Toxidromes (recognizing poisoning)

Definition

A toxidrome (toxic syndrome) is a typical combination of symptoms and findings that points to poisoning with a particular class of substances. The symptoms of poisoning depend on the substance and can vary widely between people even with the same substance; however, some symptom clusters occur frequently and narrow down the possible causes. In mixed poisonings the pictures may overlap.

Poisoning usually results from ingestion, but also from parenteral exposure, inhalation or contact with the skin, eyes or mucous membranes.

Classification

Common toxidromes

• Anticholinergic syndrome: tachycardia, hyperthermia, dilated pupils (mydriasis), warm and dry skin, urinary retention, bowel paralysis (ileus), delirium
• Cholinergic syndrome, muscarinic: salivation, lacrimation, urination, defecation, abdominal cramps, vomiting, diarrhea, constricted pupils (miosis), bronchorrhoea, bradycardia, bronchoconstriction with wheezing
• Cholinergic syndrome, nicotinic: mydriasis, tachycardia, muscle weakness, hypertension, hyperglycemia, fasciculations, sweating; abdominal pain, paresis
• Opioid syndrome: respiratory depression, hypotension, miosis, sedation, possibly hypothermia
• Sympathomimetic syndrome: tachycardia, hypertension, mydriasis, agitation, seizures, sweating, hyperthermia; psychosis after chronic use
• Abstinence syndromes: after ending the use of sedative substances (alcohol, benzodiazepines, barbiturates, GHB) agitation, hallucinations, confusion, seizures, hyperreflexia, hypertension, tachycardia and autonomic instability; in opioid abstinence among others tachycardia, mydriasis, sweating, restlessness, goose bumps, yawning, lacrimation, abdominal cramps, vomiting and diarrhea

Distinguishing features

Important distinguishing features are the pupils (dilated in the anticholinergic and sympathomimetic syndromes, constricted in the muscarinic cholinergic and opioid syndromes) and the skin (dry in the anticholinergic, sweaty in the sympathomimetic and nicotinic cholinergic syndromes).

Occurrence & epidemiology

Accidental poisoning is common in young children; usually only one substance is involved. In older people it occurs due to confusion, poor eyesight, mental illness or polypharmacy. Intentional poisoning with suicidal intent is common in older children, adolescents and adults; several substances are often involved, including alcohol, sedatives and over-the-counter painkillers.

Aetiopathogenesis

Typical substance groups for each toxidrome:

• anticholinergic: tricyclic antidepressants, many psychoactive drugs, belladonna alkaloids, angel's trumpet and jimson weed, some mushrooms
• cholinergic muscarinic: organophosphates and carbamates (e.g. in insecticides), some mushrooms
• cholinergic nicotinic: nicotine, carbamates, some organophosphates, black widow spider bites
• opioid: opioids including heroin and synthetic opioids
• sympathomimetic: amphetamines, MDMA, cocaine, synthetic cathinones (“bath salts”), synthetic cannabinoids

Clinical features

Poisoning is to be considered with unexplained symptoms, especially altered consciousness ranging from agitation to somnolence and coma. Besides the toxidrome, clues on examination are:

• breath odour
• residues of medicines or substances on the skin
• needle marks and tracks as signs of drug use with needles
• stigmata of chronic alcohol use

Even with known poisoning, other causes of altered consciousness are to be considered, such as CNS infection, head injury, hypoglycemia, stroke, hepatic or Wernicke encephalopathy.

Diagnosis

• History: often the most valuable tool; substance, route, amount and time; collateral history from relatives, friends and paramedics, as many patients cannot give reliable information; pharmacy and medical records
• Physical examination: vital signs, pupils, skin, bowel sounds, neurological findings to identify a toxidrome
• Serum levels: informative for only a few substances, e.g. paracetamol, salicylates, carbon monoxide, digoxin, ethylene glycol, iron, lithium, methanol, phenobarbital, phenytoin, theophylline; in mixed poisonings a paracetamol level is often measured
• Further laboratory tests: electrolytes, urea, creatinine, glucose, coagulation, venous blood gas analysis; depending on suspicion serum osmolality, methemoglobin, carboxyhemoglobin
• ECG with substances affecting the cardiovascular system or an unknown substance
• Imaging: abdominal X-ray or CT with iron, lead, arsenic or swallowed drug packets (body packing); head CT depending on the suspected poison and clinical situation

Keep learning in the app

Further reading (open access)

1. MSD Manual Professional: General Principles of Poisoning
2. StatPearls: Toxicology Screening

Cross-references