Antiemetics Flashcards
What is a representative anticholinergic antiemetic?
Scopolamine (Transderm Scop).
What is the mechanism of action of scopolamine?
Blocks cholinergic muscarinic receptors in vestibular apparatus sensory afferent to the vomiting center.
What is scopolamine used for?
Motion sickness, nausea/vomiting (N/V).
What is a key comment about scopolamine?
Best for motion sickness; transdermal patch worn behind the ear for slow absorption.
What are representative antihistamines used for antiemesis?
Dimenhydrinate (Dramamine), promethazine (Phenergan).
What is the mechanism of action of dimenhydrinate and promethazine?
Block histamine receptors; also block cholinergic muscarinic receptors (contributes to antiemetic effect).
What is a key comment about dimenhydrinate?
Sold OTC for motion sickness; co-formulated with CNS stimulant to reduce sedation; requires a driver chaperone due to drowsiness.
What are dimenhydrinate and promethazine used for?
Motion sickness, nausea/vomiting.
What is the additional mechanism of action of promethazine (Phenergan)?
Blocks H1 and weakly blocks dopamine D2 receptors.
What are broader uses of promethazine?
Post-operative nausea/vomiting (PONV), motion sickness, general purpose antiemetic.
What is a key comment about promethazine use?
Broader spectrum; typically used in hospital settings or via prescription.
What is a representative 5-HT3 antagonist?
Ondansetron (Zofran).
What is the mechanism of action of ondansetron?
Blocks effects of serotonin (5-HT) on 5-HT3 receptors.
What is ondansetron used for?
Cancer chemotherapy-induced nausea and vomiting (CCINV); PONV.
What are key comments about ondansetron?
Blocks 5HT from EC/ECL cells in intestinal mucosa.
Acts on 5HT3 receptors on vagal afferents in the GI and chemoreceptor trigger zone (CTZ) that detects toxins.
What is aprepitant used for?
CCINV.
What is a representative NK1 antagonist?
Aprepitant (Emend).
What is the mechanism of action of aprepitant?
Blocks substance P from binding to neurokinin-1 receptors.
What is a key comment about aprepitant?
Important adjunct to combine with 5-HT3 antagonists for highly emetogenic chemotherapy.
What is a representative cannabinoid antiemetic?
Delta-9 tetrahydrocannabinol (Marinol).
What is the mechanism of action of Marinol?
Activates CB1 receptors in the higher brain (cerebral cortex or other).
What is a key comment about Marinol?
Used for CCINV that is refractory to 5-HT3 antagonists, dexamethasone, or aprepitant.
What is a representative benzodiazepine used as an antiemetic adjunct?
Lorazepam (Ativan).
What is the mechanism of action of lorazepam?
Binds to benzodiazepine receptors in the higher brain (cerebral cortex).
