Duron 200 Tablet is used to treat various types of serious irregular heartbeat (arrhythmia) such as fibrillation and tachycardia. It is an anti-arrhythmic type of medicine and rapidly restores your heart to a steady and regular rhythm. Duron 200 Tablet may be taken with or without food, preferably at the same time each day, to avoid a missed dose. Continuous monitoring of blood pressure and heart rate may be needed while taking this medicine. It is important that you keep taking it until your doctor decides it is safe to stop it. If you stop taking this medicine, you may get dangerous uneven heartbeats, which can be life-threatening. The most common side effects of this medicine include lung damage, tachycardia, congestive heart failure, and elevation of liver enzymes. This medicine can also cause problems with your liver, lungs, nerves, and thyroid gland. Ask your doctor what signs to look out for and report any symptoms you have. It takes a long time to clear from the body. You may continue to have side effects after you stop using it. Ask your doctor about ways to prevent or reduce them. Before getting this medicine, you should let your doctor know if you have low blood pressure, drink a lot of alcohol or have liver, heart, or thyroid problems. You should also inform your doctor about all other medicines that you are taking as many can seriously affect or be affected by this medicine. Some medicines like certain antibiotics and medicines for depression and mental illness should be avoided with this medicine. Pregnant or breastfeeding women should consult their doctor before taking this medicine. Your doctor will carry out regular tests to check your liver and thyroid gland. You may also be advised other blood tests, x-rays, and eye tests both before and during treatment.