Antiemetic Agents Flashcards
Describe the brainstem “vomiting center”
Coordinates the act of vomiting through CN VIII, X, & networks in the nucleus tractus solitarius
High concentrations of M1, H1, NK1, D2, GABA, & sertonin (5-HT3) receptors
What are the 4 sources of afferent input to the vomiting center?
- “Chemoreceptor trigger zone” (D2, opioid, NK1, & 5-HT receptors)
- Vestibular system (M1 & H1 receptors)
- Vagal & spinal afferent nerves (5-HT receptors)
- CNS
What drug classes are used to relieve vomiting? (6)
Antihistamine-anticholinergics
Benzos
Corticosteroids
5 HT receptor antagonists
Phenothiazines
Substance P/Neurokinin 1 receptor antagonist
What do all 4 of the serotonin 5-HT3 antagonists end in?
“setron”
Do you need to reduce the dose of serotonin 5-HT3 antagonists in geriatric patients or patients w/ renal insufficiency?
Nope!
Which serotonin 5-HT3 antagonist may require dose reduction in patients w/ hepatic insufficiency?
Ondansetron
What is an action of serotonin 5-HT3 antagonists?
May slow colonic transit
Describe the efficacy of serotonin 5-HT3 antagonists for the prevention of delayed N/V (> 24hr after chemo) when used alone
Little to none
How is the efficacy of serotonin 5-HT3 antagonists enhanced?
By combining w/ a corticosteroid & NK-receptor antagonist
What are ADEs of serotonin 5-HT3 antagonists?
HA, dizziness, constipation
QT prolongation (most pronounced w/ dolasetron)
What can other drugs do to the 5-HT3 receptor antagonists?
Reduce hepatic clearance –> increased 1/2 life
What are the actions of substance P/neurokinin 1 receptor antagonists?
Provide relief from delayed emesis a/w emetogenic meds
Possess antidepressant, anxiolytic, & antiemetic properties
What are ADEs of dimenhydrinate (Dramamine - an antihistaminic/anticholinergic)?
Drowsiness, confusion, blurred vision, dry mouth, urinary retention
What are examples of phenothiazines?
Prochlorperazine
Promethazine
Chlorpromazine
What are ADEs of prochlorperazine?
QT prolongation
Sedation
Tardive dyskinesia
What is the MOA of chlorpromazine (a phenothiazine)?
Dopaminergic blocker
Strong alpha-adrenergic blocker
Hypothalamic depression affecting body temp
What do the substance P/NK1 receptor antagonists end in?
“pitant”
Why is dimenhydrinate (an antihistaminic/anticholinergic) problematic in the elderly?
Risk of complications in patients w/ BPH, glaucoma, or asthma
What are examples of butyrophenones?
Haloperidol
Droperidol
What are ADEs of haloperidol?
Sedation
Constipation
Hypotension
What are ADEs of droperidol?
QT prolongation &/or torsade de pointes
*Need 12 lead EKG prior to administration, followed by cardiac monitor for 2-3 hrs after administration
What are examples of benzos?
Alprazolam
Lorazepam
What are benzos used for?
Anticipatory N/V, chemo
What are ADEs of alprazolam?
Dizziness
Sedation
Appetite changes
Memory impairment
What is the MOA of dexamethasone (a corticosteroid)?
Enhance 5-HT3 receptor antagonists
What are ADEs of dexamethasone?
Insomnia
GI sx
Agitation
Appetite stimulation
What are examples of cannabinoids?
Dronabinol
Nabilone
What are the ADEs of cannabinoids?
Somnolence
Xerostomia
Vertigo (Nabilone)
Euphoria (Dronabinol)
What are ADEs of metoclopramide?
Asthenia, HA, somnolence
What is an ADE of olanzapine?
Sedation
Caution in elderly
What is 1st line pharmacologic therapy for N/V in pregnancy?
Pyridoxine w/ or w/out doxylamine
