Anti Nauseants

Question 1

What are the causes of nausea/ vomiting?

Answer 1

Bugs
(Food Poisoning/ Transmission)
–Often better to let them run their course & maintain hydration.

Question 2

Drugs that cause N/ V?

Answer 2

1. Chemotherapy Induced N/V (CINV)
   - -Chemotherapy agents target rapidly dividing cells in the GI tract, as well as increases GI peristalsis leading to increased N/V.
2. Post- operative N/V (PONV)
   - Common post surgical complication
   - Occurs due to multiple factors- not just anesthetics
3. Dopaminergic’s
4. Opioids

Question 3

What is the Emetogeic Scale?

Answer 3

A scale that measures the capability of a drug to producing vomiting.

Question 4

Key areas mediating N/V include?

Answer 4

Within the BBB:

• The Emetic Centre
• The Nucleus Tracts Solitarius (NTS)

Outside of the BBB:

• The Chemoreceptor Trigger Zone (CTZ)
• 5-HT3 and Muscarinic Receptors in the gut

Question 5

Dimenhydrinate (Gravol):

Answer 5

H1 Antagonist

• Blocks receptors in the NTS and the inner ear, and inhibits stimulation of the emetic centre.
• Drugs that blocks receptors in the inner ear (H1 and/ or M) are also useful for motion sickness
• Has anti- cholinergic effects (reduces peristalsis in the GI tract)

Various Routes of Administration: Oral, rectal and parental (injection or infusion)
*When treating for motion sickness, must allow time for absorption (minimum 30 minutes)

Side Effects:
-Drowsiness (help patients sleep)
Anti- cholinergic side effects including dry mouth.

Question 6

Scopolamine

Answer 6

-Muscarinic Antagonist
-Targets receptors in multiple areas
CNS: Inner ear (for motion sickness) and well as the NTS and CTZ
Gut: Reduces peristalsis
*Can be administered in patch form
-Readily crosses plasma membranes

Question 7

Ondansetron:

Answer 7

Serotonin 5-HT3 Antagonist

• 5-HT plays a key role in CINV
• 5-HT3 antagonists were breakthrough drugs in treating CINV

Question 8

Where are Serotonin (5-HT) receptors located?

Answer 8

5-HT receptors are located in:

• -The Gut: Peristalsis; Signal Nausea
• -The CNS: NTS and CTZ

Question 9

Dexamethasone:

Answer 9

Corticosteroid

• Mechanism isn’t well understood & is typically reserved for extreme N/V
• Useful in cases with raised ICP (reduces inflammation)
• Systemic corticosteroids have significant side effects, so should only be used for SHORT TERM.

Question 10

Aprepitant:

Answer 10

Neurokinin-1 (NK-1) Antagonist

• NK-1 receptors mediate N/V in both the emetic centre in the CNS and the CTZ
• Most used for CINV

Side Effects: Hiccups, Anorexia and Fatigue

Question 11

Metoclopramide/ Domperidone

Answer 11

D2 Antagonists

Question 12

Prochlorperazine

Answer 12

Phenothiazine (D2 Antagonist)

Question 13

Haloperidol

Answer 13

D2 Antagonist
(Butyrophenones)
-Also used as anti-psychotics

Question 14

Cannabinoids:

Answer 14

Including marijuana, have been used for many years for N/V

• Also stimulate appetite “munchies”
• Likely to reduce anxiety associated with N/ V

Question 15

Benzodipazepines

Answer 15

Unlikely to have a direct anti- nauseant effect
-Address anxiety associated with N/V

Example: Patients with CINV may be anxious about after receiving their last round of chemo.

Question 16

Treating Nausea Associated with Pregnancy (NVP):

Answer 16

“Morning Sickness” which can occur all day

• NVP is very common and can be severe
• Relatively few drugs are well established and considered safe during pregnancy…
• -Pyridoxine (Vit B6)
• -Diclectin (H1 antagonist)
• -Dimenhydrinate (H1 antagonist)