A randomized, open-label, single dose, two-way crossover design bioequivalence study with two-periods, two-treatments, and two-sequences of Sildenafil citrate Tablets 100 mg relative to Originator under fasting condition in compliance with EU requirements for GCP and bioequivalence studies

INTERVENTION: Experimental Drug,Active Comparator Drug Sildenafil citrate Tablets 100 mg,Viagra 100 mg tablets The new generic products which were recently developed. Volunteer will receive a single dose of Sildenafil citrate Tablets 100 mg of either test or reference with 250 mL of drinking water,The marketed original products which were already available in the market. Volunteer will receive a single dose of Viagra 100 mg tablets either test or reference with 250mL of drinking water. CONDITION: ; Bioequivalence Sildenafil citrate Tablets 100 mg Healthy subjects ; ; Bioequivalence Sildenafil citrate Tablets 100 mg PRIMARY OUTCOME: Cmax, AUC0‐t and AUC0‐inf 0.000, 0.083, 0.170, 0.333, 0.500, 0.667, 0.830, 1.000, 1.250, 1.500, 1.750, 2.000, 2.500, 3.000, 4.000, 8.000, 12.000, 16.000 and 24.000 Pharmacokinetics parameter SECONDARY OUTCOME: Safety; Adverse events 1.0, 2.0, 3.0, 4.0, 6.0, 12.0 and 24.0 hours Safety monitoring INCLUSION CRITERIA: 1. Willingness to provide written informed consent prior to participate in the study. 2. Healthy Thai male subjects are between 18 to 55 years of age. 3. The Body Mass Inde X(BMI) ranges from 18.5 to 30 kg/m. 4. Comprehensive of the nature and purpose of the study and compliance with the requirement of the entire protocol and allow investigators to draw 7 mL of blood for monitoring subjects safety after the completion of the study. 5. Absence of significant diseases or clinically significant abnormal laboratory values on the laboratory evaluations, medical history or surgery during the screening. Some of the laboratory values e.g. Complete blood count etc. that out of the normal range will be carefully considered by physician.