Pharma 22: Local Anaesthetics - Silencing Pain at the Source

This episode focuses on local anaesthetics as tools of precision. Rather than altering awareness, these agents selectively block pain transmission by stabilising excitable membranes at the site of action. We explore how sodium channel blockade translates into predictable sensory loss, why different fibres fall silent at different rates, and how anatomy, dose, and delivery determine both efficacy and risk. The result is a clear mental model for choosing the right agent, route, and context.Key takeaways you’ll build and reuse throughout the series:* Action potentials as targets: voltage-gated sodium channels and use-dependence explained intuitively.* Differential blockade: why pain goes before touch, and touch before motor function.* Chemistry to clinic: lipid solubility, protein binding, pKa, and onset/duration relationships.* Anatomy matters: topical, infiltration, field, regional, and neuraxial techniques in context.* Safety and vigilance: systemic toxicity, cardiac and CNS effects, and the logic of dose limits. This is a public episode. If you'd like to discuss this with other subscribers or get access to bonus episodes, visit drmanaankarray.substack.com/subscribe