Sample size: The objective of the study is to demonstrate that penicillin V is not inferior to amoxicillin. Considering a success rate of 85% for the group treated with amoxicillin [1,2]. A total of 105 patients will be required in each treatment group (total of 210) to detect a non-inferiority margin of 15% between the two treatments with a minimum power of 80% considering an alpha error of 2.5% for a unilateral hypothesis and maximum possible losses of 15%.