Quinidine

Indications
Oral
Atrial and ventricular premature contractions
Adult: As sulfate: 200-300 mg 3-4 times daily.
CrCl (ml/min)Dosage Recommendation
<10Use 75% of normal dose.
Hepatic impairment: Dose reduction may be needed.
Oral
Uncomplicated falciparum malaria
Adult: As sulfate: 300-600 mg or 10 mg/kg every 8 hr for 5-7 days.
Child: As sulfate: 300-600 mg or 10 mg/kg every 8 hr for 5-7 days.
CrCl (ml/min)Dosage Recommendation
<10Use 75% of normal dose.
Hepatic impairment: Dose reduction may be needed.
Oral
Paroxysmal supraventricular tachycardia
Adult: 400-600 mg every 2-3 hr until paroxysm is terminated.
CrCl (ml/min)Dosage Recommendation
<10Use 75% of normal dose.
Hepatic impairment: Dose reduction may be needed.
Oral
Conversion of atrial fibrillation
Adult: 200 mg every 2-3 hr for 5-8 doses. Subsequent doses may be increased on a daily basis until normal sinus rhythm is achieved or toxicity occurs. Max: 3-4 g/day. Maintenance: 200-300 mg 3-4 times daily.
CrCl (ml/min)Dosage Recommendation
<10Use 75% of normal dose.
Hepatic impairment: Dose reduction may be needed.
Intravenous
Cardiac arrhythmias
Adult: As gluconate: IV admin: 800 mg diluted in 40 ml of 5% dextrose inj and infused at a rate of 0.25 mg/kg/min. Monitor ECG and BP continuously during infusion. To discontinue treatment if conversion to sinus rhythm has not occurred after reaching the max dose. Max dose: total IV dosage: 10 mg/kg.
CrCl (ml/min)Dosage Recommendation
<10Use 75% of normal dose.
Hepatic impairment: Dose reduction may be needed.
Intravenous
Malaria
Adult: Loading dose: Infuse 15 mg/kg (diluted in 250 mL normal saline) over 4 hr. Maintenance: To start 24 hr after the start of loading dose, infuse 7.5 mg/kg over 4 hr, every 8 hr for 7 days or until oral therapy can be used. Alternatively, infuse 10 mg/kg (diluted in 250 mL normal saline) over 1-2 hr. Maintenance: Infuse 0.02 mg/kg/min for up to 72 hr or until parasitemia is reduced to <1% or oral therapy can be used.
Child: Can be given via continuous infusion or intermittent inj. Continuous infusion: initial loading dose of 6.25 mg/kg of quinidine base, diluted in 5 ml/kg of normal saline, given by IV infusion over 1-2 hr, followed by a continuous maintenance infusion of 12.5 mcg/kg of base per min, given for at least 24 hr and until parasitemia is reduced to <1% and oral quinine sulfate can be substituted. Intermittent inj: initial loading dose of 15 mg/kg of quinidine base, diluted in 250 ml of normal saline and infused over 4 hr, followed 4 hr later by maintenance doses of 7.5 mg/kg of base, given by IV infusion over 4 hr at 8-hr intervals until 3 maintenance doses have been admin and parasitemia is reduced to <1% and oral quinine sulfate can be substituted.
CrCl (ml/min)Dosage Recommendation
<10Use 75% of normal dose.
Hepatic impairment: Dose reduction may be needed.
Contraindications
Hypersensitivity, complete heart block, history of thrombocytopenia during treatment with quinine or quinidine, digitalis intoxication.
Warnings / Precautions
Test dose is recommended. Atrial flutter; widening QRS complex; incomplete AV block; uncompensated heart failure, myasthenia gravis, acute infections, fever, digitalised patients; hypokalaemia; acute MI; obstructive GI tract changes; renal or hepatic impairment; elderly. Prolonged QT interval, history of torsade de pointes, myocarditis, severe myocardial damage. Rapid infusion may result in hypotension and vascular collapse. Pregnancy and lactation.
Adverse Reactions
Muscle weakness, nausea, vomiting, diarrhoea; cinchonism symptoms including impaired hearing, headache, blurred vision, dizziness and vomiting; urticaria and skin reactions.
Potentially Fatal: Asystole, syncope, ventricular fibrillation. Thrombocytopenia, exfoliative dermatitis, granulomatous hepatitis (hypersensitivity); CHF; heart block, ventricular arrhythmias, tachycardia, seizure, coma.
Overdose Reactions
May result in ventricular arrhythmias and hypotension. Other symptoms include nausea, vomiting, tinnitus, blurred vision, confusion and delirium.
Drug Interactions
May enhance effects of antihypertensives, vasodilators, myocardiac depressants, oral anticoagulants and non-depolarizing muscle relaxants. Reduced clearance when used with drugs that alkalinise the urine eg. thiazides. Increased plasma levels when used with cimetidine or amiodarone. Increased metabolism when used with enzyme inducers eg. phenobarbital, phenytoin and rifampicin. Decreased metabolism when used with verapamil. Increased serum levels of procainamide and haloperidol.
Potentially Fatal: Increases plasma digitalis concentration.
See Below for More quinidine Drug Interactions
Mechanism of Actions
Quinidine is a class Ia antiarrhythmic. Its actions include depression of phase 0 action potential, decrease of myocardial excitability, conduction, velocity, sodium influx during depolarisation and potassium efflux in repolarisation. Quinidine prevents calcium from diffusing across cell membrane. It reduces rate of depolarisation phase of cardiac action potential, slows depolarisation and prolongs refractory period. Exerts vagal blockade, controls atrial fibrillation, ventricular and supraventricular tachycardias.
Absorption: Rapidly absorbed from the GI tract.
Distribution: Crosses the placenta and enters breast milk. Protein-binding: 80-90%.
Metabolism: Hepatic: mainly by cytochrome CYP450 isoenzymes.
Excretion: Plasma half-life: 6-8 hr.
Administration
Should be taken with food. (Best taken at meal times.)
Storage Conditions
Intravenous: Store at 20-25°C. Oral: Store at 20-25°C.
ATC Classification
C01BA01 - quinidine ; Belongs to class Ia antiarrhythmics.
Storage
Intravenous: Store at 20-25°C. Oral: Store at 20-25°C.
Available As
  • Quinidine 100 mg
  • Quinidine 200 mg
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