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Gastrointestinal > Nausea And Vomiting: Antiemetics > Flashcards

Nausea And Vomiting: Antiemetics Flashcards

1
Q

What are the 3 stages of emesis?

A
  1. Nausea - unpleasant sensation prior to vomiting
  2. Retching - spasmodic respiratory movements that generate the pressure gradient
  3. Vomiting - contraction of muscles in abdomen and chest wall and then evacuation of the stomach contents through the mouth
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2
Q

What 4 areas of the brain provide feedback to the vomiting center?

A
  1. Chemoreceptor trigger zone: detects toxins and chemicals
  2. Vestibular system: motion
  3. Stomach, intestines: irritation and distension
  4. Higher centers: anxiety, pain, hormones, smell, sight, learned nausea, migraine, tumor, ICP
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3
Q

What receptor types are present in the 4 areas associated to vomiting?

A
  1. Vomiting center: H1, M1, NK1, and 5-HT3 receptors
  2. Chemoreceptor trigger zone (CTZ): D2, NK1, 5-HT3 receptors
  3. Vestibular system: H1 and M1 receptors
  4. GI and heart: mechanoreceptors, chemoreceptors, 5-HT3 receptors
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4
Q

Which neurotransmitters are involved in vomiting (5)?

A
  1. Acetylcholine - M1 receptors - vestibular system and vomiting center
  2. Serotonin - 5-HT3 receptors - GI, heart, CTZ, vomiting center
  3. Dopamine - D2 receptors - CTZ
  4. Histamine - H1 receptors - vestibular system and vomiting center
  5. Substance P - NK1 receptors - CTZ, vomiting center
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5
Q

General MOA of antiemetics?

A

Receptor antagonists acting at the vomiting center receptors

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6
Q

What are the risk factors that increase likelihood of post-operative nausea and vomiting (PONV)? (11)

A
  1. Age less than 50
  2. Female
  3. Nonsmoker
  4. Hx of PONV or motion sickness
  5. Hydration status
  6. Use of general anesthesia
  7. Use of volatile anesthetics
  8. Nitrous oxide
  9. Use of opioids
  10. Type of surgical procedure (laparoscopic, gynecological, cholecystectomy)
  11. Duration of surgery
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7
Q

What are the risk assessment thresholds for PONV?

A

0-1 risk factors = lowest risk, 10-20%
2-3 risk factors = moderate risk, 30-40%
3-5 risk factors = highest risk, 50-80%

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8
Q

What agents can you use for PONV prior to surgery? (2)

A
  1. Aprepitant

2. Scopolamine

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9
Q

What agents can be used for PONV at the induction of surgery? (4)

A
  1. Dexamethasone
  2. Methylprednisone
  3. Palonosetron
  4. Promethazine
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10
Q

What agents can be used for PONV at the end of surgery? (4)

A
  1. Dolasetron
  2. Droperidol
  3. Granisetron
  4. Ondansetron
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11
Q

Selective Serotonin (5-HT3) Receptor Antagonists (Agents, MOA, PK, Pregnancy, Indications)

A

Agents: ondansetron, granisetron, dolasetron, palonosetron

MOA: Selectively inhibits 5-HT3 receptors peripherally on the vagal nerve terminals, and centrally in the CTZ and vomiting center

PK: Onset 30 minutes. t1/2: 3-7 hours. Duration unknown.

Pregnancy: B

Indications: Chemotherapy-induced N/V, PONV, radiation N/V

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12
Q

Selective Serotonin (5-HT3) Receptor Antagonists (ADRs and DDIs)

A

ADRs: Headaches, dizziness, constipation, prolonged QT interval (more pronounced with dolasetron)

DDIs: Combining drugs that prolong QT interval (antiarrhythmics, antipsychotics, antidepressants) may result in ventricular arrhythmias. Combining SSRIs and SNRIs may result in serotonin syndrome.

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13
Q

Substance P/Neurokinin-1 Receptor Antagonists (Agents, MOA, PK, Pregnancy, Indications)

A

Agents: Aprepitant, Fosaprepitant, Rolapitant

MOA: Selectively antagonizes substance P and neurokinin-1 (NK1) receptors in the brain; enhances efficacy of 5-HT3 receptor antagonists

PK: Onset known. t1/2: 9-13 hours. Duration unknown.

Pregnancy: N/A

Indications: Chemotherapy-induced N/V, PONV

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14
Q

Substance P/Neurokinin-1 Receptor Antagonists (ADRs, Considerations, DDIs)

A

ADRs: fatigue, dizziness, diarrhea, constipation (aprepitant)

Considerations: may decrease effectiveness of birth control

DDIs:

  • CYP3A4 inhibitors (grapefruit) INCREASE levels and toxicity risk
  • CYP3A4 inducers (St. John’s wort) DECREASE levels and lower efficacy (decreased antiemetic effect)
  • Warfarin effectiveness may be decreased; monitor INR
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15
Q

Antihistamines (Agents, MOA, PK, Pregnancy, Indications, ADRs, DDIs, Considerations)

A

Agents: diphenhydramine, dimenhydrinate, meclizine

MOA: Inhibitors of H1 receptors

PK: Onset 15 minutes. t1/2: 1-4 hours. Duration 6-8 hours.

Pregnancy: B

Indications: allergy symptoms, motion sickness, Parkinson’s disease, nighttime sleep aid

ADRs: dizziness, dry mouth, sedation

DDIs: N/A

Considerations: Meclizine for VERTIGO. Dimenhydrinate is the less sedating than diphenhydramine.

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16
Q

Antimuscarinic (Agents, MOA, PK, Pregnancy, Indications, ADRs, DDIs, Considerations)

A

Agents: Scopolamine

MOA: Inhibition of M1 receptors

PK: Onset 4 hours. t1/2: 9.5 hours. Duration: 72 hours.

Pregnancy: N/A

Indications: motion sickness, PONV

ADRs: dizziness, dry mouth, mydriasis

DDIs: N/A

Considerations: Use patch 1 hour before activity. Useful for cruises. Patient needs to wash hands after applying patch to make sure does not get into eyes.

17
Q

Phenothiazines (Agents, MOA, PK, Pregnancy, Indications, ADRs, Considerations, DDIs)

A

Agents: Prochlorperazine, promethazine, thiethylperazine

MOA: Competes for binding to dopamine, muscarinic, and histamine receptors

PK: Onset 15-60 minutes. t1/2 unknown. Duration less than 12 hours.

Pregnancy: B

Indications: allergies, motion sickness, N/V

ADRs: sedation, dermatitis, dry mouth, dizziness

Considerations: Avoid alcohol, activities that require mental alertness. May cause orthostatic HTN.

DDIs: Cocurrent use with mesoridazine may result in increased QT interval

18
Q

Butyrophenones (Agents, MOA, PK, Pregnancy, Indications, ADRs, Considerations, DDIs)

A

Agents: Droperidol, haloperidol

MOA: Exact mechanism unknown. Competitively inhibits D2 receptors.

PK: Onset 20 minutes: t1/2: 2 hours. Duration 2-4 hours.

Pregnancy: C

Indications: general anesthesia, N/V

ADRs: sedation, constipation, EPS, QT prolongation (droperidol), may impair heat regulation (haloperidol)

Considerations: Patients should be advised to report EPS.

DDIs: Cocurrent use with mesoridazine may result in increased QT interval

19
Q

Substituted Benzamides (Agents, MOA, PK, Pregnancy, Indications)

A

Agents: metoclopramide, trimethobenzamide

MOA:
Metoclopramide - dopamine receptor antagonist
Trimethobenzamide - dopamine receptor antagonist and weak muscarinic antagonist

PK:
Metoclopramide - Onset 30-60 min. t1/2: 5-6 hours. Duration 1-2 hours.
Trimethobenzamide - Onset 10-40 min. t1/2 7-9 hours. Duration 3-4 hours.

Pregnancy: N/A for both agents

Indications:
Metoclopramide - chemotherapy-induced N/V, PONV, gastroparesis, GERD
Trimethobenzamide - PONV

20
Q

Substituted Benzamides (ADRs, DDIs, Considerations)

A

ADRs:
Metoclopraminde - headache, somnolence, EPS. BLACK BOX - tardive dyskinesia.
Trimethobenzamide - dizziness, somnolence, hypotension

DDIs:
Metoclopramide - cocurrent use with vitex may result in decreased effectiveness of metoclopramide
Trimethobenzamide - N/A

Considerations:
Metoclopramide - report worsening depression, suicidal ideation; avoid alcohol and activities that require mental alertness
Trimethobenzamide - avoid alcohol and activities that require mental alertness

21
Q

Benzodiazepines (Agents, MOA, PK, Pregnancy, Indications, ADRs, DDIs)

A

Agents: lorazepam, diazepam

MOA: GABA-A receptor agonist and enhances inhibitory signals in the CNS

PK: Onset 1-3 minutes. t1/2: 12 hours. Duration: 6-8 hours

Pregnancy: D

Indications: chemotherapy-induced N/V, anxiety

ADRs: dizziness, sedation

DDIs: concomitant use of benzodiazepines and opioids may result in profound sedation, respiratory depression, coma, and death

22
Q

Step treatment of PONV (9)

A
  1. Determine if patient is low, moderate, or high risk
    A. Moderate/high risk- use prophylactic antiemetics, add propofol and hydration, and avoid the use of nitrous oxide
    I. Moderate- 1 or 2 drugs from different classes
    II. High- 2 or more drugs from different classes
    a. Benzodiazepines can decrease anxiety before procedure
    b. Scopolamine patch can be given in the evening before surgery or 2 hours prior
    c. NK-1 antagonists should be given during induction
    d. At the end of surgery, gold standard treatment is ondansetron
    e. if patient experience N/V after being given prophylactic treatment of ondansetron + dexamethasone, they should be given rescue therapy from a different drug class such as phenothiazine, metoclopramide, or droperidol
23
Q

Treatment guide for acute and delayed chemotherapy-induced N/V

A 
Acute N/V (day 1)
High risk: 5-HT3 + dexamethasone + NK1
Moderate: PALO + dexamethasone
Low: dexamethasone or 5-HT3 or D2RA
Minimal: as needed
Delayed N/V (days 1-3)
High risk: dexamethasone + NK1
Moderate: dexamethasone
Low: as needed
Minimal: as needed
24
Q

Corticosteroids (Agents, MOA, PK, Pregnancy, Indications, ADRs, DDIs, Considerations)

A

Agents: dexamethasone

MOA: synthetic adrenocortical steroid with potent anti-inflammatory effects. Antiemetic mechanism is unknown, but enhances 5-HT3 receptor antagonism.

PK: t1/2: 1-2 hours. Duration: 12-36 hours.

Pregnancy: N/A

Indications: chemotherapy-induced N/V, asthma

ADRs: HTN, abnormal vision

DDIs: concurrent use with fluoroquinolones may result in an increased risk of tendon rupture

Considerations: avoid live vaccines

25
Q

Cannabinoids (Agents, MOA, PK, Pregnancy, Indications, ADRs, DDIs)

A

Agents: dronabinol, nabilone

MOA: synthetic THC analogues. Mechanism of antiemetic action is not well understood.

PK: Onset 30-60 minutes. t1/2: 24-36 hours. Duration: 4-6 hours.

Pregnancy: N/A

Indications: chemotherapy-induced N/V, PONV

ADRs: abdominal pain, dry mouth

DDIs: N/A

26
Q

5 categories of chemotherapy-induced N/V (5)

A
  1. Acute: within 24 hours of treatment
  2. Delayed: less than 24 hours after treatment
  3. Anticipatory: prior to treatment, learned condition, or psychological response that occurs in ~25% of patients by 4th cycle of chemotherapy
  4. Breakthrough: emesis occurs despite prophylactic administration of antiemetics and requires rescue antiemetics
  5. Refractory: poor response to multiple antiemetic regimens, need to rule out other potential causes of N/V such as brain metastases, electrolyte imbalances, infections, uremia, treatment with opioids, anxiety, or bowel obstruction
    The primary goal of emesis prevention is no nausea and/or vomiting throughout the period of emetic risk. Prophylaxis should be provided through the entire period of risk; moderate risk = 2 days prophylaxis; and high risk = 3 days prophylaxis
27
Q

Step treatment in Chemotherapy-induced N/V (8)

A
  1. Prophylaxis of acute CINV: 5-HT3 RA, NK1RA, olanzapine, and dexamethasone
  2. Moderate emetogenic regiment: 2 drugs (5-HT3 RA and dexamethasone)
  3. Highly emetogenic regimen: 3 drugs (5-HT3 RA, NK1RA, dexamethasone)
  4. Delayed CINV: prevent by treating acute with adequate prophylaxis
  5. Anticipatory CINV: nonpharmacologic treatments, then move to adding BZD
  6. Breakthrough CINV: prescribe antiemetic from different class
  7. Refractory CINV: upgrade the antiemetic strategy to the next level of prophylaxis or add breakthrough antiemetics to regimen
  8. Radiation-induced N/V: 5-HT3 RA and dexamethasone
28
Q

Step Treatment in N/V in pregnancy (4)

A
  1. Try dietary changes first (smaller, more frequent meals). Avoidance of trigger foods and odors. Use GINGER. Seasickness bands useful for some. Switch off prenatal vitamins in favor of Fred Flinstone gummies as these are better tolerated.
  2. If N/V persists and patient is unable to keep food down, assess for dehydration and ketones in urine. Smaller meals.
    A. First-line: pyridoxine (vitamin B6) with or without doxylamine (unisom)
    B. Second-line: promethazine
    C. Third-line: ondansetron
  3. If patient has hyperemesis gravidarum, first-line is ondansetron.
  4. If the patient’s life is at risk for malnutrition and electrolyte abnormalities, and no interventions have been successful, worst-case scenario is pregnancy termination

Gastrointestinal (7 decks)

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