To determine the cost-effectiveness of methylphenidate immediate release available in the Brazilian market, the investigators will use a Markov model of decision analysis. The development of the model and analysis of the results will adopt the standards established in the Methodological Guidelines of the Brazilian Ministry of Health, and the perspective will be of the Brazilian National Health System. Medications prices will be obtained through the Board of Market Regulation of Medicines (CMED) at the site of ANVISA (National Health Surveillance Agency). For the treatment strategy that provides greatest cost ratio it will be calculated the incremental cost-effectiveness, compared to the lower cost. To estimate more accurately the impact on life, a Monte Carlo simulation with 10,000 random trials will be conducted.