Which local anaesthetic has highest protein binding capacity?
High-Yield Explanation
Ans. B. Tetracaine. (Ref. Clinical Anesthesia by Paul 5th/pg. 458; Table 17-2s)Physicochemical Properties of Clinically Used Local Anesthetics:LOCAL ANESTHETICpKa% IONIZED(at pH 7.4)PARTITION COEFFICIENT(LIPID SOLUBILITY)% PROTEIN BINDINGAMIDES Bupivacaine8.1833,42095Etidocaine7.7667,31794Lidocaine7.97636664Mepivacaine7.66113077Prilocaine7.97612955Ropivacaine8.18377594ESTERS Chloroprocaine8.795810not avail ableProcaine8.9971006Tetracaine8.5935,82294Additional Educational points:# Speed Of Onset Is Related To - pKa# Duration of action is related to - protein binding# Potency is related to - lipidRelative Potency of Local Anesthetics for Different Clinical Applications: BUPIVACAINECHLORO- PROCAINELIDOCAINEMEPIVACAINEPRILOCAINEROPIVACAINEPeripheral nerve3.6N/A12.60.83.6Spinal9.61111N/AEpidural40.51114Dose-Dependent Systemic Effects of LidocainePLASMA CONCENTRATION (mcg/mL)EFFECT1-5Analgesia5-10Lightheadedness Tinnitus Numbness of tongue10-15Seizures Unconsciousness15-25Coma Resp arrest>25CVS depression