Which pair correctly matches a local anaesthetic's physicochemical property with its clinical effect?
- A Protein binding determines speed of onset
- B Lipid solubility determines intrinsic potency ✓
- C pKa determines duration of action
- D Degree of ionisation determines protein binding
Correct answer: B. Lipid solubility determines intrinsic potency
Explanation
Lipid solubility governs how much drug partitions into nerve membranes, so it determines intrinsic potency (bupivacaine is highly lipid soluble and roughly four times more potent than lidocaine). Speed of onset correlates inversely with pKa, since a lower pKa means a larger unionised fraction at tissue pH. Duration of action correlates with protein binding. The distractors swap these pairings, which is the classic examination trap.
Reference: Morgan and Mikhail's Clinical Anesthesiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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