Overview
- Anti-arrhythmic drug that occurs naturally in bark of cinchona tree & prolongs myocardial recovery time.
- Protects against some tachyarrhythmias, but can also produce tachyarrhythmias by over prolongation of recovery time.
Dosing
- Quinidine sulfate tab 200-600 mg QID, consider loading 600-800 mg PO
- Quinidine gluconate IV 10 mg/kg can be used as initial load
Distribution and metabolism
- Most commonly used are the extended release formulations
- Steady stable on a given dose builds up after 24 hours
Therapeutic drug monitoring
- Draw trough level after 24-48 hours on a stable PO quinidine dose
Therapeutic plasma concentrations
- 3-6 mcg/mL
Dose adjustments
- Interestingly, risk of QT prolongation and Torsades is transiently greater at the lower range of quinidine concentration, explaining why Torsades often occurs while initially dosing the medication or during washout periods.
- Clearance is primarily hepatic (> renal).
- No specific dose adjustment is recommended by the manufacturer with hepatic or renal disease, but in practice can consider decreasing dose in these situations.
References
- Zipes, et al. Braunwald’s Heart Disease, A Textbook of Cardiovascular Medicine, 11 th edition, Chapter 36, Therapy of Cardiac Arrhythmias.
- Campbell TJ, Williams KM. Therapeutic drug monitoring: antiarrhythmic drugs. J Clinical Pharmacol. 2001;52:21S-35S.
