Quinidine

Indications

Quinidine is used for: Arrhythmias, Malaria

Adult Dose

Arrhythmias Quinidine Sulfate Test Dose: 200 mg PO quinidine sulfate several hr before full dosage Atrial fibrillation: 300-400 mg PO q6hr PSVT: 400-600 mg PO q2-3hr until paroxysm terminated Atrial/Ventricular Premature Contractions: 200-300 mg PO q6-8hr Maint: 200-400 mg PO q6-8hr or 600 mg of SR PO q8-12hr No more than 3-4 g/day Quinidine Gluconate 324-660 mg PO q8-12hr Maintenance: 648 mg PO q12hr OR 324-660 mg PO q8hr PSVT: 400 - 600 mg PO q2-3hr until paroxysm is terminated IV: Usual <5 mg/kg (but may need up to 10 mg/kg) at 0.25 mg/kg/min Malaria Quinidine gluconate for injection is no longer available in the U.S. Quinidine Gluconate Regimen I Load: 24 mg/kg diluted in 250 mL NS IV infusion over 4 hours Maintenance: Follow by 12 mg/kg IV infusion over 4 hours q8hr beginning 8 hr after initiation of loading dose except in patients able to swallow the same doses of quinidine are administered using 300 mg quinidine sulfate tablets Regimen II Load: 10 mg/kg diluted in 5 mL/kg NS IV over 1-2 hr Maintenance: Follow by 0.02 mg/kg/min continuous IV infusion; in patients able to swallow oral quinine is administered every 8 hr to give as much quinine as patient received in quinidine q8hr PO regimen: 300 mg quinidine or 650 mg quinine PO q8hr for 3 days (Africa and South America) or 7 days (Southeast Asia) or until parasitemia is reduced to 1%

Child Dose

Arrhythmias Quinidine sulfate: 30 mg/kg/day or 900 mg/m²/day PO given in 5 divided doses OR 15-60 mg/kg/day divided q6hr PO Test Dose: 2 mg/kg PO quinidine sulfate; test dose not to exceed 200 mg Malaria Quinidine gluconate for injection is no longer available in the U.S. Load: 10 mg/kg diluted in 5 mL/kg NS IV over 1-2 hr Maintenance: Follow by 0.02 mg/kg/min continuous IV infusion; in patients able to swallow oral quinine is administered every 8 hr to give as much quinine as patient received in quinidine q8hr PO regimen: 650 mg quinine PO q8hr for 3 days (Africa and South America) or 7 days (Southeast Asia) or until parasitemia is reduced to 1%

Renal Dose

Renal impairment CrCl <10 mL/min: Administer 75% of normal dose CrCl >10 L/min: Dose adjustment not necessary

Administration

Should be taken with food. Best taken at meal times.

Contra Indications

Complete AV block (w/o functional pacemaker), myasthenia gravis, history of quinidine/quinine-associated thrombocytopenic purpura.

Precautions

Patient w/ 2nd degree AV block (w/o functional pacemaker), digitalis intoxication, severe intraventricular conduction defect, prolonged QT interval or history of torsades de pointes, myocarditis, uncompensated heart failure, severe myocardial damage, pre-existing asthma, muscle weakness, infection w/ fever. Renal and hepatic impairment. Pregnancy and lactation. Monitoring Parameters Monitor cardiac function including BP and ECG (during IV admin), CBC, liver and renal function tests regularly during long-term admin.

Pregnancy-Lactation

Pregnancy There are no adequate and well-controlled studies in pregnant women Animal reproductive studies have not been conducted Lactation Lactation: crosses into breast milk, use extreme caution (AAP Committee states compatible with nursing)

Interactions

Reduced renal clearance w/ drugs that alkalinise the urine (e.g. carbonic-anhydrase inhibitors, Na bicarbonate, thiazide diuretics). Increased plasma levels w/ cimetidine, amiodarone, ketoconazole, verapamil. Decreased plasma levels w/ nifedipine. Increased hepatic elimination w/ rifampicin, phenytoin, phenobarbital. Potentiates the action of depolarising (e.g. suxamethonium) and nondepolarising (e.g. pancuronium) neuromuscular blocking agents, and warfarin. May increase plasma levels of digoxin, haloperidol, procainamide.

Adverse Effects

Side effects of Quinidine : >10% Diarrhea (35%) Stomach cramping (22%) Lightheadedness (15%) QTc prolongation (modest prolongation common; excessive prolongation rare & indicates toxicity) (>10%) Anorexia (>10%) Bitter taste (>10%) Diarrhea (>10%) Upper GI distress (>10%) Nausea (>10%) Vomiting (>10%) 1-10% Syncope (1-8%) Palpitation (7%), new or worsened arrhythmias (proarrhythmic effect), Headache (7%) Fatigue (7%) Angina (6%) Rash (5%) Weakness (5%) Sleep disturbance (3%) Nervousness (2%) Tremor (2%) Incoordination (1%) Blurred vision Tinnitus Wheezing

Mechanism of Action

Quinidine is a Class IA (membrane stabilizing) antiarrhythmic w/ antimuscarinic and α-adrenoceptor blocking properties. It depresses phase O of the action potential, reduces Na influx during depolarisation and K efflux in repolarisation, thereby decreasing myocardial excitability and conduction velocity, and myocardial contractility. It also decreases Ca transport across cell membrane.