Possible Interaction: Lidocaine and Quinidine

“Other antiarrhythmics such as beta-blockers, calcium channel blockers, and amiodarone have been used effectively also; however, some antiarrhythmics such as lidocaine , mexiletine, propafenone, and quinidine may exacerbate neuromuscular symptoms and should be used cautiously.”

“ Lidocaine is one of the most frequently used drugs to suppress ventricular arrhythmias; however, it has caused sinus arrest when given in excess or along with other antiarrhythmics ( quinidine , phenytoin, amiodorane).”

“Bupivacaine, disopyramide, and quinidine (in concentrations that are observed clinically) caused a significant increase (p < 0.01) in the free fraction of lidocaine in serum (23%, 21%, and 34%, respectively).”

“Thus, prolongation of refractoriness may be more pronounced with quinidine while lidocaine may be more effective on raising the excitability threshold and in this way suppress the ventricular arrhythmias induced by quinidine.”

“Alternatively, it has been suggested that lidocaine and quinidine bind to different but related receptor sites, since lidocaine may induce allosteric changes in quinidine's receptor.”

“ Lidocaine interfered with the use-dependent blocking effects on $$\dot V_{\max }$$ of quinidine , by decreasing the fraction of sodium channels blocked by quinidine during the conditioning action potential, in an apparently competitive way.”

“In contrast, when acini were pretreated with 10 mM dinitrophenol, 10(‐4) M amiloride, 1 mM lidocaine or 1 mM quinidine there were significant (P < 0.001) decreases in net Mg2+ efflux.”

“… quinidine inhibited sodium inward current (INa) even when this current was elicited … from a holding potential of -90 mV. For amiodarone and lidocaine , the inhibition was observed when INa was elicited from a holding potential of -… INa by amiodarone and lidocaine was observed at frequencies higher than 1 Hz.”

“Furthermore, if a drug that has relatively rapid post-stimulation recovery kinetics (e.g., lidocaine ) displaces another drug with relatively slow recovery kinetics (i.e., quinidine or bupivacaine), then a net reduction in sodium channel blockade is expected at certain stimulation rates.”

“In the presence of a mixture of 43 μM lidocaine and 15 μM quinidine , this slow component was significantly reduced to 16 ± 7% (n = 5; P < 0.01), while 71 ± 13% of maximum upstroke velocity recovered with a time constant of 115 ± 21 msec, typical of lidocaine-blocked channels.”

“At therapeutic concentrations (5 μg/ml), lidocaine shortened the duration of the action potential while quinidine lengthened it.”

“4) Combinations of lidocaine and quinidine have a superadditive effect on the Vmax of early extrasystoles.”