Pharm 13: Drugs of Abuse 1 (general/cannabis) Flashcards

1
Q

Why are drugs abused ?

A
  • all drugs can all cause euphoria

euphoria = rewarding feeling - mediated by
reward pathway

  • dopaminergic pathway
    organ in Ventral Tegmental Area (VTA) projects down (via axons) to ventral striatum

nucleus accumbens (NAcc) = area of the striatum –> dopamine release here –> causes euphoria

–> drugs hijack the central reward pathway

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2
Q

list different methods of administrating the main drugs of abuse

and compare rates of absorption (ROA)

A
  • intranasal –> (ROA = slow)
  • orally –> (ROA = very slow)
  • inhalational –> (ROA = rapid- fastest–> rapid passive diffusion by alveolar gas exchange)
  • intravenous –> (ROA =rapid )
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3
Q

What are the 4 main classification of drugs of abuse ?

give examples of each

A
  1. narcotics/ painkillers
    - -> opiate like drugs
    - -> e.g heroin/morphine
  2. depressants
    - -> downers
    - -> decreases brain function
    - -> e.g alcohol, benzodiazepines, barbiturates
  3. stimulants
    - -> uppers
    - -> increases brain function
    - -> cocaine, methamphetamine, caffeine
  4. Misc.
    - -> e.g Cannabis, ecstasy (MDMA)
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4
Q

describe the pharmacokinetics of cannabis

A

oral = 5-15% enters blood
–> delayed onset

inhalation = 25-35% enters blood

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5
Q

cannabis = lipid soluble / non lipid soluble

A

cannabis = very lipid soluble

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6
Q

chronic cannabis users have huge cannabis store in fat how is this?

A
  • cannabis = very lipid soluble
  • it slowly accumulates in poorly-perfused fatty tissues –> which is a major storage site

then it is slowly released into blood –> greater accumulation –> stronger effects

note:
10^4 : 1 (fatty tissue vs plasma)

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7
Q

How long after smoking a cannabis

cigarette will the effects persist in the body?

A

If non-smoker had 1 cannabis cigarette, effects persist for 30 days (still detectable)

–> because it takes 5 days to accumulate in fat

–> then slowly released from then on

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8
Q

what is a Endogenous cannabinoid-like substance =

A

Anandamide

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9
Q

where are the 2 different types of cannabinoid receptors located at?

A

Cannabinoid receptors:

o CB1 receptors = (mostly) in Hippocampus/cerebellum/cerebral cortex/basal ganglia

o CB2 receptors in Immune cell / WBC

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10
Q

How is the state of ‘euphoria’ reached?

A

Normally, GABA neurones supress DA-nergic neurones projecting from VTA

–> so GABA supresses reward pathway

o CB1 receptors are on GABA neurones –> cannabis binds

(causes disinhibition)
–> decreases firing rate of GABA neurones –> less suppression –> more reward path activity + DA release

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11
Q

Anterior Cingulate Cortex (ACC) is hyperactive/hypoactive in cannabis users

A

Anterior Cingulate Cortex (ACC) is hypoactive in cannabis users

–> can lead to psychosis + schizophrenia

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12
Q

What is Anterior Cingulate Cortex (ACC) responsible for?

A

involved with error detection, performance monitoring, and behavioural adjustment in order to avoid losses (e.g. concentrating on road when driving rather than conversation)

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13
Q

what effect does cannabis have on food intake

A

(increases food intake)

Positive effect on orexigenic neurones in Lateral Hypothalamus by:

a) –>Presynaptic inhibition of GABA –> increases MCH neuronal activity
b) –> Increased orexin production

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14
Q

How does taking cannabis affect the immune system?

A

CB2 receptor expression

o CBs impair functions of different immune cells

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15
Q

What are some peripheral effects of cannabis?

A

Peripheral effects:

o Immunosupressant

o Tachycardia/vasodilation (e.g. in conjunctivae –> (bloodshot eyes) – both involves TRPV1 receptor, NOT CB receptors

o Medulla has low CB1 expression –> important because it means small effect on CVS/respiratory system

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16
Q

Medical application of cannabis

A
  • vast expression of cannabinoid receptors in the brain –> potentially useful
  • e.g in MS/ pain/ stroke
    CB receptors tend to go up –> tends to help + decrease these symptoms

MS –> less spasticity
Stroke –> helps deal with post stroke infarct

17
Q

What is the tissue half life of cannabis?

A

7 days

but in actuality you can still see the effects 30 days later

18
Q

How might cannabis be eliminated

A

11-OH THC metabolite produced which is constantly recirculated by Gut via bile (65%), excreted in urine (25%)

19
Q

what is the importance of the 2 types of cannabinoids

a) THC
b) cannabidiol

A

a) THC = most potent –> causes most medical symptoms

b) cannabidiol –> medical symptoms of THC reduced if cannabidiol is present to an extent

20
Q

plasma levels of cannabinoid conc = not a very god measure because –>

A

plasma levels of cannabinoid conc = not a very god measure because –>
1) of enteroheptic recycling

2) chronic cannabis user have a permanent cannabis like effect on the brain due to long term accumulation of both the active component + metabolite

21
Q

What type of receptors are Cannabinoid receptors?

A

G protein coupled

22
Q

What effect does cannabis have on cannabinoid receptors

A

Cannabinoid receptors = G protein coupled

  • cannabis = depressant
  • -> -vely regulates adenylate cyclase
  • decreases cellular activity
23
Q

Lateral hypothalamus = involved in increased/decreased feeding

A

Lateral hypothalamus = involved in increased feeding

24
Q

o Medulla has low CB1 expression - why is this important?

A

o Medulla has low CB1 expression –> important because it means it is difficult to overdose on cannabis –> cant really kill you –> medulla = has Cardiovascular / respiratory centre
–> so overall there is small effect on CVS/Resp –> won’t really die

25
Q

What types of medically useful drugs have agonistic effects on CB receptors and what are they used for?

A

a) dronabinol –> aids / cancer patients
- -> acts as an appetite stimulant
- -> reduce weight loss

b) Nabilone –> cancer chemotherapy
- -> to try and suppress vomitting
- -> anti nausea

c) Sativex –> used for MS / pain
- -> control spasticity + pain

26
Q

What types of medically useful drugs have antagonistic effects on CB receptors and what are they used for?

A

Rimonabant (withdrawn)

  • anti obesity agent
  • -> suppress appetite
  • -> suicide increased