Local Anaesthetic Cardiotoxicity — FRCA Primary MCQ

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EasyPharmacology - AnalgesicsLocal Anaesthetic CardiotoxicityFRCA Primary

Among the following amide local anaesthetics, which has the greatest intrinsic propensity to cause severe cardiotoxicity during local anaesthetic systemic toxicity?

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Correct answer: A — Bupivacaine

Bupivacaine is the most cardiotoxic agent listed. It binds rapidly to inactivated cardiac voltage-gated sodium channels but dissociates slowly during diastole—the “fast-in, slow-out” pattern. Block therefore accumulates with successive depolarisations, producing conduction slowing, QRS widening, negative inotropy and potentially refractory ventricular arrhythmias or cardiovascular collapse. Racemic bupivacaine contains the more cardiotoxic R(+)-enantiomer. Levobupivacaine, the S(−)-enantiomer, and ropivacaine have wider cardiovascular safety margins, although both can still cause fatal systemic toxicity. Lidocaine dissociates more rapidly from cardiac sodium channels and is less cardiotoxic at equipotent exposure. Prilocaine is also less intrinsically cardiotoxic; its characteristic dose-related toxicity is methaemoglobinaemia rather than refractory ventricular arrhythmia.

Reference: Mather LE, Chang DH. Cardiotoxicity with modern local anaesthetics: is there a safer choice? Drugs. 2001;61(3):333–342. https://pubmed.ncbi.nlm.nih.gov/11293644/