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Flashcards in Lower GI Pharm Deck (13)
1

Serotonin (5-Hydroxytryptamine) Receptor Antagonists

Ondansetron (Zofran)

Block of serotonin (5-HT3) receptors at chemoreceptor trigger zone (CTZ in CNS), solitary tract nucleus, and on visceral afferents (GI tract)

Side effects: CONSTIPATION, QT prolongation so caution if underlying heart condition-hypomagnesemia-hypokalemia

2

Dopamine Receptor Antagonists

Metoclopramide, Prochlorperazine

Blockade of dopamine receptors in CTZ

Side effects: Extrapyramidal symptoms

3

Metoclopramide

D2 antagonist

used for n/v of chemotherapy

4

Prochlorperazine

D2 antagonist

less effective against emetic stimuli in gut, but block of M and H1 receptors increases utility in nausea with motion sickness

Blocking alpha 1 receptors can cause hypotension

5

Antihistamines

meclizine, promethazine, diphenhydramine

First generation agents with good CNS penetration and additional muscarinic receptor blocking actions

Used for motion sickness and less-severe post-op n/v

6

Anticholinergic agents

scopolamine

Usually transdermal

Primary use is prevention and treatment of motion sickness; some efficacy in post-operative nausea and vomiting

7

Dronabinol

Mechanism of action: Unknown, probably related to stimulation of CB1 cannabinoid receptors on neurons in and around area postrema.

8

Substance P Receptor Antagonists

Block the actions of the neurotransmitter substance P at the neurokinin 1 (NK1) receptor that are mediated via vagal afferent fibers to the solitary tract nucleus and the area postrema.

9

Anti-inflammatory glucocorticoids

Possible anti-emetic action via mechanism to suppress peritumoral inflammation and prostaglandin production

10

Benzodiazepines

Sedative, anti-anxiety, and amnestic properties can reduce the anticipatory component of nausea and vomiting

11

Treatment of Nausea and Vomiting of Pregnancy

Ginger (improved nausea compared to placebo but did not decrease episodes of vomiting)

Pyridoxine (Reasonable first-line treatment that is effective in mild to moderate nausea, but no effect on vomiting); Most often used in combination with doxylamine

H1 antagonists (Doxylamine, diphenhydramine, dimenhydrinate, and meclizine): . Acts on the vestibular system to decrease stimulation of the vomiting center

Dopamine antagonists (Second line: Prochlorperazine, Metoclopramide for hyperemesis, Promethazine)

5HT3 antagonists. Oral-IV routes Ondansetron most commonly used agent - greater efficacy in reducing both nausea and vomiting than pyridoxine-doxylamine

12

Side effects of Metoclopramide

movement disorders

13

Side effects of Promethazine

Sedation and dystonic reactions