Procainamide absorption studies to test the feasibility of using a sustained-release preparation.

Using in vitro techniques it was confirmed that whilst the release of procainamide from the conventional formulation (Pronestyl) was rapid, that from the sustained-release preparation (Cardiorytmin Retard) occurred over a prolonged period. 2 The peak plasma procainamide concentrations after single doses of Cardiorytmin Retard were relatively lower and occurred later than those after single doses of Pronestyl. Furthermore, after reaching a peak, the fall in plasma procainamide concentration was less rapid after the sustained-release preparation. Early urinary recovery of procainamide in patients and in healthy volunteers was greater after Pronestyl than after Cardiorytmin Retard, though overall recovery in urine was similar. These findings indicate that the absorption of the sustained-release preparation is slower, though the overall bioavailabilities of the two preparations are almost the same. 3 These results confirm the feasibility of using a sustained-release procainamide preparation, such as Cardiorytmin Retard, since it would be possible to administer the same amount of drug in fewer daily doses without plasma concentrations becoming ineffective towards the end of each dosing interval.