Opioids for Pain Flashcards
1
Q
Ad fibers
A
- pain
- thinly myelinated
- 6-30m/sec
2
Q
C fibers
A
- pain
- unmyelinated
- .5-2m/sec
3
Q
Consequences of Pain Processing
A
1) modulation of peripheral receptor/ion channel properties
2) modified gene expression
3) decreased threshold for AP generation
4
Q
Spinoreticular tract
A
spine -> reticular formation
5
Q
Spinothalamic tract
A
- localizing type of pain
- regional identity
6
Q
Mu (MOP)
A
- mediates analgesia
- respiratory depression
- miosis
- euphoria
- sedation
- decreased gastrointestinal motility
- physical dependence
7
Q
Kappa (KOP)
A
- mediates analgesia
- enteric: decreased gastro motility
- ** DYSPHORIA/DISOREIENTATION/ANXIETY ***
- – no used much in clinical settings
8
Q
Delta (DOP)
A
- caused siezures in rats: not for human use
9
Q
Must “classic” opiates bind to an exert their actions at ___ receptor categories
A
- all 3 receptor categories
- to different degrees
10
Q
Opiod Motif
A
- YGGFM
- YGGFL
11
Q
Enkephalins
Dynorphins
B-Endorphins
A
- cross reactions
- not very specific
12
Q
Phernathrenes
A
5 rings
- heroin
- codeine
- hydrocodone
- oxycodone
- ** RAPID CNS PENETRATIONS ***
- v fast at getting into brain and causing effect
13
Q
Morphinans
A
4 rings
- levophanol
- butorphanol
- levallorphan
14
Q
Benzomorphans
A
3 rings
- pentazcine
15
Q
Diphenoxylate
A
Phenylpiperidines
16
Q
Merepiridine
A
Phenylpiperidines
17
Q
Fentanyl
A
Phenylpiperidines
18
Q
Loperamide
A
Phenylpiperidines
19
Q
Primary Actions of Opiates
A
- Analgesia
- Pupil constriction
- Respiration
- Cough
- Euphoria
- Sedation
- Nausea
- GI tract
- Biliary tract
- Bladder
- Uterus
20
Q
Analgesia
A
- reduce reactive component of pain
- reduce sensory threshold
- more effective against continuous dull pain than sharp, intermittent pain
21
Q
Respiration
A
- reduce sensitivity of medullary control center
- primary action on repiratiory rate (<3,4/min leading to death)
22
Q
Cough
A
- antitussive
- receptors not stereospecific
- dextromethorphan is antitussive but produces no respiratory depression
23
Q
Dextromethorphan & Respiration
A
dextromethorphan is antitussive but produces no respiratory depression
24
Q
Euphoria
A
- generally seen with a patient in pain or an addict
- occasionally dysphoric
25
Methadone
- synthetic my agonist
- 85% oral bioavailability
- t1/2 25-52 hours (long t1/2, less withdrawal)
— withdrawal mild though prolonged compared to morphine
- pharmacological actions virtually identical to morphine
- cross-tolerance and dependence with morphine
*** oral maintenance programs for heroin users ***
— heroine wont work if they’re on methadone (because of cross-tolerance)
26
Fentanyl
- highly potent mu agonist
- actions similar to morphine but 100x more potent
- used in anesthesia
— rapid onset, short duration of action
- transdermal patches and oral lozenge
27
Oxycodone
- semi-synthetic moderate mu agonist
- need biotransformation for activity
- high oral bioavailability
- metabolites can accumulate and cause renal failure
- widely used to treat terminal cancer
28
Oxymorphone
- Very potent mu agonist (10x more than morphine)
| - prominent euphoric effects
29
Pentazocine
- kappa agonist (causes anxiety)
- weak mu partial agonist
- less effective than morphine
- used for mild-to-moderate pain
- low abuse potential; can’t get high off it
30
Buprenorphine
- high affinity mu partial agonist
- prolonged t1/2 due to slow dissociation from mu receptor
- slow mild withdrawal
- FDA approved as an alternative to methadone for treatment of opioid dependence
31
Additional Opiate Agonist Indications
- Cough (dextromethorphan)
| - Diarrhea (Loperamide)
32
Dextromethorphan
- used to treat cough
- does NOT bind to the mu receptor
- binds to the receptor which mediates cough suppression
- no abuse potential
- large TI
33
Loperamide
- diarrhea
- acts locally to diminish the peristaltic refleX
- poorly absorbed, restricted to gut
- not absorbed enough elsewhere to cause effect (poor CNS penetration)
- low abuse potential
34
Pharmacological activity of opioid antagonists dependent on:
- whether endogenous opioids have been released
- whether an opiate agonist has been administered previously
- the pharmacological profile of the opiate
- the degree to which physician dependence to an opiate has developed
35
Halo one, Naltrexone, and Nalmefene
ANTAGONISTS at MOP, KOP, and DOP
— work against all receptors
- reversibility of a drug’s effect
- no pharmacological utility when used alone
- reverse all pharmacological effects mediated by mu and kappa receptors
- precipitates withdrawal syndrome in patients physically dependent
36
Naloxone
- short t1/2
| - repeated doses may be needed
37
Naltrexone and Nalmefene
- longer t1/2
38
Naloxone and Nalmefene absorption
- not well absorbed orally
| - better IV
