GasGasGas - Anaesthetic Science for Anaesthesia! Local Anaesthetics Summary: Complete Review for FRCA Primary Exam
Aug 22, 2025
Dive into the fascinating world of local anesthetics! Discover the chemical structures that differentiate esters from amides, and learn essential mnemonics for memorizing pKa values. Compare the onset and offset times of various anesthetics while grasping their mechanisms of action. Uncover the potential side effects, including cardiotoxicity and methemoglobinemia, plus how to recognize systemic toxicity signs. Lastly, hear about innovative solutions like intralipid for toxicity management. Get ready to test your knowledge with an exciting quiz!
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Ester Vs Amide Determines Metabolism
- Local anaesthetics are chemically esters or amides determined by their linkage between benzene and amine ends.
- This linkage predicts metabolism: esters by plasma esterases and amides by hepatic metabolism.
Use Name Patterns To Classify Drugs
- Memorise name patterns: amide local anaesthetics classically have two 'i's in their names.
- Use simple heuristics to recall metabolism and classification for exam recall.
pKa Predicts Onset Via Unionised Fraction
- pKa influences the fraction of drug unionised at physiological pH and thus onset.
- Bupivacaine group has pKa ~8.1 (≈15% unionised) while lidocaine ~7.7 (≈25% unionised).