Dosing

• Disopyramide SR 12-hour capsule 100 – 300 mg BID, no initial load

Distribution and metabolism

• Peak plasma levels occur 1-2 hours after dosing.
• Two enantiomers (S-Disopyramide and R–Disopyramide) which have similar antiarrhythmic effect. However, S-Disopyramide may have stronger anticholinergic effect than R–Disopyramide.
• There are several metabolites that do not have likely antiarrhythmic effect but one has 24 times the anticholinergic potency, responsible for disopyramide’s anticholinergic effects.

Therapeutic drug monitoring

• Draw trough level after steady state is reached, typically 25-30 hours after stable dosing

Therapeutic plasma concentrations

• 2–5 mcg/mL
• Note: significant protein binding, free concentration may correlate better with antiarrhythmic effects and QT prolongation, but total concentration is reported

Dose adjustments

• Renally excreted. Therefore, with renal disease, it is typically recommended to either decrease dose or more commonly, increase interval in dosing.

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.