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yr 2 lcrs - pharm > 13 - Drugs of Abuse 1 > Flashcards

13 - Drugs of Abuse 1 Flashcards

1
Q

Why are psychoactive drugs abused?

A

They can cause a sense of euphoria (to a certain degree, depending on route of administration)

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2
Q

What is the mechanism for creating euphoria in the brain?

A

Euphoria = rewarding feeling

  • Dopaminergic Pathway
  • Starts in ventral tegmental area
  • Projects down to ventral striatum (nucleus accumbens is an area in the ventral striatum)
  • Dopamine released in the nucleus causes the sense of euphoria
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3
Q

What can cause a sense of euphoria?

A

Rewarding stimuli

  • Certain drugs
  • Certain foods

These stimuli activate the VTA - NAcc pathway

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4
Q

What route of administration allows the effects of a drug to occur fastest?

A
  1. Inhalation
    * Followed by:*
  2. IV
  3. Intra-Nasal
  4. Oral
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5
Q

What are the colloquial names for different routes of drug administration?

A

Intra-Nasal

  • “snort”

Oral

  • “eat”

Inhalation

  • “smoke”

Intra-Venous

  • “inject”
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6
Q

What causes the different absorption rates of different drug administration routes?

A

​Inhalation = rapid absorption​​

  • Fastest route of administration
  • Small airways and alveoli
  • Alveoli aren’t much of a barrier and are very thin-walled
  • Designed for fast exchange
  • Straight to LHS of heart

I.V. = rapid absorption

  • ​​Next fastest route
  • Veins
  • Has to go to RHS of heart, then LHS

Intra-nasal = slow absorption

  • Next fastest route
  • Mucous membranes of nasal sinuses
  • Then into venous drainage
  • RHS of heart, then LHS

Oral = very slow absorption

  • Slowest route
  • GI tract
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7
Q

Name the 4 different classifications for drugs of abuse and give examples of each

A

NARCOTICS/PAINKILLERS

  • opiate-like drugs
  • e.g. heroin

DEPRESSANTS

  • ‘downers’
  • decrease brain activity
  • e.g. alcohol, benzodiazepines (valium), barbiturates

STIMULANTS

  • ‘uppers’
  • increase brain activity
  • e.g. cocaine, amphetamine (speed), caffeine, metamphetamine (crystal meth)

MISCELLANEOUS

  • e.g. cannabis, ecstasy (MDMA)
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8
Q

What is name for the central ‘reward’ pathway?

A

Mesolimbic Dopamine System

  • Ventral Tegmental Area (VTA) -> Nucleus Accumbens (NAcc)
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9
Q

What is the end-point for drugs of abuse?

A

The reward (e.g. euphoria)

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10
Q

Where does cannabis come from?

A

Cannabis Sativa Plant

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11
Q

What is cannabis made up of?

A

More than 400 compounds, which includes more than 60 active cannabinoids which cause effects

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12
Q

Which part of the cannabis plant is the most highly concentrated?

A

The glandular hairs (trichomes) of the plant, at the top

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13
Q

How is hashish/resin made?

A

From trichomes (glandular hairs) of the cannabis plant

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14
Q

How is hash oil made?

A

Solvent extraction from the cannabis plant

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15
Q

Which two cannabinoids are known to be particuarly important in causing effects upon administration of cannabis?

A

CANNABIDIOL

  • Has ability to reduce some of the bad effects of THC

TETRAHYDROCANNABINOL (THC)

  • Causes the bad effects of cannabis
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16
Q

What has changed over time with regards to cannabis dosing?

A

Amount of THC in cannabis has been increasing over the years

1960s/70s

  • ‘Reefer’ = 10mg THC

21st Century

  • ‘Skunkweed’/’Netherweed’ = 150-300mg THC + hashish oil
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17
Q

What about cannabis is dose dependent?

A

Negative effects are more dose dependent than positive effects. Positive effects don’t change much with dose.

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18
Q

Is use of cannabis in the population increasing or decreasing over time?

A

Increasing

19
Q

What are the major routes of administration of cannabis?

A

TWO MAJOR ROUTES OF ADMINISTRATION:

ORAL

INHALATION

20
Q

What are the differences in the pharmacokinetics of cannabis when its orally administered compared to when it’s inhaled?

A

ORAL

  • 5-15% of dose gets into circulation
  • Delayed onset/slow absorption
  • High rate of first pass metabolism due to it entering the GIT first (bioavailability is therefore limited)
  • Has to bypass stomach environment, then into small intestine where absorption is good but then into liver where metabolism occurs all before getting into the circulation

INHALATION

  • 25-35% of dose gets into circulation
  • Pretty much any drug that gets into the alveoli is absorbed
  • However, some of the drug is swallowed or exhaled
21
Q

Where do cannabinoids tend to accumulate?

A

Cannabinoids are very lipid soluble compounds

Therefore, they slowly accumulate in fatty tissues

These tissues tend to be poorly perfused because they are fat (2% of CO)

For people who take a lot of cannabis, you can have a 104:1 ratio of cannabis in fat to plamsa

Chronic users will have a slow leak of cannabis back out into the bloodstream over time

Cannabis metabolites (conjugates) build up in fatty tissues, not necessarily the cannabinoids themselves

22
Q

What does this graph show?

A

Level of cannabis in blood starts to drop as it starts to enter other tissues

Amount of cannabis in fat increases slowly over time

23
Q

What is the main metabolite of THC?

A

11-hydroxy-THC

Produced in liver

More potent than THC

These metabolites build up in the fatty tissue and re-enter the blood slowly over time

24
Q

How much of cannabis is excreted in the urine and how much undergoes enterohepatic recycling (eventually excreted in the faeces)?

A

25% - urine

65% - enterohepatic recycling and then faeces

25
Q

What is important to remember about the enterohepatic recycling of cannabis?

A

Cannabis is very lipid soluble

  • its metabolites are very lipid soluble
  • the drug just gets reabsorbed again in the gut
  • more cannabis then re-enters the bloodstream
26
Q

What is often seen in the post-mortem blood cannabinoid levels of regular cannabis users?

A

Poor correlation between plasma cannabinoid concentration and degree of intoxication

THC-COOH is an inactive metabolite

11-OH-THC is an active metabolite

High levels of metabolites have accumulated in the brain of chronic users

  • brain is approx. 60% fat
  • cannabinoids and their metabolites are very lipid soluble
27
Q

How long after smoking a cannabis cigarettes will the effects persist in the body?

A

30 days

On the graph you can see that it has built up to a significant level in the fatty tissue at 120 hours, and this will have a slow releasse.

Effects of cannabis over time will be lesser than when the cigarette is initially smoked because the amount released over time is in small increments

28
Q

What cannabinoid receptors exist and where are they found?

A

CB1 Receptors

  • Hippocampus
  • Cerebellum
  • Cerebral Cortex
  • Basal Ganglia

CB2 Receptors

  • Immune cells

They re the most prevalent G-protein coupled receptors in the brain

29
Q

Why do cannabinoid receptors exist in the body?

A

They are endogenous receptors because endogenous cannabinoid agonists exist in the body

  • e.g. Anandamide
30
Q

What actions do cannabinoid receptors allow to be carried out?

A

Generally, cannabis decreases cellular activity (depressant)

Therefore, cannabinoid receptors have the effect of slowing things down at a cellular level

31
Q

How does cannabis cause euphoria?

A
  • CB1 receptor present on GABA neurone
  • VTA to NAcc is the reward pathway
  • GABA is the inhibitory brake on the reward system

When reward pathway needs to be activated, endogenous cannabinoids bind to the CB1 receptor. This switches off the GABA neurone as acting a brake on the reward system.

Cannabis hijacks this pathway and causes powerful activation of the CB1 receptor. Massive suppression of the GABA neurone. THIS IS KNOWN AS DISINHIBITION

32
Q

What is the function of The Anterior Cingulate Cortex (ACC)?

A

Error detection

Involved in performance monitoring with behavioural adjustment in order to avoid losses (For example, consider the ability to drive a car while simultaneously engaging in a discussion with a passenger. If we enter a narrow mountain road and a heavy storm breaks out, we might feel the need to discontinue our conversation in order to better focus our cognitive resources on safe driving.)

33
Q

What happens to the Anterior Cingulate Cortex (ACC) in cannabis users?

A

There is hypoactivity of the ACC in cannabis users.

This is thought to link to the negative effects of cannabis, such as inappropriate behaviour in certain situations, psychosis and schizophrenia.

34
Q

What is the effect of cannabis on food intake?

A

Cannabis has a positive effect on food intake (i.e. it causes an increase in food consumption)

Positive effect on orexigenic neurones in the lateral hypothalamus

  1. Presynaptic inhibition of GABA increases MCH neuronal activity
  2. Increased orexin activity
  3. Promotes feeding behaviour via overactivity of this part of the hypothalamus
35
Q

What three regions of the brain are particularly involved in regulating food intake?

A

Hypothalamus

  • Arcuate Nucleus
  • Lateral Hypothalamus
  • Ventromedial Hypothalamus
36
Q

How do certain regions of the brain regulate food intake?

A

ARCUATE NUCLEUS

  • Makes the decision based on peripheral information
  • AgRP increases feeding
  • POMC decreases feeding
  • Sends signals to either the ventromedial hypothalamus or the lateral hypothalamus

VENTROMEDIAL HYPOTHALAMUS

  • Causes inhbition of feeding

LATERAL HYPOTHALAMUS

  • Causes increase in feeding
37
Q

What is a problem associated with the presence of cannabinoid receptors on immune receptors in cannabis users?

A

Peripherally, cannabis is an immunosuppressant. Therefore, chronic cannabis users are more susceptible to infection.

CB Receptors are present on immune cells

  • cannabinoids depress the activity of these cells
  • i.e. depressed activity of macrophages causing less immunity
  • this causes an antiinflammatory effect

Anti-inflammatory in infection is not good, however, it may be beneficial in autoimmune disease

38
Q

What are the overall negative central effects of cannabis use?

A

Pyschosis, Schizophrenia

Increased Food Intake

  • hypothalamus

Memory Loss

  • limbic regions (amnestic effects/decreased BDNF)

Bad Psychomotor Performance

  • cerebral cortex
39
Q

What are the overall negative peripheral effects of cannabis use?

A

Immunosuppressant

  • due to CB2 receptors on immune cells

Tachycardia/Vasodilation

  • especially in the conjunctivae
  • bloodshot eyes therefore can help in diagnosis
  • not via CB receptors, but via TRPV1 receptors
40
Q

Why are there low levels of CB1 receptor expression in the medulla?

A

The medulla controls some very important life functions, especially via the cardio-respiratory control centre

Therefore, we wouldn’t want lots of CB receptors in the medulla as these cause a depression in cellular function, which would lead to breathing/heart failure if it were to happen in the medulla.

It is therefore very hard to overdose on cannabis to the point of death

41
Q

What is the relationship between obesity and cannabinoids?

A

Endocannabinoids (endogeneous cannabindoids) and CB1 receptors are up-regulated in the liver/adipose tissue in obesity

CB receptors seem to be related to development of obesity and its negative effects

To prevent this cannabinoid effect, you need antagonists of CB receptors

42
Q

In what conditions is upregulation of CB receptors regulatory?

A

Multiple Sclerosis

Chronic Pain

Stroke

43
Q

In what conditions is upregulation of CB receptors pathological?

A

Fertility

Obesity

44
Q

What CB receptor related drugs have been developed and what are they used for?

A

DRONABINOL

  • agonist of CB receptors
  • helps in patients with uncontrolled weight loss (e.g. AIDS) as an appetite stimulant

NABILONE

  • mainly used in chemotherapy to try and suppress vomiting
  • anti-nausea agent

SATIVEX

  • used in MS and pain
  • control pain and spatiscity

RIMONABANT

  • antagonist of CB receptors
  • relatively good at suppressing appeitite and decreasing weight gain
  • however, a people taking the drug committed suicide
  • no longer available

yr 2 lcrs - pharm (44 decks)

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