This is a randomized, double-blind, clinical trial, comparing the association of Chlorthalidone plus amiloride 25 and 5 mg daily, versus amlodipine 10 mg daily as first drug option in patients older than 40 years of age with Stage I hypertension (140-159/90-99 mmHg) and moderate obstructive sleep apnea (15-30 apneas/hour of sleep). The primary outcomes will be the variation of apneas/hour and blood pressure. The secondary outcomes will be adverse events, somnolence scale (Epworth), ventilatory parameters and C reactive protein. The follow up will last 8 weeks. The sample size will be of 29 participants per group. The project was approved by the Ethics committee of our institution.