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What is Which of the following acts by decreasing the action potential duration in Purkinje fibers? and explain in detail?
Ans. d (Lignocaine) (Ref. KDT 6th/ 511; Katzung 11th/Table 14-2)DrugNormal cellsDepolarized cellsPolarizedHyperpola rizedCalcium channel blockadeEffect on pacemaker activitySympatholytic actionAdenosine000000+Amiodarone++++||||+||+Bretylium00||||||0||++Diltiazem0000+++||0Disopyramide++++|||?|0Dofetilide00|?000Esmolol0+0Na20||+++Flecainide++++0|0||0Ibutilide00|?000Lidocaine0+++?||0||0Mexiletine0+++0||0||0Moricizine+++|||0||0Procainamide++++||||0|+Propafenone+++|||+|+Propranolol0+|||0|+++Quinidine+++|||0|+Sotalol00|||||0||++Tocainide0+++0||0||0Verapamil0+0|+++||+ Clinical Pharmacologic Properties of Antiarrhythmic DrugsUsefulness in ArrhythmiasDrugEffect on SA nodal rateEffect on AV nodal refractory periodPR intervalQRS durationQT intervalSuper ventricularVentricularHalf-lifeAdenosineLittle||||||00++++?< 10sAmiodarone||it||||||++++++(weeks)Bretylium||2||20000-4 hDiltiazem|||||00+++-4-8 hDisopyramlde||1,3||3||3||||++++6-8 hDofetilide|(?)000|| None Esmolol||||-00++10 minFlecainideNone|||||0+4++++20 hIbulitide|(?)000||++?6 hLidocaineNone 1None000None5+++1-2 hMexiletineNone 1None000None6+++12 hMoricizineNoneNone|||0None+++2-6 hProcainamide|l||3||3||||++++3-4 hPropafenone0|||||0++++5-7 hPropranolol|||||00++8 hQuinidine||||||||||+ 6 hSotalol||||||0|||++++++7 hTocainideNone 1None000None5++f12 hVerapamil||||||00+++-/7 h1 - May suppress diseased sinus nodes2 - Anticholinergic effect and direct depressant action3 - ESP in WPW syndrome4 - May be off in atrial arrhythmia by digitalis5 - Half life of active metabolites much longer