Local Anaesthetic Toxicity — MFDS Part 1 MCQ
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Correct answer: D — Generalised urticaria
Generalised urticaria is not a feature of dose-related local anaesthetic systemic toxicity; it suggests an immediate hypersensitivity reaction. In contrast, early lidocaine toxicity causes CNS excitation, including unpleasant perioral sensations or circumoral paraesthesia, tinnitus, dizziness and agitation. Muscular twitching may progress to generalised convulsions as toxicity increases. Hypertension can occur early because of sympathetic stimulation, often with tachycardia and flushing, so it is not the exception. At higher concentrations, myocardial depression and conduction disturbance may produce hypotension, bradycardia and arrhythmias. The key distinction is between predictable concentration-related toxicity and the rare immune-mediated reaction represented by urticaria.
Reference: B. Braun Medical Ltd. Lidocaine Injection BP 1% w/v: Summary of Product Characteristics, sections 4.8 and 4.9; last updated 23 February 2026. https://www.medicines.org.uk/emc/product/15149/smpc