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PHARMACOLOGY OF ADDICTIONS
September 2015
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Understanding the pharmacological basis of medications used
to manage dependence
Understanding how pharmacological agents are used to treat
dependence
Understanding that different medications are needed in the
different phases of addiction
Describing the medications commonly prescribed in
dependence
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Substance dependence encompasses physical and
psychological problems
Physical dependence: on cessation of a drug to which the
body has become adjusted, withdrawal symptoms occur.
This can be life-threatening
Psychological dependence: emotional and mental
preoccupation with substances and craving
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Treat emergencies: overdose, seizures, dehydration,
hypothermia/hyperthermia, acute confusional state, delirium
tremens
Treat detoxification and withdrawal syndromes: diazepam,
chlordiazepoxide, lofexidine, methadone, buprenorphine
Substitution: methadone, buprenorphine, nicotine
replacement therapy, bupropion
Relapse prevention: naltrexone, acamprosate, disulfiram
Treatment of vitamin deficiency
Treatment of comorbid psychiatric and physical disorders
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Patients should have the opportunity to make informed decisions
about their care in partnership with professionals
Special groups will need their treatment managed appropriately eg
older and younger people will need lower doses and account
needs to be taken of comorbid illnesses in older people
Psychosocial interventions must be part of the package
A full detailed assessment, including blood, urine, saliva
investigations to ensure that substances have been used, has to be
made before decisions about pharmacological treatment can be
made
Observations of withdrawal should be elicited if possible
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Antagonists at post synaptic receptor ie block synaptic
transmission eg naltrexone
Agonists have strong or 100% action on the receptor eg
methadone
Partial agonists induce less effect ie less than 100% eg
buprenorphine
Partial agonists will act like an antagonist if there is a full
agonist present
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Methadone: long acting, half life 24 hours, can be used once a day
Can be reduced slowly over weeks, has less euphoria than heroin
Side effects: lethargy, respiratory depression at high doses
especially with alcohol and benzodiazepines, constipation, reduced
saliva (contributing to poor dental hygiene)
Buprenorphine: partial agonist, long half life, administered once
daily
Attenuates the effects of opiates
Produces less sedation, less euphoria and positive reinforcement,
less respiratory depression
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Naltrexone: used when patient is abstinent; blocks the effects
of heroin or opiate agonists and prevents reinforcing effects.
Naloxone is a short acting opiate antagonist used in
emergencies
Lofexidine: adjunctive medication which reduces withdrawal
symptoms
Adjunctive medication i.e. anti inflammatory, anti-emetics,
anti- depressants should only be prescribed at the lowest
effective dosage, when clinically indicated ie when specific
symptoms are present, and risk interactions should be
considered
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Benzodiazepines:
Reduce symptoms of withdrawal
Reduce occurrence of delirium tremens
Reduce seizures
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Disulfiram: used when patient is abstinent.
Acts by inhibition of acetaldehyde dehydrogenase with leads to
accumulation of acetaldehyde which interacts with alcohol to
produce nausea, vomiting, headache, flushing, palpitations and
hypotension, which can lead to collapse and death
Acamprosate: commences once patient is abstinent and can
improve rates of abstinence. It is hypothesised to reduce craving
and urge to drink
Naltrexone: better than placebo at reducing risk of lapse
Nicotine
Nicotine gum or patches, bupropion, varenicline
E-cigarettes
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Stimulant
No agents have been found to be useful
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Cannabis: No pharmacological agents have been shown to be
helpful, but MET, CBT, CM have shown benefits
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Rarely present with dependence
Rarely require substitute medication
Most pharmacological preparations are not licensed for
adolescents
Initiation should be offered by a specialist addiction
psychiatrists or specially qualified doctors
Sometimes they require symptomatic medication
Non-pharmacological interventions should be part of the
treatment whether pharmacological treatments are being
administered
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Require dosage reduction and careful monitoring
Needs to take account of comorbid mental and physical health
problems e.g. neuropsychiatric disorders, hepatic and respiratory
complications
Need to take account of other medications prescribed and the
interactions with medications for substance use disorders
Should be undertaken with the expertise of professionals trained in
geriatric medicine, addiction psychiatry, old age psychiatry
Initiation of detoxification and reduction regimes should be
undertaken by the advice of specialists in addiction
Particular caution should be taken with acamprosate, disulfiram,
naltrexone
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Pharmacological treatment is one part of an integrated
coordinated treatment plan
A range of professional staff are involved in providing
different components
Coordination is necessary so that patients do not seek
medication from different GPs, doctors and hospitals
Pharmacists should be included in the multidisciplinary team
to discuss issues e.g. choice of treatment, initi ation of
medication, dosing regime, interactions with other
medications
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Crome I.B (2009) Substance misuse and addiction in adolescence – issues for the practising GP in Care of Children and young
people for the MRCGP (ed K.Mohanna). London. Royal College of General Practitioners.
Department of Health (2007) Drug misuse and dependence – guidelines on clinical management:
http://www.nta.nhs.uk/guidelines.aspx
Lingford-Hughes, A. R., Welch, S., Peters, L and Nutt, D. J., with expert reviewers Ball, D., Buntwal, N., Chick, J., Crome, I. B., et al.
BAP updated guidelines: evidence based guidelines for the pharmacological management of substance abuse, harmful use,
addiction and comorbidity: recommendations
from BAP (2012) Journal of Psychopharmacology 1-54 http://jop.sagepub.com/content/26/7/899
Findings (2014) Authoritative review reveals limitations of medicatingdependence
http://findings.org.uk/count/downloads/download.php?file=Lingford_Hughes_AR_2.txt.
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Luty. J., (2015) Drug and alcohol addiction: new pharmacotherapies. B J Prych Advances (21), 33-41 doi:
10.1192/apt.bp.114.013367
NICE (2007) Drug Misuse: naltrexone for the management of opioid dependence (NICE technology appraisal,TA115)
http://www.nice.org.uk/guidance/TA115
NICE (2007) Drug misuse: methadone and buprenorphine maintenance (NICE technology appraisal, TA114)
http://www.nice.org.uk/guidance/TA114
NICE (2007) Drug misuse: opioid detoxification (NICE clinical guideline, CG52) http://www.nice.org.uk/CG52
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NICE (2007) Drug misuse: psychosocial interventions (NICE clinical guideline, CG51) http://www.nice.org.uk/CG51
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NICE (2010) Alcohol-use disorders: physical complications (NICE clinical guideline, CG100)
http://guidance.nice.org.uk/CG100
NICE (2011) Alcohol use disorders: diagnosis, assessment and management of harmful drinking and alcohol dependence (NICE
clinical guideline, CG115) http://guidance.nice.org.uk/CG115
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Royal College of Psychiatrists (2011) Our invisible addicts First Report of the Older Persons’ Substance Misuse Working Group of
the Royal College of Psychiatrists. http://www.rcpsych.ac.uk/files/pdfversion/cr165.pdf