Week 6: Antiemetics and Prokinetics

Question 1

Ondansetron (Zofran) Indications for use and MOA

Answer 1

Indication: ideopathic N/V - non-sedating

5HT3 receptor antagonist - blocks serotonin peripherally on the vagal nerve terminals and centrally in the CTZ

Question 2

5HT3 Receptor Antagonists (Zofran) ADRs

Answer 2

• serotonin syndrome, QT prolongation

Question 3

Dramamine (Meclizine) Indication and MOA

Answer 3

antihistamine - anticholinergic

Indication: Dizziness/spinning

• competes with histamine for H1 receptor sites, blocks the CTZ, and diminishes vestibular stimulation, and depresses labyrinthine functions through its central anticholinergic activity

Dries up the vestibular area - decreases dizziness

Question 4

Dramamine/Meclizine ADRs

Answer 4

• drowsiness
• dry mouth
• blurred vision
• urinary retention
• paradoxical excitation in children may occur

Question 5

Dramamine / Antihistamines cautions/ contraindications

Answer 5

• additive CNS depression when combined with CNS depressants
• avoid in patients with BPH, glaucoma, thickened respiratory secretions d/t anticholinergic effects
• Avoid in elderly patients
• ok in pregnancy- avoid in lactation

Question 6

Scopolamine (Transderm Scop) Indication and MOA

Answer 6

Indication: sea sickness

Anticholinergic drug that blocks the action of acetylcholine at the parasympathetic sites in smooth muscle, CNS and secretory glands

Question 7

Scopolamine ADRs

Answer 7

• drowsiness, dry mouth, blurred vision, urinary retention, dilated pupils

Question 8

Scopolamine cautions/ contraindications

Answer 8

• Avoid in pts with glaucoma, BPH, thickened respiratory secretions d/t anticholinergic effects
• Avoid in pregnancy and lactation
• Not for use in pediatrics
• Avoid in elderly pts

Question 9

Promethazine (Phenergan) and Prochlorperazine (Compazine) MOA

Answer 9

Blocks dopamine receptors in the CTZ as well as cholinergic, alpha 1 adrenergic, and histamine 1 receptors

Question 10

Phenothiazines (Phenergan and Compazine) ADRs

Answer 10

• sedation - agranulocytosis - dry mouth - blurred vision - constipations - bradycardia - hypotension

Compazine is a 1st generation antipsycotic - can cause blood dyscrasias

Promethazine - fatal respiratory depression in children < 2 y/o - should be avoided in pediatrics < 5 y/o

Extra parametal side effects (EPS) such as dystonia, akathisia and tardive dyskinesia

Question 11

Phenothiazines (Phenergan/Compazine) cautions/ contraindications

Answer 11

• additive CNS depression with given with CNS depressants
• avoid in pts with glaucoma, BPH, thickened resp. secretions d/t anticholinergic effects
• avoid in elderly pts
• not safe in pregnancy/lactation
• bradycardia, hypotension (because Alpha 1 receptors are blocked)

Question 12

Dronabinol (Marinol) MOA

Answer 12

Cannabinoids - synthetic THC

-activates CB1 receptors in the brain, which prevents the pro-emetic effects of endogenous compounds such as dopamine and serotonin

Question 13

Dronabinol (Marinol) ADRs

Answer 13

• depression
• dizziness
• paranoid thoughts
• somnolence
• palpitations
• tachycardia
• hypotension

Question 14

Cannabinoids (Dronabinol/Marinol) cautions/ contraindications

Answer 14

• cautions in pts with hx of seizures - decreases the seizure threshold
• monitor pts w/ cardiac dz
• high potential for abuse
• not safe in pregnancy/lactation

Question 15

PROKINETICS: Metoclopramide (Reglan) Indications and MOA

Answer 15

Indication: diabetic gastroparesis, GERD than is not responsive to H2/PPIs

Prokinetic agent - dopamine receptor antagonist in the CNS - stimulates motility in the upper GI tract

Question 16

Metoclopramide (Reglan) ADRs -

Answer 16

• extrapyramidal side effects (tardive dyskinesia)
• depression
• drowsiness
• dizziness
• diarreha
• hypoglycemia

Question 17

Metoclopramide (Reglan) cautions contraindications

Answer 17

• avoid is bowel obstruction is suspected or active
• can cause prolonged QT
• high potential for abuse
• OK in pregnancy - avoid in lactation
• OK in pediatrics