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 - aucre galucoma, 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 are contraindications and cautions with metoclopramide?

Answer 5

Significant drug interactions exist.

Question 6

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

Answer 6

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 7

What are adverse effects of metoclopramide?

Answer 7

Can cause tardive dyskinesia (a serious movement disorder, often irreversible). Risk increases with duration of treatment and total cumulative dose.

Drowsiness
Fatigue
Lassitude
Restlessness

Question 8

Metoclopramide is primarily metabolized by which enzyme?

Answer 8

CYP2D6 major and CYP1A2 minor

Question 9

Can metoclopramide be taken during pregnancy and lactation?

Answer 9

May increase prolactin concentrations; hyperprolactinemia may suppress hypothalalmic GnRH = may inhibit reproductive funciton.

Crosses placenta but may be considered for use in pregancy.

Sometimes used to promote milk supply.

Question 10

What are the cost/compliance considerations for metoclopramide?

Answer 10

partial pharmacare coverage.

Question 11

What drug classification is ondansetron?

Answer 11

5-HT3 receptor antagonist = serotonin receptor antagonist

Question 12

What are contraindications for ondansetron?

Answer 12

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 13

What are pregnancy and lactation considerations for ondansetron?

Answer 13

Used in pregnancy (not first line).

Lactation unknown - avoid if possible.

Question 14

What are cost/compliance considerations for ondansetron?

Answer 14

Partial pharmacare coverage. Requires special authority.

Question 15

What enzymes are involved in ondansetron metabolism?

Answer 15

CYP1A2
CYP2C9
CYP2D6
CYP2E1
CYP3A4

Question 16

What are adverse effects for ondansetron?

Answer 16

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

Question 17

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

Answer 17

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