Quinidine levels can be reduced by the concurrent use of
phenobarbital or
primidone. Loss of arrhythmia
control is possible if the
quinidine dosage is not increased.
Concurrent use need not be avoided, but be alert for the need to increase the
quinidine dosage. If
phenobarbital or
primidone are withdrawn the
quinidine dosage may need to be reduced to avoid
quinidine toxicity.
Quinidine serum levels should be monitored if possible.