GI: Anti-emetics Flashcards

1
Q

Common causes of emesis

A
  • Infection
  • Meds
  • Pregnancy
  • Dysmotility
  • Motion sickness
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2
Q

Areas of body that communicate to cause emesis

A
  • CNS
  • Vestibular system
  • Chemoreceptor Trigger zone
  • GI Tract & Heart
  • Vomiting center

targeted in drug therapy

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3
Q

CNS: role in emesis

A

Anticipatory N/V, e.g., in cancer pts. Triggering memory

Cortex, thalamus, hypothalamus, meninges

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4
Q

Vestibular system: role in emesis

A

Motion sickness

H1 and M1 receptors- M1 -muscarinic

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5
Q

Chemoreceptor Trigger Zone: role in emesis

A

Next to VC

Before BBB, so direct exposure to blood – anything toxic goes to this area, VC –> emesis

Chemoreceptors, D2, NK1, 5-HT3 receptors

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6
Q

GI Tract & Heart: role in emesis

A

Mechanoreceptors, chemoreceptors, 5HT3 receptors

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7
Q

Vomiting Center: role in emesis

A

In medulla oblongata

Mainly responsible for coordinating – all other areas communicate to VC

H1, M1, NK1, and 5-HT3 receptors

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8
Q

Types of anti-emetics

A

5-HT3 receptor antagonists

D2 Receptor Antagonists

Antihistamines & Antimuscarinics

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9
Q

5-HT3 receptor antagonists: where are 5HT3 receptors involved in emesis located?

A

CTZ, GI Tract & heart, VC

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10
Q

5-HT3 receptor antagonists: indications

A
  • Prevention of chemo/radiation induced N/V
  • Post-op N/V (PONV)
  • Severe refractory hyperemesis gravidum
  • Cyclic vomiting syndrome (pedi)
  • Viral gastroenteritis (pedi)
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11
Q

5-HT3 receptor antagonists:​ MOA

A

Block central and peripheral 5-HT3 receptors

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12
Q

5-HT3 receptor antagonists:​​ absorption

A

well=absorbed from GI tract

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13
Q

5-HT3 receptor antagonists: 1/2 life

A

½ life: 4-9h (except palonosetron = 40h)

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14
Q

5-HT3 receptor antagonists:​ Metabolism

A

extensive hepatic via CYP2D6 & CYP3A4

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15
Q

5-HT3 receptor antagonists: ADRs

A

HA, dizziness, constipation, diarrhea

Caution: QTc interval prolongation

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16
Q

5-HT3 receptor antagonists: Agents

A
  • Ondansetron (Zofran)
  • Granisetron (Kytril)
  • Dolasetron (Anzemet)
  • Palonosetron (Aloxi)
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17
Q

Ondansetron (Zofran): formulation and indication

A

Tablet, ODT, solution: CINV, once or twice; PONV, once

Injection: CINV & PONV, once

5HT3 Antagonist

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18
Q

Granisetron (Kytril) : formulation and indication

A

Tablet, solution: CINV once

Injection: CINV & PONV once

Transdermal patch: CINV 24h before chemo

(5HT3 antagonist)

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19
Q

Dolasetron (Anzemet): formulation and indication

A

Tablet, injection: CINV & PONV once

(5HT3 antagonist)

20
Q

Palonosetron (Aloxi): formulation and indication

A

Injection: CINV & PONV once

(5HT3 antagonist)

21
Q

Recommended Tx: Viral Gastroenteritis

A

Pedi pts: ondansetron effective in 1) facilitating ORT, 2) decreasing need for IVF and immediate hospitalization risk

22
Q

Recommended Tx: General N/V

A

ED studies find ondansetron equivalent to metoclopramide and prochlorperazine in reducing N/V

23
Q

D2 Receptor Antagonists: agents

A
  • Phenothiazines
  • Butyrophenones
  • Substituted Benzamides
24
Q

D2 Receptor Antagonists: Indications

A
  • Most common “general purpose” anti-emetic
  • Motion sickness
  • Low risk emesis chemotherapy
25
Q

D2 Receptor Antagonists: MOA

A

Block dopamine receptors in the CTZ

Sedative effects d/t blockade of histamine receptors

26
Q

D2 Receptor Antagonists: absorption

A

well absorbed from GI track, onset 20-30min

27
Q

D2 Receptor Antagonists​: metabolism

A

hepatic via CYP enzymes, significant 1st pass metabolism

28
Q

D2 Receptor Antagonists​:​ ADRs

A
  • EPS (dystonia, restlessness)
  • Drug induced Parkinson’s
  • Drowsiness (phenothiazines, butyrophenones)
  • QTc prolongation (phenothiazines, butyrophenones)
29
Q

Phenothiazine: agents

A

Prochlorperazine (Compazine), Promethazine (Phenergan)

(D2 receptor antagonists)

30
Q

Prochlorperazine (Compazine): dosing & formulations

A
  • Tablet: 3-4x daily
  • Suppository: BID
  • Injection: Q 3-4h prn

(D2RA, phenothiazine)

31
Q

Phenothiazines: MOA

A

Same as other D2RAs + Phenothiazines also block muscarinic receptors at VC

(D2RA)

32
Q

Promethazine (Phenergan): formulations and dosing

A
  • Tablet, solution, suppository, injection
  • Q4-6h prn

(D2RA, phenothiazine)

33
Q

Butyrophenones: Agents

A

Droperidol

(D2RA)

34
Q

Droperidol: formulation and dosing

A

Injection: PONV once

(D2RA, Butyrophenone)

35
Q

Substituted Benzamides: agents

A

Metoclopramide (Reglan)

(D2RA)

36
Q

Metoclopramide (Reglan): dosing and formulations

A
  • Tablet, solution, injection
  • Q6h prn

(D2RA, Substituted Benzamide)

37
Q

Antihistamines & Antimuscarinic: Indication

A

Motion sickness

38
Q

Antihistamines & Antimuscarinic: MOA

A

Block H1 receptors mainly in vestibular system

Anticholinergic effects d/t systemic muscarinic blockade

39
Q

Antihistamines & Antimuscarinic:​ ADRs

A

Drowsiness, confusion, blurred vision, dry mouth, urinary retention, tachycardia

40
Q

Antihistamines: Agents

A

Diphenhydramine (Benadryl), Dramamine, Meclizine

41
Q

Diphenhydramine (Benadryl: formulations and dosing

A
  • Tablet, solution, injection

Q6-8h prn

(antihistamine, antiemetic)

42
Q

Dramamine: formulation and dosing

A

Tablet, injection

Q4-6h prn

(antihistamine, antiemetic)

43
Q

Meclizine: formulations and dosing

A

Tablet: 1hr before travel

(antihistamine, antiemetic)

44
Q

Antimuscarinics: Agents

A

Scopolamine (Transderm-Scop)

45
Q

Scopolamine (Transderm-Scop): formulations and dosing

A

Patch: 1 q72h

Injection: once SQ

(antimuscarinic, antiemetic)

46
Q

1st line anti-emetic in pregnancy

A

Pyridoxine (Vit B-6) 10-25mg 1-4x daily +/- doxylamine 12.5-20mg 1-4x daily

Now available: Doxylamine succinate/pyridoxine hydrochloride delayed release tabs 10 mg/10mg (Diclegis)

47
Q

2nd line/additional antiemetic agents in pregnancy

A
  • Diphenhydramine
  • Dimenhydrinate
  • Meclizine
  • ondansetron
  • metoclopramide, promethazine, prochlorperazine