Possible Interaction: Isoproterenol and Quinidine

“However, the amount of decrease in QRS duration and VTCL with isoproterenol was greater during procainamide and quinidine than in the drug-free state (ANOVA interaction, p<0.02 for all).”

“ Isoproterenol shortened the sinus cycle length, QT interval during ventricular pacing, and ventricular effective and functional refractory periods before and during procainamide and quinidine therapy (ANOVA; isoproterenol effect, p.0.0002 for all).”

“The following results were obtained: (1) quinidine had a depressant effect on myocardial contractile force; (2) quinidine reduced the maximal upstroke velocity of … prolonged the terminal repolarization of the action potential; (4) at higher concentrations quinidine reduced the resting potential; and (5) the depression by quinidine of … by isoprenaline.”

“Abstract A prolongation of conduction time induced by sublethal doses of quinidine (as shown by a broadening of the QRS interval), as well as a decrease in myocardial contractility are prevented by simultaneous administration of isoproterenol.”

“When isoproterenol is in combination with fatal doses of quinidine , it reduces lethality from 100 to 25 per cent; the dose of isoproterenol required is, however, a critical one, since high doses even increase quinidine toxicity.”

“ Quinidine , a class I antiarrhythmic agent has been found to exhibit a protective role in isoproterenol induced myocardial ischaemia.”

“ Quinidine (class I), verapamil (IV), diltiazem (IV), dilazep (IV), nifedipine (IV), tetrodotoxin and butoxamine, at a concentration of 10 μmol/l, significantly decreased the extraneuronal accumulation of isoprenaline.”

“The antiarrhythmic effects of quinidine and calcium channel blockers in this experimental model may be partly due to a decrease in the extraneuronal accumulation of isoprenaline.”

“The present study demonstrated that quinidine (class I) and all of the calcium channel blockers (class IV) had potent inhibitory effects on the extraneuronal accumulation of isoprenaline.”

“The effects of quinidine on slow inward current and force of contraction in ventricular muscle were antagonized by isoprenaline (1 micrometer).”

“Procaine and quinidine inhibit Ca 2+ accumulation by fraction and suppress the relaxation of this tissue induced by papaverine, isoprenaline and phenylephrine.”

“All the drugs are antiarrhythmic agents with local anesthetic activity, but propranolol and quinidine are known also to have beta-receptor-blocking actions in that they can prevent the cardiac effects of isoprenaline and depress the myocardium.”

“In the presence of 25 µg/liter of isoproterenol , 8 mg/liter of quinidine decreased the ERP 27% from the controls (P < .05).”