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PYB260 > Week 12 - Opiates > Flashcards

Week 12 - Opiates Flashcards

1
Q

What are opiates

A
  • opium
  • opiates/opioids
  • morphine & codeine
  • heroin
  • synthetic opiates
  • endogenous ‘opiates’
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2
Q

what are opiates also known as?

A

narcotics or narcotic analgesics

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3
Q

nacrcotic analgesics

A

decrease sensitivity to pain and induce sleep

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4
Q

what criteria must opiates meet

A
  1. sedative-hynotic & analgesic properties
  2. acts on endorphin/enkephalin receptors
  3. actions antagonized by naloxone
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5
Q

Opium

A
  • extracted from poppies
  • active ingredients in seedpod sap
  • 2 main ingredients: morphine & codeine
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6
Q

heroin

A
  • derived from morphine
  • semi-synthetic opiate
  • 10 x more lipid soluble vs morphine = faster absoprtion in increased concentrations
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7
Q

synthetic opiods

A
  • opiate-like effects (stimulate opiod receptors) but different chemical structure
  • egs: meperidine, gentanyl, dextromethorphan & LAAM
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8
Q

Morphine

A
  • base, pKa 8.0
  • less effective when taken orally (vs injection)
  • oral administration undergos significant first pass metabolism in liver, absorbed slowly (desirable for analgesic properties)
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9
Q

administration of heroin

A
  • usually injected
  • can be taken intranasally (snuff)
  • inhaled (chasing the dragon)
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10
Q

distribution

A
  • concentrated in heart, lungs, kidney, liver, spleen & bound to proteins in blood
  • pass through placental more readily than BBB (low lipid solubility) heroin is highly lipid soluble
  • within brain, opiates are concentrated in basal ganglia, amygdala & periaquaductal gray matter
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11
Q

active ingredients of opiates

A
  • morphine itself
  • heroin: molecules are inactive in the brain but it’s metabolites are active
  • codeine: primary action through metabolites
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12
Q

2 phases of metabolism in liver

A
  1. digestive system enzymes (CP450)
  2. metabolic interference - conjugation btwn metabolite/drug molecule & water loving substance
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13
Q

excretion of morphine

A
  • active transport mechanism from brain
  • 10% excreted unchanged (in urine)
  • 1/2 life = 2-4.5hrs
  • 90% eliminated <24 hrs
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14
Q

excretion rates of other opiates

A
  • varies
  • codeine: 1/2 life = 1.4-3.5 hrs
  • methadone has a very long half-life (25-40 hrs)
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15
Q

opiate receptors & endogenous opiates

A
  • 4 types in the brain, also exist outside CNS - classical and non-classical
  • endorphines are an endogenous morphine
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16
Q

endogenous opioids

A
  • enkephalins
  • endorphins
  • endomorphins
  • dynophins
  • nociceptin
    thought to function as NTs, NMs or hormones
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17
Q

3 classical opiate receptors

A

Mu (MOR) - limbic system, hippocampus, amygdala, thalamus, nucleus accumbens, VTA, hypthalamus
Kappa (KOR) - hypothalamus, thalamus, nucleus accumbens, amygdala, VTA
Delta (DOR) - limbic system, pfc, hypothalamus, nucleus acucmbens, medulla

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18
Q

non-classical opiate receptor

A

opiod receptor-like or nociceptin (ORL): non-typical, different pharmacological profile

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19
Q

neurophysiology of opiates

A
  • receptors do not always act independently
  • some opiates act on more than one receptor
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20
Q

all opiod receptors are metbotropic and work on

A
  • second messengers (inhibitory effects on postsynaptic cell & inhibitory neuromodulator of NTs from presynaptic membrane or)
  • kinases directly from inside the cell
21
Q

opiate receptors on pre-synaptic and post-synaptic cells

A

presynaptic: inhibit Ca+ influx - inhibitory neuromodulator
post-synaptic: enhance K+ flow out of neurons causing hyperpolarization - inhibitory NT

22
Q

neurophysiology of synthetic opiates

A
  • similar action to morphine
  • act as antagonists to opiates - block the action of any other opiate
  • known as mixed agonist-antagonists: have some opiate like activity of their own but block other opiates
23
Q

neurophysiology of naloxone

A
  • opiate antagonist
  • block Mu receptors but has no opiate effects
  • used to treat opiate overdoses
24
Q

neurophysiology of pain effects

A
  1. blunt sensory information to areas of spinal cord responsible for pain (inhibits transmission dull/burning pain)
  2. stimulates receptors in periaqueductal gray & thalamus (physical pain)
  3. stimulates receptors in limbic system (emotional pain)
25
Q

what opiate receptors are associated with different pain types

A

Mu - most pain types except phantom limb
kappa - visceral pain
delta - thermal or mechanical pain

26
Q

other CNS effects of opiates

A
  • VTA contains Mu receptors and opiates stimulate the mesolimbic DA system (reinforcing properties)
  • repeated injection of morphine into PV gray area results in physical dependence
  • 3 vital life functions mediated by brain stem areas are depressed (respiration, vomiting, coughing)
27
Q

effects of opiates on body

A
  • nausea and vomiting after 1st dose
  • constricted pupils
  • dilated peripheral blood vessels - decrease BP, flushed face, sweating
  • constipation (GI tract mu receptors) & decreased urine flow
  • decreased sex hormones, sex drive, fertility
28
Q

effects on sleep

A

regular users:
- doesn’t increase sleep but induces drowsiness and lethargy
- indirect sleep benefits (alleviation of pain)
- alters nature of slepe (increase muscle tension and decrease slow wave & REM)
- acute admin causes insomnia

29
Q

subjective effects of opiates

A
  • euphoria
  • creativity/dream states
  • rush
30
Q

effects on mood

A
  • initially decreases anxiety and depression; after tolerance - unpleasant mood
  • depends on prior opiate experience
  • when in pain no experience of sleepiness & other subjective effects
31
Q

effects of performance

A
  • slows performance in non-users
  • tolerance develops to these effects
32
Q

unconditioned behaviour

A

rodents: morphine has a biphasic effect on SMA (low doses increase movement, high doses decrease movement)
primates: no excitatory phase (just decrease SMA)

33
Q

conditioned behaviour

A

low doses: increased response rate for positive reinforcers and increased avoidance of shock
high doses: decrease response rates and decreased avoidance behaviour but not escape

34
Q

self-administration in animals

A
  • responding for food not affected by morphine unless withdrawing
  • can continue normal activities with little effect for some time
  • self administration increases with deprivation and cocaine
35
Q

self-administration in humans

A

In lab studies
- opiates are reinforcing by various routes of admin
- morphine > codeine > propoxyphine
- only reinforcing in non users if they experience pain
out of lab data
- chipping (using sporadically or socially)
- addiction & maturing out (5-10 yrs of use once adults reach 40s decrease of use)

36
Q

discrimination

A
  • discriminated from saline
  • morphine generalizes to all other mu opiates, but only partly to mixed agonist-antagonists
  • can discriminate between morphine & mixed agonist-antagonists
  • tolerance to discriminative effects in 1-3 days (increase with dose)
37
Q

tolerance

A
  • rapid tolerance to most effects
  • tolerance develops at different rates for different effects
38
Q

tolerance due to

A
  • metabolism
  • receptors
  • learning (context-dependent effects)
39
Q

opiates and cross tolerance

A
  • occurs with other opiates
  • not with depressants, stimulants or hallucinogens
  • partially occurs with alcohol
40
Q

withdrawal

A
  • never fatal
  • starts 6-12 hours after last dose; peak 1-3 days usually over <1 week
  • resembles the flu
  • dose dependent
41
Q

withdrawal stages

A

restlessness, agitation, yawning, chills, hot flashes, short breathing, goose bumps, drowsiness, sleep, cramps in stomach back and legs, vomiting, diarrhea, twitching/kicking & sweating

42
Q

acute effects

A

at high doses
- comatose state
- decreased breathing
- convulsions
- accidental overdose
- death

43
Q

overdose

A
  • potentiated effect with alcohol, barbituates
  • cut heroin with quinine (can be lethal when admin IV)
  • conditioned tolerance
44
Q

chronic use

A

Medical problems:
- constipation
- cancer
- possibly increased AIDS and Hep B risk (sharing needles)
other
- socio-cultural effects (addiction)

45
Q

reproduction: males

A
  • lowers testosterone
  • lowers sex drive
  • lowers fertility
46
Q

reproduction: females

A
  • menstrual irregularities
  • amenorrhea
  • lowers fertility
  • pregnancy (increases need for opiates and effects lifestyle)
47
Q

fetal development

A
  • mothers opiate withdrawal decreased blood oxygen levels
  • decreases birth weight, premature, illness & complications
  • withdrawal: starts <72 hours of birth and lasts 6-8 week and includes irritability, yawning, tremors, difficulty sucking, seizures
48
Q

maintenance therapies

A
  • methadone
  • buprenorphine
  • trial therapies: ultra-rapid detox using naltrexone

PYB260 (10 decks)

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