Opioid agonist-antagonists Flashcards by Michael Sokol

Advantages of opioid agonist-antagonists include

Analgesia
Limited depression of ventilation (still some but limited)
low potential for physical dependence
ceiling effect prevents additional responses

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Phenomena where a drug’s impact on the body plateaus

Ceiling effect

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Pentazocine as agonistic effects on which receptors?

delta(δ) and kappa (k) receptors

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Pentazocine potency compared to Nalorphine

1/5th as potent as nalorphine

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“gold standard” for comparing opioid agonist-antagonists

Nalorphine (equivalent to morphine)

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Pentazocine is antagonized by

Naloxone (narcan)

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How much is Pentazocine affected by 1st pass metabolism

highly, 20% available post PO

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Pentazocine excretion

Glucuronide conjugates via urine

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Pentazocine chronic pain dose

10-30mg IV, or 50mg PO (equivalent to 60mg codeine)

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A common CV side effect from opioid agonist-antagonists is

decreased BP and increased HR as compensatory mechanism

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Butorphanol agonist effect is ______ and antagonist effect is ____ to ____ compared to Pentazocine

agonist 20x and antagonist 10-30x higher than Pentazocine

(stronger than morphine)

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Butorphanol has a _____ affinity for μ receptors, _____ affinity for k receptors, and _______ affinity for σ receptors

μ= low (antagonism)
k=moderate (analgesia and anti-shivering)
σ= minimal (low dysphoria)

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E1/2 time of Butorphanol is

2.5-3.5hrs

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Metabolism and Elimination of Butorphanol

Metab= liver
excretion = Bile/fecal > urine

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Which receptor has a moderate affinity for Butorphanol’s effects to mitigate shivering and produce analgesia?

k- kappa receptors

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Nalbuphine agonistic effect compared to morphine

equally potent

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Nalbuphine antagonist effect compared to Nalorphine

1/4th as potent as Nalorphine

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E1/2time of Nalbuphine

3-6hrs

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A benefit of Nalbuphine that is different than the others

No increase in HR/BP, good for cardiac patients

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Buprenorphine potency compared to morphine

μ receptor agonists 50x higher than morphine

(0.3mg IM = 10mg morphine)

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DOA of Buprenorphine

8hrs

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Because of its long duration of action, Buprenorphine has a _____ resistance to naloxone

prolonged/high resistance to naloxone

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Which opioid agonist-antagonist is equally potent to morphine but causes higher amounts of dysphoria, so it is not commonly used?

Nalorphine

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Meptazinol protein binding amount

25%

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Naloxone, Naltrexone, and Nalmefene are considered

μ-opioid receptor antagonists, no agonist activity competitive antagonists -> high affinity to opioid receptors

Naloxone uses

- opioid-induced depression in post-op - neonate* (from mom) - opioid overdose - detect dependence - Hypovolemic/septic shock (inc. myocardial contract.) - Antagonism of general anesthesia (high doses)

Naloxone doses

- 1-4 mcg/kg IV - 5 mcg/kg continuous infusion - >1mg/kg IV for shock - epidural s/e= 0.25mcg/kg/hr IV

Naloxone DOA

30-45min, will likely require redosing

A dangerous s/e to Naloxone

cardiac dysrhythmias (v-fib), recommend to give slowly to avoid

Naltrexone is more effective when given _____

Naltrexone DOA

24hrs

Naltrexone is primarily used for

alcoholism

Nalmefene is _______ potent compared to naloxone

equipotent

Nalmefene dose

15-25mcg IV q2-5min til 1mcg/kg

Nalmefene E1/2time

10.8hrs

Methylnaltrexone is highly ionized and quarternary, meaning it

does not cross BBB, effects only peripherally

Methylnaltrexone is used to

promote gastric emptying and antagonizes N/V; no alteration in centrally mediated analgesia

Alvimopan is primarily used for

newer μ-selected PO opioid antagonist, used for post-op ileus metabolized by gut flora limited in long term use s/t CV events

Suboxone is a combination of _____ and ______

buprenorphine and naloxone

Embeda is a combination of ______ and ______

extended-release morphine and naltrexone

OxyNal is a combination of _____ and _____

oxycodone and naltrexone

Fentanyl decreases MAC of Iso and Desflurane by how much

50%

PCA dosing of morphine

basal= 0-2mg/hr, bolus= 1-2mg, interval= 6-10min

PCA dosing of hydromorphone

basal=0-0.4mg/hr, bolus= 0.2-0.4mg, interval 6-10min

PCA dosing of fentanyl

basal = 0-60mcg/hr, bolus= 20-50mcg, interval= 5-10min

Neuraxial analgesia targets

opioid receptors in Lamina 2 (substantia gelatinosa) of spinal cord

The 2 types of neuraxial analgesia includes

epidural and spinal/intrathecal/subarachnoid block (SAB)

epidural dosing is _____ compared to spinal

5-10x higher

In what analgesia does the drug diffuse across the dura

epidural

which neuraxial used opioids are highly lipophilic

fentanyl and sufentanil

which neuraxial used opioids are highly hydrophilic

morphine (slower onset, longer duration)

Epidural uptake can occur via

- epidural fat - epidural venous plexus

Which epidural uptake can cause systemic effects?

uptake via epidural venous plexus

which is a method used to reduce venous uptake in epidurals

use of vasoconstrictor in conjunction

which vasoconstrictors can be used in epidurals

Epi (primary), phenylephrine

Lipid solubility of fentanyl compared to morphine

800x more lipophilic than morphine

lipid solubility of sufentanil compared to morphine

1600x more lipophilic than morphine

_________ is when neuraxial opioids migrate upward

Cephalad movement

Which spinal level are cardiac accelerator fibers located

T1-T4

Which spinal level dermatome is at the nipple line

Which spinal level dermatome is the xiphoid

T6-8

Which spinal level dermatome is the umbilical region

T10

Which opioid when given spinally is more likely have cephalad migration

morphine (mixes with CSF d/t its hydrophilic property)

What causes an increase in cephalad movement

coughing and straining (valsalva)

What is baracity?

whether the drug sinks or floats

Hyperbaric drugs ____

sink

Hypobaric drugs _____

float

What local anesthetic baracity would affect the right hip of a patient positioned in the left lateral position?

hypobaric

Opioid epidural admin/CSF peak times

fentanyl= 20min sufentanil= 6min morphine= 1-4hrs

Opioid epidural admin/plasma peak

fentanyl= 5-10min, similar to IM sufentanil= <5min, similar to IM morphine= 10-15min, similar to IM

Opioid intrathecal/CSF/cervical levels

fentanyl= minimal sufentanil= minimal morphine= 1-5hrs

Neuraxial anesthesia can cause pruritis if it reaches the ________

trigeminal nucleus in brainstem

Treatment of pruritis due to neuraxial analgesia

Naloxone, antihistamines, gabapentin, propofol 10-20mg IV

S/e of neuraxial analgesia include

- ventilatory depression - "neuropathic" Pruritis - N/V - urinary retention in men - sedation - CNS excitation (tonic skeletal muscle rigidity like seizure activity) - herpes simplex labialis viral reactivation 2-5days after epidural opioid - neonatal morbidity

Women are instructed not to breastfeed for how long after given neuraxial analgesia

24hrs

Opioid agonist-antagonists Flashcards

(75 cards)