CALCIUM-CHANNEL BLOCKERS AND QUINIDINE - OTHERCALCIUM-CHANNELBLOCKERS

The quinidine levels of a number of patients have increased when nifedipine was stopped, but no interaction has occurred in others. One study even suggests that quinidine serum levels may be slightly raised by nifedipine. One study with diltiazem found that it did not interact with quinidine, whereas another found that diltiazem increased the quinidine AUC by 51%, with resulting significant increases in QTc and PR intervals, and a significant decrease in heart rate and diastolic blood pressure.
Monitor the outcome of concurrent use, being aware that the quinidine dose may need to be reduced.