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Drug Abuse Notes

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Lecture 29, 30 & 33 Drug Abuse

Classes of drugs o Alcohol; Nicotine; Caffeine o Solvents/Inhalants (legal to have, but not to sell) o Anxiolytic/Sedatives/Hypnotics o Antidepressants o Anaesthetics o Opiates (narcotics) o Stimulants (cocaine, amphetamine, khat, methamphetamine (speed) &
MDMA) o Cannabis (low doses=no hallucinations; high doses=hallucinations) o Hallucinogens (LSD, mescaline, psilocybin & phencyclidine) Dependence o Need to continue drug taking
 Psychological (craving)
 Physical (withdrawal syndrome)

• Put into detox and clear body of drug, should get rid of this

• But, fails quite often so PSYCHOLOGICAL must be main driving force o Important brain neurotransmitters
 Dopamine

• Cocaine, heroin, nicotine, alcohol etc.

• Reward/euphoric
 5-Hydroxytryptamine (serotonin)

• Elevation of mood (bit happy)

• E.g. Ecstasy The 'reward pathway' o Dopaminergic pathway (drugs over-activate this) o Ventral Tegmental Area (VTA) to nucleus accumbens o Enhanced dopamine levels at synaptic cleft o Natural rewards= food, water, sex, nurturing o Drugs acting on this pathway
 Cocaine and amphetamine act on nucleus accumbens
 Morphine acts on GABAergic inhibitory interneurone=disinhibition of VTA
 Heroin acts on VTS

• Long term o Rise in DA in nucleus accumbens=paraphernalia and process of drug taking o I.e. euphoria from seeing blood sucked back into needle Tolerance o General
 (Not for all drugs e.g. cocaine)
 More of drug required to induce same effect

• Changes in metabolism

• Changes in sensitivity of target site

o

o

Types
 Dispositional (metabolic)

• Ethanol, barbiturates

• Liver gets bigger over weeks so drug more easily metabolised
 Functional (cellular or pharmacodynamic)

• Opioids, ethanol, benzodiazepines
 Behavioural

• Overcome effect of stimulant (alcoholics hiding fact they're drunk)
 Sensitisation

• May occur with cocaine Other things to know
 Cross tolerance

• Drugs acting in same way

• Ethanol & benzodiazepines; Different opioids
 Tolerance reversal

• Abstinence e.g. detox or prison (tolerance falls when stop taking)

• Overdose when subject takes same dose they took when tolerant
 Polypharmacology

• Opioid addicts rarely take on drug

• Problem as don't know interactions

• Alcohol + Cocaine= Toxic metabolite

Heroin o Why do people take it?
 Buzz and euphoria
 Remove from reality of situation
 Many have other mental health problems o Treatment of heroin addiction
 Methadone maintenance

• Orally active, long t½

• Side effects: general state of activity
 Stabilise (onto methadone) and maintain (not going through withdrawal)
 Stabilise and withdraw (withdrawal from methadone not as bad as heroin)
 Buprenorphine

• + naloxone (antagonist)= Prevents effect of heroin in case of relapse

• Give as sublingual tablet as naloxone not absorbed sublingual or in gut, so can't crush up and inject/sell. No effect when injected

• Most addicts prefer methadone (mental health problems)
 Safely controlled heroin supply

• Failure rate lower than first two (people not involved in crime) Stimulants o Cocaine
 Weak base
 Mechanism

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