Task: Translation
Input (Spanish): Al formular comprimidos con principios activos que se utilizan a dosis relativamente bajas es necesario adicionar excipientes cuya función primordial es obtener un comprimido de un tamaño razonable. ¿Cómo se denominan esos excipientes?
Output (English): When formulating tablets with active ingredients that are used at relatively low doses, it is necessary to add excipients whose primary function is to obtain a tablet of a reasonable size. What are these excipients called?