Sympathomimetic Toxidrome

Introduction

Sympathomimetics act to activate the sympathetic nervous system through adrenergic stimulation.  Cocaine, amphetamines and their derivatives, ephedrine, pseudoephedrine, theophylline and caffeine all act as sympathomimetics. The vast majority of agents in this class are taken recreationally.

Risk Assessment

Clinical features:

  • Mild– euphoria, increased alertness, bruxism (MDMA), tachycardia, hypertension, mydriasis, tremor
  • Moderate– agitation, paranoia, hallucinations, diaphoresis, vomiting abdominal pain, chest pain, dysrhythmia
  • Severe– hyperthermia, metabolic acidosis, rhabdomyolysis, acute renal failure, vascular accident, seizures, coma

Baseline bloods including renal function and CK should be performed in all patients presenting with features of moderate or severe toxicity. A CT head should be considered in patients presenting with headache given the association with intracranial haemorrhage. An ECG should be performed on all patients.

Management

The majority of patients can be effectively treated with good supportive care including diazepam 5-10mg PO PRN.  

Resuscitation

Acute behavioural disturbance should be managed as outlined in module 1.6 Acute Behavioural Disturbance. Droperidol 10mg IM is first line for acute behavioural disturbance.  

Titrated intravenous benzodiazepines are indicated for all other sympathomimetic related emergencies.  

Further specific therapy includes;

            Hyperthermic crisis

Active cooling measures

            Hypertensive crisis

     GTN or SNIP infusion

     Hydralazine

     Beta blockersSee additional information

            Ventricular arrhythmia

            Bicarbonate 1mmol/kg bolus

            Defibrillation

            Lignocaine 1.5mg/kg bolus

Supportive therapy 

Titrated benzodiazepines and good supportive care are paramount until the toxidrome subsides. 

Disposition

The majority of patients will be suitable for transfer to SSU under the toxicology team for observation and supportive care.  For those with more serious sympathomimetic related complications intensive care input may be necessary.

Additional Information

  • Traditional teaching suggests beta blockers are theoretically contra-indicated in sympathomimetic toxicity because of the potential for unopposed alpha-adrenergic stimulation leading to profound vasoconstriction and hypertension.  However, a recent literature review suggests otherwise,1concluding that, based on the available evidence, beta blockers are recommended in the armament of treatment of hyperadrenergic states.
  • Cocaine in particular is associated with coronary vasospasm and myocardial infarction, however vasospasm, dissection and vessel rupture can occur in all sympathomimetic toxicity and needs to be considered in a patient presenting with concerning symptoms.
  • Psychosis is a feature of acute methamphetamine intoxication. It commonly resolves with resolution of intoxication.  Patients admitting to having used methamphetamine within the previous 24 hours presenting to the Princess Alexandra Hospital should be referred for admission to the Clinical Toxicology Unit in the first instance rather than the mental health team.

References

  1. Richards, J.R., et al., Treatment of toxicity from amphetamines, related derivatives, and analogues: Asystematic clinical review. Drug Alcohol Depend. (2015), http://dx.doi.org/10.1016/j.drugalcdep.2015.01.040