Module 2: Nausea & Vomiting

Question 1

What are differentials to consider with N/V?

Answer 1

CNS - head injury, ICP, migraine
GI - functional (gastroparesis, IBS), obstruction, organic (appendicitis, PUD etc.)
Infections - bacterial, viral, toxins
Metabolic - adrenal, diabetic, ketoacidosis, thyroid, uremia
Misc - acute glaucoma, AMMI, renal, pain, psych and eating disorders
Pregnancy, post-op, cannaboid hyperemesis syndrome, chemo, medication-induced.

Question 2

What are the steps in managing nausea and vomiting?

Answer 2

1. Etiology - treat underlying cause
2. Correct complications of N/V including fluid depletion and electrolyte imbalance
3. Targeted therapy for known etiology of symptom management

Question 3

When is a dopamine antagonist preferred for treatment of N/V?

Answer 3

When N/V associated with GI irritation or delayed gastric emptying for its prokinetic (speeds up movement effects (e.g. metoclopramide)

Question 4

When is a serotonin antagonist more effective for tx of N/V?

Answer 4

N/V triggered by the chemoreceptor trigger zone (CTZ) = located in the brainstem, detects chemicals in the blood and cerebrospinal fluid.

Question 5

What is the dose and duration for Metoclopramide in N/V tx?

Answer 5

IV: 10-20mg as single dose; avoid rapid administration in doses >10mg

PO: 10mg as a single dose. Repeat after 4-6 hours if needed.

Question 6

What are the cost/compliance considerations for metoclopramide?

Answer 6

partial pharmacare coverage.

Question 7

What drug classification is ondansetron?

Answer 7

5-HT3 receptor antagonist = serotonin receptor antagonist

Question 8

What are contraindications for ondansetron?

Answer 8

Serotonin syndrome, particularly when used with other serotonergic agents. S&S include mental status changes, autonomic instability, neuromuscular changes, GI symptoms, and/or siezures.

Cautious of derivatives containing benzyl alcohol for risk of toxicity (gasping syndrome).

Question 9

What are pregnancy and lactation considerations for ondansetron?

Answer 9

Used in pregnancy (not first line).

Lactation unknown - avoid if possible.

Question 10

What are cost/compliance considerations for ondansetron?

Answer 10

Partial pharmacare coverage. Requires special authority.

Question 11

What enzymes are involved in ondansetron metabolism?

Answer 11

CYP1A2
CYP2C9
CYP2D6
CYP2E1
CYP3A4

Question 12

What are adverse effects for ondansetron?

Answer 12

• constipation
• headache
• QT prolongation (increased with IV route)

Question 13

What is the dose and duration for ondansetron in the treatment of non-specific N/V?

Answer 13

PO/IV/IM: 4-8mg single dose, may repeat 4-8mg q4-8hrs