Bioequivalence of Sildenafil

INTERVENTION: Citrato de Sildenafil Group Sildenafil and then Viagra(R): Patients will receive a unique dose of 50mg (a tablet) of Sildenafil by oral route between 8:00 and 9:00am. After a washout period of 7 days, they will receive a unique dose of 50mg (a tablet) of Viagra(R) by oral route between 8:00 and 9:00am too. Group Viagra(R) and then Sildenafil: Patients will receive a unique dose of 50mg (a tablet) of Viagra(R) by oral route between 8:00 and 9:00am. After a washout period of 7 days, they will receive a unique dose of 50mg (a tablet) of Sildenafil by oral route between 8:00 and 9:00am too. Sildenafil, Viagra CONDITION: Healthy volunteers PRIMARY OUTCOME: ‐ Plasma levels of sildenafil (values expressed in mcg/mL): Measuring time: At the beginning and at 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8, 10, 12, 16, 20 and 24 hours after administration. SECONDARY OUTCOME: ‐ Presence of adverse events (AE) ‐ distribution frequency for the appearance of adverse events (Yes, No), ‐ type of event (name of the AE), ‐ duration (time from appearance to end of the event), ‐ severity (severe, non‐severe), ‐ intensity of AE (grades 1‐5), ‐ relation of causality (remote, possible, probable, very probable), ‐ result of AE (recuperate, improvement, persist or sequels), ‐ attitude concerning the studied treatment (without changes, dose modification, temporal or definitive treatment discontinuation). Measuring time: At each administration and during the whole study. Clinical laboratory tests: ‐ Hematology (hemoglobin, hematocrit, erythrocytes count, white blood cells counts, platelet count) and ‐ Biochemistry (glycemia, cholesterol, triglycerides, transaminases, alkaline phosphatase, urea, creatinine, total proteins, total bilirubin) determinations (numerical values as units of measurement for each determination). Measuring time: At the beginning and end of the study. ‐ Vital signs (body temperature in degrees centigrade, heart rate in beats / minute, blood pressure in mm Hg and respiration rate in breaths per minute). Measuring time: Prior to administration of the tablets, during the first 4 hours after administration, and at the end of each period. INCLUSION CRITERIA: 1‐ Written informed consent. 2‐ Aged between 18‐50 years. 3‐ Male subjects. 4‐ Volunteers' weight: +/‐ 15% of their ideal weight for height. 5‐ Failure to submit evidence of organic or psychiatric disease according to interrogation, physical examination and laboratory tests. 6‐ Not have evidence or history of diseases such as bronchial asthma, hypertension, bad‐absorption syndrome, peptic ulcer or duodenal present, liver failure, kidney failure, severe allergic reactions, atopic dermatitis, cardiovascular disorders, diabetes mellitus. 7‐ Satisfactory physical examination. 8‐ Present vital signs values within the following reference ranges. Systolic blood pressure between 90 and 130 mm Hg and diastolic blood pressure between 60 and 80 mm Hg, heart rate between 60 to 100 beats per minute, respiratory rate between 12 to 20 breaths per minute. 9‐ Not having consumed alcohol, drinks containing xanthines (tea, coffee, and cola) and carbonated beverages three days before t