drug abuse 2

Question 1

compare and contrast differing types of addiction

Answer 1

psychological addiction:
- not due to changes in brain chemistry
- no change in NT release, receptor expression, receptor sensitivity
- associated with occasional use

e.g. cocaine, cannabis
- user gets addicted due to strong emotional/mental craving to perceived positive effects and reinforcement
cocaine - intense euphoria + relaxation
cannabis - mood enhancing effects, dealing with stress

physical addiction:
- associated with harder drugs
- changes in brain neurochemistry
- activation of mesolimbic, mesocorticol systems
- withdrawal symptoms
- mechanisms of addiction:
increased NT release
decreased NT synthesis
increased/decreased receptor expression
increased receptor sensitivity
e.g. nicotine, heroin, amphetamine, ethanol

Question 2

explain the physical addiction mechanism in nicotine/heroin?

Answer 2

nicotine:
- activation of mesolimbic system stimulates reward pathway
- increases dopamine
- increased dopamine decreases dopamine production to compensate
- reduces sensitivity of nAChr
- brain increases levels of nAChr to compensate
- increases reward pathway sensitivity

intensifies reinforcing effects making it more difficult to quit

Question 3

physical addiction mechanism of amphetamines?

Answer 3

potentiates CNS biogenic amine stimulation - by blocking biogenic amine reuptake

receptor downregulation occurs

reduces biogenic amine synthesis
- bad trip

erodes pharmacological effect
- leads to tolerance and addiction

users take higher doses + co-administer drugs - tweaking

Question 4

cellular effects of withdrawal

Answer 4

increased expression of receptor
increased sensitivity of receptor
decreased synthesis of endogenous NTs

Question 5

withdrawal effects of alcohol

Answer 5

sweating
anxiety
insomnia
cold sweats
watery eyes
involuntary muscle spasms - kicking the habit

Question 6

how does methadone aid gradual withdrawal from heroin/other opiates

Answer 6

methadone aids gradual withdrawal
- full mu opioid receptor agonist - still occupies the receptors - similar effects
- longer half life (24hrs) - so won’t experience fluctuations and intense bursts of euphoria - helps suppress their cravings as it provides a steady level of opioid receptor activation
- suppresses withdrawal symptoms
- tapering dose down gradually

Question 7

ethanol metabolism and disulfiram alcohol reaction

Answer 7

ethanol - acetaldehyde - acetate

disulfiram (antabuse) - inhibits acetaldehyde dehydrogenase - results in accumulation of acetaldehyde
- flushing
- rapid heartbeat
- sweating
- nausea and vomiting
- dizziness

Question 8

drug testing of ethanol

Answer 8

roadside breath test:
- conversion of ethanol to acetic acid at anode + reduction of oxygen at cathode produces current
- limit is 35 ug per 100ml breath
- positive result confirmed at police station using evidential analyser
- blood alcohol level can be requested - 100mg per 100ml blood

Question 9

drug testing of cannabis

Answer 9

based on cannabis metabolism
- 9-THC (pyschoactive substance) gets metabolised by liver into 11-hydroxy-THC (primary active metabolite) and this is broken down into 9-carboxy-THC (inactive metabolite)
- but it is the major one

Question 10

drug testing of heroin

Answer 10

based on heroin metabolism:
- heroin - initial hydrolysis catalysed by esterases into 6-MAM and morphine

• 6-MAM - specific metabolite of heroin - measure this during drug test
• more potent than morphine
• basis of relapse test
• morphine further metabolised by liver via glucuronidation into M3G and M6G
• M6G - more potent than morpine
• readily crosses the BBB
• levels higher in chronic heroin addicts

Question 11

problems with methadone