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Drugs in Pharmacology > 93 - Anti-emetics > Flashcards

93 - Anti-emetics Flashcards

1
Q

Nausea measurement is subjective. It can be associated with changes in ____ and _________ as a biomarker.

A

EGG;

vasopressin release

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2
Q

______________ is the final destination to cause nausea. _______ and ______ receptors are present.

A 
Vomiting centre (VC);
NK1 and opioids
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3
Q

Nucleus tractus solitarius (NTS) may receive signals and send them to the vomiting centre. Which 4 receptors are present?

A
  1. 5-HT3
    - vagal (5-HT3) and sympathetic afferents
  2. D2
  3. M
    - Glossopharyngeal and Trigeminal afferents (gagging in pharynx)
  4. H1
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4
Q

What receptors are present in the area of postrema? (AP)

AP receives signals and send them to the vomiting centre.

A
  1. Opioid
  2. 5-HT3
    - from blood-borne emetics (cytotoxic drugs, opioids, L-DOPA,…)
    - from stomach, small intestine (5-HT3) due to local irritants (cytotoxic drugs, CUSO4, radiation, bacteria)
  3. D2
    - vagal (5-HT3) and sympathetic afferents
  4. M
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5
Q

2 sources of stimulating the higher centres, thus the vomiting centre.

A
  1. Sensory input (pain, smell, sight)

2. Memory, fear, dread, anticipation

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6
Q

Inner ear (motion) aminoglycosides might stimulate H1 and M receptors in the _________, and thus the vomiting centre.

A

Hypothalamus

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7
Q

List the 3 ways to remove toxins from GI tract.

Briefly describe them.

A
  1. Gastric lavage
    - in unconscious patients
  2. Emetic drugs
    - in conscious patients with gag reflex within 4 hours of toxin ingestion
    - do not use with distillates or corrosive substances
  3. Activated charcoal
    - used as an adjunct to emesis, binds to many toxins
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8
Q

What is retching?

A

Unsuccessful vomiting movements against a closed glottis.

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9
Q

Which 2 pharmacological classes of drug are used to inhibit nausea/ emesis due to motion sickness > vestibular nuclei?

A
  1. H1 receptor antagonists

2. M1 Muscarinic receptor antagonists

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10
Q

Which 3 pharmacological classes of drug are used to inhibit nausea/ emesis arose from the CTZ (Chemoreceptor trigger zone) = AP (area of postrema)?

A
  1. Dopamine antagonists
  2. 5-HT3 antagonists
  3. Aprepitant
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11
Q

Which pharmacological class of drug are used to inhibit nausea/ emesis arose from visceral afferents due to stimuli from pharynx and stomach?

A

5-HT3 receptor antagonists

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12
Q

Which 2 pharmacological classes of drug are used to inhibit nausea/ emesis arose from the NTS (Nucleus Tractus Solitarius)?

A
  1. Muscarinic receptor antagonists

2. H1 receptor antagonists

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13
Q

Which pharmacological class of drug are used to inhibit nausea/ emesis arose from the vomiting centre?

A

Muscarinic receptor antagonists.

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14
Q

Area of postrema is _______ of the BBB, acted by circulating drugs ______.

A

outside;
directly

Cerebrum, NTS, VC are all inside the BBB.

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15
Q

Which 2 kinds of drugs are used to induce emesis in emergency?

A
  1. Apomorphine
  2. Syrup of Ipecacuanha

(like choking: Ipe-ca-cuan-haaaaa)

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16
Q

How does apomorphine work to induce emesis in emergency?

A
  • Activate D2 receptor at the Area of Postrema (D2 agonist)
  • but is blocked by neuroleptics or drugs that block D2 receptors

Same MAO for L-DOPA, and domperidone

Used in Parkinson’s disease as well

17
Q

How does Syrup of Ipecacuanha work to induce emesis in emergency?

A
  • Contains emetine and cephaline that releases 5-HT from ECF cells (5-HT3 involvement)
  • Worked in GI via vagus nerve or in Area of Postrema when absorbed
18
Q

5 Major drug classes to antagonize emesis.

A
  1. H1 antagonists (motion/pregnancy sickness)
  2. Muscarinic antagonists
    (motion sickness)
  3. 5-HT3 antagonists
    (Chemo-radiotherapy-emesis & PONV)
  4. NK1 antagonists
    (Chemo-radiotherapy-emesis & PONV)
  5. Dopamine antagonists
    - domperidone
    - metoclopramide
    - phenothiazines
19
Q

Cyclizine, cinnarizine and dimenhyrinate are ____________ to stop ____-induced emesis.

A

H1 receptor antagonists;

opioid

20
Q

Promethazine, meclizine are ___________ to stop ______-induced emesis.

A

H1 receptor antagonists;
pregnancy

*Diphenhydramine will become promethazine when used in morning sickness (first time pregnancy)

21
Q

Give to examples of muscarinic antagonist.

What are their actions?

A

Hyoscine, scopolamine;

Block M1 receptor at vestibular nuclei and NTS
For motion sickness.

22
Q

Drugs should be given prior to sickness for motion sickness. Side effects related to muscarinic receptor blockage include:

A

Blurred vision , sedation (calm?), dry mouth, constipation

23
Q

What and where is the action of dopamine receptor antagonists?

A

Blocking D2 receptors at the Area of Postrema

24
Q

What are the 3 potential consequences of nausea and emesis? Give examples for each consequence.

A
  1. Physical
    - fatigue
    - esophageal tears
    - gastric herniation
    - rupture of stitches
  2. Metabolic
    - loss of K+
    - loss of Na+
    - resulting in alkalosis
  3. Psychological
    - aversion to food
    - anticipatory nausea and vomiting
    - discontinuation of therapy.
25
Q

Motion-induced emesis:
Vestibular system (semi-canicular canals and otolith orgnas)
+
Other sensory input like visual memory
>
___ and ____ receptors in the vestibular nucleus.

___ and ___ levels increase during motion.

> CerebellumNTS and Area of Postrema and VC

A

H1 and M1 receptors

Histamine and Acetylcholine

26
Q

Drugs used in motion sickness

A
  1. Hyoscine/ Scopolamine (M)
  2. Diphenhydramine (H, weak M)
  3. Promethazine (H, weak M)
27
Q

____________ is a broad inhibitory anti-emetics. Give 2 examples of it.

A

NK1 blockers / receptor antagonists.

They inhibit the NK1 receptor at dorsal vagal complex at brainstem.

Aprepitant, netupitant

28
Q

CINV = Chemotherapy induced nausea and vomiting.
At high dose, it casues ______induced emesis.

What are the 2 phases of this type of emesis and briefly explain the mechanisms.

A

Cisplatin

  1. Acute phase
    - Cisplatin induced the rapidly-dividing and turn over of GI cells, EC cells disrupted and thus high 5-HT3 released, act on the 5-HT3 receptors on vagus nerve

(5-HT3 involvement in the intensity of emesis)

  1. Delayed phase
    - Cell breakdown products causes amino acid cascade, potential inflammatory mediator release

(Other factors in the intensity of emesis)

29
Q

5-HT3 antagonists can be used in CINV. They are highly selective and have less side effects than metoclopramide.
Give examples of them and briefly describe their actions and locations.

A
  • Block 5-HT3 receptor at vagus nerve and Area of Postrema.
  • Ondansetron, Granisetron
  • Palonosetron (more potent PA 10.5, longer half time)
  • High dose metoclopramide
  • also used for postoperative nausea and and vomiting.
30
Q

What is nabilone?

What is its action?

A

It is a cannabinoid 1/2 receptor agonist.
It is a synthetic cannabinoid,

Endogenous cannabinoids inhibit the release of neurotransmitters via multi-step retrograde signalling pathway; while nabilone potentiates this pathway.

Drugs in Pharmacology (5 decks)

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