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PHAR > PHAR3 - Applying PD/PK Theory (Depressants) > Flashcards

PHAR3 - Applying PD/PK Theory (Depressants) Flashcards

1
Q

Name three types of psychoactive drugs.

A

Depressants.
Stimulants.
Opioids.

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2
Q

What is the public health view of psychoactive drugs?

A

Considering the dangers that the drugs pose to the health of the public.

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3
Q

Give general overview of depressants.

A

Drugs that suppress/slow the central nervous system.

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4
Q

Give 6 types of depressants.

A 
Alcohol. 
Cannabis. 
Opioids. 
Barbiturates (anxiety and insomnia). 
Benzodiazepines ( tranquillisers). 
Narcotics (pain relievers).
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5
Q

What are barbiturates?

A

Drugs used in anxiety and insomnia treatment. Depressant effects.

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6
Q

What are benzodiazepines?

A

Depressant drugs used as tranquillisers.

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7
Q

What are narcotics?

A

Pain relieving depressant drugs.

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8
Q

What are opioids?

A

Depressant drugs that act as pain relief and anaesthetics.

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9
Q

What are cannabinoids.

A

Cannabis-like drugs.

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10
Q

What is the main chemical compound in alcoholic beverages?

A

Ethanol or ethyl alcohol.

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11
Q

What is the main active ingredient in cocaine?

A

Delta-9 tetrahydrocannabinol.

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12
Q

What is the definition of an alcohol?

A

Chemical compound containing a OH group.

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13
Q

Where do cannabinoids originate from?

A

Cannabis sativa plant.

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14
Q

How many chemical compounds are present in the cannabis plant? Discuss their activity.

A

Contains over 400 total compounds.

Approx. just over 60 are active cannabinoids

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15
Q

Discuss the different values of oceanography/water partition coefficient and what they represent.

A

Less than 1 - greater water solubility than lipid solubility.
Equal to 1 - equally water and lipid soluble.
More than 1 - greater lipid solubility than water solubility.

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16
Q

Discuss the octanol/water partition coefficient for ethanol and its implications on drug properties.

A

Low octanol/water partition coefficient. Ethanol is considered water soluble. However, it is a small uncharged polar molecule therefore is able to diffuse across lipid membranes. Also, as it is water soluble and small, can pass through aqueous pores.

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17
Q

Discuss the octanol/water partition coefficient for cannabis and its implications on drug properties.

A

High octanol/water partition coefficient. Highly lipid soluble so can cross lipid membranes relatively easily.

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18
Q

Which drug are we more able to determine drug dosage for: alcohol or cannabis?

A

Alcohol - blood alcohol level can be monitored and used to calculate drug dosage, by making some approximations. Cannabis is difficult to determine drug dosage.

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19
Q

What are the two ways of measuring alcohol?

A

Absolute alcohol.

Alcohol units.

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20
Q

Discuss what alcohol by volume is.

A

ABV refers to the percentage of alcohol in a drink.

E.g. 5% beer, 12% wine, 40% spirit.

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21
Q

What is the equation for calculating absolute alcohol consumed?

A

Alcohol by volume multiplied by 0.78 multiplied by volume consumed (in 100mls).

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22
Q

What is the equation for calculating alcoholic units consumed?

A

Alcohol by volume multiplied by volume in ml/1000.

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23
Q

Discuss bioavailability for alcohol.

A

Blood alcohol levels give indication of the bioavailability. This is the amount that enters and is present in systemic circulation.

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24
Q

What is the link between alcohol tolerance and blood alcohol content?

A

Higher alcohol tolerance is associated with lower BAC as acohol is metabolised at a faster rate.

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25
Q

What are the two main factors affecting blood alcohol content?

A

Weight and gender.

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26
Q

What conditions are associated with a slower alcohol metabolism?

A

Defective alcohol metabolising enzymes.

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27
Q

What is the main factor that makes determining cannabis dosage difficult?

A

Different cannabis products contain different amounts of cannabis.
E.g. a mild cannabis cigarette may contain approx. 10 mg of cannabis however a powerful skunk can contain approx. 150 mg.

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28
Q

Does knowing the dosage of cannabis administered allow accurate prediction of the drug effects? Why?

A

No, cannabis has specific pharmacokinetics for each of the various active compounds therefore the drug effects vary a great deal.

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29
Q

What is the common route of administration for alcohol?

A

Oral.

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30
Q

What lipid membranes need to be crossed via the oral route of administration for alcohol?

A

Membrane of small intestine/ileum into blood stream.

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31
Q

What is the common route of administration for cannabis?

A

Inhalation.

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32
Q

What lipid membrane must be crossed for the inhalation always route of drug administration?

A

Lipid membrane of alveolar sacs.

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33
Q

Discuss factors of the lipid membrane of the ileum and alveolar sac that aid the absorption of drugs.

A

Thin surfaces (1-200 nM) and vascularised so short distance to surrounding blood capillaries.

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34
Q

Discuss factors that limit drug absorption via the inhalational route e.g. cannabis.

A

Penetration of drug deep into lungs.
Approx. half of drug dosage gets far into the lungs.
Only small proportion of this actually becomes absorbed into the bloodstream.

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35
Q

Define pyrolysis.

A

Thermal decomposition.

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36
Q

Discuss the limiting factors for drugs via the oral route e.g. alcohol.

A

Presence or absence of food in the stomach.
Absence of food - empty stomach promotes passage of alcohol into bloodstream via ileum.
Presence of food - causes slow absorption of alcohol into bloodstream.

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37
Q

Discuss the link between the stomach and alcohol blood levels.

A

Empty stomach - alcohol absorbed into blood faster - increased blood alcohol levels.
Full stomach - alcohol absorbed into blood slower - slower increase to blood alcohol levels.

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38
Q

What are the four factors that affect drug distribution?

A

Capillary permeability. Plasma protein binding. Regional blood flow.
Tissue localisation.

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39
Q

Which factor affects the drug distribution of alcohol and cannabis the least? Why?

A

Capillary permeability.
Alcohol - small uncharged polar molecule so can cross lipid membrane. Size and water solubility also allows access through aqueous pores.
Cannabis - highly lipid soluble so diffuses across lipid membranes readily.

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40
Q

Which is more heavily plasma protein bound, alcohol or cannabis?

A

Cannabis - 90% bound.

Alcohol - 10% bound.

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41
Q

Discuss the link between plasma protein binding and drug distribution.

A

Drug molecules bound to plasma proteins are unable to leave the bloodstream and access tissues.

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42
Q

Discuss link between plasma protein binding and hepatic metabolism.

A

Drugs that are bound to plasma proteins following oral administration, will travel to the liver in the blood. Here they can undergo first pass metabolism. However, if plasma protein bound, they are unable to move into hepatocytes therefore are not metabolised.

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43
Q

Based on the plasma protein binding capabilities of alcohol and cannabis, and the link to first pass hepatic metabolism, which drug is likely to be eliminated faster?

A

Alcohol is less plasma protein bound. Enters hepatocytes and undergoes first pass metabolism. Eliminated faster.

Cannabis is more plasma protein bound. Unable to enter hepatocytes so will not undergo metabolism yet. Eliminated slower.

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44
Q

Discuss the effect of regional blood flow on drug distribution.

A

Body regions that receive a greater proportion of cardiac output are likely to have more drugs distributed here as more blood flows here.

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45
Q

Give examples of tissues with high and low regional blood flow.

A

High - liver, brain, kidney.

Low - adipose tissue.

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46
Q

What three factors affect tissue localisation?

A

Octanol:water partition coefficient (lipid vs. water solubility).
Water/fat content of tissue.
Regional blood flow to tissue.

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47
Q

Place the following tissues in order of water content (highest first):
Liver, adipose tissue, brain, blood plasma.

A

Blood plasma, liver, brain, adipose tissue.

48
Q

Place the following tissues in order of fat content (highest first):
Liver, adipose tissue, brain, blood plasma.

A

Adipose tissue, liver, brain, blood plasma.

49
Q

Discuss the distribution of alcohol between the blood and the brain.

A

Alcohol is highly water soluble therefore goes to tissue with higher water content - blood plasma.
However, regional blood flow to brain is high allowing alcohol to be distributed here also. This requires a high concentration gradient.

50
Q

Discuss ability of alcohol to be distributed to adipose tissue.

A

Unlikely.
Alcohol has low lipid solubility therefore is not compatible with high lipid content of adipose tissue. In addition, blood flow to adipose tissue is very low so further prevents alcohol from accumulating in adipose tissue.

51
Q

Discuss distribution of cannabis between the brain and blood.

A

Cannabis has high lipid solubility. Brain has higher fat content than blood therefore cannabis is more likely to be distributed to this tissue. Regional blood flow is also relatively high to the brain.

52
Q

Discuss the distribution of cannabis to adipose tissue.

A

Cannabis is highly lipid soluble so is likely to be distributed to adipose tissue due to high lipid content, despite a low regional blood flow.

53
Q

Give examples of factors affecting an individuals sensitivity to alcohol and cannabis.

A

Gender. Weight. Body fat. Body water.

54
Q

Are males or females more sensitive to alcohol? Discuss briefly.

A

Females are more sensitive to alcohol as they have a lower blood water %. Alcohol is more concentrated in blood plasma. Greater effects of alcohol therefore increased sensitivity.

55
Q

Are males or females less sensitive to alcohol? Discuss briefly.

A

Males are less sensitive to alcohol due to high per water content. Alcohol is not as concentrated in blood plasma. Effects are weaker therefore males are less sensitive.

56
Q

Are males or females more sensitive to cannabis? Discuss briefly.

A

Males are more sensitive to cannabis. Lower body fat content so cannabis cannot accumulate in adipose tissue. Remains in bloodstream, continuing to cause effects.

57
Q

Are males or females less sensitive to cannabis? Discuss briefly.

A

Females are less sensitive to cannabis due to increased body fat %. Cannabis is able to accumulate in adipose tissue meaning effects are less so sensitivity is less.

58
Q

Are obese or non-obese individuals more sensitive to alcohol? Discuss briefly.

A

Obese individuals are more sensitive to alcohol. Reduced body water % comparative to non-obese individuals. Alcohol is more concentrated in blood with lower water content. Effects are greater, so sensitivity is greater.

59
Q

Are obese or non-obese individuals less sensitive to alcohol? Discuss briefly.

A

Non obese individuals are less sensitive. Higher water content in non obese people than obese believe. Alcohol in blood is less concentrated due to more water. Effects are less so sensitivity is less.

60
Q

Are obese or non-obese individuals more sensitive to cannabis? Discuss briefly.

A

Non obese individuals are more sensitive to cannabis due to lower body fat content. Cannabis unable to accumulate in adipose tissue so remains in bloodstream causing strong effects. Higher sensitivity.

61
Q

Are obese or non-obese individuals less sensitive to cannabis? Discuss briefly.

A

Obese individuals are less sensitive due to higher body fat %. Cannabis can accumulate in adipose tissue. Not present in bloodstream therefore effects are smaller thus lower sensitivity.

62
Q

What are the two phases of metabolism?

A

Phase 1 and phase 2 metabolism.

63
Q

What is the main function of metabolism?

A

Production of metabolites with lower lipid solubility and higher water solubility, aiding the excretion of the drug.

64
Q

What are the chemical intermediates produced in the phase 1 metabolism of alcohol? Name the type of reaction.

A

Ethanol oxidised to acetaldehyde.

Acetaldehyde oxidised to acetic acid.

65
Q

What enzymes are involved in phase 1 metabolism of alcohol?

A 
Alcohol dehydrogenase (production of acetaldehyde from ethanol). 
Cytochrome P450 enzymes are also used for this process. 
Aldehyde dehydrogenase (production of acetic acid from acetaldehyde).
66
Q

Alcohol dehydrogenase enzymes are more/less in number in males/females. Discuss the link to alcohol metabolism/drug effects, in males and females.

A

Fewer alcohol dehydrogenase enzymes present in females. Reduced alcohol metabolism, there alcohol effects are greater.

67
Q

Give one way in which chronic alcohol use increases alcohol tolerance.

A

Upregulation of cytochrome P450 enzymes meaning increased alcohol metabolism(rapidly). More alcohol required to produce drug effects therefore higher alcohol tolerance.

68
Q

Discuss how the metabolism of alcohol can be used as an energy source.

A

Acetic acid produced in phase 1 alcohol metabolism can be converted to acetyl coA. This can enter TCA cycle.

69
Q

What do breathalysers actually measure?

A

Unmetabolised alcohol excreted via lungs. This gives indication of blood alcohol level.

70
Q

What two types of reactions are required in phase 1 metabolism of cannabis?

A

Hydroxylation. Oxidation.

71
Q

Discuss the lipid solubility of metabolites produced in phase 1 metabolism of cannabis. What occurs in the kidney as a result of the lipid solubility?

A

Intermediate metabolite and final phase 1 metabolite have reduced lipid solubility compared to delta 9 THC. Some lipid solubility is still present therefore can be reabsorbed into bloodstream via kidney tubule.

72
Q

Why are cannabis phase 1 metabolites reabsorbed into the bloodstream at the kidney?

A

Lipid soluble component is still larger than the new water soluble component. Results in diffusion across lipid membrane therefore reabsorption into bloodstream.

73
Q

What phases of metabolism are required for alcohol and cannabis? Why?

A

Phase 1 metabolism only for alcohol. Small water soluble molecule already, relatively easy to eliminate.

Phase 1 and 2 metabolism for cannabis. Large lipid soluble molecule so needs to be metabolised to form water soluble metabolites to aid elimination of drug.

74
Q

What type of reaction occurs in the phase 2 metabolism of cannabis?

A

Glucuronidation.

75
Q

What are the metabolites produced in phase 1 metabolism of cannabis?

A

11-OH THC following first hydroxylation step.

THC-COOH following second oxidation step.

76
Q

What is the phase 2 metabolite of cannabis?

A

THC-COOH-glucuronide

77
Q

Define an active metabolite.

A

Metabolite produced during metabolism of a drug which is considered pharmacologically active so can have drug effects.

78
Q

How can the effect of active metabolites be increased?

A

Chronic/daily use of drug.

Delays between phase 1 and phase 2metabolism.

79
Q

Which phase 1 metabolite of alcohol behaves as an active metabolite?

A

Acetaldehyde.

80
Q

What are symptoms associated with acetaldehyde accumulation?

A

Nausea due to gastric irritation.
Flushing due to peripheral vasodilation.
Headaches due to central vasodilation.

81
Q

What is a genetic factor that can cause acetaldehyde to accumulate?

A

Genetic polymorphisms to the aldehyde dehydrogenase enzymes can cause accumulation of acetaldehyde.

82
Q

What is the active metabolite for cannabis? Discuss its potency relative to cannabis.

A

11-OH THC. Considered more potent than cannabis as it has greater drug effects in the body.

83
Q

What is one factor that allows the active metabolite of cannabis to cause drug effects?

A

11-OH THC, a phase 1 metabolite of cannabis, has a high lipid solubility. Able to cross lipid membranes reading and access tissue.

84
Q

What is the drug target for cannabis?

A

G protein coupled receptor. Coupled to adenylate cyclAse.

85
Q

Discuss the selectivity, affinity and efficacy of cannabis for its target.

A

High selectivity. High affinity. High efficacy.

86
Q

What is the most common endogenous agonist for the GPCR target of cannabis?

A

Anandamide.

87
Q

How does cannabis produced a depressant effect?

A

Binds to GPCR. Adenylqte cyclise activity is reduced. Cellular activity decreased hence depressant effect.

88
Q

What is the drug target of alcohol?

A

Does not have one specific drug target. However, able to bind to general opioid receptors.

89
Q

Discuss the affinity and efficacy of alcohol binding to opioid receptors.

A

Weak affinity and weak efficacy.

90
Q

Discuss the binding of alcohol with opioid receptors. Link this to potency.

A

Low affinity is apparent. Alcohol binds to few of the multiple binding sites. As a result, potency is not has high as only few of multiple receptors are interacted with.

91
Q

If a drug has a high potency via interaction with opioid receptors, discuss its binding/affinity.

A

High affinity to all binding sites of the opioid receptors. Multiple interactions which can cause greater drug effects hence higher potency.

92
Q

Give four examples of drug targets for alcohol .

A

Opioid receptors.
GABA receptor.
NMDA receptor.
Calcium ion channels.

93
Q

What is the effect of alcohol behind to GABA receptors?

A

GABA receptors are involved in inhibitory effects. Alcohol increases this, thus the depressant effect.

94
Q

What is the effect of alcohol behind to NMDA receptors?

A

NMDA receptors are excitatory. Binding of alcohol decreases their effects, thus the depressant effect.

95
Q

What is the effect of alcohol behind to calcium ion channel receptors?

A

Calcium ion channels have an excitatory effect. Binding of alcohol reduces their activity, thus the depressant effect.

96
Q

What are two shared drug effects of alcohol and cannabis?

A

Memory loss.

Impaired psychomotor performance.

97
Q

Where is the dentate gurus located?

A

Part of the hippocampus trisynaptic circuit. Located in the temporal lobe.

98
Q

How does cannabis cause memory loss? Discuss specific brain structures that it interacts with.

A

Cannabis interacts with cannabinoids receptors within the dentate gyrus. This causes them to become activated which impairs memory formation.

99
Q

How does alcohol cause memory loss? Discuss specific brain structures that it interacts with.

A

Lacks specificity for one drug target so unable to deduce a specific receptor.

100
Q

Define psychomotor performance.

A

The production of learned physical activities e.g. reading, driving, riding a bike etc.

101
Q

What structures in the brain mediate psychomotor performance?

A

Basal ganglia.
Cerebral cortex.
Cerebellum.

102
Q

What is the specific receptor involved in the impairment of psychomotor performance in the presence of cannabis?

A

Multiple cannabinoid receptors are present however most important is yet to be deduced.

103
Q

What is the specific receptor involved in the impairment of psychomotor performance in the presence of alcohol?

A

Selectivity is very low therefore receptors cannot be deduced.

104
Q

Discuss the term ‘respiratory depression’.

A

State where lungs are unable to efficiently exchange oxygen and carbon dioxide.

105
Q

What drug causes respiratory depression?

A

Alcohol.

106
Q

Discuss the respiratory rhythm and where it is produced.

A

The rhythm that ensures that individuals are activity breathing. Produced by the medulla in the brain.

107
Q

What effects can arise as a result of impairment of the respiratory rhythm?

A

Decreased breathing rate. May lead to suffocation due to lack of oxygen.

108
Q

What receptors are thought to be involved in the respiratory depression effect of alcohol?

A

Opioid receptors. Cannot be confirmed due to alcohols lack of selectivity.

109
Q

Discuss the ability of cannabis to produce respiratory depression as a toxic effect.

A

Unable to produce respiratory depression as toxic effect due to lack of cannabinoid receptors in medulla.

110
Q

Discuss the role of NAD+/NADH in alcohol induced liver damage.

A

NADH is produced from NAD+ which is used as a cofactor by alcohol dehydrogenase and aldehyde hydrogenate enzymes during alcohol metabolism. NADH builds up and impairs beta-oxidation of fatty acids. Fatty acids build up and are deposited around the liver forming a fatty acid covered liver.

111
Q

Discuss the role of the cytochrome P450 system in contributing to alcohol induced liver damage.

A

Up regulation of the cytochrome P450 system occurs as a result of chronic alcohol intake. Oxygen free radicals can be leaked as a result. If cellular defence is less than the oxygen free radical production, hepatocytes can become damaged. Mitochondrial damage and inflammation occur specifically.

112
Q

Discuss the role of acetaldehyde as part of alcohol induced liver damage.

A

Acetaldehyde, a phase 1 metabolite of alcohol, and an active metabolite, can accumulate. Key metabolic enzyme activity is reduced and hepatocyte cell death can be induced. Further reduction to alcohol metabolism occurs.

113
Q

How are hepatocytes replaced during alcohol induced liver damage? What is the effect of their replacement?

A

By fibroblasts. Metabolic capacity of liver becomes reduced.

114
Q

Define psychosis.

A

Mental disorder which alters reality causing changes to experienced emotions.

115
Q

What part of the brain is involved in the controlling of an appropriate response to an experience?

A

Anterior cingulate cortex.

116
Q

How does cannabis cause psychosis ?

A

Interacts with cannabinoid receptors in the anterior cingulate cortex. Causes a depressant effect which can cause psychosis in extreme effects.

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