Chapter 10 - Opioids Flashcards
What are opiods?
a class of psychoactive substances that acy on opioid receptors in the CNS and other parts of the body; produces euphoria (highly abused)
Opioids are called ____ and are used for ____
pain relief (also used to treat diarrhea and as a cough suppressant)
Opioid death in Canada
major drugs of abuse and causes of many accidental overdose; today fentanyl is the main concern; ~20 deaths a day;
Opioids are derived from ____
papaver somniferum (sap of the poppy is raw opium)
Three naturally occurring opiates (from opium)
Morphine, codeine, thebaine
Morphine can be further processed into ____
Heroine
(Heroine = morphine + acetic anhydride)
Five semisynthetic opioids
Diacetylmorphine (heroine), desomorphine (krokodil), buprenorphind, hydrocodone, oxycodone
Two fully synthetic opioids
Fentanyl, methadone
-not derived from naturally occurring opioids
History of opium use
Used for 1000s of years; sold in drug stores in 19th century
Absorption (pharmacokinetic properties)
Oral administration (codéine, méthadone); IV injection (heroine; most common for illicit use); inhalation (used to be smoked)
Distribution (pharmacokinetic properties)
readily cross BB ; differ in speed (ex heroine crosses faster than morphine, produces greater high, more potent, 4-8x more addictive)
Metabolism (pharmacokinetic properties)
Occurs in the liver; active metabolites with similar psychoactive properties are common
Elimination (pharmacokinetic properties)
Rates vary from drug to drug
- methadone and buprenophine and long elimination rates (not as potent)
What is the endogenous opioid system?
Comprised of several NT and receptors; NTs consist of β- endorphin, met-enkephalin, leu-enkephalin, dynorphin A, dynorphin B, and neoendorphin (they are neuropeptides that are cleaved from larger propeptide molecules)
What is proopiomelanocortin?
source of β-endorphin
what is proenkephalin
the source of met- and leu- enkephalin
what is prodynorphine
the source of dynorphin A, dynorphin B, and neoendorphin
endogenous opioids bind to what 3 types of opioid receptors?
µ (pronounced “mu”)
Δ (“delta”)
κ (“kappa”)
most opioids act on the ____ receptor
µ
-opioids are classified by the effects on the receptor
pure opioid receptor agonists are ____ and ____
fentanyl and morphone
partial opioid receptor agonists
lower efficacy for activating receptors than full agonists
-buprenorphine
pure opioid receptor antagonists
block receptors; used to treat opioid addiction or emergency antidote
-naloxone and naltrexone
2 ways opioids increase dopamine release in nucleus accumbens
- inhibiting GABA neurons in the VTA that synapse on DA neurons (leads to disinhibition of DA neurons therefor incr DA in the mesolimbic projection)
- inhibiting GABA neurons in the NA that project to the VTA (also leads to disinhibition.. same as prev)
2 ways opioids affect the pain system
2 pathways affecting nociception
1. Pain information is carried by Aδ and C fibers through the dorsal horn of the spinal cord and release glutamate and substance P at synapses with spinothalamic neurons.
2. Spinothalamic neurons send nociceptive information to the thalamus which routes the information to somatosensory cortex, the cingulate cortex, and the amygdala
opioids weaken neurotransmission within the ____ pain pathways
nociception
Neurons in the Periaqueductal Gray (PAG) release endogenous opioids in the medulla, which contains a high density of μ opioid receptors. What does this mean?
Inhibits the activity of spinothalamic neurons passing through the medulla, thus reducing nociceptive information flow to the thalamus
other effects of opioids
inhibit respiration; inhibit cardiovascular function; inhibit digestion; chronic administration suppresses immune function
rush (stages of opioid effects)
initial rapid onset of euphoria
high (stages of opioid effects)
feelings of joy and ease
nod (stages of opioid effects)
calm, disinterest, unawareness of surroundings
straight (stages of opioid effects)
period of normalcy between craving an opioid and feeling the euphoric or other positive effects of an opioid
self-administration procedures in animals indicate that opioid agonists produce potent ____
reinforcing effects
medicinal use of opioids
diarrhea, cough suppressant; fentanyl and oxycodone are often prescribed for severe pain management; itchiness side effect
opioid overdose
severe depression of respiration; weakness; inability to speak; blush lips and skin; unconsciousness; effects magnified by other depressants
withdrawal from opioids usual gives the ____ effect
opposite (ex. used for relaxation, restless in withdrawal. used for constipation, diarrhea in withdrawal)
-withdrawal is not life threatening
long term opioid detoxification (treating addiction)
lasts ~180 days; involves drug replacement therapy with agonist (methadone)
short term detoxification (treating addiction)
lasts ~30 days and uses drug replacement (methadone); more aggressive form of detox and will have moderate withdrawal symptoms
rapid detox + ultra rapid detox (treating addiction)
up to 10 days for rapid; 2 days for ultra rapid; both use opioid receptor antagonists (naltrexone); withdrawal symptoms can be severe and patients are often anesthetized
what else may have to be treated alongside opioid addiction
psychological disorders or medical conditions like HIV or HepB
