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Flashcards in Opioids Deck (47):
1

Which opioid is Fentanyl chemically related to?

Meperidine

2

Describe chemical component of opioids:
-acid/base
-protein binding
-neutral o rionized

weak base
high protein binding
largely ionized at physiologic pH

3

How would causing decreased protein binding and un=ionized forms of opioids effect their behavior?

- shorter latency to peak effect

4

MOA of opioids (general/basic)

Bind opioid receptor- G protein linked
downstream effects cause hyperpolarization of cell, and decreased neuronal excitability

mediators- K+ channel, AC, MAPK, Voltage gated Ca+ channels

5

Name the types of opioid receptors

mu
kappa
delta
(ORL1)- unclear clinical relevance

6

Major effect of opioids at
1. spinal cord
2. brainstem
3. forebrain

1. Spinal cord
a. inhibit release of substance P from primary sensory neurons in DH (mitigates painful sensation transfer to brain)

2. Brainstem- block nociceptive transmission from DH of SC via descending inhibitory signals

3. Forebrain- alter affective response to pain

7

General metabolism of opioids

Hepatic microsomal metabolism (conjugation)

Excreted by kidney

**not case with all**

8

Order the following opioids from QUICKEST peak effect to SLOWEST peak effect for a BOLUS

morphine
fentanyl
sufentanil
alfentanil
remifentanyl

Alfentanil/Remifentanil --> Fentanyl -->Sufentanil -->Morphine

9

Order the following opioids from QUICKEST peak effect to SLOWEST peak effect for a INFUSION

morphine
fentanyl
sufentanil
alfentanil
remifentanyl

Remifentanil -->Alfentanil --> Sufentanil -->Fentanyl/Morphine

10

Which opioids would be preferred in bolus form if you desire a brief duration with rapid dissipation?

Remifentanil or Alfentanil

11

Which opioid is best suited for a PCA? Why?

Fentanyl > Morphine

Peak effect as seen on front end kinetics shows that greatest effect of Fenatnyl occurs before "lock out period" ends for PCA...avoiding dose stacking and OD risk

12

What determines the latency to peak effect?

which factors effect this most?

speed that plasma and effect site come to equilibrium

i.e. Faster = Higher proportion of drug that is "diffusible", i.e. unbound and un-ionized.

Faster = higher lipid solubility

13

Clinical implication of stead-state concentration of opioid constant rate infusion? Exception to this?

- Latency to reach steady state effect

- demonstrates need for bolus prior to infusion to bridge to peak effect

Exception: Remifentanil

14

Which drug is a good choice for total IV anesthesia for opioids?

Remifentanil- reaches a steady state quickly (drug will not be continuing to increase in concentration for hours despite continued or lowered infusion rate)

15

Define Context Sensitive Half Time (CSHT)

Time required to achieve a 50% decrease in concentration of drug after stopping continuious steady state infusion

16

How does decrease in opioid rate change over time re: infusion duration?

Longer duration = longer CSHT (Except Remifentanil)

Helps to determine which opioid is best based on case duration and length of time needed for drug

17

Major Mu opioids

morphine, fentanil

18

Major opioid group with venitilatory depression

mu

19

major opioid group with GI effects

mu and kappa

20

major opioid groups causing sedation

mu and kappa

21

Major side effects of opioids

1. Supraspinal/spinal analgesia
2. Miosis (small pupils)
3. cough suppression
4. vasodilation (hypotension)
5. Bradycardia
6. ventilatory depression
7. increased biliary pressure
8. n/v
9. constipation/illeus
10. delayed gastric emptying
11urinary retention
12. muscle rigidity
13. pruritis

22

Which "type" of pain are mu opioids best at treating?

"second pain" - slow conducting unmyelinated C fiber pain

vs "first pain" via small myelinated A delta fibers or neuropathic pain

23

MOA of opioid induced vent depression

alter vent response to arterial CO2 in medulla (threshold for increase is paCO2 of 40 mmHg, linear increase there after, but slowed)

Both Vt and RR decrease --> progress linearly with increased conc until apnea

regulated via mu receptor

24

Factors increasing risk for opioid OD

1. large opioid dose
2. old age
3. use of other CNS depressants (benzos, etc)
4. renal insufficiency (for morphine)
5. natural sleep

25

CV effects of opioids (fentanyl, morphine)

Fentayl vs Morphine, greater CV effects?

Bradycardia (increased vagal nerve tone)

hypotension (vasodilation via brain effects, decrease pre and afterload)

Morphine > Fentanyl

26

Side effect that may make ventilation difficult with bolus doses of fentanyl?

muscle rigidity, causing vocal cord rigid/closure (hard to ventilate)

can be eliminated by NM blocking drugs

27

MOA of opioid induced nausea

chemoreceptors in area postrema on floor of 4th ventricle

worse with movement

28

Major pharmacokinetic interaction of opioids with other drugs

Propofol

Opioids given with propofol infusion result in higher opioid concentrations

29

Major pharmacodynamic effect of opioids with other medications

synergy when combined with sedatives

moderate opioid levels dramatically reduce MAC of inhaled anesthetics (substantially, up to 75%).

Reduction is NOT complete...opioids are not a complete anesthetic

30

Which opioid is completely unaffected by the anhepatic phase of a liver transplant?

remifentanil- metabolism is completely unrelated to hepatic clearance

31

Pt population at increased risk of sedative effects of opioids?

pts with hepatic encephalopathy

32

Which opioids are affected by renal failure?

morphine - nearly half of the conjugation of morphine occurs in the kidney (in addition to excretion of m3g and m6g*active)

meperidine - active metabolites are excreted by kidneys. build up of normeperidine causes tremors, anxiety, frank seizures

33

Gender differences in opioid effects

Morphine - more potent in women, slower onset in women

34

Age differences in opioid effects

older = more potency of fentanyl cogeners

Decreased clearance and decreased distribution volume

RESULT: decreased dose requirements (50% reductions) for pts > 65yo

35

Obesity effects on opioids

Opioid requirements based on lean total body mass, not TBW

extremely obese people will not require doses suggested by their weight because lean body mass is smaller

36

What is the active component of codeine?

morphine is active compound of this prodrug

37

Side effects of morphine limiting its use intraoperatively? why?

Histamine release = hypotension (and itching)

38

Fentanyl routes of administration

IV
transdermal
transmucosal
transnasal
transpulmonary

39

Describe metabolism of alfentanil

liver via cyp3a4 (somewhat unrpredictable due to interindividual variation in this enzyme)

40

most potent opioid used in anesthesia practice

sufentanil

41

metabolism of remifentanyl

ester hydrolysis

loses mu reactivity = short half life

42

speed and duration of action of remifentanyl

quick on and quick off (due to hydrolysis)

short CSHT (5 min)

- latency similar to alfentanil
- potency slightly less than fentanyl

43

Commonly used meds in total IV anesthesia

Remifentanil + Propofol

44

Questions to ask when choosing and opioid

1. how quick does it need to work?
2. how long will i need it to work?
3. How important is it that vent depression/sedation go away quickly?
4. will the opioid need to be titrated intraop (big changes in analgesia requirements)?
5. will there be a lot of pain post-op?

45

Your patient is getting a retrobulbar block and you need a brief pulse of opioid effect and then rapid recovery:

What med?

Bolus Remifentanil/Alfentanil

46

Your patient is getting a craniotomy, and neurosurgery wants to do a neuro exam on table immediately post-op (need good pain control, but awake/alert soon after procedure:

what med?

remifentanil infusion

47

Need long-lasting pain control, and post-op pain likely to be high?

fentanyl infusion