indication

For the treatment of ventricular pre-excitation and cardiac dysrhythmias

pharmacology

Quinidine, a hydantoin anticonvulsant, is used alone or with phenobarbital or other anticonvulsants to manage tonic-clonic seizures, psychomotor seizures, neuropathic pain syndromes including diabetic neuropathy, digitalis-induced cardiac arrhythmias, and cardiac arrhythmias associated with QT-interval prolongation.

mechanism of action

Quinidine acts on sodium channels on the neuronal cell membrane, limiting the spread of seizure activity and reducing seizure propagation. The antiarrhythmic actions are mediated through effects on sodium channels in Purkinje fibers. Quinidine may also act on the slow inward calcium current (ICa), the rapid (IKr) and slow (IKs) components of the delayed potassium rectifier current, the inward potassium rectifier current (IKI), the ATP-sensitive potassium channel (IKATP) and Ito.

half life

6-8 hours

route of elimination

When the urine pH is less than 7, about 20% of administered quinidine appears unchanged in the urine, but this fraction drops to as little as 5% when the urine is more alkaline.

drug interactions

Acenocoumarol: Quinidine may increase the anticoagulant effect of acenocoumarol.

Amiloride: Amiloride may decrease the therapeutic effect of quinidine. Monitor for changes in the therapeutic and adverse effects of quinidine if amiloride if initiated, discontinued or dose changed.

Amiodarone: Amiodarone may increase the effect of quinidine.

Amitriptyline: Additive QTc-prolonging effects may occur. Quinidine may also increase the serum concentration of the tricyclic antidepressant, amitriptyline, by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of amitriptyline if quinidine is initiated, discontinued or dose changed. Monitor for the development of torsades de pointes during concomitant therapy.

Amobarbital: The anticonvulsant, amobarbital, decreases the effect of quinidine.

Anisindione: Quinidine may increase the anticoagulant effect of anisindione.

Aprobarbital: The anticonvulsant, aprobarbital, decreases the effect of quinidine.

Aripiprazole: Quinidine increases the effect and toxicity of aripiprazole

Artemether: Additive QTc-prolongation may occur. Concomitant therapy should be avoided.

Atazanavir: Increased risk of cardiotoxicity and arrhythmias.

Atomoxetine: The CYP2D6 inhibitor could increase the effect and toxicity of atomoxetine

Atracurium: The quinine derivative increases the effect of the muscle relaxant

Bromazepam: Quinidine, a strong CYP3A4 inhibitor, may increase the serum concentration of bromazepam by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of bromazepam if quinidine is initiated, discontinued or dose changed. Dosage adjustments may be required.

Butabarbital: The anticonvulsant, butabarbital, decreases the effect of quinidine.

Butalbital: The anticonvulsant, butalbital, decreases the effect of quinidine.

Butethal: The anticonvulsant, butethal, decreases the effect of quinidine.

Cimetidine: Cimetidine may increase the serum concentration of quinidine. Monitor for changes in the therapeutic and adverse effects of quinidine if cimetidine is initiated, discontinued or dose changed.

Cisapride: Increased risk of cardiotoxicity and arrhythmias

Clarithromycin: Increased risk of cardiotoxicity and arrhythmias

Clomipramine: Additive QTc-prolonging effects may occur. Quinidine may also increase the serum concentration of the tricyclic antidepressant, clomipramine, by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of clomipramine if quinidine is initiated, discontinued or dose changed. Monitor for the development of torsades de pointes during concomitant therapy.

Codeine: Quinidine decreases the analgesic effect of codeine

Dabigatran etexilate: Quinidine may increase the serum concentration of dabigatran etexilate, resulting in increased bleeding. Consider modification of therapy.

Dantrolene: Quinidine may increase the serum concentration of dantrolene by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of dantrolene if quinidine is initiated, discontinued or dose changed.

Desipramine: Additive QTc-prolonging effects may occur. Quinidine may also increase the serum concentration of the tricyclic antidepressant, desipramine, by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of desipramine if quinidine is initiated, discontinued or dose changed. Monitor for the development of torsades de pointes during concomitant therapy.

Dextromethorphan: Quinidine increases the toxicity of dextromethorphan

Dicumarol: Quinidine may increase the anticoagulant effect of dicumarol.

Digitoxin: Quinine/quinidine increases the effect of digoxin

Digoxin: Quinine/quinidine increases the effect of digoxin

Dihydroquinidine barbiturate: The anticonvulsant, dihydroquinidine. barbiturate, decreases the effect of quinidine.

Diltiazem: Diltiazem may increase the serum concentration of quinidine. Monitor for changes in the therapeutic and adverse effects of quinidine if diltiazem is initiated, discontinued or dose changed.

Donepezil: Possible antagonism of action

Doxepin: Additive QTc-prolonging effects may occur. Quinidine may also increase the serum concentration of the tricyclic antidepressant, doxepin, by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of doxepin if quinidine is initiated, discontinued or dose changed. Monitor for the development of torsades de pointes during concomitant therapy.

Erythromycin: Increased risk of cardiotoxicity and arrhythmias

Fosphenytoin: The anticonvulsant, fosphenytoin, decreases the effect of quinidine.

Galantamine: Possible antagonism of action

Gatifloxacin: Increased risk of cardiotoxicity and arrhythmias

Grepafloxacin: Increased risk of cardiotoxicity and arrhythmias

Heptabarbital: The anticonvulsant, heptabarbital, decreases the effect of quinidine.

Hexobarbital: The anticonvulsant, hexobarbital, decreases the effect of quinidine.

Imipramine: Additive QTc-prolonging effects may occur. Quinidine may also increase the serum concentration of the tricyclic antidepressant, imipramine, by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of imipramine if quinidine is initiated, discontinued or dose changed. Monitor for the development of torsades de pointes during concomitant therapy.

Itraconazole: Itraconazole may increase the effect and toxicity of quinidine.

Ketoconazole: Ketoconazole may increase the effect and toxicity of quinidine.

Levofloxacin: Increased risk of cardiotoxicity and arrhythmias

Lumefantrine: Additive QTc-prolongation may occur. Concomitant therapy should be avoided.

Magnesium: Magnesium antacids may decrease the absorption of quindine.

Magnesium salicylate: The antacid increases the effect of quinidine

Mesoridazine: Increased risk of cardiotoxicity and arrhythmias

Methohexital: The anticonvulsant, methohexital, decreases the effect of quinidine.

Methylphenobarbital: The anticonvulsant, methylphenobarbital, decreases the effect of quinidine.

Metocurine: The quinine derivative increases the effect of the muscle relaxant

Moxifloxacin: Increased risk of cardiotoxicity and arrhythmias

Nelfinavir: Nelfinavir increases the effect and toxicity of quinidine

Nifedipine: Decreased quinidine effect, increased nifedipine effect

Nortriptyline: Additive QTc-prolonging effects may occur. Quinidine may also increase the serum concentration of the tricyclic antidepressant, nortriptyline, by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of nortriptyline if quinidine is initiated, discontinued or dose changed. Monitor for the development of torsades de pointes during concomitant therapy.

Ofloxacin: Increased risk of cardiotoxicity and arrhythmias

Pancuronium: The quinine derivative increases the effect of the muscle relaxant

Pentobarbital: The anticonvulsant, pentobarbital, decreases the effect of quinidine.

Phenobarbital: The anticonvulsant, phenobarbital, decreases the effect of quinidine.

Phenytoin: The anticonvulsant, phenytoin, decreases the effect of quinidine.

Posaconazole: Contraindicated co-administration

Primidone: The anticonvulsant, primidone, decreases the effect of quinidine.

Procainamide: Quinidine increases the effect of procainamide

Propafenone: Quinidine increases the effect of propafenone

Protriptyline: Additive QTc-prolonging effects may occur. Quinidine may also increase the serum concentration of the tricyclic antidepressant, protriptyline, by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of protriptyline if quinidine is initiated, discontinued or dose changed. Monitor for the development of torsades de pointes during concomitant therapy.

Quinidine barbiturate: The anticonvulsant, quinidine. barbiturate, decreases the effect of quinidine.

Quinupristin: This combination presents an increased risk of toxicity

Ranolazine: Possible additive effect on QT prolongation

Rifampin: Rifampin decreases the effect of quinidine

Ritonavir: Ritonavir increases the effect and toxicity of quinidine

Rivastigmine: Possible antagonism of action

Secobarbital: The anticonvulsant, secobarbital, decreases the effect of quinidine.

Sodium bicarbonate: The antacid increases the effect of quinidine

Sparfloxacin: Increased risk of cardiotoxicity and arrhythmias

Succinylcholine: The quinine derivative increases the effect of the muscle relaxant

Tacrolimus: Additive QTc-prolongation may occur increasing the risk of serious ventricular arrhythmias. Concomitant therapy should be used with caution. Quinidine, a strong CYP3A4 inhibitor, may also increase the serum concentration of Tacrolimus by inhibiting its metabolism and clearance.

Tadalafil: Quinidine may reduce the metabolism of Tadalafil. Concomitant therapy should be avoided if possible due to high risk of Tadalafil toxicity.

Talbutal: The anticonvulsant, talbutal, decreases the effect of quinidine.

Tamoxifen: Quinidine may decrease the therapeutic effect of Tamoxifen by decreasing the production of active metabolites. Concomitant therapy should be avoided.

Tamsulosin: Quinidine, a CYP3A4/2D6 inhibitor, may decrease the metabolism and clearance of Tamsulosin, a CYP3A4/2D6 substrate. Monitor for changes in therapeutic/adverse effects of Tamsulosin if Quinidine is initiated, discontinued, or dose changed.

Telithromycin: Co-administration may result in altered plasma concentrations of Quinidine and/or Telithromycin. Consider alternate therapy or monitor for changes in the the therapeutic/adverse effects of both agents during concomitant therapy.

Temsirolimus: Quinidine may inhibit the metabolism and clearance of Temsirolimus. Concomitant therapy should be avoided.

Teniposide: The strong CYP3A4 inhibitor, Quinidine, may decrease the metabolism and clearance of Teniposide, a CYP3A4 substrate. Consider alternate therapy or monitor for changes in the therapeutic/adverse effects of Teniposide if Quinidine is initiated, discontinued or dose changed.

Terfenadine: Increased risk of cardiotoxicity and arrhythmias

Thiopental: Thiopental may increase the metabolism and clearance of Quinidine. Monitor for decreased therapeutic effect of Quinidine if Thiopental is initiated.

Thioridazine: Increased risk of cardiotoxicity and arrhythmias

Tiagabine: The strong CYP3A4 inhibitor, Quinidine, may decrease the metabolism and clearance of Tiagabine, a CYP3A4 substrate. Consider alternate therapy or monitor for changes in the therapeutic/adverse effects of Tiagabine if Quinidine is initiated, discontinued or dose changed.

Tipranavir: Tipranavir, co-administered with Ritonavir, may increase the plasma concentration of Quinidine. Concomitant therapy is contraindicated.

Tolterodine: Quinidine may decrease the metabolism and clearance of Tolterodine. Adjust Tolterodine dose and monitor for efficacy and toxicity.

Topotecan: The p-glycoprotein inhibitor, Quinidine, may increase the bioavailability of oral Topotecan. A clinically significant effect is also expected with IV Topotecan. Concomitant therapy should be avoided.

Toremifene: Additive QTc-prolongation may occur, increasing the risk of serious ventricular arrhythmias. Consider alternate therapy. A thorough risk:benefit assessment is required prior to co-administration.

Tramadol: Quinidine may increase Tramadol toxicity by decreasing Tramadol metabolism and clearance. Quinidine may decrease the effect of Tramadol by decreasing active metabolite production.

Trazodone: The CYP3A4 inhibitor, Quinidine, may increase Trazodone efficacy/toxicity by decreasing Trazodone metabolism and clearance. Consider alternate therapy or monitor for changes in Trazodone efficacy/toxicity if Quinidine is initiated, discontinued or dose changed.

Trimipramine: Additive QTc-prolonging effects may occur, increasing the risk of serious cardiac arrhythmias. Quinidine, a CYP2D6/CYP3A4 inhibitor, may also inhibit the metabolism of Trimipramine, a CYP2D6/CYP3A4 substrate. Monitor for signs of cardiac arrhythmias and for changes in Trimipramine efficacy and toxicity if Quinidine is initiated, discontinued or dose changed.

Vardenafil: Quinidine, a strong CYP3A4 inhibitor, may reduce the metabolism and clearance of Vardenafil. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of Vardenafil.

Vecuronium: The quinine derivative increases the effect of the muscle relaxant

Venlafaxine: Quinidine, a CYP2D6 and CYP3A4 inhibitor, may decrease the metabolism and clearance of Venlafaxine, a CYP2D6 and CYP3A4 substrate. Monitor for changes in therapeutic/adverse effects of Venlafaxine if Quinidine is initiated, discontinued, or dose changed.

Verapamil: Concurrent therapy may result in increased serum levels of both agents. Both agents are CYP3A4 inhibitors and substrates. Consider alternate therapy or monitor for changes in the therapeutic/adverse effects of the agent if the other is initiated, discontinued or dose changed.

Vilazodone: CYP3A4 Inhibitors (Strong) may increase the serum concentration of Vilazodone. imit maximum adult vilazodone dose to 20 mg/day in patients receiving strong CYP3A4 inhibitors.

Vinblastine: Quinidine, a strong CYP3A4 inhibitor, may decrease the metabolism of Vinblastine. Consider alternate therapy to avoid Vinblastine toxicity. Monitor for changes in the therapeutic/adverse effects of Vinblastine if Quinidine is initiated, discontinued or dose changed.

Vincristine: Quinidine, a strong CYP3A4 inhibitor, may increase the serum concentration of Vincristine by decreasing its metabolism. Consider alternate therapy to avoid Vincristine toxicity. Monitor for changes in the therapeutic and adverse effects of Vincristine if Quinidine is initiated, discontinued or dose changed.

Vinorelbine: Quinidine, a strong CYP3A4 inhibitor, may increase the serum concentration of Vinorelbine by decreasing its metabolism. Consider alternate therapy to avoid Vinorelbine toxicity. Monitor for changes in the therapeutic and adverse effects of Vinorelbine if Quinidine is initiated, discontinued or dose changed.

Voriconazole: Voriconazole may increase the serum concentration of quinidine likely by inhibiting its metabolism by CYP3A4. Additive QTc prolongation may also occur. Consider alternate therapy or monitor for changes in the serum concentration and toxic effects of quinidine if voriconazole is initiated, discontinued or dose changed.

Vorinostat: Additive QTc prolongation may occur. Consider alternate therapy or monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP).

Warfarin: Quinidine may increase the anticoagulant effect of warfarin.

Ziprasidone: Additive QTc-prolonging effects may increase the risk of severe arrhythmias. Concomitant therapy should be avoided.

Zolpidem: Quinidine, a strong CYP3A4 inhibitor, may increase the serum concentration of zolpidem by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of zolpidem if quinidine is initiated, discontinued or dose changed.

Zonisamide: Quinidine, a strong CYP3A4 inhibitor, may increase the serum concentration of zonisamide by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of zonisamide if quinidine is initiated, discontinued or dose changed.

Zopiclone: Quinidine, a strong CYP3A4 inhibitor, may increase the serum concentration of zopiclone by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of zopiclone if quinidine is initiated, discontinued or dose changed.

Zuclopenthixol: Additive QTc prolongation may occur. Consider alternate therapy or use caution and monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP). Quinidine, a strong CYP2D6 inhibitor, may increase the serum concentration of zuclopenthixol by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of zuclopenthixol if quinidine is initiated, discontinued or dose changed.