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Pharmacology and Therapeutics > 13. Drugs of abuse 2 > Flashcards

13. Drugs of abuse 2 Flashcards

1
Q

Where is cocaine derived from?

A
  • Plant-based compound (alkaloid)
  • Erythroxylum coca plant
  • Cocaine in the leaves on the plant
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2
Q

How is cocaine (and crack cocaine) made?

A

• Crush leaves to make organic solvent to form a paste (extracts around 80% cocaine)
• Dissolve the leaves in acidic solution to form cocaine HCl
- degrades when heated, so solution is crack cocaine
• Precipitate with an alkaline solution (e.g. baking soda)
• Purify by dissolving in a non-polar solvent e.g. ammonia or ether
• ‘Freebase’ formed, which can be inhaled

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3
Q

Describe the solubility of cocaine?

A
  • Cocaine HCl - water soluble

* Crack cocaine - lipid soluble

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4
Q

Why does the regular snorting of cocaine cause septal defects?

A
  • Powerful vasoconstriction
  • Reduced blood flow
  • Necrosis
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5
Q

Compare the speed of onset and bioavailability of cocaine for the different routes of administration

A
  • Inhalation and IV speed of onset is virtually the same
  • Inhalation - lot of drug lost due to absorption issues: lowest bioavailability
  • IV bioavailability: 100%

• Snorting (intranasal) has a slower speed of onset
• Oral administration has the slowest speed of onset
- pKa = 8.7
- ionised in acidic GIT
- slower absorption (less in stomach)

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6
Q

How does absorption time affect time of action?

A
  • Slower absorption = prolonged action
  • This is because the liver deals with a smaller dose (over a longer time)
  • Metabolised more slowly
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7
Q

How is cocaine metabolised?

A

• Metabolised by plasma and liver cholinesterases
• 75-90% of cocaine is broken down into inactive, inert metabolites
- ecgonine methyl esther
- benzoylecgonine
• Rapid due to the enzymes in the blood as well as the liver

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8
Q

Why is cocaine so addictive?

A
  • High speed of onset - faster onset => more powerful behavioural stimulus
  • High speed of breakdown - fast clearance leads to continuously taking it (binging) to reinforce the effect

(crack cocaine is the most addictive drug in the world)

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9
Q

How can cocaine be used as a local anaesthetic (high dose effect)?

A
  • Cocaine diffuses from inside the cell membrane into the cytoplasm
  • Can move into an open channel (hydrophilic pathway) or diffuse into a closed channel (hydrophobic pathway)
  • Uncharged in membrane, charged in channels
  • Blocks sodium channels in the nerves
  • Less depolarisation - reduced propagation of APs
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10
Q

How does cocaine inhibit reuptake at synapses?

A
  • Dopamine transporters reuptake dopamine back into the pre-synaptic cell (type of monamine transporter)
  • Found in the nucleus accumbens
  • Cocaine blocks these transporters
  • This can affect dopamine, NA and serotonin
  • Euphoria
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11
Q

How does cocaine affect dopamine affinity and efficacy for the dopamine receptor?

A

It doesn’t

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12
Q

What are positive/reinforcing effects, and give some examples of these effects of cocaine

A
  • Acute affects of increased dopamine in synaptic cleft

* Euphoria, dysphoria, insomnia, motor excitement, increased libido, anger

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13
Q

What are negative/stereotypic effects, and give some examples of these effects of cocaine

A
  • More common with chronic use
  • Associated with cocaine binging leading to tolerance, due to depletion of dopamine vesicles
  • Anxiety, extreme exhaustion, incoherent speech, decreased libido, anorexia
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14
Q

There is a strong link between cocaine and which cardiovascular condition?

A

Myocardial infarction

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15
Q

Describe the effects of cocaine on the sympathetic nervous system and the subsequent effects

A 
• Inhibits catecholamine reuptake at sympathetic nerve terminals
• Stimulated central symapthetic outflow
• Increased NA:
- Increased work of the heart
- Increased BP
- Increased oxygen demands
  • platelet activation
  • platelet adherence
  • decreased oxygen supply

• Cocaine stimulates release of endothelin-1 (potent vasoconstrictor)

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16
Q

Describe the effects of using cocaine as a local anaesthetic, on the CVS

A
  • Blocks sodium channels
  • Depressed CVS parameters
  • Interference with rhythm and left ventricular function
17
Q

Why can cocaine cause seizures?

A
  • Vasoconstriction in the brain
  • Reduced blood flow to certain parts
  • Also stimulation of hyperpyrexia (high fever)
  • Combination are associated with seizure induction and epilepsy
18
Q

How can cocaine lead to hyperthermia (rare)?

A
  • Increased agitation, locomotor activity and involuntary muscle contraction all increase body temperature
  • Sweat production is enhanced as it is SNS, but the threshold is elevated
  • Cutaneous vasodilation is inhibited
  • Causes rapid increase in body temperature before these cooling mechanisms can kick in
19
Q

Which form of cocaine is used intranasally?

A

Cocaine HCl

20
Q

What is the onset and half life time of cocaine?

A
  • Onset - seconds

* Half life - <90 minutes

21
Q

What percentage of cigarettes is volatile matter and particulate matter?

A
  • 95% volatile (N, CO, benzene, HCN)

* 5% particulate (alkaloids, tar)

22
Q

How is nicotine delivered from the cigarette to the lungs?

A
  • When a cigarette is heated, tar droplets form, in which the nicotine dissolves
  • Droplets enter the lungs and nicotine diffuses across the alveoli
23
Q

How much nicotine is there per cigarette?

A

9-17mg

24
Q

What are replacement methods of nicotine administration to wean smokers of cigarettes?

A
  • Nicotine spray (1mg)
  • Nicotine gum (2-4mg)
  • Nicotine patch (15-22mg/day)

(cigarettes have a lower bioavailability than all these methods)

25
Q

Why is cigarette smoke an ineffective method of administering nicotine?

A
  • The smoke is quite acidic
  • Nicotine has a high pKa of 7.9
  • Nicotine is heavily ionised in the smoke, therefore poorly absorbed
  • No buccal absorption
  • Absorption in alveoli is independent of pH and nicotine will get into the bloodstream once it gets there
26
Q

How do replacement methods help with nicotine addiction?

A
  • Maintain a low level of nicotine in the blood
  • Meant to interfere with the craving to smoke
  • However, it is the rapid and short lasting spike of nicotine that people want to replace when smoking
  • This is not produced by replacements as it’s dangerous
27
Q

How is nicotine metabolised?

A
  • 70-80% broken down in the liver very quickly by hepatic CYP2A6
  • Major metabolite is cotinine - inactive and inert
  • Slightly slower metabolism than cocaine (half life of 1-4 hours) (still quite fast)
28
Q

How does nicotine work?

A
  • Binds to the nicotinic ACh receptor
  • These are found throughout the autonomic nervous system
  • Nicotine opens sodium channels causing depolarisation and an AP at all ganglia and adrenal medulla
  • Interference with a lot of autonomic function
29
Q

How does nicotine cause euphoria?

A
  • Nicotinic ACh receptors are found on the cell bodies of the dopaminergic neurones in the ventral tegmental area
  • Nicotine activates the receptors and increases the firing rate of the dopaminergic neurones
  • More dopamine secretion => euphoria
30
Q

What are the cardiovascular effects associated with long term nicotine use?

A
  • Increase in cardiac work (HR and SV)
  • Vasoconstriction of coronary arterioles => reduced oxygen supply
  • Nicotine is pro-atherogenic - negative effect on lipid profile
  • Increases thromboxane (promotes platelet aggregation) and decreases NO
  • These pro-atherogenic effects may be mitigated by exercise and diet
  • Effects are similar but more chronic than cocaine
31
Q

Why does vaping still a lot of the negative effects on the body as cigarette smoking?

A
  • Lung cancers and emphysema are predominantly associated with volatile matter so can be avoided
  • Therefore vaping is better for lung health, however it still has nicotine
  • Negative CVS effects can still be seen
32
Q

What effect does nicotine have on weight?

A
  • Nicotine increases metabolic rate => catabolic effect
  • Weight loss
  • Smoking cessation => weight gain
33
Q

Describe the impact of nicotine on Parkinson’s disease?

A

(positive impact)
• Long-term nicotine use
• Increased number of brain cytochromes (CYPs) in the CYP450 system
• These CYPs metabolise neurotoxins
• This decreases the toxins that contribute to disease development

34
Q

Describe the impact of nicotine on Alzheimer’s disease?

A

(positive impact)
• Long-term nicotine use
• Decreased beta-amyloid toxicity
• Decreased amyloid precursor protein (APP)
• Helps decrease progression of Alzheimer’s

35
Q

What is nicotine derived from?

A

Alkaloid from the Nicotiana tabacum plant

36
Q

How does caffeine cause a euphoric effect?

A
  • Normally, adenosine acts on adenosine receptors which downregulates D1 function
  • Caffeine is an adenosine receptor antagonist
  • Therefore, caffeine increases dopamine release and enhances tissue response to dopamine
  • Adenosine doesn’t contribute very much to the pathway so the effect is very small
37
Q

How does food like chocolate affect the reward pathway?

A
  • Some compounds in chocolate have stimulant properties
  • No evidence of direct interaction with reward pathway
  • Just a natural, behavioural effect

Pharmacology and Therapeutics (33 decks)

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