Adulterants, Mixed Toxidromes and Implications for Prehospital Care in the UK**

Abstract

Cocaine use remains prevalent in the United Kingdom; however, the substance encountered clinically is frequently adulterated with pharmacologically active agents. These adulterants can significantly alter the expected toxidrome, resulting in atypical or mixed clinical presentations. This article explores common cocaine adulterants, their physiological effects, and the implications for prehospital assessment and management. It emphasises the importance of avoiding diagnostic anchoring and adopting a syndromic approach aligned with UK guidance.

Introduction

Cocaine is a potent sympathomimetic agent associated with predictable clinical features including tachycardia, hypertension, agitation and chest pain. However, surveillance data from the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) demonstrate that cocaine is rarely consumed in a pure form, with widespread adulteration across European drug markets (EMCDDA, 2023).

For prehospital clinicians, this creates a diagnostic challenge. Patients may present with features inconsistent with a pure stimulant toxidrome, increasing the risk of misinterpretation and inappropriate management. A reliance on patient-reported substance use is therefore unreliable. This article examines the clinical impact of cocaine adulterants and outlines a pragmatic approach to prehospital care.

Cocaine Adulteration in the UK

Adulteration occurs for economic and pharmacological reasons, including bulking, enhancing perceived potency, and mimicking cocaine’s sensory effects such as mucosal anaesthesia (Public Health England, 2020). Common adulterants identified in UK and European samples include levamisole, local anaesthetics, synthetic stimulants, and opioids (EMCDDA, 2023).

Levamisole

Levamisole is an antihelminthic agent frequently identified in cocaine samples. It has been detected in a significant proportion of seized cocaine and is associated with serious complications including agranulocytosis and vasculitis (Larocque and Hoffman, 2012).

Clinically, patients may present with:

  • Fever and systemic illness

  • Mouth ulcers

  • Necrotic skin lesions, particularly affecting ears and extremities

These findings may initially be misattributed to infection or unrelated dermatological conditions.

Local Anaesthetics

Local anaesthetics such as lidocaine and benzocaine are commonly used to replicate the numbing effect of cocaine. However, these substances carry a risk of inducing methemoglobinaemia (Hoffman et al., 2015).

Clinical features include:

  • Cyanosis

  • Low oxygen saturation readings

  • Poor response to supplemental oxygen

This creates a risk of under-recognised hypoxia and inappropriate reassurance based on misleading pulse oximetry values.

Synthetic Stimulants

Synthetic cathinones and other novel psychoactive substances may be present as adulterants or substitutes. These agents are associated with:

  • Severe agitation

  • Prolonged psychosis

  • Hyperthermia

  • Increased risk of excited delirium

Compared to cocaine, these effects may be more sustained and less responsive to standard benzodiazepine therapy (EMCDDA, 2023).

Opioid Contamination

Opioid contamination, including fentanyl analogues, is increasingly recognised in European drug markets, although less prevalent than in North America (EMCDDA, 2023).

This introduces the risk of:

  • Respiratory depression

  • Reduced level of consciousness

  • Mixed stimulant and opioid toxidromes

Importantly, stimulant effects may initially mask opioid toxicity, delaying recognition and treatment.

Clinical Presentation and Diagnostic Challenges

Typical Cocaine Toxidrome

The classical presentation of cocaine toxicity reflects sympathetic nervous system activation and includes:

  • Tachycardia

  • Hypertension

  • Dilated pupils

  • Agitation

  • Chest pain

These features are well described in toxicology literature (LITFL, 2024).

Atypical and Mixed Presentations

Adulteration frequently results in presentations that deviate from this classical pattern. Clinicians should maintain a high index of suspicion when encountering:

  • Hypoxia or cyanosis not improving with oxygen

  • Reduced Glasgow Coma Scale score

  • Pinpoint pupils

  • Severe or refractory agitation

  • Hyperthermia

  • Unexplained dermatological findings

Such features suggest a mixed toxidrome and require a broader differential diagnosis.

Implications for Prehospital Management

Prehospital care should be guided by a syndromic approach, consistent with UK clinical practice guidelines (JRCALC, latest edition; NICE, 2019).

Assessment

  • Structured ABCDE assessment

  • Early identification of life-threatening features

  • Continuous monitoring, including ECG where indicated

Management

  • Oxygen therapy for hypoxia

  • Benzodiazepines for agitation, seizures or sympathetic overactivity

  • Naloxone administration where opioid toxicity is suspected

  • Active cooling for hyperthermia

  • Early conveyance for high-risk presentations, including chest pain, reduced consciousness and abnormal observations

Pharmacological Considerations

Beta blockers should generally be avoided in acute cocaine toxicity due to the risk of unopposed alpha-adrenergic stimulation, which may exacerbate hypertension and coronary vasospasm (LITFL, 2024).

Discussion

The presence of adulterants significantly alters the clinical landscape of cocaine-related presentations. Diagnostic anchoring based on reported substance use is unreliable and may lead to inappropriate or delayed treatment.

A syndromic approach, focusing on observed physiological derangement rather than assumed causation, is essential. This aligns with established toxicological principles and supports safer clinical decision making in the prehospital setting.

Conclusion

Cocaine encountered in the UK is frequently a heterogeneous mixture of substances with diverse pharmacological effects. Prehospital clinicians must recognise the limitations of patient history and adopt a structured, evidence-based approach to assessment and management.

Failure to consider adulterants and mixed toxidromes risks missing critical diagnoses, including opioid toxicity and methemoglobinaemia, with potentially serious consequences.

CPD REFLECTION EXAMPLE

CPD Reflection

What?

This article explored the prevalence of cocaine adulteration in the UK and the resulting impact on clinical presentation, highlighting the risk of atypical and mixed toxidromes in prehospital care.

So What?

For frontline clinicians, this reinforces the need to move beyond reliance on patient-reported substance use. Recognising inconsistencies in presentation is essential to avoid misdiagnosis, particularly in cases involving opioid contamination or functional hypoxia.

Now What?

In future practice, I will adopt a syndromic approach to suspected drug toxicity, actively considering adulterants and mixed toxidromes. I will maintain a lower threshold for naloxone administration and escalate care early when clinical findings do not align with expected patterns.

Estimate Time: to read, digest and read any links that are referred to:

20 minutes

References (Harvard Style)

European Monitoring Centre for Drugs and Drug Addiction (2023) European Drug Report 2023: Trends and Developments. Luxembourg: Publications Office of the European Union.

Hoffman, R.S., Howland, M.A., Lewin, N.A., Nelson, L.S. and Goldfrank, L.R. (2015) Goldfrank’s Toxicologic Emergencies. 10th edn. New York: McGraw-Hill.

Joint Royal Colleges Ambulance Liaison Committee (JRCALC) (latest edition) UK Ambulance Service Clinical Practice Guidelines.

Larocque, A. and Hoffman, R.S. (2012) ‘Levamisole in cocaine: unexpected news from an old acquaintance’, Clinical Toxicology, 50(4), pp. 231–241.

Life in the Fast Lane (2024) Cocaine toxicity. Available at: https://litfl.com

National Institute for Health and Care Excellence (2019) Drug misuse in over 16s: management (NG135). London: NICE.

Public Health England (2020) Review of drug adulterants in the UK drug supply. London: PHE.