10.4 Assessment and management of drug misuse

Assessment

• History: ask calmly and without judgement about every substance, prescribed and non-prescribed, covering quantity, frequency, route, source, context, purpose, impaired control and harms.

• Ask about previous treatment: what it gave them, why it ended and what they want now.

• Opioid toxicity gives small pupils and slow breathing. Opioid withdrawal gives dilated pupils, lacrimation, piloerection and diarrhoea, and is rarely fatal, unlike alcohol or benzodiazepine withdrawal.

• Examine injection sites, circulation and nutrition, because contaminated heroin injected into skin or muscle can cause wound botulism or injectional anthrax.

• Identify pregnancy, suicide risk, coexisting mental illness and exploitation such as county lines or cuckooing.

• Capacity is specific to the decision and the time, and dependence does not by itself remove it.

• Offer HIV, hepatitis B and hepatitis C testing, and arrange an electrocardiogram where methadone may lengthen the QT interval.

Tap to enlarge

Urine drug testing

A positive result shows exposure within a variable window. It does not show current impairment, dependence or the date of use.

Tap to enlarge

• Confirm an unexpected result with serious consequences by mass spectrometry, but do not delay urgent treatment while you wait.

• Cannabis metabolites can persist for weeks after sustained use because the drug accumulates in fat, while cocaine metabolites usually last several days.

• Temperature below the fresh-void range of about 32 to 38 degrees Celsius shortly after voiding signals substitution or tampering.

• Specific gravity well below normal, near that of water, marks a diluted sample.

Opioid overdose

• Naloxone is a competitive opioid antagonist that can wear off before the opioid does, so give repeat doses, keep observing and sometimes run an infusion.

• Naloxone can precipitate withdrawal, but that is no reason to withhold it.

• Supply take-home naloxone with training to people at risk and likely witnesses. Since December 2024, trained nurses, pharmacists, paramedics, police, prison and probation services can supply it without a prescription.

• Overdose risk rises when tolerance has fallen: after detoxification, a break in treatment or release from prison.

Opioid substitution maintenance

• Continued illicit use, or withdrawal before the next dose, usually means the methadone or buprenorphine dose is too low. Have a low threshold for raising it rather than sanctioning the person or adding another drug.

• Buprenorphine is a partial mu agonist with little effect on the QT interval, so it replaces methadone when methadone has lengthened the corrected QT interval.

• Buprenorphine with naloxone deters injection and diversion: under the tongue the naloxone is barely absorbed, but injected it blocks buprenorphine and can precipitate withdrawal.

• Supervised injectable diamorphine is the UK option for people who keep using heroin despite adequately dosed oral methadone and buprenorphine. Other oral opioids are not licensed for dependence.

• Physical dependence on a prescribed painkiller for chronic non-cancer pain is managed by planned gradual dose reduction. Substitution therapy is for illicit or high-dose opioid dependence.

Tap to enlarge

Detoxification and relapse prevention

The National Institute for Health and Care Excellence (NICE) says opioid detoxification should not routinely be offered:

• in custody or during a short sentence;

• with an urgent medical illness;

• at an emergency presentation.

Alcohol dependence, age, past failed attempts and comorbid mental illness change only the sequencing or the support.

• Ultra-rapid detoxification under general anaesthesia or heavy sedation risks serious harm, including death, and NICE says it must not be offered.

Pregnancy and breastfeeding

Stabilisation is preferred to detoxification, because withdrawal harms the fetus.

• Buprenorphine is not started in pregnancy because induction risks precipitated withdrawal.

• Little drug reaches the infant in breast milk, and breastfeeding lessens neonatal abstinence syndrome.

Stimulants

• Contingency management rewards agreed, verified goals such as negative drug tests, often with vouchers.

• Contingency management alone or with community reinforcement or cognitive behavioural therapy (CBT) has the most consistent evidence for abstinence and retention in cocaine and amphetamine use disorder. No UK medicine is licensed for it.

• Contingency management also improves engagement and cuts illicit use during opioid substitution.

• Benzodiazepines are usually first-line for stimulant-related agitation. Antipsychotics treat stimulant psychosis where indicated, with no blanket ban on haloperidol.

• Symptoms alone will not separate stimulant psychosis from primary psychosis, so establish the timeline and revisit the diagnosis at follow-up.

Psychosocial care and harm reduction

• Offer motivational work and CBT relapse prevention, and treat coexisting mental illness at the same time.

• Provide needle and syringe access, infection screening, vaccination and safer-use advice whether or not abstinence is the goal.

• Bottled lemon juice used to acidify heroin introduces Candida and causes Candida endophthalmitis. Advise single-use acid sachets and sterile water instead.

• Safer-injecting advice includes rotating injection sites.

• Offer family and peer support, such as Narcotics Anonymous or SMART Recovery, and coordinate with primary care, mental health, housing, criminal justice, safeguarding and antenatal services.