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