Gait and balance problems are a significant source of disability in patients with Parkinson disease. Physical therapy remains one of the main treatments. On the other hand some medications, such as methyphenidate and atomoxetine, have been tried with promising results. The outcomes in gait and balance in Parkinson disease after a combination of physical therapy and the medications mentioned above have not been explored yet. The investigators want to evaluate whether the addition of medication, either low dose of methylphenidate or atomoxetine, to physical therapy will achieve improvement in gait and balance in Parkinson disease more than physical therapy alone. The investigators propose a pilot, single center, rater blind, prospective randomized trial. 2-arm-parallel group, intention-to-treat analysis.