Substance Misuse

 

• Pathophysiology

  • Most dependencies feature excess activity of the mesolimbic system, a dopaminergic reward pathway running from the ventral tegmental area (VTA) in the midbrain to the nucleus accumbens (NA) in the striatum.
  • This makes substances extremely rewarding, leading to craving and compulsive use.

• Signs and symptoms

  Definitions

  Dependency

  ≥3 out of 6 of WANTIN:

  • Physical Withdrawal symptoms.
  • Persisting despite Adverse effects.
  • Neglect of other things.
  • Tolerance: need more to get the same effect.
  • Intense desire (craving).
  • No control over use in terms of starting, stopping, or amount.

  Harmful use

  • Physical or mental health damage resulting from substance use.

  Acute intoxication

  • Acutely altered consciousness, behaviour, perception, affect, and/or cognition, due to substance use.

  Substance-specific signs and symptoms

  Injection drug use:

  • Track marks: injection scars along the route of a vein.
  • Vascular: thrombophlebitis, VTE.
  • Infection: abscesses, endocarditis, hepatitis, HIV.

  Opioid withdrawal:

  • ↑RR, sweating.
  • Face: rhinorrhea, lacrimation, yawning, mydriasis.
  • Abdo pain.
  • Later: ↑HR, tremor, fever, diarrhoea and vomiting.

  Cannabis:

  • Paranoid ideation.
  • Cannabinoid hyperemesis syndrome, in which vomiting is relieved by taking a hot shower.

  Cocaine and crack cocaine:

  • Paranoid psychosis.
  • Formication: sensation of insects crawling on skin.
  • Nasal discharge.

  Others:

  • Amphetamines: florid psychosis.
  • Hallucinogens: flashbacks.

• Investigations

  Urine drug testing:

  • Indications: initial assessment for detox, including for substances besides the one being treated. Also for monitoring use during contingency management.
  • Bedside testing is usually sufficient, but laboratory analysis should be used at first assessment or when bedside tests are inconsistent with the clinical impression.

  Consider testing for blood-borne viruses in injection drug users.

• Management of opioid dependency

  Overview

  General principles:

  • First step is to establish goals: withdrawal and abstinence, replacement and maintenance, or harm reduction. This can be part of a therapeutic approach – motivational interviewing – which is a non-confrontational way of guiding a user towards positive change.
  • Involve family in so far as the patient is happy for this to be done.
  • Inpatient or residential treatment can be offered to those with significant physical, psychiatric, or social problems (e.g. homelessness). Range of treatments is the same, however.

  A biopsychosocial approach should be used regardless of the goal.

  If withdrawal is the goal:

  • Opioid detoxification is a planned process designed to minimize withdrawal symptoms. It should combine drug and psychosocial interventions.
  • Typically takes 4 weeks as an inpatient or 12 weeks as an outpatient. It should not be initiated when an acute medical problem needs treatment, and it should only be done cautiously in pregnant women.
  • Consider other dependencies when initiating detox e.g. alcohol, benzodiazepines. Withdrawal can be done concurrently or sequentially.

  Biological

  Opioid replacement:

  • Methadone or buprenorphine can be used for maintenance, or to help minimize withdrawal symptoms during opioid detoxification.
  • Lofexidine – an α2 adrenergic agonist – is a 2nd line choice for detoxification.
  • If there are concerns about diversion, supervised consumption may be necessary. Similarly, buprenorphine can be given as Suboxone, which contains naloxone and thus removes enjoyment from injection use.

  Opioid receptor blockers:

  • Naltrexone is used after detoxification for at least 6 months to help prevent relapse. Combining with psychological interventions improves adherence.
  • Naloxone is used in overdose.

  Psychological

  Brief interventions and self-help:

  • Opportunistically use any contact with services – drug misuse or otherwise – as a chance for basic interventions. Use motivational interviewing to encourage change, and provide advice on harm-reduction e.g. safe injection behaviour.
  • Narcotics Anonymous is a self-help group using 12-step. Facilitate attendance if required e.g. have them accompanied to their first session.

  Formal interventions:

  • Contingency management: aims to encourage change by rewarding positive behaviour – e.g. a clean drug test – as opposed to punishing negative behaviour. Incentives should be agreed with the patient and can include vouchers, modest financial rewards, or certain 'privileges' (e.g. take-home methadone). For detoxification, should be used during and for 6 months afterwards.
  • Behavioural couples therapy: 12 weekly sessions for those with a partner who doesn't misuse drugs.
  • CBT should only be used for co-morbid depression, not for drug misuse itself.

  Social

  • They will need to inform the DVLA if they are drivers.
  • Support with any difficulties regarding income, work, or housing.
  • Assess needs and provide support for family. Offer guided self-help and information on support groups.

• Smoking cessation

  Treatment can be in primary care or from specialist smoking cessation services.

  Psychological interventions

  • Brief interventions: use any contact with services to advise smoking cessation. Provide self-help material if interested.
  • Individual behavioural counselling or group behavioural therapy, which include psychoeducation and elements of CBT. Provide at least 4 weekly sessions after quitting. Combine with pharmacotherapy.

  Pharmacotherapy

  Treatment approach:

  • Treatment should be started before cessation, to reduce withdrawal symptoms.
  • Avoid combining different drugs, but people with severe dependency can be offered multiple NRT types.

  Nicotine replacement therapy (NRT):

  • Patches, nasal spray, gum, or lozenges.
  • Generally safe in all those ≥12 years old.
  • Carries risks in pregnant women, but is preferable to smoking, so can be offered if willpower alone is ineffective.
  • Avoid in cardiac disease.

  Alternative 1st line treatments to NRT:

  • Bupropion, a dopamine and noradrenaline reuptake inhibitor. Contraindicated in epilepsy.
  • Varenicline, a nicotine receptor partial agonist. Can cause suicidal thoughts, so caution in those with history of depression or self-harm
  • Neither should be used in breastfeeding or pregnancy, or in people under 18.