Drug Abuse Notes

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This is an extract of our Drug Abuse document, which we sell as part of our Neurology Notes collection written by the top tier of Bristol University students.

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Lecture 29, 30 & 33 Drug Abuse

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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

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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 t1/2

* 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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