Antiemetics

Question 0

Location of histamine receptors with respect to antihistamines working as an antiemetic

Answer 0

Inner ear (motion) -> Cerebellum(H1) -> medulla ( emetic center)

Pharynx (gagging)->glossopharyngeal and trigem afferents -> solitary tract nucleus(H1) -> medulla

Question 1

Antihistamine - as a group side effects seen

Answer 1

CNS: confusion, dizziness, tinnitus, incoordination, tremors

Anti-muscarinic effects from antihistamines : sedation, urinary retention, blurred vision, exacerbation of narrow angle glaucoma.

Question 3

Scopolamine

Answer 3

Anticholinergic- block at the cerebellum . Info from inner ear and also solitary tract nucleus

Used for motion sickness , post op n/v , no role in chemo induced nausea

Side effects: dry mouth, urinary retention, blurred vision, exacerbation narrow angle glaucoma

Question 4

Promethazine

Answer 4

Antihistamine with wek anti-d2 activity ( motion)

maybe be more effective than cyclizine and Meclizine

Question 6

5-HT3 receptor antagonists blocks what peripherally and centrally

Answer 6

Peripheral - 5-HT released for enterochromaffin of the sm intestine in response to chemo agents that stim vagal efferents

Central : 5-ht receptors in the solitary tract nucleus and area postrema

Question 8

Prochloroperazine

Answer 8

Dopamine receptor antagonist. D2 reports in the chemo receptor trigger zone (area postrema)

Also has some antihistamine and anticholinergic properties

Question 9

Glucocorticoid and ant inflammatory agents

Answer 9

Used in treatment of nausea in pts with wide spread cancer

- may suppress peritumoral inflammation and prostaglandin production

Question 11

Meclizine

Answer 11

Antihistamine

Used exclusively for motion sickness

Question 12

Dopamine receptor antagonist side effects

Answer 12

Sedation, dystonia, orthostatic hypotension , extrapyramidal symptoms, impaired thermoregulation

Question 13

Benzodiazepines

Answer 13

Not effect alone

Cause : sedation, amnesic and anti anxiety properties. Av reduce anticipatory nausea and vomititng

Question 14

Ondansetron

Answer 14

5-HT3 receptor antagonist
- drug persits even aft serum levels have decreased ( take once a day)
- metabolized in the liver by p450 ( decrease dose with liver probs)
-

SE: constipation, diarrhea, headache, minor electrocardiographic changes

Use: chemo,upper abdominal irradiation, hyperemesis in pregnancy

Question 15

Aprepitant

Answer 15

Substance P receptor antagonist

• tachykinin family
• present in vagal afferents inner acting the solitary tract nucleus
• p450

Question 16

Migraine use

Answer 16

Metoclopramide or procholorperazine ( dopamine antagonist )

If nausea alone use adjunct 5-ht antagonist

Question 17

Vestibular use

Answer 17

Antihistamines or anticholinergics

Question 18

Pregnancy use

Answer 18

Nausea : Ginger, vit b6

Hyperemesis: promethazine , 5-HT antagonist , methylprednisolone

Question 19

Gastroenteritis use

Answer 19

First line: da antagonist ( cheaper)

Second lien: 5-HT antagonist

Question 20

Metoclopramide

Answer 20

Dopamine receptor antagonist - area postrema

Pro kinetic agent - coordinated contractions of GI tract that enhance transit

• blocks 5-HT3 receptors centrally and on vagus
• sensitizes muscarinic receptors
• agonist at 5-HT4

**greatest utility is it’s ability to ameliorate the no nausea and vomiting accompany GI dysmotility syndromes

Question 21

Dronabinol

Answer 21

Cannabinoid
- stim CB1 type cannabinoid receptor

CNS effects: sympathomimetic activity, marijuana high, paranoid rxn.

Use : cancer chemo, stimulates appetite

Question 22

Cyclizine

Answer 22

Antihistamine ( H1) and some anti-muscarinic activity

Used exclusively for motion sickness

Question 23

Diphenhydramine

Answer 23

Antihistamine ( motion)

maybe be more effective than cyclizine and Meclizine