ventricular arrhythmias: an open-label intravenous trail in 10 patients was conducted using a dose of 1.7 mg/kg/min under constant monitoring. An oral short-term in-hospital trial in 20 patients (8 patients entered directly from the intravenous short-term trial) was conducted using a single-blind placebo dose titration protocol in which 50 mg of indecainide every 8 hours was increased at 3-day intervals to 75 mg, and then 100 mg every 8 hours depending on the observed change in ventricular arrhythmia frequency by Holter monitoring. Finally, an outpatient long-term oral trial was conducted in 17 of the 20 patients who completed the inpatient oral short-term trail.

The effects of indecainide have been studied on rabbit sinoatrial (SA) node and atrioventricular (AV) node. Indecainide at concentrations up to 2.9 mumol/L in 5 preparations did not produce a sinus bradycardia, nor reduce the maximum rate of rise of the intracellular action potential of sinus node cells, but it did antagonize the tachycardia induced by increasing the extracellular calcium concentration. Indecainide slightly prolonged AV conduction time [from 49.07 +/- 4.43 ms to 57.37 +/- 0.90 ms at 2.9 mumol/L (means +/- SEM in four preparations)], but this small delay could be attributed to slowing of conduction in atrial fibres leading to the node, rather than to an effect on the AV nodal cells themselves. It is concluded that indecainide does not block channels carrying inward calcium current in nodal tissues.