Pharmacology

1. ANTIEMETIC AGENTS
By Dr Zarish Ghafoor

2. • Emesis????
Vomiting (also known as emesis and throwing up) is the
involuntary, forceful expulsion of the contents of one's
stomach through the mouth and sometimes the nose

3. Causes of Emesis
• Adverse effects from medications
• Systemic disorders
• Pregnancy
• Vestibular dysfunction
• Central nervous system infection or increased pressure
• Gastrointestinal obstruction
• Peritonitis
• Radiation or Chemotherapy

4. PATHOPHYSIOLOGY

5. Classification
Histamine 1 receptor
blockers
PromrtahzineDiphenhydramineMeclizine,cyclizine
5HT3 Receptor antagonist Ondansetron, Granisetron, Dolasetron, and Palonosetron.
Prokinetics Metocloperamide,Domperidone
Muscarinic receptor
Blocker
Hyoscine (scopolamine),
Antipsychotics, prochlorperazine, promethazine, thiethylperazine and Droperidol
NK1 Receptor Blocker Aprepitant , Fosaprepitant

6. Histamine 1 Receptor Blockers
MOA : Inhibit histamine receptors in vestibular system and vomiting
centers
Uses:
Morning sickness or motion sickness
Tx of vertigo due to labyrinth dysfunction
Adverse effects:
Drowsiness
Sedation

7. 5HT3Receptor Antagonist
MOA: Blocks 5HT3 Serotonin receptors in CTZ and GIT.
Uses:
Prevention and Tx of chemotherapy induced nausea and
vomiting
Post operative
Adverse effects:
Headache
GI Upset

8. Prokinetics
Metocloperamide
MOA:
D2 receptors antagonist
Activate GI activity
It can cross Blood Brain Barrier
Uses:
Dyspepsia
GERD
Hepatic or Biliary dysfunction
Adverse Effects:
Sedation
Dizziness
Loose stool
Muscle dystrophy
Extrapyramidal effects

9. Domperidone
MOA: Inhibit D2 Receptors
It can’t cross Blood Brain Barrier
Uses:
GERD
Dyspepsia
Hepatic and Biliary
Dysfunction
Adverse Effects:
Dizziness.
Fainting.
Irregular heartbeat.
Lightheadedness.
Loss of muscle control or
balance.
Difficulty speaking.

10. Muscarinic Receptor Blocker
MOA: Inhibits muscarinic receptors on vomiting center and vestibular
system
Uses:
 Prevention of motion sickness.
Adverse Effects:
Dry mouth
Blurred vision
Drowsiness

11. Antipsychotics
MOA: They act mainly as antagonists of the dopamine D2 receptors in
the CTZ but they also block histamine and muscarinic receptors.
Uses:
Severe nausea and vomiting associated with cancer, radiation
therapy, cytotoxic drugs, opioids, anesthetics and other drugs.
Adverse effects:
Sedation
Hypotension
Extrapyramidal effects

12. NK1 receptor antagonists
• Substance P :released by GIT as
well as from vomiting centre
itself.
• Receptor: NK1 receptor
MOA: Aprepitant blocks
substance P (NK1) receptors in the
CTZ and vomiting center.
Aprepitant
Uses:
Emesis caused by cytotoxic
drugs
Adverse Effects:
 Sleepiness
Diarrhea
Weakness
Tiredness
Constipation
Stomach pain
 Heartburn
• Fosaprepitant is a prodrug of
aprepitant,

13. Others
Cannabinoids (nabilone)
MAO: found to decrease
vomiting caused by agents that
stimulate the CTZ.
Adverse Effects
Drowsiness,
Dizziness
Dry mouth
Mood changes
 Postural hypotension
Hallucinations
Psychotic reaction
High-dose glucocorticoids
• MOA: mechanism of action is
not clear
• Uses: emesis caused by
cytotoxic drugs.