The analysis is performed in three hierarchical steps. First step is an analysis of covariance to compare the group with an initial P dosage of 60 mg (V60) and the placebo group (Pl). In case of a statistical significant result (α = 0.05), a comparison of the group starting with 10 mg P (V10) and Pl will be done in a second step (α = 0.05). In case of superiority of V10 versus Pl, a third step will be a non-inferiority test for V10 versus V60 (α = 0.025).