GI: Prokinetics & Antiemetics

Question 1

What are prokinetics, they are classified into?

Answer 1

Drugs which enhance gi motility and hasten gastric emptying.

1) D2 Antagonists
2) Anticholineasterases(Neostigmine)
3) Motilin Receptor Agonist (Erythromycin)
4) Others: Cusapride (Banned cause c. arrhythmias)
Mosapride and Renzapride
Itopride

Question 2

Prokinetics: Examples of D2 Antagonists drugs wrt GI

Answer 2

1) Metoclopramide
2) Domperidone

Question 3

Prokinetics: D2 Antagonists: Metoclopramide: MOA, Pharmacokinetics

Answer 3

Acts thru Dopaminergic & Serotonergic Receptors
1) D2 Blockage: Stimulation of D2 receptors in gut reduces gi motility and delayes gastric emptying. Metoclopramide blocks the D2 receptors and reverses the effects and thereby increasing gi motility

It also blocks D2 receptors in CTZ (Chemoreceptor trigger zone)

2) Serotonergic Receptors: It is an 5HT4 Receptor agonist which stimulates release of Ach and increase the gi motility.

It is also an 5HT3 Receptor antagonist in high doses and blocks 5HT3 receptors in NTS And CTZ giving antiemetic effects

Pharmacokinetics: Oral Administration, Crosses BBB and Placenta. T1/2 : 3-6hrs. Immeditate action in IV, 30-60mins for Oral

Question 4

Prokinetics: D2 Antagonists: Metoclopramide: Uses & ADRs

Answer 4

GERD
Antiemetics
Preanaesthetic Medication
Endoscopy
Delayed Gastric Emptying

ADRs: Sedation, Restlessness, Anxiety, Darrhoea.
Extrapyramidal Symptoms (EPS) : Dystonia, dyskinesia.
Dopamine receptor blockage-> Increase PL levels -> Gynaecomastia & Galactorrhoea

Question 5

Prokinetics: D2 Antagonists: Drug Interactions

Answer 5

Blocks action of Levodopa

Question 6

Prokinetics: D2 Antagonists: Domperidone: MOA, PhK

Answer 6

D2 Receptor Blocker-> Increases GI motility. Also acts in CTZ (Outside BBB) and acts like Antiemetics.

Question 7

Prokinetics: D2 Antagonists: Domperidone: Uses & ADRs (why better than metoclopramide)

Answer 7

GERD
Antiemetics
Preanaesthetic Medication
Endoscopy
Delayed Gastric Emptying

ADRs: Headache, Dryness of Mouth, darrhoea.
It doesn’t cross BBB so no adrs like in Metoclopramide

Question 8

Antiemetics: Define

Answer 8

Drugs used in prevention and treatment of vommiting

Question 9

Antiemetics: Classification

Answer 9

1) D2 Antagonists (Prokinetics) : Metoclopramide, Domperidone
2) 5-HT3 Antagonists: Ondansetron, granisetron, etc
3) Antimuscarinics: Hyoscine, promethazine, cyclizine
4) Neuroleptics: Chlorpromazine, Prochlorpromazine, Haloperidol
5) Neurokinin receptor antagonists: Aprepitant, fosaprepitant
6) Others: Glucocorticoid, cannabinoids