Is the S-isomer of ofloxacin. Recently, quinolone-related medication has been used in neonates and infants without apparent side effects. It trespasses in tiny amounts into breast milk. Absorption through the child’s gut may be interfered by the calcium contained in the milk. Should it be necessary to prescribe it to a nursing mother, Norfloxacine, Ofloxacine and Ciprofloxacine have shown a lower level in the milk and thus must be the preferred drugs. Because a case of pseudomembranose colitis has been described possibly related to mother ingestion of Ciporfloxacine in a premature infant previously affected of NEC, a close follow-up for diarrhea is warranted. Be aware of the possibility of false negative results of bacterial cultures when the mother is on antibiotics.