The INN stem system is operating according to the WHO Executive Board resolution EB15.R7 (as amended by the resolution EB115.R4), which requests that "a group relationship of pharmacologically related substances should, if possible, be shown in the name by using a common stem." A stem is a syllable (or 2-3 syllables) inserted to the new INN, in most cases as a suffix, to indicate the pharmacological relationship.
