Nalidixic acid (tradenames Nevigramon, Neggram, Wintomylon and WIN 18,320) is the first of the synthetic quinolone antibiotics. In the technical sense, it is a naphthyridone, not a quinolone: its ring structure is a 1,8-naphthyridine nucleus that contains two nitrogen atoms, unlike quinoline, which has a single nitrogen atom.