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AS - N926 Pharmacology > Antiemetics > Flashcards

Antiemetics Flashcards

1
Q

How many patients experience PONV?

A

20-30%
Increased in pediatrics (children >3yo)
Patients w/ risk factors increases to 70-80%

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2
Q

PONV associated with

A

Delayed recovery
Patient dissatisfaction
Most common complication observed in PACU
Reason for hospitalization following ambulatory surgery
50% patients w/ emesis in PACU will continue to experience PONV when d/c home

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3
Q

How to prevent and treat PONV

A

Target various pathways associated w/ N/V (different receptors)
Peripherally & centrally acting
Combination therapies

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4
Q

Patient Risk Factors

A

Female (unknown genetic cause)
History PONV or motion sickness
Non-smoker
Age (risk decreases by 10% per decade in adults >50yo)
Pediatrics 3-12yo highest age risk
Apprehension = swallowing air → abdominal distension & ↑ catecholamines
Gastroparesis & recent food ingestion r/t stomach contents

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5
Q

Surgical Risk Factors

A

Increased anesthetic or surgery duration
Each 30min increases PONV risk by 60% from initial score
Surgery type - laparoscopic, ophthalmic, ENT, T&A, breast, GU, & GYN

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6
Q

Anesthesia Risk Factors

A

Pre-op opioid analgesics administration - receptor site stimulation & serotonin release
Inhalational induction - PPV causes gastric distension
Volatile anesthetic agents (dose dependent & exposure time w/ surgery duration)
Nitrous oxide causes ↑ middle ear pressure, GI distension, & sympathetic nerve activation
*Maintenance - longer anesthesia time, general, opioid admin → highest risk
Consider Propofol as maintenance anesthetic rather than volatile gas for high risk patients
Propofol found to result in less PONV than other hypnotic agents

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7
Q

Post-op Risk Factors

A

Ambulation
Postural hypotension
Uncontrolled pain ↑ catecholamines & endogenous nociceptor activators such as serotonin
Post-op opioid administration (regardless if opioid-free anesthesia)
Early PO intake
Lower FiO2 concentration
Reversal agents such as Neostigmine >2.5mg

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8
Q

How to treat at-risk patients?

A

MULTI-MODAL APPROACH
Benefit from one or more prophylactic measures
Target different receptors & pathways

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9
Q

SAMBA

A

Society of Ambulatory Anesthesia
Identify at-risk patients for PONV
Employ management strategies to reduce risk
1-2 prophylactic measures in moderate risk adults
Multiple interventions in patients at high risk

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10
Q

Failed prophylaxis treatment

A

Try another antiemetic to target different receptor

Different pharmacological class

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11
Q

Apfel Score

A

Female gender
Nonsmoker
PONV history
Post-op opioids

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12
Q

Combination Therapy

A

Targets multiple receptors
Rapid onset & longer duration to cover post-op period
High risk patients will benefit from combo therapy
Utilize for certain surgical procedures including gastric, esophageal, plastics, ↑ ICP, mandibular jaw wiring, & eye

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13
Q

Direct Triggers

A

Noxious stimuli, toxins, drugs, or irritants

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14
Q

Indirect Triggers

A

Vomiting center in medulla oblongata stimulation

  • Cerebral cortex/thalamus
  • Vestibular apparatus
  • Vagal afferent GI tracts
  • Chemoreceptor trigger zone (CTZ)
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15
Q

Pathway

A

Efferent motor nerves travel through cranial nerves V, VII, IX, X, XII, sympathetic, & spinal nerves to stimulate various areas

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16
Q

Receptors

A 
5-hydroxytryptamine (serotonin)
- Ondansetron, Palonosetron, Dolasetron
Dopamine (D2)
- Droperidol, Prochlorperazine, Metoclopramide
Histamine
- Dimenhydrinate, Promethazine
Muscarinic
-  Promethazine, Scopolamine
Opioid
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17
Q

Serotonin Receptor Antagonists

A

Most common in practice
5-HT3 receptor subtype mediates vomiting
Ion channel found in the GI tract (abdominal vagal afferents) & brain (CTZ area postrema & NTS)
- Outside the blood-brain barrier
- Trigger zone activated by anesthetics & opioids
- Signals nucleus tractus solitarius resulting in PONV
- GI emetogenic stimuli
Antagonists inhibit central & peripheral stimulation
Effective, well-tolerated, & no sedation
Administer near end surgery

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18
Q

Ondansetron (Zofran)

A

Selective serotonin type 3 receptor antagonist
Most common antiemetic
Effective prophylactic & post-op antiemetic to prevent & treat PONV
Most effective when administered toward end surgical procedure

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19
Q

Ondansetron PK

A

Onset 30min
Peak plasma almost immediate
60% bioavailability
70% protein binding
Metabolism: CYP450 (liver) hydroxylation & conjugation
Decrease dose in liver failure patients - severe hepatic impairment will decrease clearance d/t ↑ plasma half-life (do not exceed 8mg/day)
No renal dose adjustment <5% metabolized by kidneys
Half-life 4hrs
Excreted via urine/feces

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20
Q

Ondansetron Dose

A 
PO 4-8mg pre-op prophylaxis
16mg 1x prior to induction
IV 4mg 
Do not administer > 16mg IV
FDA warning based on 32mg
QT prolongation risk
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21
Q

Ondansetron SE

A 
Headache (mild to moderate)
Dizziness
Diarrhea
Constipation
QTc prolongation
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22
Q

Palonosetron

A

Selective serotonin type 3 receptor antagonist
Newest & most selective agent
Effective treatment for chemotherapy induced N/V
No safety/efficacy data in patients <18yo
NOT safe for pediatric patients

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23
Q

Palonosetron PK

A

Increased serotonin receptor affinity 100x
Half-life 40hrs
Therapeutic effects for 72hrs (long-acting)
80% excreted in urine over 6 days

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24
Q

Palonosetron Dose

A

0.75mg PONV
0.25mg chemo-induced N/V
No dosage adjustments for elderly, renal, or hepatic patients

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25
Dolasetron (Anzemet)
Selective serotonin type 3 receptor antagonist
26
Dolasetron MOA
Reduce vagus nerve activity to limit vomiting center activation in the medulla oblongata
27
Dolasetron PK
``` Immediate onset (fast-acting) 75% protein binding Peak plasma ≈ 40min Duration 4-9hrs Elimination half-life 8hrs Metabolism: CYP450 & kidneys Active metabolite - hydrodolasetron Excreted in urine/feces ```
28
Dolasetron SE
Headache Dizziness Constipation Potential QT prolongation
29
Dolasetron Dose
12.5mg IV 4x dose needed to reach = efficacy to 4mg Zofran Administer 15min prior to anesthesia off Single PO 100mg 1-2hrs pre-op effective
30
Droperiol
Butyrophenone/dopamine receptor antagonist Derivative structurally similar to Haloperidol Anxiolytic, sedative, hypnotic, & antiemetic properties
31
Droperiol MOA
Blocks dopamine receptors (D2) | Antagonist
32
Droperiol PK
``` Onset 3-10min (fast-acting) Peak 30min Duration 2-4hrs Metabolism: Liver Excreted via urine 10% unchanged & feces ```
33
Droperiol PD
``` QT prolongation FDA black box warning (5-15mg) Do NOT administer to patients w/ QT interval prolongation Obtain baseline EKG Monitor EKG 2-3hrs after surgery (PACU) ```
34
Droperiol Dose
0.625-1.25mg IV/IM
35
Prochlorperazine (Compazine)
Phenothiazine Antipsychotic/antiemetic PONV prophylaxis
36
Prochlorperazine MOA
Dopaminergic D2 blockade (antagonist) Histaminergic Muscarinic
37
Prochlorperazine PK
``` Duration 3-4hrs High protein binding 90-99% Peak 2-4hrs Metabolism: Liver primarily Elimination half-life 6-10hrs Excreted via biliary & inactive metabolites in urine ```
38
Prochlorperazine PD
Extrapyramidal & anticholinergic SE Antipsychotic working on muscarinic receptors Sedation, blurred vision, hypotension, dizziness, restlessness, dystonia Neuroleptic malignant syndrome NMS S/S ↑HR, arrhythmias, irregular BP, fever, stiff muscles, diaphoresis, spasms → LIFE THREATENING
39
Prochlorperazine Dose
5-10mg IV/IM prior to induction | IM onset 5-10min
40
Metoclopramide (Reglan)
Dopamine receptor antagonist, antiemetic, upper GI motility stimulant Pro-kinetic stimulates motility (gastric emptying) & ↑ lower esophageal sphincter tone 1° choice aspiration risk patients Gastroparesis, GERD, aspiration pneumonia prophylaxis patients
41
Metoclopramide MOA
Centrally acting Dopamine receptor antagonist in CTZ or vomiting center Peripherally acting as cholinomimetic in GI tract (facilitates ACh transmission at muscarinic receptors)
42
Metoclopramide PK
Onset 3-5min Peak 1-2hrs Duration 1-2hrs Elimination half-life 5-6hrs Metabolism: Liver Excreted via kidneys (modify dose for impaired renal function) urine/feces Lack sedative properties - does not ↑ PACU stay
43
Metoclopramide SE
Higher dosages or chronic medication as pro-kinetic → extrapyramidal SE Contraindicated in seizure, GI obstruction, & Parkinson's Avoid in pheochromocytoma - hypertension crisis by releasing catecholamines from tumor
44
Metoclopramide Dose
``` 10mg IV (5-20mg) 0.1-0.25mg/kg IV Q6-8hrs Slow push over 1-2min to prevent abdominal cramping, anxiety, & restlessness ```
45
Aprepitant (Emend)
Neurokinin-1 receptor antagonist | Inhibit substance P at central & peripheral receptors
46
Aprepitant PK
Elim 1/2 life 9-13hr | Hepatic CYP3A4 metabolism
47
Aprepitant Dose
40-80mg PO preop
48
Aprepitant SE
Non-sedative Fatigue, dizziness, hiccups, heartburn, hypoesthesia, diarrhea, disorientation, anorexia, constipation, dyspepsia, abdominal pain, gastritis, duodenal ulcer Birth control ineffective for 28 days Patient teaching use back-up birth control 1mos
49
Dexamethasone (Decadron)
Long-acting corticosteroid Exact MOA unknown Possibly vomiting center but not area postrema
50
Dexamethasone PK
``` Onset 2hr Earlier administration more effective Elim 1/2 life 36-54hr Plasma 4-5hr Hepatic metabolism ```
51
Dexamethasone Dose
4-10mg
52
Dexamethasone SE
Perineal pruritis Contraindicated in uncontrolled infections Immediate
53
Dimehydrinate (Dramamine)
Histamine receptor antagonist Competes w/ histamine at H1 receptors Blocks CTZ, depresses labyrinthine function, & vestibular stimulation
54
Dimehydrinate PK
Hepatic metabolism w/ metabolites excreted via urine
55
Dimehydrinate Dose
1-2mg/kg 50-100mg IV/IM Q4H Max 100mg
56
Dimehydrinate Onset & DOA
Immediate | DOA 4-6hr
57
Dimehydrinate SE
Anticholinergic Drowsiness, urinary retention, dry mouth, blurred vision, extrapyramidal effects Sedation common
58
Promethazine (Phenergan)
Antihistamine H1 antagonist Anticholinergic Muscarinic Avoid in patients >65yo
59
Promethazine PK
Glucuronidation Sulfoxidation Elim 1/2 time 10-19hr
60
Promethazine Dose
12.5-25mg Q4-6H IM route preferred 6.25-12.5mg IV
61
Promethazine Onset & DOA
IM 20min IV 5min DOA 4-6hr IV dilute in 10 or 20mL NS Admin over 10-15min
62
Promethazine SE
``` Confusion, dizziness, dry mouth, constipation Significant sedation (especially w/ opioids) Hypotension ```
63
Scopolamine
Muscarinic antagonist Tertiary amine Inhibits ACh at PSNS site in CNS, smooth muscle, & secretory glands Blocks communication b/w vestibule nerves & vomiting center Avoid in patients w/ closed-angle glaucoma or >65yo Place night before surgery & keep on at least 24hrs
64
Scopolamine PK
Onset 2-4hr DOA 72hr Elim 1/2 life 4.5hr Hepatic metabolism
65
Scopolamine Dose
1.5mg patch | Lipid solubility allows transdermal absorption
66
Scopolamine SE
Tachycardia (blocks SA node), ↓secretions, relaxes bronchial smooth muscle, ↓GI motility, prolonged gastric emptying, mydriasis, blurred vision, urinary retention CNS cerebral depression, sedation, & amnesia
67
Scopolamine Reversal
Physostigmine 0.01-0.03mg/kg IV repeat after 15-30min
68
Ephedrine
Indirect acting sympathomimetic | Recommended to treat N/V associated w/ postural hypotension
69
Ephedrine Dose
10-25mg
70
Midazolam (Versed)
Benzodiazepine GABA receptor antagonism Inhibit dopamine release
71
Midazolam Dose
2mg IV | Pediatric 50-75mcg/kg

AS - N926 Pharmacology (18 decks)

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