Addiction

Question 1

What is tolerance?

Answer 1

Reduced responsiveness to a drug caused by previous administration.

Question 2

What is dispositional tolerance?

Answer 2

• less drug reaches active site
• dec. rate of absorbtion
• inc. rate of metabolism to inactive metabolites
• dec. rate of absorbtion to active metabolites
• inc. rate of excretion

* i.e. less drug absorbed
drug metabolised faster
more drug excreted

Question 3

What is pharmacodynamic tolerance?

Answer 3

• site of action is less affected by drug
• down-regulation/internalisation of drug receptors
• dec. signalling down stream of drug receptors
• some other compensatory mechanisms

* i.e. fewer drug receptors
less efficient drug receptors

Question 4

What is dependance?

Answer 4

• body physiologically adapts to an external substance
• removal of substance causes withdrawal symtoms
• can lead to physical dependance on the drug

e. g.
- drug dec. transmitter release
- adapts to inc. sensitivity to transmittor to maintain homeostasis
- removal of drug but adaptive response remains, symptoms opposite (inc. transmitter release)

Question 5

What is withdrawal phenomena?

Answer 5

• the withdrawal effect of the drug is the reverse of the acute affect

e. g.
- opioids- constipation (acute) + diarrhoea (withdrawal)
- cocaine- elevated mood (acute) + depressed mood (withdrawal)

Question 6

How is the psychological effect of craving produced?

Answer 6

• drugs of abuse affect the reward pathway of the brain + inc. dopamine levels