravidarum (pregnancy)
• not good for delayed CINV, motion sickness
• well-tolerated

Question 12

(1) is the NK1 antagonist, which function as (2) and are used for (3).

Answer 12

NK1- neurokinin
1- Aprepitant / fosaprepitant (parenteral formulation)

2- NK receptor antagonist for substance P

3- prophylaxis against delayed CINV (caused by moderate / highly emetogenic drugs)

Question 13

NK1 antagonists are administered with (1) and has a (2) effect on metabolism.

Answer 13

1- dexamethasone, 5-HT3 antagonist

2- metabolized by CYP3A4 –> affecting warfarin and oral contraceptives

Question 14

list the corticosteroids + indications

Answer 14

• dexamethasone
• methylprednisolone

-CINV, in adjunct

Question 15

describe MOA of corticosteroids + indications

Answer 15

• suppresses periumoral inflammation and PG production

- CINV, in adjunct

Question 16

list the benzodiazepines

Answer 16

• lorazepam
• alprazolam
• diazepam

Question 17

describe benzodiazepine MOA and AEs

Answer 17

-NO intrinsic antiemetic effects

• used as adjunct due to sedative, amnesic, anti-anxiety –> reduces anticipatory component of n/v
• inc GABAa by inc Cl influx

AEs: CNS depression, dependence

Question 18

(1) is the natural cannabinoid that stimulates (2) and is used for (3)

Answer 18

1- Dronabinol (9-tetrahydrocannabinol)

2- CB1 receptors in brainstem

3- prophylaxis in CINV when others aren’t effective

Question 19

Cannabinoids AEs

Answer 19

• palpitations, tachycardia (paranoia)
• vasodilation, hypotension
• conjunctival injection