7 July 2008

Concord Dependency Seminar Series, Tues 20th May 2008.

Treating the Addicted Brain: Agonists, Antagonists and Modulators.

Speaker: Stephen Jurd, Psychiatrist, RNSH and RANZCP director of training.

Dear Colleagues,

Dr Jurd commenced by almost stating the obvious: the problem of addiction starts with the brain. The origin of the behaviour does not lie in reasoned thoughts, which are late in evolution, but in reward pathways, organised in the hind-brain. From this ancient part of the nervous system, the responses are transferred to the frontal lobes where conscious thoughts, decisions and deductions are made regarding diverse ways to satisfy the more primitive urges. While most reward pathways are related to survival and procreation, drug use mimics such responses chemically, causing satisfaction, pleasure and desire to repeat the experience. The concept of craving was discussed in depth - it is not easy to define and perhaps best to simply call it ‘the motivation to use the drug’.

Equally, a definition of clinical or behavioural ‘salience’ is difficult, yet it is crucial to understanding and defining addiction, first clearly done by the redoubtable Griffith Edwards. Dr Jurd suggested one way to define ‘salience’ is to look at the person’s ‘top-40’ items of interest which for non-addicted people would range across a variety of things from food to music to work, family and hobbies. For the compulsive drug user or alcoholic, gambler, etc this would be a very short list, largely related to their drug or behaviour of interest. This is the ‘narrowed repertoire’ of drug use behaviour.

We were told of a recent pivotal study by Anne Rose Childress working at Philadelphia with Charles O’Brien’s group. They found significant brain responses on real-time PET scanning from ‘split-second’ projections of drug-related images, despite them not being seen or recognised consciously in a group of 22 long term cocaine users. These were also closely correlated with drug, violence or sexually explicit images shown several days later in relevant cases (and not in controls). So, despite not realizing it at the time, these long-term cocaine users’ brains had registered the brief images unconsciously and committed them to memory. Thus for the first time we have evidence of addiction related cues and/or priming occurring ‘outside awareness’. There was also some corroboration of this remarkable finding from another study involving similar brain responses to cues for ‘‘unseen’’ monetary rewards (Pessiglione). The advertising industry may have known of these matters for years!

Decisions in adolescence are agreed to be most important in learning and memory, and some regard drug addiction as an ‘illness of youth’ [cf Stanton Peele ref below]. We were told that there are maximal numbers of synapses in the adolescent brain which then decrease with age. Synaptic structures are highly dynamic, and adult brains are able to make new cells. Both exercise and stroke can lead to increased neural production and brain cells move towards the injury site. All of this is contrary to traditional teaching about the CNS being unable to repair or replace damaged areas.

Addiction is not simply withdrawal, but craving, the inclination to use, the very nature of dependence and a whole clinical syndrome which persists, sometimes well after drug/alcohol use has ceased. DSM defines ‘early remission’ as up to 12 months. We were told that addiction is common, has social and medical impacts, as well as numerous psychiatric complications.

There must be a system of reward, hard-wired into the mammalian brain where intuitively certain people and/or events are memorable, striking and causing a ‘yearning’. And such a system would just be normal. Dopamine has been identified as the relevant neurotransmitter.

However one defines them, ‘cravings’ lead to the conscious motivation to seek and use the drug, with a euphoric recall, and with often pleasant associations. “This feels sooo … good”. This is the case for both stimulatory and sedating drugs. Dopamine from the nucleus accumbens is crucial for reinforcement and reward; attention, memory and learning. These mesolimbic pathways are not unique to opiates but are similar for nicotine, alcohol, benzodiazepines, stimulants, etc.

The next result is to trigger ‘yearning’ for the experience to be repeated. Drugs excite the reward pathway and this then leads to addiction. At a certain point the individual becomes aware of the dangers and the illogical nature of their behaviour, yet continues with it. Similarly, they may be able to rationalise with a counsellor, doctor or family member that it is harmful to continue (cortical), yet the behaviour persists (driven by limbic pathways).

We were shown a familiar brain diagram from The New England Journal of Medicine: Neural Reward Circuits Important in the Reinforcing Effects of Drugs of Abuse [Cami J, Farre M. 2003 349:975-986].

Stimulants may also cause direct stimulation of dopamine production. On the other hand, sedatives inhibit the production of inhibitors of dopamine and so lead to increased dopamine concentrations. Thus in the reward pathway all drugs lead to increased dopamine at critical points in the hind-brain and so lead to increased learning, attention and focus on the drug use.

Aversive Agents

Disulfiram does not affect the dopamine pathway, but has its action through the frontal lobe using logic and reasoning. With this the person learns that “it is dumb to take alcohol with this”, and so even when cravings are strong the addict may choose not to consume alcohol, knowing the likely consequences.


Most of these provide a longer acting form of the drug which avoids the cycle of intoxication and withdrawal. For example methadone is a long half life drug, decreasing heroin use and improving quality of life. The person learns that they simply do not need to use additional opiates as there is little gain.

Nicotine is the same drug, with a safer delivery of drug via patches, gums and inhalers. Post-myocardial infarct patients do better on patches.

Dexamphetamine - there is no pharmacological basis to change to this from methamphetamine as the half-life of ‘dex’ is 10-12 hours compared to 9-15 hours for methamphetamine. A longer acting form may be more appropriate for addiction treatment.

Benzodiazepines – theoretically for alcohol but they are not satisfactory, both are disinhibitory agents, acting on GABA receptors.

Partial agonists

Buprenorphine (for opiate dependence).
Varenicline (a nicotine receptor blocker).


Naltrexone – a long acting opioid antagonist, works when taken but does not chemically modulate cravings for opioids (might do so psychologically according to Brewer). For alcohol with time it can modulate cravings but unlike disulfiram the person will not become ill if alcohol is consumed.

Rimonaband – cannabinoid antagonist - not yet available in Australia – used overseas for obesity(?).

Odansetron (Zofran) – serotonin-3 antagonist with promise for alcohol abuse in very low dose [see RCT Bankole Johnson link below].


These take time to work, and act less on receptors but modulate other areas which then lead to change in receptors and/or their neurotransmitters.

Acamprosate modulates the balance of GABA. We were reminded that this drug is really only of benefit for those wishing to cease alcohol use completely whereas those on naltrexone are more likely to be able to manage controlled drinking better (although this is not approved under PBS prescribing criteria). In a similar way in depressives, SSRI drugs also take time to have their clinical effects, rather than a chemical effect on receptors which theoretically occurs straight away.

We were then brought back to the traditional in-patient treatment of alcoholism and drug addiction, something which is now rare as authorities have closed down many detox and rehab wards. The justification has often been that they were “not cost-effective”. Dr Jurd quoted the highly reputed “Project Match” which found double the rate of abstinence at one year in those who received an in-patient stay as part of their treatment when compared with those who only received out-patient services. Note that entrants were not randomised so the significance is limited to an non-causal association.

Two case histories were then presented and ‘work-shopped’ in some detail:

Case 1: A youth with excess alcohol use causing serious health, legal, and social problems.

Case 2: A middle-aged set-in-his-ways professional with smoking and alcohol excess with hypertension. He stopped nicotine after 12 months but unable to decrease his alcohol.

Summary written by Judith Meldrum and Andrew Byrne. Further details of the case histories and workshop discussion will be sent as a supplement later when time allows. See our summary of “The neurobiology of addictive behaviours” on web page: http://www.redfernclinic.com/c/2005/12/alcohol-pharmacotherapy-macquarie.php4 Web site: http://www.redfernclinic.com/concord/

References: Childress AR, Ehrman RN, Wang Z, Li Y, Sciortino N,,, O’Brien CP. (2008) Prelude to Passion: Limbic Activation by "Unseen" Drug and Sexual Cues. PLoS ONE 3(1): e1506

Johnson BA, Roache JD et al. Ondansetron for Reduction of Drinking Among Biologically Predisposed Alcoholic Patients. A Randomized Controlled Trial. JAMA (2000) 284:963-97

Peele S. The Surprising Truth About Addiction. Psychology Today (2004) May-June: 43-46 http://www.peele.net/lib/surprising.html

Pessiglione M, Schmidt L, Draganski B, Kalisch R, Lau H, et al. (2007) How the brain translates money into force: a neuroimaging study of subliminal motivation. Science 316: 904–906 http://www.sciencemag.org/cgi/content/abstract/316/5826/904