Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX
Differentiating between common types of overdose in a primary care setting primarily involves a systematic assessment, detailed history taking, and clinical examination, with a focus on specific signs and symptoms (toxidromes) associated with different substances NICE CKS.
- Initial Assessment and Emergency Transfer: Regardless of the suspected substance, immediately assess the person using the ABCDE approach (Airway, Breathing, Circulation, Disability, Exposure) NICE CKS. If the person is unconscious, has a reduced level of consciousness, reduced respiratory rate or oxygen saturation, hypotension, significant heart rate abnormalities (tachycardia, bradycardia, irregular pulse), hypothermia or hyperthermia, or has had a seizure, arrange emergency transfer to hospital immediately NICE CKS. Investigations are generally not routinely necessary or appropriate in primary care for those who do not need emergency referral to hospital NICE CKS.
- History Taking: If emergency transfer is not required, gather a detailed history from the person, friends, or family NICE CKS:
- Substance Taken: Identify the specific substance(s), the amount, and if any other medicines or alcohol were involved NICE CKS. Prompt for quantities in terms of strips or packets, as initial accounts may be unreliable NICE CKS.
- Timing: Establish the exact timing of ingestion, especially for substances like paracetamol NICE CKS.
- Route of Administration: Determine if it was by mouth, inhalation, or injection NICE CKS.
- Intent: Ascertain if it was accidental, deliberate, or a therapeutic error NICE CKS.
- Other Details: Gather information on age, weight, sex, medical history (including psychiatric history and self-harm), current medications, and factors affecting metabolism or excretion (e.g., renal or hepatic impairment) NICE CKS.
- Clinical Examination and Toxidromes: Perform an examination to look for signs consistent with specific poisons or drug classes NICE CKS:
- General Observations: Look for track marks (intravenous drug misuse), alcohol or solvents on breath, stigmata of liver disease (alcohol dependence), atypical bruising, or skin blisters NICE CKS.
- Neurological Examination: This is crucial for differentiation NICE CKS.
- Pupil Size and Reaction: Widely dilated pupils that react poorly to light can indicate agents with anticholinergic activity (e.g., tricyclic antidepressants) or sympathomimetic activity (e.g., amphetamines) NICE CKS. Pinpoint pupils (miosis) suggest exposure to opioids or agents with cholinergic activity (e.g., pesticides) NICE CKS.
- Eye Movements: Strabismus, internuclear ophthalmoplegia, dysconjugate roving eye movements, and total external ophthalmoplegia may be seen with poisoning from tricyclic antidepressants, barbiturates, phenothiazines, and anticonvulsants (e.g., phenytoin, carbamazepine) NICE CKS.
- Abnormal Movements: Assess for acute dystonic movements (antidopaminergics like antipsychotics), hypertonia, hyperreflexia, and extensor plantar response (tricyclic antidepressant poisoning) NICE CKS.
- Visual Changes: Blurring, loss of vision, or tunnel vision can occur with some drugs, such as quinine NICE CKS.
- Toxidromes: Compare the person's symptoms and examination findings to commonly associated toxidromes to help identify the unknown poison NICE CKS.
- Information Sources: Consult the poisons information database TOXBASE for specific poison information and management guidance NICE CKS. If poisoning is severe or complex, the poison is unknown, or there are significant comorbidities or uncertainties, telephone the National Poisons Information Service (NPIS) for advice NICE CKS. For pregnant individuals, contact the UK Teratology Information Service (UKTIS) NICE CKS.
- Safeguarding: Consider child maltreatment if there are repeated presentations of accidental ingestion of poisons in a child, or if the explanation for the poisoning is absent or unsuitable NICE CKS,NICE CG89.