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Anesthesia > Opioids 1 > Flashcards

Opioids 1 Flashcards

1
Q

Opioids

A

-chemically related to compounds purified from juice of poppy

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2
Q

Opium

A

-unrefined extract from the poppy
-contains apprx 20 naturally occurring pharmacologically active compounds

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3
Q

Opiates

A

-group of purified natural agents
-morphine and codeine

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4
Q

Opioid

A

-any natural, synthetic, endogenous substance with morphine-like properties

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5
Q

Endogenous opioid peptides

A

-small molecules that are naturally produced in CNS and various glands in body (pituitary and adrenal)

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6
Q

4 distinct families of endogenous opioid peptides

A
  1. beta-endorphin (mu)
  2. Enkephalins (delta)
  3. Dynorphins (kappa)
  4. Nociception (NOP)
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7
Q

Opioid receptors in supraspinal

A

-brain stem (periaqueductal grey area)
-hypothalamus
-amygdala
-corpus striatum

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8
Q

Opioid receptors in spine

A

-dorsal horn (substantia gelatinosa)

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9
Q

Opioid receptors in periphery

A

-Identified on the processes of sensory neurons
-upregulated during inflammatory pain states

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10
Q

Where do opioids act along pain pathway?

A

-Perception in brain
-Modulation in spinal cord
-Transduction in nociceptors

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11
Q

Opioid receptors

A

All G-protein coupled receptors that mediate inhibition of neurotransmission and endocrine secretion

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12
Q

Opioid receptor Steps

A

Pre-synapse
1. Inhibit adenyl cyclase activity
2. Inhibit pre-synaptic voltage gated Ca channels; decreased Ca influx
3. Reduction in NT release and therefore inhibition of synaptic transmission of nociceptive input

Post-synpase
1. Increased K efflux due to opioid receptor, resulting in neuronal hyperpolarization of post synaptic spinal cord projection neurons
>inhibition of ascending nociceptive pathways

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13
Q

Opioid receptor types

A

**located in central and peripheral nervous system

  1. Mu= MOP=OP3
  2. Delta= DOP = OP1
  3. Kappa= KOP= OP2
  4. Nociceptin= NOP= ORL-1
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14
Q

Mu receptor agonist effects

A

**Profound analgesia- spinal cord and supraspinal

-respiratory depression effects
-bradycardia
-sedation (dose-dependent)
-euphoria/dysphoria
-miosis
-hypothermia
-antitussive
-decreased GI motility
-urinary retention
-emesis (chemoreceptor trigger zone)
-anti-emetic center
-min cardio effects

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15
Q

Kappa receptor agonist effects

A

**spinal analgesia (mild to moderate pain)

-mild sedation
-miosis
-min respiratory depression and vagally mediated bradycardia
-dysphoria
-diuresis

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16
Q

General opioid Effects

A

-Analgesia
-Sedation (part of premed)
-Anesthetic sparing
-Reversible

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17
Q

Clinical significant opioid effects

A

-bradycardia
-resp depression
-emesis
-abuse potential
-dysphoria

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18
Q

Opioid effect variation in species

A

Occurs because opioid receptor distribution in CNS differs

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19
Q

Mu receptor agonists differences in species

A

CNS depression in dogs, monkeys, humans

VS.

Excitement/spontaneous locomotor activity in pain free mice, cats, horses, goats, sheep, pigs, cows

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20
Q

Morphine mania in cats

A

**historical reluctance to administer opioids in cats
BUT morphine mania was seen at doses 100 fold higher than used in clinic

-Excitement and mydriasis

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21
Q

Opioids in birds

A

Raptors: mu opioid provide analgesia; kappa opioid appear ineffective

Psittacines: kappa opioids appear more effective than mu opioids

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22
Q

Opioids in reptiles

A

mu opioid receptor agonists provide effective analgesia

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23
Q

Individual variability with opioid use

A

-individuals respond differently; depend on receptor distribution due to varying genetics

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24
Q

Drug-receptor interaction- affinity vs intrinsic activity

A

Affinity- how well a drug binds to receptor

Intrinsic activity or efficacy- magnitude of effect that drug has once bound

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25
Q

Full agonist

A

-high affinity and high intrinsic activity
-able to generate maximal response from receptor
-stimulate both mu and kappa

eg. morphine

26
Q

Partial agonist

A

-produces a submaximal effect compared with full agonist
-has lower intrinsic activity
-less analgesia
-ceiling effect
-generally higher affinity

Eg. Buprenorphine- higher affinity but less intrinsic activity than morphine

27
Q

Antagonist

A

-no intrinsic activity but high affinity for opioid receptor

-rapidly reverses all opioid induced clinical effects

-should be kept for use during emergency situations; inappropriate use may cause the development of intense acute pain and activation of sympathetic nervous system

  • non emergent effect always titrate to effect
28
Q

Competitive antagonist

A

-can displace opioid agonists from mu and kappa receptors

29
Q

Opioid antagonist drugs

A

-Naloxone
-Naltrexone

30
Q

Naloxine

A
  • pure mu, delta, kappa opioid antagonist
    -can reverse all opioid agonist effects producing increased allertness, responsiveness, coordination, and perception of pain
    -watch for renarcotization
31
Q

Naloxone duration

A

30-60 mins

32
Q

Naltrexone

A

-Reversal of potent opioids for wildlife immobilization
-clinical effects last ~2x as long as those with naloxone

33
Q

Agonist-Antagonist

A

-agonistic effects at one receptor (kappa) but antagonist on another receptor (mu)

Eg. Butorphanol
-Kappa agonist
-Mu antagonist

34
Q

Butorphanol as a reversal to mu opioid induced respiratory depression or sedation

A

Give butorphanol because mu antagonist, but kappa agonist.

**means that analgesia is maintained

35
Q

Potency

A

Amount of a drug needed to produce a given effect

36
Q

Efficacy

A

-Maximum effect that a drug can produce regardless of dose

37
Q

Opioid agonists potency

A

**potency is compared to morphine on an “equal-analgesic basis”

-Morphine =1
-Meperidine = 1/5
-Fentanyl = 100
-Carfentanil= 10000
-Buprenorphine= 80
-Butorphanol= 3-5

38
Q

Efficacy vs. duration for Meperidine

A

mild and short

39
Q

Efficacy vs. duration= profound and long

A

-morphine
-hydromorphine
-methadone

40
Q

Buprenorphine efficacy vs duration

A

Moderate effect, long duration

41
Q

Fentanyl, sufentanil efficacy vs. duration

A

profound effect, short duration

42
Q

Opioid pharmacology

A

-highly lipid soluble
-mostly hepatic transformation
-poor bioavailability orally due to high first pass effect in liver
-eliminated: bile and urine

43
Q

Opioids given IV, IM

A

-onset rapid (except buprenorphine)
-histamine release after IV administration (morphine, meperidine)

44
Q

Continuous rate infusions of opioids

A

-medication continuously given IV to maintain consistent plasma levels and analgesia

-reduces unwanted side effects (after intermittent bolus administration)

45
Q

Which opioids are good for continuous rate infusions?

A

-shorter acting mu agonists: fentanyl, remifentanil, sufentanil

-morphine, hydromorphine

46
Q

SC opioids

A

-unreliable absorption
-great individual variability in pain relief

47
Q

High-concentrated formulation of Buprenorphine= 1.8mg/ml simbadol)

A

-up to 24hr of post-operative analgesia in cats after one SC dose of 0.24mg/kg

-may be administered for up to 3 consecutive days

48
Q

Buccal opioid administration

A

-noninvasive, pain free; minimal restraint needed

-opioids have poor oral bioavailability, but buccal route bypasses first pass effect and allows for higher bioavailability

49
Q

Buprenorphine buccal administration

A

Cats: acceptable bioavailability and analgesia

Dogs: high dose needed (cost prohibitive and risk of swallowing)

**IV and IM route better in clinic but would still be a suitable late post-operative analgesia

50
Q

Transdermal opioid administration

A

Fentanyl Patch
-delayed onset
-human safety concern; so patch evolved to reduce abuse potential
-reservoir is filled with liquid, and drug in adhesive matrix (drug+polymer)

51
Q

Fentanyl patch species differences

A

Dogs: 63.8% bioavailability; 12-24hrs, duration 3 days

Cats: 35.9% bioavailability; 8-18hrs, duration 5 days

52
Q

Pain assessment and monitoring in opioid transdermal administration

A

-Delayed onset
-variation in individuals
-changes in body temperature, skin preparation and patch placement may affect rate of absorption, plasma fentanyl levels and analgesic efficacy
-care with heating pads which increases uptake due to increased circulation

53
Q

Transdermal fentanyl solution (Recuvyra) use

A

-licensed for the control of postoperative pain associated with major orthopaedic and soft tissue surgery in healthy dogs

54
Q

Transdermal fentanyl solution (Recuvyra) application

A

-liquid solution applied to skin dorsally between shoulder blades (depot of fentanyl with lipid layer of stratum corneum)

-no needle needed

55
Q

Transdermal fentanyl solution (Recuvyra) timing

A

-applied 2-4hrs prior to surgery
-lasts up to 4 days in dogs
-no peak effect
-adverse effects are long lasting (require repeated doses of naloxone)

56
Q

Epidural/spinal administration of opioids

A

-used in epidural or subarachnoid space to manage acute or chronic pain
-all opioids are lipid soluble but solubility differs between opioids

57
Q

Opioids with lower lipid solubility

A

-less systemic absorption
-slower onset time (passage across dura mater)
-longer duration and further cranial migration

58
Q

Duration of morphine

A

12-24hrs

59
Q

Duration of hydromorphine

A

8hrs

60
Q

Duration of fentanyl

A

short duration and segmental analgesia

61
Q

Intraarticular administration of opioids

A

-significant increase in mu opioid receptors in articular and peri-articular tissues occurs after joint inflammation

**used with morphine after arthroscopy surgery (knee, elbow) as part of multimodal analgesia plan

Anesthesia (24 decks)

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