Pharmacology of Nausea And Vomiting Flashcards
Families of drugs used to tx nausea/vomiting
Serotonin (5-HT3) Receptor Antagonists Neurokinin (NK1) Receptor Antagonists Histamine (H1) Receptor Antagonists Dopamine (D2) Receptor Antagonists Muscarinic (M1) Receptor Antagonists Cannabinoid Receptor Agonists
Glucocorticosteroids (e.g., dexamethasone) and Benzodiazepines (e.g., alprazolam/lorazepam) are also commonly utilized
5-HT3 receptor antagonists
Dolasetron
Granisetron
Ondansetron
Palonosetron
5-HT3 receptor antagonist NOT utilized for N/V because it is only indicated for IBS-D
Alosetron
Strength and MOA of 5-HT3 receptor antagonists for N/V
Strong anti-emetic agents
MOA: blockade of 5-HT3 receptors at vagal nerve terminals; blocks signal transmission to CTZ [blocks receptor activation after serotonin release from intestinal enterochromaffin cells]
Therapeutic uses for 5-HT3 receptor antagonists in terms of N/V
CINV
RINV
PONV
NVP
Adverse effects of 5-HT3 receptor antagonists
CNS - headache
GI - constipation/diarrhea
MOST WORRISOME = dose-dependent QT prolongation and Torsade’s (extreme caution required when using with other QT-prolonging agents or in patients with electrolyte imbalances
Which 5-HT3 receptor antagonist drug is considered highest risk for the AE of QT prolongation and Torsade’s?
Dolasetron — no longer recommended for CINV prophylaxis
All 5-HT3 receptor antagonists have short half-lives, except ________ and sustained release formation of ________
Palonosetron
Granisetron
Drug interactions with 5-HT3 receptor antagonists
QT-prolonging agents
Antiarrhythmics
Neurokinin (NK1) receptor antagonists
Aprepitant Fosaprepitant Netupitant Fosnetupitant Rolapitant
_______, and its prodrug _______, are NK1 antagonists that are only used in combination with ________
Netupitant; Fosnetupitant; Palonosetron (5HT3 receptor antagonist)
Strength and MOA of NK1 receptor antagonists
Moderate antiemetic agents
MOA: blockade of NK1 (substance P) receptors in CTZ/VC
Therapeutic uses of NK1 receptor antagonists
CINV - most effective when used in combo with glucocorticosteroid and 5-HT3 antagonist
Prophylaxis of PONV — only aprepitant! - given up to 3 hours prior to anesthesia induction
What is the only NK1 receptor antagonist that is utilized for prophylaxis of PONV?
Aprepitant
adverse effects of NK1 receptor antagonists
GI - dyspepsia, constipation, diarrhea
CNS - dizziness, fatigue, somnolence
Which NK1 receptor antagonists have longer half-lives?
Netupitant
Rolapitant
What pharmacokinetic property of NK1 receptor antagonists is important to remember regarding drug interactions?
NK1 receptor antagonists exhibit mild-moderate inhibition of a few key CYP450 enzymes
Histamine (H1) receptor antagonists
Diphenhydramine Dimenhydrinate Hydroxyzine Promethazine Meclizine Cyclizine
______ is an H1 receptor antagonist administered with _______ as initial therapy for NVP
Doxylamine; pyridoxine (B6)
Strength and MOA of histamine receptor antagonists
Weak antiemetic agents
MOA: blockade of histamine-1 receptors in VC and vestibular system; agents exhibit varying levels of central anticholinergic properties at level of CTZ
Therapeutic uses of histamine receptor antagonists
Idiopathic, mild N/V
PONV
NVP (doxylamine+B6)
Motion sickness/vertigo (meclizine, cyclizine)
CINV - as add-on therapy only
RINV - as add-on therapy only
Adverse effects of histamine receptor antagonists
Drowsiness (CNS depression) Dry mouth Constipation Urinary retention Blurred vision Decreased BP
[note classic anticholinergic effects]
IV administration of which histaminen receptor antagonist requires dilution and lower dose than the oral form?
Promethazine
What drug interactions should be considered when giving histamine receptor antagonists?
Other agents that induce anti-cholinergic related side effects, as these will become cumulative
D2 receptor antagonists
Phenothiazines: chlorpromazine, perphenazine, prochlorperazine
Other: metoclopramide
Strength and MOA of dopamine receptor antagonists
Weak-to-moderate antiemetic agents [originally developed as anti-psychotics]
MOA: block D2 receptors in CTZ, exhibiting varying levels of anticholinergic properties
______ is a D2 receptor antagonist with the additional MOA of stimulating ACh actions in GI tract, enhancing motility and increasing lower esophageal sphincter tone
Metoclopramide
Therapeutic uses of D2 receptor angatonists
Idiopathic, mild N/V
Gastroparesis/dysmotility (metoclopramide)
PONV
NVP
CINV and RINV - often as part of combination therapy
Adverse effects of dopamine receptor antagonists
Drowsiness (CNS depression) Dry mouth Constipation Urinary retention Blurred vision Hypotension (arrhythmias and extrapyramidal SE’s (EPS) are possible - usually seen with larger (psychiatric) doses)
[note classic anticholinergic effects]
Potential drug interactions with dopamine receptor antagonists
Other agents that also induce anticholinergic-related side effects (cumulative)
Antiarrhythmics (esp. QT-prolonging agents)
Anti-hypertensives
Muscarinic (M1) receptor antagonist used for N/V
Scopolamine
Strength and MOA of M1 receptor blocker Scopolamine
Weak antiemetic agent - most commonly utilized for motion sickness
MOA: Blockade of muscarinic receptors in neural pathways from the vestibular nuclei in inner ear to brainstem and from reticular formation to VC — significant anticholinergic properties!
Adverse effects of muscarinic receptor blockers
Drowsiness (CNS depression) Dry mouth Constipation Urinary retention Blurred vision
[note classic anticholinergic effects]
Interactions with M1 receptor blockers
Other agents that also induce anticholinergic related side effects
Cannabinoid receptor agonists utilized for N/V and their controlled status
Dronabinol (C-III)
Nabilone (C-II)
Strength and MOA of cannabinoid receptor agonists
Strong antiemetic agents - reserved for treatment-resistant CINV
MOA: stimulation of cannabinoid receptors - stimulates predominantly-central (CB1) and predominantly-peripheral (CB2) cannabinoid receptors in VC/CTZ - exert transduction effects through GPCRs —> decreased excitability of neurons
Therapeutic uses of cannabinoid receptor agonists
CINV — d/t FDA scheduling, commonly reserved for treatment-resistant clinical scenarios; can be given in combo with other agents
Appetite stimulation in select (anorexic/cachectic) pts due to severe disease (e.g., cancer or AIDS)
Adverse effects of cannabinoid receptor agonists
Euphoria/irritability (emotional lability) Vertigo Sedation Impaired cognition/memory Alterations in perception of reality Xerostomia Sympathomimetic (increased HR/BP) Appetite stimulation
Pharmacokinetics of cannabinoids
Dronabinol —a large first-pass effect and metabolized to ONE active metabolite
Nabilon — metabolized to SEVERAL active metabolites - so it has longer MOA than Dronabinol
Both have short-time to onset of activity and a long duration of action (24-36 hours)
Interactions with cannabinoid receptor agonists
Caution in use with other CNS depressants, CV agents, and sympathomimetics
What organizations provide guidelines on treatment of CINV?
National Comprehensive Cancer Network (NCCN)
American Society of Clinical Oncology (ASCO)
Typical high-emetogenic regimen for CINV
3-drug regimen including:
- NK1 receptor antagonist
- 5-HT3 receptor antagonist
- Corticosteroid (dexamethasone)
Give regimen on the day of, and prior to, chemotherapy AND for 3 days after chemotherapy
Options for supplementing the typical high-emetogenic regimen for CINV
May add olanzapine (D2 receptor antagonist)
May add cannabinoid in treatment resistance
Typical moderately-emetogenic regimen for CINV
2-drug regimen including:
- 5-HT3 receptor antagonist
- Corticosteroid (dexamethasone)
Give regimen on the day of, and prior to, chemotherapy AND for 2 days after chemotherapy
Options for supplementing typical moderately-emetogenic regimen for CINV
May add NK1 antagonist or olanzapine, if necessary
May add cannabinoid in treatment resistance (after going up to 3-drug regimen)
Typical low-emetogenic regimen for CINV
1-drug regimen including one of the following:
Corticosteroid (dexamethasone)
5-HT3 receptor antagonist
Metoclopramide
Prochlorperazine
Give regimen day of, and prior to, chemotherapy for acute N/V
Typical minimal-emetogenic regimen for CINV
0-drug regimen! No routine prophylaxis therapy recommended
However, like all CINV drug regimens, therapy must be provided for breakthrough N/V for all patients, and for anticipatory N/V as needed
Breakthrough emesis regimen
The general principle of breakthrough treatment is to add one agent from a different class to current regimen
N/V drugs used for motion sickness
Scopolamine
Dimenhydrinate
Meclizine
N/V drugs used for vertigo
Meclizine
Cyclizine
N/V drugs used for diabetic gastroparesis
Metoclopramide
Drugs used for pregnancy-induced N/V
- Vitamin B6, histamine antagonist+B6, or 5-HT3 antagonist
- Dopamine antagonist
- Steroid or different dopamine antagonist