Disopyramide plasma levels in cardiac patients on maintenance therapy.

The antiarrhythmic agent disopyramide, in a dosage of 200 mg/8 h, was given to 7 cardiac patients. The drug was fairly rapidly absorbed, and the mean peak plasma concentration (3.5 microgram/ml) was measured 1 h after administration of the first dose. The mean biological half-life (7.8 h) was slightly prolonged compared to that reported in normal volunteer subjects. Mean steady state plasma concentrations within the therapeutic range were attained 24--32 h after the start of medication. The fluctuations in the plasma levels were in the order or 30 percent; however, a wide spread of the values was observed. The drug was well tolerated.