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6a > Pain medications > Flashcards

Pain medications Flashcards

1
Q

Definition of pain

A

unpleasant sensory and emotional experience associated with actual/potential tissue damage

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2
Q

Analgesia

A

absence of pain in response to stimulation which would normally be painful

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3
Q

Narcotics

A

drugs that produce sleep

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4
Q

Opiates

A

drugs derived from opium

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5
Q

Opioids

A

drugs that bind to opioid receptors

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6
Q

Mu1 receptor

A

Morphine
supraspinal analgesia
High density in the brain

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7
Q

Mu2 receptor

A

morphine
respiratory depression
high density in respiratory centre of the brainstem

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8
Q

Delta receptors

A

Enkephalins
spinal analgesia
high density in spinal cord - use for epidural

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9
Q

Kappa receptor

A

Dynorphin A
spinal analgesia
sedation

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10
Q

NOP (ORL1) receptors

A

non-opioid
opioid-receptor-like
Nociceptin/orphanin FQ binds
action not fully understood

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11
Q

Opioid receptor structures

A 
7 transmembrane segments (G-protein)
K+ and Ca2+ channels
opioid binding --> conformational change
K+ channel opens --> hyperpolarization
Ca channel closes in presynaptic membranes --> block conductance
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12
Q

Opioid sites of action

A

brain
brainstem
spinal cord
primary afferent neurons
medullary respiratory centre –> could lead to death
medullary chemoceptor zone –> activation triggers vomiting
Gut

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13
Q

opioid action in GI

A

slows down contractile frequency
paralyzes gut
constipation

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14
Q

Opioid MOA

A

Postsynaptic: hyperpolarization by opening of K+ channels (inhibitory)
Presynaptic: reduction of excitatory transmitter release (glutamate, peptides, tachykinin) by closing of calcium channels (inhibitory)

Activation of inhibitory enkephalin interneurons in dorsal horn of spinal cord
Activation of inhibitory descending pathways: endogenous analgesic mechanism (built in opioids)

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15
Q

Endogenous opioid peptide examples

A

beta-endorphin
Leu-enkephalin, met-enkephalin
Dynorphin

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16
Q

Endogenous opioid peptide characteristics

A

Mimic most effects of morphine
Antagonized by naloxene
Produce tolerance and physical dependence
Participate in endogenous control mechanisms
Modulate nociceptive transmission
May be responsible for placebo effect

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17
Q

Phenanthrene examples

A 
Morphine
Hydromorphone
Diacetylmorphine (heroin)
Codeine
Oxycodone
Nalbuphine
Naloxone
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18
Q

Phenylheptylamine example

A

Methadone

19
Q

Benzomorphan example

A

Pentazocine

20
Q

Phenylpiperidine examples

A

Fentanyl
Sufentanil
Ramifentanil
Meperidine

21
Q

Morphinians examples

A

Levorphanol

22
Q

Pure opioid agonists

A 
Morphine
fentanyl
Codeine
Hydromorphone
Oxycodone
Meperidine
Methadone
23
Q

Opioid agonist-antagonists

A

Nalbuphine

Pentazocine

24
Q

Opioid partial agonists

A

Buprenorphine

25
Q

Dosing of opioids

A

Most drugs used clinically are pure agonists
Different oral bioavailability
Codeine 12x less potent than morphine parenterally
Fentanyl 100x more potent than morphine parenterally
Agonist-antagonist decrease respiratory depression (agonist at kappa, antagonist at mu)

26
Q

Absorption of opioids

A

Most absorbed readily

27
Q

Absorption of morphine

A

increased hepatic first-pass, decreased oral bioavailability (25%)

28
Q

Absorption of codeine

A

increased oral bioavailability (60%)

29
Q

Absorption of heroin

A

increased lipid solubility –> BBB penetration

30
Q

Metabolism of morphine

A

hepatically converted to morphine-6-glucuronide (active) and morphine-3-glucuronide (excitatory and toxic at higher concentrations, myoclonic seizures)

31
Q

Metabolism of meperidine

A

hepatic conversion to normeperidine (excitatory and toxic)

32
Q

Heroine/Codeine metabolism

A

converted to morphine

33
Q

Remifentanil metabolism

A

rapidly hydrolyzed by nonspecific esterases

useful for continuous, easily adjustable iv infusion

34
Q

Morphine excretion

A

90% as glucuronides (urine), 10% unchanged (bile, feces)

35
Q

Central effects of morphine

A 
analgesia
hyperalgesia (at high doses)
cough suppression
euphoria (also dysphoria)
sedation
respiratory depression
Nausea and vomiting
Pruritis
Miosis
Truncal rigidity
Convulsions
36
Q

Peripheral effects of morphine

A

constipation
urinary retention
constriction of sphincter of Oddi (increased biliary colic)
Histamine release (direct mast cell degranulation; particularly morphine)
bradycardia (no other significant direct effects on the heart)
hypotension due to v/d

37
Q

Indications of morphine

A

analgesia for acute pain (mod to severe), cancer pain, anesthesia
Cough suppression - codeine, dextromethorphan
Antidiarrheal: loperamide, diphenoxylate
Acute pulmonary edema: iv morphine for pulmonary vasodilation

38
Q

Opioid tolerance

A

Begins with first opioid dose
no tolerance to miosis or constipation
cross-tolerance among opioids

39
Q

Opioid dependence

A

Occurrence of withdrawal symptoms (physical)

and/or craving (psychological)

40
Q

Opioid addiction

A

dependence accompanied by abuse and drug-seeking behaviour

All opioids carry abuse potential

41
Q

Naloxene/naltrexone MOA

A

antagonists at mu/delta/kappa receptors
almost no effects when given in the absence of agonists
rapid reversal of agonist effects
no tolerance
potential to precipitate withdrawal symptoms in dependent patients

42
Q

Opioid OD presentation

A

clinical triad:
coma
miosis
respiratory depression

43
Q

Opioid OD tx

A

general measures - ABCs, 100% O2

Specific: naloxene iv

44
Q

CI and cautions of opioids

A

Respiratory disease (COPD, OSA)
Drug interactions: meperidine+ MAOi –> hyperpyrexic coma
Opioids + sedatives/ethanol –> high CNS depression
Pregnancy - physical dependence of fetus
Use of pure agonists with agonist-antagonists: less analgesia, withdrawal

6a (26 decks)

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