Healthy subjects will be randomised to either arm A (sequential metoprolol single dose and Pyramax 3 days course + metoprolol on the last day starting 7 days after Pyramax single dose followed by Pyramax redosing with another 3 days course 90 days later) or arm B (2 courses of 3-days Pyramax separated by 60 days). Each arm will include 22 subjects.