You should not use this medicine if you have had an allergic reaction to quinidine or quinine, or if you started to have blood problems after taking one of these medicines. You should not receive this medicine if you have myasthenia gravis (a muscle-nerve disease), or certain heart rhythm problems.
Make sure your doctor knows if you are pregnant or breast feeding. Make sure your doctor knows if you have a history of heart rhythm problems, congestive heart failure, or other heart problems. Tell your doctor if you have a history of liver or kidney disease, or any other health problem.