GasGasGas - Anaesthetic Science for Anaesthesia! Lidocaine Pharmacology: Amide Local Anaesthetic not for Spinal Anaesthesia
Jul 31, 2025
This episode dives into lidocaine, a local anaesthetic used extensively in clinical settings. It explores its mechanisms, various formulations like sprays and patches, and its effects on the cardiovascular and central nervous systems. Listeners learn about lidocaine's unique properties, including its role in pain management through IV infusions. It also covers dosing limits, pitfalls in spinal applications, and highlights the complexities of its pharmacokinetics. A practical discussion on enhancing efficacy and safety wraps up the enlightening session.
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Use Lidocaine Broadly And Know Its Forms
- Use lidocaine for a wide range of clinical applications including infiltration, airway topicalisation, and regional blocks.
- Remember it comes in many formulations (1–2% solutions, sprays, patches, ointments, Instillagel).
Why pKa And Use-Dependence Matter
- Local anaesthetics must cross the membrane un-ionised then bind intracellularly as ionised cations to sodium channels.
- This explains pKa-dependent onset and use-dependent block where active channels are more susceptible.
Expect Fast Onset And Short Duration
- Expect rapid onset for cutaneous infiltration (seconds) and 3–5 minutes for peripheral nerve blocks.
- Plain lidocaine lasts ~90–180 minutes; with adrenaline duration can extend to ~4–5 hours.