All are true about lidocaine except:

Ans. b. It is most cardiotoxic local anesthetic (Ref: Katzung 11/e p239)LidocaineMOA: Blocks both activated and inactivated Na+ channels with rapid kineticsQ.Pharmacokinetics: Has extensive first pass hepatic metabolismQ, only 3% of orally administered lidocaine appears in the plasma.Most physicians administer IV lidocaine only to patients with arrhythmias.Lidocaine ToxicityLidocaine is the least cardiotoxicQ of currently used Na+ channel blocker.Other side effects are:Neurologic: Paraesthesia, tremorsLight headedness.Hearing disturbancesSlurred speechConvulsionsUses of LidocaineVentricular tachycardiaQPrevention of ventricular fibrillationQLocal AnestheticsAminoesters (single 'i')Aminoamides (double 'i')* Procaine* Chlorprocaine* Tetracaine* Benzocaine* Cocaine* Esters are metabolized by pseudocholinesterase (except cocaine which is metabolized by liver)* High incidence of allergic reactions which are because of para aminobenzoic acid* Solutions are not stable* Lignocaine* Mepivacaine* Prilocaine* Bupivacaine* Etidocaine* Ropivacaine* Amides are metabolized primarily in liver.* Low incidence of allergic reactions* Solutions are stable (Not destroyed even by autoclaving)Local Anesthetics: Mechanism of actionLA blocks Na+ channel from insideQ of cell membrane and raises the threshold of channel openingQ.Resting nerve is resistant to block and blockage develop rapidly when the nerve is stimulated repeatedlyQ.High Ca2+ conc, lessens the degree of block.