We anticipate the detection of a 15% absolute risk reduction of POUR in the Experimental group in comparison with the Placebo group. To detect a 15% reduction of POUR in the Experimental group (10% anticipated) in comparison with the Placebo group (25% anticipated) and to assure a study power of 80% with a unilateral Chi2 and a significance level of 5%, we need 158 patients in total; 79 in each group.