The success rates for drugs to maintain sinus rhythm varies. Commonly used rhythm controlling drugs are flecainide, propafenone, sotalol and amiodarone. As mentioned above all cardiac rhythm drugs have side effects and rarely these can be fatal .The most effective drug is amiodarone which maintains sinus rhythm after 3 years in between 50-80% of patients.
However, amiodarone is not usually the first choice of many doctors because of the side effects which includes thyroid disease (1%) pulmonary fibrosis (3%) and liver problems. Unlike with most drugs these side effects do not go if the drug is withdrawn. Drugs are usually tried before catheter ablation because if they work then they are safer (except possibly amiodarone) and easier than catheter ablation.
Drugs are easy to administer and usually safe.
The best drugs maintain normal rhythm in 50-80% of patients
Side effects are common but will often resolve if the drugs are stopped. Amiodarone can be an exception to this rule.