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Pharmacology > Lecture 9: Pain Pharmacology > Flashcards

Lecture 9: Pain Pharmacology Flashcards

1
Q

What is the key difference between an anesthetic and an analgesic?

A

Anesthetics involve depressing all CNS characteristics, aka loss of all sensory modalities. Usually accompanied by LOC.

Analgesics are pain only, no LOC.

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2
Q

What is the gate-control theory?

A

Non-painful stimuli shut the gate to painful stimuli, preventing pain sensation from traveling to the CNS.

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3
Q

non opiod medications are called ___
what are their uses (3)

A

Adjuvant medications
- medications that enhance the efficacy of primary medications
- can also be used WITHOUT opiods
- can be used as a first-line treatement before considering opiods.

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4
Q

what is the prototype for all neuropathic pain meds. what is its MOA. what is its downfall

A

lidocaine
blocks Na+ channels
no oral admin

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5
Q

what are corticosteriods and how are they administered

A

glucocorticoids commonly used as an anti-inflammatory, administered orally and injectable

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6
Q

What are the side effects of corticosteroids?

A

Adrenal suppression
Appetite stimulation/weight gain
Cataracts formation
Impaired glucose metabolism
Edema
CHF
Osteoporosis
PUD
Bleeding
Mood changes
Steroid Psychosis
Joint degradation/atrophy at injection site with repeated injections.

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7
Q

What is the mechanism of action of corticosteroids?

A

Inhibition of phospholipase A2, which decreases the production of arachidonic acid and the inflammatory mediators.

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8
Q

What are the two pathways NSAIDs target?

A

COX-1
COX-2

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9
Q

What is the MoA of an NSAID?

A

Inhibition of the COX pathway. Subsequently inhibits prostaglandin formation.

Inhibits urate crystal phagocytosis (gout)

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10
Q

What does COX-1 inhibition commonly cause?

A

GI issues

Some prostaglandins are protective to mucosa which inhibit acid erosion

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11
Q

What does COX-2 inhibition commonly cause?

A

Decreases prostaglandins which therefore decrease inflammation, pain, fever

ALSO causes platelet aggregation and vasoconstriction, which is why celebrex has a cardiac black box warning.

(NSAIDS AND TYLENOL)

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12
Q

What is the PK of an NSAID?

A

absorption: Low pH causes absorption by intestinal and gastric mucosa.

distribution: Binds to albumin

metabolized: hepatically and conjugated to inactive metabolites,

Exccretion: renal excretion.

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13
Q

how does NSAIDS cause renal toxicity

A

prostaglandins are used to vasodilate the afferent arterioles in the glomeruli.

nsaids decrease prostaglandins

unnopposed constriction of arterioles = decreased renal perfusion = renal failure.

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14
Q

What lab test should I order before giving someone NSAIDs?

A

Renal function test, to check GFR
(BMP)

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15
Q

What are the other names for tylenol?

A

Acetaminophen/Paracetamol.

Scientific name: N-acetyl-p-aminophenol (APAP)

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16
Q

What is the MoA for Tylenol?

A

It is a selective COX inhibitor that generally targets COX-2.

Metabolites of APAP bind to TRPA-1 receptors (receptors for pain, stretch, temp), suppressing signal transduction of dorsal horn which supresses the pain/temp/stretch.

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17
Q

Why is tylenol an antipyretic?

A

COX enzyme reduction decreases formation for prostaglandin H2, which decreases prostaglandin E2 in hypothalamus (responsible for thermoregulation) which decreases temp

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18
Q

What is the max dose of tylenol in adults?

A

it was 4000mg/day but they recently decreased this to 3000mg/day

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19
Q

What kind of toxicity does excessive tylenol cause?

A

Hepatotoxicity

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20
Q

What two conditions can cause hepatotoxicity with tylenol?

A

High dosages and/or low glutathione, which is caused by excessive ETOH.

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21
Q

What kind of lab test should I order prior to tylenol use?

A

Liver function tests. (LFT) every 6 months

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22
Q

What are other non-opioid medications?

A

Lidocaine patch/cream (complete block of Na+ in neuron membrane = less pain)
Antispasmodics (decreased myofascial spasticity)
Compounding pharmacy topicals
Membrane stabilizers

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23
Q

what is the difference between opioids and opiates

A

opiates are natural opium alkaloids and semi-synthetics whereas opioids are morphine-like synthetics

the term opioids are used for both.

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24
Q

How do opiates work in general? howe do opioids work?

A

Alkaloid opiates mimic the action of endogenous endorphins (enkephalins) that are normally produced for analgesia by attaching to opioid receptors.

opiates act as ligands to attach to G-protein coupled (opioid) receptors in the brainstem/medial thalamus, spinal cord, and gastrointestinal regions.

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25
Q

What kind of receptor interaction are opioids?

A

Ligands binding to G-Protein coupled receptors.

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26
Q

What are the 3 opioid receptor subtypes?

A

Mu (u)

Kappa (k)

Delta

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27
Q

What is the main opioid receptor subtype? what does it control

A

Mu: responsible for analgesia, respiratory depression, GI SE, sedation, and pruritis.

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28
Q

What do kappa receptor subtypes control?

A

Analgesia, but mainly the consciousness effects, like hallucinations, euphoria, etc.

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29
Q

What do delta receptor subtypes control?

A

Analgesia possible.

Might offset respiratory depression from mu receptor subtypes.

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30
Q

What NTs does an opioid affect? How?

A

GABA inhibition, which inhibits substance P(pain).

Activates dopamine(causes euphoria).

Activation of receptor inhibits adenylate cyclase, decreases intracellular cAMP. Overall effect is reducing flow of nociceptive(pain) flow.

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31
Q

What are the two types of Mu receptors? What do they control?

A

Mu1 is responsible for analgesia and physical dependence.

Mu2 causes euphoria, respiratory depression, and constipation.

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32
Q

What are NMDA receptors? What is the significance?

A

Responsible for memory, enhances response to pain stimuli, suppresses CNS sensitization.

Antagonizing the NMDA receptors can help decrease tolerance to opioids. (Methadone)

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33
Q

What exactly is opium?

A

Dried milky latex from the opium poppy plant.

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34
Q

What are the 5 schedules of controlled substances? What are most opioids under?

A

Schedule 1-5, with schedule 1 being the most dangerous/addictive substances, such as LSD, heroin, cocaine, ecstasy, cannabis.

Most opioids are schedule II.

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35
Q

What are the pros and cons of short acting opioids?

A

Pros:
Good starter drug
Good for PRN use
Commonly prescribed

Cons:
Quick tolerance
Easy to abuse bc commonly prescribed
Highs and lows

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36
Q

What are the pros and cons of long-acting opioids?

A

Pros:
Sustained releases, long acting

Cons:
High risk for abuse
Not for opioid naive patients

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37
Q

What are the general SE of opioids?

A

Constipation, drowsiness, pruritis, respiratory depression, Hyperhidrosis, mental blunting, edema, dental loss, hypotestoteronism

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38
Q

What two medications are commonly used as adjuvants for opioids?

A

Ibuprofen and APAP/tylenol

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39
Q

What is the difference between dependence and addiction?

A

Dependence is when discontinuing an opioid causes withdrawal effects.

Addiction is when there is a psychological dependence and preoccupation with obtaining a supply despite harm to themselves or others. High incidence of recidivism.

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40
Q

Is tolerance inevitable?

A

Yes, due to neuroadaptation of the receptor.

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41
Q

When does pseudoaddiction occur?

A

Patients with both malignant and chronic pain. Most often seen in under-treatment of pain.

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42
Q

What are some drugs we give for opioid withdrawal?

A

Methadone

Clonidine

Suboxone

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43
Q

What is the weakest opioid agonist?

A

Tramadol

44
Q

What schedule drug is tramadol?

A

Schedule IV

45
Q

What is the MOA of tramadol?

A

weak mu opioid agonist. Also NMDA antagonist.

Acts on NE reuptake, increasing synaptic serotonin levels.

5-HT blocker!

Note: Tramadol is a prodrug. Its metabolite is more potent than its prodrug form.

46
Q

What kind of pain is tramadol indicated for?

A

Mild to intermediate.

47
Q

What are side effects and interactions I should be concerned about when prescribing tramadol?

A

N/V, pruritis, hyperhidrosis, minor drowsiness.
Can cause withdrawal if stopped abruptly.

Watch out for concomitant use of SSRIs/TCAs/SNRIs, other opioids, and serotinergic meds, as it can lower seizure threshold.

Note: It is a 5-HT blocker.

48
Q

What is codeine metabolized to?

A

Morphine.
Morphine has a half-life of 2-3 hours, just like codeine.

49
Q

What is codeine indicated for?

A

Mild to moderate pain
Antitussive

50
Q

What is the PK of codeine?

A

Requires CYP450 to be metabolized to morphine and another codeine metabolite.

51
Q

Why is codeine so important?

A

Prototype of weak opioids, such as tramadol, propoxyphene, hydrocodone, and oxycodone.

52
Q

What should I be concerned about when prescribing codeine?

A

SE: somnolence, constipation, pruritis, N/V, miosis, depression, resp depression, dependence, addiction, and tolerance.

Caution in renally-impaired pts.

Note: 2D6 inhibitors as well, but not on exam.

53
Q

What is codeine often combined with?

A

APAP 500mg.
Also butalbital-type HA preps.

54
Q

What is morphine the prototype for?

A

All opioids!

55
Q

What drug is morphine very closely related to?

A

Heroin

56
Q

What is the PK of morphine?

A

Metabolized by liver into M6G, codeine, and hydromorphone.
Renal excretion.

57
Q

Is morphine hydrophilic or lipophilic?

A

Hydrophilic. It crosses the BBB poorly, so it has very low PO bioavailability.

58
Q

What does morphine act on and its onset?

A

High affinity for mu receptors.
Short half-life (2-3 hours)
However, slow onset.

59
Q

Why do we dose morphine PO much lower than its parenteral dosing?

A

First pass metabolism. Morphine gets converted into many stronger metabolites, so we sometimes want to skip the liver.

Dosing is 1:3.

60
Q

What additional SE does morphine have besides the common opioid ones?

A

Histamine release, which can induce significant pruritis, hypotension, and nausea.

61
Q

What is the PK of hydrocodone?

A

Hepatic metabolism to hydromorphone and norhydrocodone.
Renal excretion.

62
Q

What is the MOA of hydrocodone?

A

Mu receptor agonist.

63
Q

What is the half-life of hydrocodone?

A

around 4 hours.
Crosses the BBB easily.

64
Q

How much strong is hydrocodone over morphine and codeine?

A

5x more potent at the same dose for morphine.
Greater binding than codeine.

65
Q

What is hydrocodone indicated for?

A

Moderate to severe post-op pain.
Acute, chronic pain.
Antitussive in cough syrups.

66
Q

What is hydrocodone typically prepared with?

A

APAP (325mg)
Ibuprofen

67
Q

What is the most prescribed and consequently abused analgesic in the US?

A

Hydrocodone ):

Note:
All SE are the same as opioids.

68
Q

What is the PK of oxycodone?

A

Hepatic metabolism to active metabolites.
Lipophilic
Renal excretion
HL: 3-4 hours.

It is unsure whether its metabolites or its prodrug form is responsible for the analgesia.

69
Q

What is oxycodone indicated for?

A

Moderate to severe pain.

70
Q

What is oxycodone often prepared with?

A

APAP.

71
Q

What are the SE and black box warnings for oxycodone?

A

SE: similar to opioids but less than morphine.

Black box warning: abuse, resp depression, accidental OD/overexposure.

72
Q

What is the PK of oxymorphone?

A

Active metabolite of oxycodone.
5x stronger than oxycodone.
More lipophilic than morphine, with a half-life of 7-8 hours.

Acts primarily on mu receptors.

73
Q

What is oxymorphone indicated for?

A

Moderate to severe pain.

74
Q

What is the PK of hydromorphone?

A

Identical to morphine.

Note: It is a hydrogenated ketone of morphine, as well as one of its metabolites.

5-10x more potent than morphine. Lipophilic. Faster acting.

Half-life: 2.25 hours.

High mu affinity.

75
Q

What is hydromorphone indicated for?

A

Chronic and acute moderate to severe pain.

76
Q

What are the SE of hydromorphone?

A

Same as morphine, but less histamine release and has inactive opioid metabolites.

77
Q

What is the PK of fentanyl?

A

Highly lipophilic, immediate onset.
Short half-life, no active metabolites.
Hepatic EXCRETION, so safe for renal impaired pts.
It can settle in adipose tissue, so clearing the body can take 24 hours.

Selective mu binding, 100x stronger than morphine.

78
Q

What are the SE of fentanyl?

A

Much lower than morphine.
Significant OD potential!!!
If losing weight, dosage must be adjusted.

79
Q

What is the more potent analog of fentanyl?

A

Sufentanil, 5-10x more potent with 400-1000x more potency than morphine.

80
Q

What is the unavailable opioid?

A

Tapentadol.

81
Q

What is significant about the PK of methadone?

A

15-60 hour half life!

Highly lipophilic.
Hepatic metabolism, but renal clearance.

It acts on mu, but also has NMDA antagonism, which can decrease tolerance long-term.

82
Q

What is methadone indicated for?

A

Prevent withdrawal in opioid addiction.

83
Q

What are the SE of methadone?

A

Prolonged QT interval/Torsades
You need a baseline EKG and cardiac history before giving methadone.
Other SE similar to opioids.

84
Q

What is the PK of Pentazocine?

A

Quick onset. (minutes)
Half-life 2-3h
Hepatic metabolism, renal clearance.
Activates mu AND kappa, so higher hallucination potential and abuse potential.

85
Q

How is pentazocine prepared?

A

Mixed with naloxone, which will negate the opioid effects if the medication is crushed or dissolved.

86
Q

What is pentazocine indicated for?

A

HA

Note: It is an agonist-antagonist.

87
Q

What is the PK of buprenorphine?

A

Partial mu agonist (less resp depression)
K and D antagonists
Hepatic metabolism, mixed clearance.
Half-life 20-40h

88
Q

What is Suboxone indicated for?

A

Opioid addiction/dependency therapy.

89
Q

What is suboxone a combination of?

A

Buprenorphine and naloxone.

90
Q

What is naloxone indicated for?

A

Emergent opioid overdose reversal.

It can decrease opioid side effects quickly and can be used to treat opioid addiction.

91
Q

What is the MOA of naloxone?

A

Blocks mu.
Antagonizes K and D receptors.

Note:
It has higher affinity for mu than opioids.

92
Q

What is the half-life of naloxone?

A

1 hour.

93
Q

What is naloxegol indicated for?

A

Opioid-induced constipation.

94
Q

What is the MOA of naloxegol?

A

Peripherally selective opioid antagonist. It cannot cross the BBB, so it only goes to the gut.

Note:
It has the complete opposite effect of loperamide, which is a colon-only mu agonist.

95
Q

What is the main CYP inhibitor to be wary of when prescribing opioids?

A

Grapefruit juice!!!!!!

96
Q

What is the strongest opioid we learned?

A

Fentanyl, along with its analog, sufentanil.

97
Q

What opioids double as antitussives?

A

Codeine and hydrocodone.

98
Q

What medication requires lower PO dosing than parenteral dosing?

A

Morphine.
1:3 ratio.

99
Q

How many morphine equivalents can be given a day for non-maligant pain per the CDC?

A

50-90.

100
Q

What should I test pts for before starting methadone?

A

EKG and cardiac history.

101
Q

What should I test pts for before starting opioids?

A

Urine Drug Screens.

Perform a baseline and annual at random.

102
Q

What two opioids do I use to treat addiction?

A

Suboxone
Methadone

103
Q

If someone if in opioid overdose, what should I give them?

A

Naloxone!

104
Q

What is the weakest opioid agonist?

A

Tramadol.

105
Q

What are the 2 most potent prescribed opioids?

A

Methadone
Fentanyl

Pharmacology (19 decks)

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