IC5 GI Sx (CINV, C&D, mucositis) Flashcards
What are the two phases of CINV and what systems are involved in these phases?
Acute - peripheral pathway (gut)
Delayed - central pathway (CNS)
Briefly describe the pathophysiology of the acute CINV
chemotherapy interacts with enterochromaffin cells of the GI tract causing the release of 5-HT3
stimulates n&v via vagal afferent nerves
Briefly describe the pathophysiology of the delayed CINV
chemotherapy directly affects the vomiting center
causes vagus nerves to release substance P to NK1 receptors
What are the 5 main types of CINV?
acute
delayed
breakthrough
anticipatory
refractory
What is the timeframe for acute CINV?
usually starts within 1-2 hours of administration, peak intensity within 5-6 hours, resolution at 12-24 hours
What is the timeframe for delayed CINV?
peak onset 48-72h after chemotherapy, diminishing after 1-3 days
Define refractory CINV
n&v occurring during subsequent cycles of chemotherapy when antiemetic prophylaxis or rescue therapy has failed in previous cycles
What are the 3 main steps in treating CINV
1) assess emetic risk group
2) assess patient risk factors for CINV
3) select antiemetic combinations
Whats the one important drug combination for high emetogenic risk to remember?
AC combination:
anthracycline (doxorubicin) + cyclophosphamide
What are the 7 patient-specific risk factors for CINV?
- Younger age (<50 years old)
- Female gender
- History of low chronic prior alcohol intake ( <1 glass of alcohol a day)
- History of previous chemotherapy induced emesis
- History of motion sickness
- History of emesis during past pregnancy
- Anxiety
What are the rough combinations for high emetogenic risk for
- day 1
- day 2-4
- Day 1 → NK1 antagonist + 5HT3 antagonist + Dexamethasone +/- Olanzapine
(i.e. Aprepitant + Ondansetron + Dexamethasone +/- Olanzapine) - Day 2 onwards → Dexamethasone D2-4 + Olanzapine D2-4 (if used on day 1)
What are the rough combinations for moderate emetogenic risk for
- day 1
- day 2-3
- Day 1 → 5HT3 antagonist + Dexamethasone
(i.e. Ondansetron + Dexamethasone) - Day 2 onwards → Dexamethasone D2-3
What are the rough combinations for low emetogenic risk
5HT3 antagonist / Dexamethasone / Dopamine angatonist
(Ondansetron / Dexamethasone / Metoclopramide)
What are the neurokinin 1 antagonist drugs and which phase of CINV are they helpful for?
Aprepitant, Netupitant
useful for acute and delayed CINV
What are NK1 antagonist (aprepitant, netupitant) MOA?
binds to NK-1 receptors, preventing substance P (nociceptive neurotransmitter) from binding and attenuates vagal afferent signals to exert antiemetic effect
How should aprepitant (emend) be dosed?
day 1 - 125mg PO
days 2-3 - 80mg PO
How should netupitant (akynzeo) be dosed?
0.5mg on day 1 (single dose)
given w palonosetron
What are the side effects associated with NK1 antagonists (aprepitant, netupitant)?
low frequency of fatigue, weakness, nausea, hiccups
What are the DDIs associated with NK1 antagonists (aprepitant, netupitant)? (4)
steroids
warfarin
benzodiazepines (increases bzd conc due to reduced metabolism)
certain chemotherapy drugs (like ifosfamide (decreases ifosfamide metabolism))
What are the 5HT3 antagonist drugs and which phase of CINV are they helpful for?
Ondansetron, Granisetron, Palonosetron
useful for acute CINV
What are 5HT3 antagonist (ondansetron, granisetron, palonosetron) MOA?
blocks 5HT-3 receptors peripherally in the GI tract and centrally in the medulla (2 pathways)
What is the difference between granisetron and ondansetron
Granisetron is longer acting but more costly
How should ondansetron be dosed?
day 1 - PO/IV 8-16mg OD
day 2-4 - PO/IV 8mg BD (max 16mg)
How should granisetron be dosed?
day 1 - PO/IV 1mg OD
day 2-4 - PO/IV 1mg OM
What are the side effects associated with 5HT3 antagonists (ondansetron, granisetron, palonosetron)? (2+1)
headache and constipation (in 15% of patients)
may cause QTc prolongation (black box warning)
What is the concern when 5HT3 antagonists are given with SSRIs?
5HT3 antagonists may have interactions with SSRIs (serotonin syndrome), but since ondansetron is usually given as a once off dose, evaluate the risk vs benefit (usually not significant)
What is dexamethasone’s place in therapy for CINV?
useful for acute and delayed CINV
How should dexamethasone be dosed?
day 1 - PO/IV 12mg OD
day 2-4 - PO/IV 8mg OD
What are side effects associated with dexamethasone? (4+2)
transient elevations in glucose
insomnia
anxiety
gastric upset
less common ones include psychosis (young pts) and reactication of ulcers
What are two potential counselling points for dexamethasone based on side effects?
If insomnia then counsel to take at night, if GI concerns then take with or after food
What is olanzapine place in therapy for CINV?
useful for acute and delayed CINV
What is olanzapine’s MOA?
Antagonist of multiple receptors involved in CINV (i.e. dopamine, serotonin, histamine, cholinergic)
How should olanzapine be dosed
PO Olanzapine 5-10mg OD (consider 2.5mg for elderly) for 4 days
What are the side effects associated with olanzapine?
fatigue
sedation
postural hypotension
anticholinergic side effects
What DDI is important to take note of for olanzapine?
Olanzapine has a DDI with metoclopramide, category X (both are dopamine antagonists and will result in EPSE and NMS), hence if patient is on high emetogenic risk regimen, they will likely be on olanzapine already and should avoid metoclopramide until day 5