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Moving Exam 2 > Opioid Agonists/antagonists > Flashcards

Opioid Agonists/antagonists Flashcards

1
Q

Opioid receptor

A

Serpentine molecule embedded in cell membrane
- 1 terminal ending exposed to extracellular envi
- other terminus is intracellular

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2
Q

Types of opioid receptors

A

Mu, Kappa, Delta, Sigma

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3
Q

Presynaptic function of opioid receptors

A

Inhibits neurotransmitter release (ACh, Dopamine, norepinephrine, substance P, GABA)

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4
Q

postsynaptic function of opioid receptors

A

Decreases neuronal excitability through hyperpolarization of cell membranes

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5
Q

Mu receptor subtypes

A

Analgesia (supraspinal & spinal)
Euphoria, ventilatory depression, bradycardia, urinary retention, physical dependence

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6
Q

Kappa subtype receptors

A

Analgesia (supraspinal & spinal)
Dysphoria, sedation, miosis

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7
Q

Delta subtypes receptors

A

Analgesia (supraspinal & spinal)
Ventilatory depression, urinary retention, modulation of Mu activity

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8
Q

Tissues for receptor distribution

A

Brain
Spinal cord
GIT
UIT
Synovium
Leukocytes
Uterus

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9
Q

Pure opioid agonist binding affinity

A

Produces dose-dependent increase in effect until max stimulation of receptor achieved
Effect increases as dose (or plasma concentration) increases until it plateaus at max effect

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10
Q

Partial opioid agonist binding affinity

A

Binding at given receptors causes an effect that is less pronounced than that of a pure agonist
Produces dose-dependent increase in effect, but plateaus at max effect less than max effect of full agonist

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11
Q

Opioid agonist-antagonist binding affinity

A

Causes stimulators effect at one receptor but blocks effect or causes less pronounced effect at another
Effects of these drugs depends on previous opioid exposure

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12
Q

Opioid antagonist affinity

A

Binds to receptor with high affinity & produces no effect
- reverses receptor mediated effects of agonists by inhibiting binding of agonist & displacing previously bound agonist due to greater receptor affinity of antagonist (competitive binding)

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13
Q

Full agonist classifications

A

Morphine, hydromorphone , methadone, oxymorphone, fentanyl

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14
Q

Partial agonist classifications

A

Buprenophine

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15
Q

Agonist-antagonist classifications

A

Butorphanol

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16
Q

Antagonist classifications

A

Naloxone, nalmefene, naltrexone

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17
Q

Different potency

A

Ex fentanyl and morphine have different potency meaning one will act quicker with less drug

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18
Q

Different efficacy

A

Ex morphine and buprenophine
Drugs given at same amount will have greater or less effect than the other

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19
Q

PD absorption considerations

A

Lipophilic /absorption rate
Bioavailability via SQ & IM
Low oral bioavailability
Transdermal absorption - fentanyl bypasses GIT and skips first pass hepatic effects
Transmucosal absorption - buprenorphine by passes first pass metabolism, variable absorption

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20
Q

PD considerations - distribution

A

Morphine is hydrophilic
P-glycoprotein efflux pumps limit CNS effects
- limit BBB crossing
- ex loperamide ->reduced central effects

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21
Q

PD considerations - mutations

A

Homozygous mutation in MDR1 gene
- BC, Aussie, GS, shetlands, sheepdogs, whippets
- significant central effects
- morphine, methadone, fentanyl, buprenophine, oxycodone

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22
Q

PD considerations - metabolism & elimination

A

Metabolized through hepatic microsomal enzyme
Morphine - phase III glucuronidation to morphine-3-glucuronide (EXCEPTION, poor glucur, rapidly metabolizes morphine through sulfate conjugate
Elim through biliary or renal
^ elim time in geriatric
Remifentanil met is via plasma esterase

23
Q

Which of the following best describes the opioid & classification?
Buprenophine - full Mu agonist
Methadone - partial Mu agonist
Fentanyl - Mu antagonist & K agonist
Oxymorphone - full Mu agonist

A

Oxymorphone - full mu agonist

24
Q

CNS effects - analgesia

A

Inhibition of presynaptic NT release & post hyperpolarization of neuronal membranes = v excitability = v transmission within spinal cord
^^regulation of supraspinal descending antinociception pathways
- epidural = saturate spinal opioid receptors = effects on C-fibers & A-delta fiber nociceptors

25
Q

Which opioid is more hydrophilic ?

A

Morphine

26
Q

CNS effects - sedation

A

Dose-dependent sedation, more profound sedation w phenothiazines and alpha-2s

27
Q

CNS effects - excitation

A

High does or rapid IV= excitation (^ plasma concentration quickly achieved)
Cats & horses can exhibit Dysphoric /excitatory behavior lasting few hours

28
Q

CNS effects - dysphoria & euphoria

A

Vocalizing, thrashing, ataxia, hypersensitivity

29
Q

CNS effects - thermoregulation

A

Hypo response: dogs, rabbits, birds (more profound w phenothiazines/inhalants)
Hyper response: cats, horses, rum, pigs
Cats: hydromorphone, morphine, buprenophine, butorphanol, up to 5 hours post extubation

30
Q

Respiratory effects

A

Direct depression from brainstem
(Mediated by supraspinal Mu2 opioid receptors)
Decreased responsiveness to ^ CO2
Dose dependent resp depression
(Consider ICP, lung disease)
Antitussives effects
Panting
Opioids cross placenta = resp depression of neo

31
Q

Cardiovascular effects - Bradycardia

A

Opioid induced medullary vagal stim
2nd degree atrioventricular block
Anti-muscarinics block/reverse this effect
Caution in young patients
-minimal effects of myocardial contractility, C output, arterial blood pressure (at clinical doses)

32
Q

Peristaltic effects

A

Propulsion contractions decreased
- constipation, ileum, concerning in horses & rum
Non-propulsive contractions increased
- occasionally causing defecation
- dogs>cats

33
Q

Endocrine effects

A

Histamine release - morphine, meperidine
Nausea & vomiting - direct stim of CTZ, IV<IM

34
Q

Urinary effects

A

Mu effect - increases ADH & natriuretic peptide, v urine production
Kappa effect - decreases ADH, diuresis

35
Q

Immune system effects

A

Morphine, fentanyl, codeine, methadone = Immunosuppression

36
Q

Ocular effects

A

Dogs, rabbits, rats = miosis
Cats, horses, rum = mydriasis

37
Q

Potential for substance abuse

A

Regulated substance
Tolerance & physical dependence
Opioid induced hyperalgesia
Gene expression affecting opioid metabolism

38
Q

Process of selection opioids

A

Degree of pain
Duration of pain/procedure
Sedation requirement
Adverse effects
Specific species requirements/limits
Available routes of admin
Cost

39
Q

Morphine
Analgesia, sedation, peak onset, side effects, routes

A

Analgesia - severe pain
sedation - excellent sedation
peak onset - 15-30 minutes, duration 3-4 hrs
side effects - histamine release, mania in cats/horses, vomiting, renal disease may impair clearance
routes - SQ, IM, IV, epidural

40
Q

Hydromorphone
Analgesia, sedation, peak onset, side effects, routes

A

Analgesia - severe pain
sedation - good sedation
peak onset - 15 min, dur 4-6 hours
side effects - vomiting if IM, less histamine release, panting in dogs, hyperthermia in cats
routes - SQ, IM, IV

41
Q

Methadone
Analgesia, sedation, peak onset, side effects, routes

A

Analgesia - severe
sedation - good
peak onset - 15, dur 4-6hr
side effects - no histamine release, no vomit, panting in dogs
routes - SQ, IM, IV

42
Q

Fentanyl
Analgesia, sedation, peak onset, side effects, routes

A

Analgesia - severe
sedation - good
peak onset - 6-8 minutes, duration 30-60 minutes
side effects - no histamine, no vomiting, bradycardia, chest rigidity (v compliance)
routes - IM, IV, transdermal

43
Q

Buprenorphine
Analgesia, sedation, peak onset, side effects, routes

A

Analgesia - mild to moderate
sedation - minimal
peak onset - 45-90 minutes, dur 6-8 hrs
side effects - high affinity for receptor, plateau effect, not effectively reversed w antagonist
routes - PO, Transmucosal, IM, IV

44
Q

Butorphanol
Analgesia, sedation, peak onset, side effects, routes

A

Analgesia - mild
sedation - good
peak onset - 10-15 minutes, dur 1-2 hrs
side effects - high affinity for receptor, plateau effect, can reverser effect of pure Mu agonists
routes - SQ, IM, IV

45
Q

Which of the following opioids should be avoided in a dog diagnosed w cutaneous & visceral mast cell tumors?
Buprenorphine
Methadone
Morphine
Oxymorphone

A

Morphine
Because of histamine release

46
Q

Reasons and effects of reversing effects with antagonists

A

Opioid overdose or excessively sedated or obtunded from opioids
^ alertness, responsiveness, coordination, ^awareness of pain

47
Q

Naloxone

A

Prototypical Mu antagonist
Onset: 2-5 min
0.01-0.04 mg/kg IV -> lasts 20-40 min
Opioid effects could reoccur

48
Q

Nalmefene, naltrexone

A

4x as potent as Naloxone
Onset: 2-5 min
Duration: 1-2 hours

49
Q

Methlynaltrexone

A

Quaternary derivative of naltrexone
Controls GIT side effects of opioids (ileus) without effecting centrally mediated analgesia

50
Q

Considerations for clinical use

A

Systemic use
Regional or local admin
Parenteral sustained release
Injectable subcutaneous

51
Q

Which is the best option in a cat that needs an abdominal explore, but also presented w hepatic and renal dysfunction?
Buprenorphine
Remifentanil
Methadone

A

Remifentanil - metabolized by plasma esterases

52
Q

Oral opioids

A

Tramadol, codeine, hydrocodone

53
Q

Tramadol with dogs & horses

A

Metabolized by O-desmethyltramadol (M1) via P450 enzymes which determines the strength of analgesia
Dogs & horses produce less M1 = weak analgesia
Cats produce substantial M1 = effective analgesia

Moving Exam 2 (26 decks)

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