A.36.Antiemetic agents. prokinetic agents. drugs for IBS Flashcards
list the group of antiemetic agents
- H₁ histamine blockers
- Antimuscarinic agents
- 5-HT₃ receptor blockers
- D₂ dopamine receptor blocker
- NK₁ receptor antagonists
- CB₁ cannabinoid agonist
what is Dimenhydrinate?
H₁ histamine blocker
a combination drug of diphenhydramine and theophylline derivative (reduce sedative effects and abuse liability due to H₁ blockade)
what is the function of Dimenhydrinate and scopolamine as antiemetic agents?
inhibits muscarinic receptors in the vomiting center–> inhibitory effect on the emetic pathway
*in addition to the central and peripheral H₁ blockade effect of dimenhydrinate
how is Dimenhydrinate given?
oral or parenteral
what are the indications for Dimenhydrinate?
motion sickness, Meniere’s disease (vestibular nausea)
antiemetic (chemotherapy-induced)
when do we give scopolamine?
motion sickness (vestibular nausea)
what is scopolamine?
antimuscarinic agent
What is Ondansetron and Palonosetron?
5-HT₃ receptor blockers
how is Ondansetron given?
oral or IV
how is Palonosteron given?
IV
what are the side effects of Dimenhydrinate?
CNS effects
atropine-like effects
𝝰-blockade (orthostatic hypotension)
abuse liability
which antiemetic agents are the most potent?
5-HT₃ receptor blockers (Ondansetron)
what is the duration of action of Ondansetron and Palonosetron?
3-6 hours
what are the indications for giving Ondansetron and Palonosetron?
chemotherapy-induced nausea and vomiting
post-operative nausea and vomiting
side effects of Ondansetron and Palonosetron
constipation
QT prolongation, arrhythmias
serotonin syn. (milder risk than SSRI’s and TCA’s)
what is the function of 5-HT₃ receptor blockers?
block serotonin receptors (excitatory) in the chemoreceptor trigger zone and enteric nervous system
what is the T1/2 of palonosetron?
long
40 hours
what are Metoclopramide and Droperidol?
D₂ dopamine receptor blockers
how are Metoclopramide and Droperidol given?
oral or parenterally
which D₂ dopamine receptor blocker is both an antiemetic and prokinetic agent?
metoclopramide
what is the function of D₂ dopamine receptor blockers?
central effects–> inhibition of dopamine D₂-receptor in the chemoreceptor trigger zone (area postrema)–> anti-nausea and antiemetic action
peripheral effects–> in the GI, dopamine acts as an inhibitor of Ach release–> ↓ this inhibition causes a prokinetic effect
what are the side effects of Metoclopramide?
CNS effects: restlessness, drowsiness, insomnia
extrapyramidal symptoms (drug-induced parkinsonism)
hyperprolactinemia -galactorrhea, gynecomastia, impotence
what are the side effects of droperidol?
CNS depression (additive effect) 𝝰-blockade (orthostatic hypotension)
what are the indications of droperidol?
antiemetic (used in surgical and diagnostic procedures)
*also antipsychotic agent-similar to haloperidol
what is Aprepitant?
NK₁ receptor antagonist
what is the function of Aprepitant
blocks neurokinin receptors in the spinal cord and area postrema–> blocking pain-induced vomiting
how is Aprepitant given?
orally
what are the indications for Aprepitant
chemotherapy induces nausea and vomiting
post-operative nausea and vomiting
Aprepitant is usually given in combination with
dexamethasone and palonosetron
side effects of Aprepitant
fatigue, dizziness
diarrhea
Aprepitant is an inhibitor of..?
cytochrome P450
what is Dronabinol?
CB₁ cannabinoid agonist
what is the function of a CB₁ cannabinoid agonist?
inhibitory CB receptors, act to inhibit the presynaptic release of dopamine
what are the indications for Dronabinol?
chemotherapy-induced nausea and vomiting
AIDS wasting syndrome (appetite stimulant)
side effects of Dronabinol
tachycardia, hypotension
hallucination
reddening of the conjunctiva
what is the commonly used combination drug regimen for chemotherapy-induced nausea and vomiting?
Aprepitant
Ondansetron
Dexamethasone
what are prokinetic agents?
drugs that selectively stimulate gut motor function
when are prokinetic agents contraindicated?
suspected obstructive ileus
indications for metoclopramide
GERD (↑ lower esophageal sphincter tone) conditions with delayed gastric emptying (post-operative, diabetic gastroparesis) non-ulcer (chronic) dyspepsia anti-emetics preparation of upper GI endoscopy post-partum lactation stimulation
list the prokinetic agents
- metoclopramide- D₂ dopamine receptor blocker
- Erythromycin-macrolide antibiotics
- neostigmine -cholinomimetics
what is the function of erythromycin as a prokinetic agent
directly stimulates motilin receptors on GI smooth muscle cells
prokinetic indications of giving erythromycin
gastroparesis
preparation to upper GI endoscopy
what are the side effects of erythromycin
GI symptoms
skin rash
eosinophilia
QT prolongation
prokinetic indication of Neostigmine
postoperative ileus
