In diverse contexts comparison of groups is giving frequently. Particularly, comparison of groups based on non-inferiority statistical tests is becoming more frequent and have had a very special boom in clinical trials, especially in trials related to testing new anti-infective products. Non-inferiority tests are statistical procedures that allow verify whether a sample provides sufficient evidence that the efficacy of a new treatment is not substantially inferior to the known efficacy of a standard treatment. For the selection of the non-inferiority margin for anti-infective trials, the Food and Drug Administration (FDA) and the Committee for Proprietary of Medical Products (CPMP) have provided some general guidance. In this investigation we propose a new parametric family of margin functions for testing non-inferiority in the context of anti-infective trials. One important feature of this parametric family is that fit together recommendations of FDA and CPMP jointly with some other important mathematical properties underlined in this research.