Amphetamines & Cocaine

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Overview

  1. Amphetamines: Central & peripheral sympathomimetic effects that can lead to life-threatening complications. Repeated use can cause neuropsychiatric sequelae. Incl. Metamphetamine (crystal meth or ice), methylphenidate (Ritalin), 3,4-Methylenedioxymethamphetamine (MDMA,Ecstasy).
  2. Cocaine: Sympathomimetic and local anaesthetic effects that can lead to lethal complications

Toxic mechanism

  1. Amphetamines: Enhance catecholamine release and block their re-uptake and inhibit MAO. NA, D & 5HT stimulation results. MDMA may induce SIADH.
  2. Cocaine: Blocks catecholamine re-uptake, causes vasospasm and blocks fast Na channels.

Toxicokinetics

  1. Amphetamines: Well abs orally or insufflation. Large Vd (lipophilic weak bases)
  2. Cocaine: Well abs through mucosal membranes of URT & LRT & GIT.Bioavail dependent on route. Moderate Vd (lipid soluble). Rapidly metab by liver & plasma cholinesterases. T½30–90min.

Clinical features

  1. May present with acute intoxication, complications of abuse or psychiatric sequelae. Acutely:
    1. CNS/PNS: Euphoria, anxiety, agitation, aggression, paranoia (may persist), hallucinations, mydriasis, sweating, tremor, fever, serotonin syndrome
    2. CVS: HR, BP, ACS, dysrhythmias, APO
  2. Cx: Rhabdo, dehydration, RF; hypoNa/cerebral oedema (from MDMA SIADH polydipsia), aortic/carotid dissection, SAH/ICH, ischaemic colitis, pneumothorax, pneumomediastinum.

Investigations

  1. Screening: ECG, paracetamol, BSL
  2. Specific: UEC, CK, Trop, CXR (dissection, aspiration), CT brain (if LOC)

Risk assessment

  1. Small doses may still produce significant intoxication. Seizures in 4%. A paediatric 1 pill can kill.

Management (see Toxidromes)

Resus

  1. ABCs O2. Anticipate agitated delirium & seizures, hypertension, hyperthermia, SVT, VT

Supportive Care

  1. BDZ PO/IV used for initial Mx of all these except VT
  2. If still BP then phentolamine, GTN or nitroprusside IV titrated to effect.
  3. If hyperthermia >39.5ºC intubate & paralysis may be needed.
  4. If SVT refractory to BDZ: adenosine 6–12mg IV or verapamil 5mg IV or DC if unstable.
  5. If VT(cocaine) treat with bicarbonate and if refractory use lignocaine 1.5mg/kg IV
  6. Careful fluid management.
  7. If hypoNa & fitting/LOC then give ~3ml/kg 3% Saline over 30mins and reassess. Aim to get [Na ]>120mmol/L. If not fitting, fluid restrict, & allow slow spontaneous correction.
  8. Treat serotonin syndrome (see Toxidromes)
  9. Manage ACS as usual but BB are contra-indicated.

Decontamination:

  1. Charcoal & WBI may be considered with cocaine body packers/stuffers.

Disposition

  1. If asymptomatic d/c after 4hr, otherwise supportive care. If SIADH, serotonin syndrome, or severe symptoms incl complications admit to HDU/ICU.