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PHARMACOLOGY > OPIOD ANALGESICS > Flashcards

OPIOD ANALGESICS Flashcards

1
Q

ANALGESICS

A

pain relief

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2
Q

what is pain

A
  1. unpleasant sensation accompanying tissue damage that is detected and transmitted to the CNS by SOMATIC NOCICEPTIVE AFFERENT NEURONS
    . alpha delta - sharp pain
    . C - aches (muscle strain)
  2. sensation that persists long after an injury // not associated with any injury NEURALGIA / PHANTOM LIMB SYNDROME
    - as a result of spontaneous activation of pain mediators in CNS
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3
Q

how is pain sensed by the body

A

primary pain receptor = CALCIUM - triggers A.P

.ATP facilitates DEP entering P2X R / VG Na+ channels
. NGF - survival/health of neurons in CNS
affect expression for Trk R / upregulate expression of TRPV
(more TRPV - neuron more sensitive to pain stimuli
.GPCR - facilitate opening of TRPV//Na+

. VG K+ inhibit DEP/HYPER = limit pain sensation

. opioids/cannabinoids/NE = inhibitory effects

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4
Q

explain pain perception

A

.excitatory pathways enter DORSAL HORN of SC (both alpha delta + C afferent neurons)
. ascending tract of pain sensory network = glutamate NT

.descending tract - pain suppressor sites feeds down to gate control system
- Serotonin/ Enkephalin/ GABA = block activity of alpha delta + C afferent neurons

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5
Q

opioids

A

agonists

group of analgesic (pain relief) drugs - bind to opioid receptors

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6
Q

what blocks the effects of opioids

A

opioid antagonists

NALOXONE / NALTREXONE

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7
Q

opioids target neurons in both PNS + CNS

A

periaqueductal grey matter (midbrain)
nucleus reticularis (medulla)
= enhance pain suppressive effects of descending pathway

blocks transmission of nociceptive afferent neurons
block upward pathway of pain sensation - Dorsal horn

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8
Q

what kind of molecules are opioids

A

amphipathic
.benzene ring
. bind to GPCR (no need to get inside cells like LA)
.transmembrane receptors - external domain that binds to ligands
= get pass BBB -> CNS
(need to be hydrophobic to pass endothelial cells)

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9
Q

what is naloxone

A

competitive antagonist

similar to heroin/morphine (drugs of abuse)

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10
Q

3 opioid receptors

A
  1. mu (u) binds agonist MORPHINE
    natural ligands: met-enkephalin, B-endorphin, dynorphin
  2. kappa (k) bind KETOCYCLOZAINE
    natural ligands: B-endorphin, dynorphin
  3. delta (D) in VAS DEFERNS of mouse
    natural ligands: met-enkephalin, leu-enkephalin B-endorphin (no clinically used drugs bind to this R)
    = no serious side effects
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11
Q

opioids mimics the structure of naturally occurring opioid peptides

A

Tyr-Gly-Gly-Phe
amino acid sequence shared by leu-enkephalin, met-enkephalin, B-endorphin and dynorphin

others pain enhancing peptides fall into the class of tachykinins

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12
Q

opioid mechanism of action

A
  1. opioid receptors are coupled to Gi
  2. activation of Gi = inhibits adenylate cyclase = decreased levels of cAMP
  3. MAP kinase pathway also activated
    immediate result = increased K+ efflux and inactivation of VG Ca2+ channels

net result: HYPERPOLARISATION of neuron + INHIBITION of NT release

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13
Q

pharmacokinetics

A

absorption, distribution, metabolism, and elimination of drugs

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14
Q

opioid pharmacokinetics

A
  1. rate of anesthetic effect onset is dependant on LIPID SOLUBILITY of drug *passing BBB
  2. most opioids metabolized > more polar + water-soluble compounds = LESS ACTIVE than original drugs
  3. some opioids metabolized to compounds with GREATER ACTIVITY:
    CODEINE&raquo_space; Morphine = higher affinity of (u) receptors
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15
Q

uses of opioids

A

analgesic/euphoric :
MORPHINE
FENTANYL - very potent = used with GE
OXYCODONE - post surgery/chronic moderate-severe pain

CODEINE (cough suppressant) - slowly converted to morphine (20% potency)
LOPERAMIDE - antidiarrheal activity (R on GI tract)

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16
Q

what is nalbuphine

A 
antagonist of (u) receptors 
agonist of (D) receptors
partial agonist of (k) receptors
17
Q

side effect of opioids

A
  1. respiratory depression
  2. sedation
  3. constipation
  4. nausea
  5. irregular menstrual cyles/male impotence
  6. myosis (constriction of pupil)
  7. immunosuppression
  8. increase pain associated with gall bladder
  9. dysphoria (state of discomfort/unease)
18
Q

what do opioid antagonists do

A

reduce opioid side effects
. methylnaltrexone
. used to treat constipation associated with (u) agonists
. cannot cross BBB - does not alter CNS effect of agonists

19
Q

explain side effects of all the receptors

A

mu - affects everything except dysphoria/hallucinations

D - decrease GI movement/respiratory depression

K - causes dysphoria/hallucinations

20
Q

tolerance

A

increasing doses of drug to produce same effect (habituation)

21
Q

cross-tolerance

A

tolerance to one opioid often accompanied by tolerance to others

22
Q

physical dependence

A 
sudden end of long-term opioid use
. increased irritability
. fever
.sweating
.nausea 
. diarrhea 
. piloerection 
. hyperalgesia (increased sensitivity to pain)
23
Q

what is used to treat physical addiction to morphine or heroin

A

METHADONE - opioid agonist - no physical dependance

24
Q

psychological dependence

A

strong cravings for the drug for months after physical symptoms have ended
(rarely in patients who use morphine to control pain)

25
Q

what receptors are key to hyperalgesia (increased sensitivity to pain)

A

NMDA glutamate receptors

26
Q

what normally happens with opioid withdrawal and how can you prevent this

A

normally opioid agonist decreases pain, then when stopped = increases pain further

give antagonist = pain decreases (less) but no rebound effect when stop taking drug

27
Q

how can you repackage old drugs to reduce abuse

A

extended-release opioids reduce maximum dose:
OxyContin - extended-release form of oycodone

crush-resistant DETERx extended-release oxycodone
= less likely to be snorted

OXN Naloxene-treated hydrocodone prevents IV administration of the crushed compound

28
Q

explain the mechanism of physical dependence

A

.(mu) receptor expression is regulated by CREB (activator gene)
. CREB activated by cAMP
. (mu) receptor agonists bind to (mu) receptors activating Galpha i = inhibits adenylate cyclase

.decreased expression of (mu) receptors = make cells less sensitive to (mu) agonists
= need higher dose to achieve same effects

29
Q

what drug prevents opioid addiction

A

AT-121

30
Q

how does AT-121 work

A

bifunctional agonist = binds to both (mu) and NOP R
100x more EFFICACY than morphine
without respiratory/cardiovascular depression, sedation, inhibition of motor activity, or dependance
(pretreatment with AT-121 - prevented dependence associated with oxycodone)

PHARMACOLOGY (24 decks)

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