GI: Anti-emetics Flashcards
Common causes of emesis
- Infection
- Meds
- Pregnancy
- Dysmotility
- Motion sickness
Areas of body that communicate to cause emesis
- CNS
- Vestibular system
- Chemoreceptor Trigger zone
- GI Tract & Heart
- Vomiting center
targeted in drug therapy
CNS: role in emesis
Anticipatory N/V, e.g., in cancer pts. Triggering memory
Cortex, thalamus, hypothalamus, meninges
Vestibular system: role in emesis
Motion sickness
H1 and M1 receptors- M1 -muscarinic
Chemoreceptor Trigger Zone: role in emesis
Next to VC
Before BBB, so direct exposure to blood – anything toxic goes to this area, VC –> emesis
Chemoreceptors, D2, NK1, 5-HT3 receptors
GI Tract & Heart: role in emesis
Mechanoreceptors, chemoreceptors, 5HT3 receptors
Vomiting Center: role in emesis
In medulla oblongata
Mainly responsible for coordinating – all other areas communicate to VC
H1, M1, NK1, and 5-HT3 receptors
Types of anti-emetics
5-HT3 receptor antagonists
D2 Receptor Antagonists
Antihistamines & Antimuscarinics
5-HT3 receptor antagonists: where are 5HT3 receptors involved in emesis located?
CTZ, GI Tract & heart, VC
5-HT3 receptor antagonists: indications
- Prevention of chemo/radiation induced N/V
- Post-op N/V (PONV)
- Severe refractory hyperemesis gravidum
- Cyclic vomiting syndrome (pedi)
- Viral gastroenteritis (pedi)
5-HT3 receptor antagonists: MOA
Block central and peripheral 5-HT3 receptors
5-HT3 receptor antagonists: absorption
well=absorbed from GI tract
5-HT3 receptor antagonists: 1/2 life
½ life: 4-9h (except palonosetron = 40h)
5-HT3 receptor antagonists: Metabolism
extensive hepatic via CYP2D6 & CYP3A4
5-HT3 receptor antagonists: ADRs
HA, dizziness, constipation, diarrhea
Caution: QTc interval prolongation
5-HT3 receptor antagonists: Agents
- Ondansetron (Zofran)
- Granisetron (Kytril)
- Dolasetron (Anzemet)
- Palonosetron (Aloxi)
Ondansetron (Zofran): formulation and indication
Tablet, ODT, solution: CINV, once or twice; PONV, once
Injection: CINV & PONV, once
5HT3 Antagonist
Granisetron (Kytril) : formulation and indication
Tablet, solution: CINV once
Injection: CINV & PONV once
Transdermal patch: CINV 24h before chemo
(5HT3 antagonist)