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PH3113 > Tolerance and Dependence on CNS active drugs (DONE) > Flashcards

Tolerance and Dependence on CNS active drugs (DONE) Flashcards

1
Q

Definition of drug abuse

A

Administration of any pharmacological substance in a way which deviates from approved medical or social patterns

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2
Q

Self administration drug abuse

A

Excessive self medication
Abuse of drugs in sport
Patient non-compliance

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3
Q

Administration by others drug abuse

A

Over or mis-prescribing
Unnecessary counter prescribing
Excessive antibiotic addition to animal foodstuffs in factory farming

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4
Q

Tolerance definition

A

The need to employ increasing doses of drug in order to produce the same effect as on first exposure
Dispositional tolerance
Functional tolerance
Conditioned tolerance

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5
Q

Dependence definition

A

A state or condition where there is a compulsion to take a drug continually in order to experience its psychic effects and sometimes to avoid the physical discomfort of its absence

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6
Q

What is dispositional tolerance?

A

Adaptations in drug- ADME, less drug at active site so need to take more
e.g. barbiturates or alcohol- induce hepatic microsomal enzymes

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7
Q

What is functional tolerance?

A 
Changes in properties and function of target tissue rendering it less sensitive to the substance
Changes in receptor number
Receptor uncoupling
Exhaustion of modulators
Tolerance at reuptake transporter
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8
Q

What are the different types of changes in receptor density?

A

Receptor down-regulation: usually with agonists on prolonged exposure
Receptor up-regulation: usually occurs with antagonists or low levels of endogenous agonist/ transmitter e.g. denervation

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9
Q

How does receptor up regulation differ between new drugs and tolerance?

A

Dug naïve- antagonist blocks endogenous transmitter or endogenous agonist
Tolerance- cell synthesises and inserts new receptors into cell membrane

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10
Q

How does receptor second messenger uncoupling differ between new drugs and tolerance?

A

Drug naïve- agonist stimulates adenylyl cyclase linked to G protein
Tolerance- repeated drug exposure uncouples enzyme from G-protein

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11
Q

How does receptor ion channel uncoupling differ between new drugs and tolerance?

A

Drug naïve- drug causes a change in ion flux to alter ion concentration and potential across membrane
Tolerance- receptor ion channel uncoupling impairs ion fluxes, ion concentration and potential across membrane

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12
Q

What happens in the exhaustion of mediators?

A

In some cases, tolerance is associated with depletion of intermediate substances
e.g. amphetamines and cocaine release neuronal NA, DA and other amines
These releasable transmitter stores can be depleted

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13
Q

Tolerance at reuptake transporters

A

Cocaine frequent use tolerance (dependence prone person):
Tolerance to inhibition of DA uptake i.e. transporters
Tolerance to NA uptake and positive chronotropic action
Probably longer term- some down regulation of DA receptors
Some exhaustion of DA stores

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14
Q

Conditioned tolerance

A

Repeated administration of drug in given circumstances
Psychological tolerance factor- variable
Psychological anticipation of drug effect
Conditioned response can lead to positive tolerance and negative tolerance

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15
Q

Negative conditioned tolerance

A

Reverse tolerance- abuser learns to enhance the so-called desired effect of the drug

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16
Q

Positive conditioned tolerance

A

Conditioned response opposite to that expected of drug- abuser learns to behave in opposition to the drug

17
Q

High grade tolerance

A

Usually associated with functional tolerance
Person can take 10-20x the naïve dose
e.g. opioids, cocaine, CNS stimulants

18
Q

Low grade tolerance

A

Sometimes dispositional tolerance
Person can take 2-3x the naïve dose
e.g. CNS depressants, alcohol, barbiturates

19
Q

Acute vs chronic tolerance

A

Acute: develops after single exposure to drug, may develop during exposure to drug
Chronic: develops after several exposures to drug

20
Q

Cross tolerance

A

Occurs when an increased amount of a second drug is required to produce the same effect after tolerance to a first drug has been established

21
Q

Difference between abuse dependence and therapeutic dependence

A

Insulin dependent diabetic- wishes to avoid discomfort of its absence i.e. compulsion to take the drug
B-blockers- long term withdrawal causes hypertensive rebound i.e. compulsion to take the drug

22
Q

Drug abstinence

A

Caused by drug taking cessation or antagonism by drugs

Severity depends on drug, dose or duration of use

23
Q

Withdrawal relief and salience

A

Withdrawal relief- suppression of withdrawal symptoms by administration of a further dose of drug
Salience- compulsion to continue taking the drug in spite of all other considerations (legal, financial, health)

24
Q

Classification of drugs of dependence

A 
Alcohol
Amphetamine
Cannabis
Cocaine
Hallucinogen
Khat
Opioid
Volatile solvent
25
Q

Psychological dependence

A

Condition where there is an emotional or mental drive to continue taking drug to maintain a sense of well being
On drug withdrawal: emotional discomfort, ill-defined dissatisfaction, mild desire to take drug, intense craving for drug, drug seeking behaviour

26
Q

Drug dependence and reward

A

Humans and animals engage in behaviours that are rewarding

Reward- pleasurable feelings that provide positive reinforcement so that the behaviour is repeated

27
Q

Physical dependence

A

Altered or adaptive physiological state produced by repeated administration of drug
When drug (or metabolites) are necessary for continued functioning of certain body processes
Related to dose and pharmacological action of drug
On withdrawal of drug, physical and psychological signs

28
Q

Opioid tolerance and dependence

A

Natural- opium alkaloids
Synthetic- heroin, pethidine, methadone
Endogenous- enkephalins, endorphins, dynorphins
Opioid receptors:
mu- central analgesia- euphoria, dependence
kappa- analgesia via receptors other than mu
sigma- analgesia- stress induced analgesia

29
Q

Opioid tolerance

A

Tolerance develops to some opioid effects (not mioisis or constipation)
High grade tolerance
Mechanisms- some enzyme induction, receptor uncoupling
No change in receptor number or affinity

30
Q

Withdrawal syndrome

A 
Psychological craving
Thermoregulatory disturbance
Sexual disturbances
Sympatho-adrenal overactivity
GI reactions
31
Q

Dependence mechanisms

A

Continual opioid inhibitory influence (on soma or terminals) causes hypertrophy of cells linked down stream
Withdrawal syndrome expresses overactivity of NA, ACh, DA and 5-HT

PH3113 (30 decks)

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