Cardiac arrhythmias in pediatric patients have different mechanisms and frequencies compared to adult patients. There are many physiological differences between children and adults that may affect the pharmacodynamic and pharmacokinetic of the antiarrhythmic drugs in pediatric population. Children, and specially breast feeding children, cannot be considered low weighted adults to select antiarrhythmic drug doses. Although radiofrequency ablation has experienced great technological advances, it is performed in selected pediatric patients. Therefore, the main therapeutic strategy is the use of antiarrhythmic drugs in children. The medical management of arrhythmias in pediatric patients is challenging and complex. There are few clinical guidelines. There is scarce and incomplete information about the efficacy and safety of antiarrhythmic drugs in pediatric population. Most of the doses and drug administration intervals are extrapolated from adult population and applied to children. Antiarrhythmic drug doses have been extensively studied in adult population. However, in pediatric population, there are very few clinical trials and the safety of these drugs is not well known. In general, dose regimens are based on small uncontrolled studies, extrapolation of drug doses from studies performed in the adult population or physician experience. As a consequence, there is a need for further studies to assess the most effective antiarrhythmic drug regimens in children reducing the risk of side effects. Evidence suggests that medical research in pediatric population is necessary and morally valuable. But investigators involved must take care of moral and ethical values, including the respect for the child-subject and his parents or legal representatives, and this respect compels them to consider the patient and family in the decision making process. The participation request and the informed consent must be obtained according to the competitions the patient exhibits, trying to anticipate information about benefits and possible damages derived from the investigation in an understandable language for him. In our opinion the pharmacologic clinical investigation of antiarrhythmic treatments in pediatrics is necessary. More clinical studies must be carried out under rigorous scientific rules that contemplate the particular ethical dilemmas this population faces.