mystic_eye_cda replied: "Firstly "Category B" refers to pregnancy only. Safety during breastfeeding is rated L1-L5. I would call the doctor back or go to a walk-in clinic. There are certainly safer antibiotics for both you and baby. ?./temp/~08qXJg:1 Summary of Use during Lactation: Cephalexin is acceptable to use during breastfeeding. Limited information indicates that maternal doses of cephalexin up to 1 gram produce low levels in milk that are not expected to cause adverse effects in breastfed infants. Occasionally, disruption of the infant's gastrointestinal flora, resulting in diarrhea or thrush, have been reported with cephalosporins, but these effects have not been adequately evaluated. [...] Effects in Breastfed Infants: In a prospective follow-up study, 7 nursing mothers reported taking cephalexin (dosage not specified). Two mothers reported diarrhea in their infants. No rashes or candidiasis were reported among the exposed infants.[4] A prospective, controlled study asked mothers who called an information service about adverse reactions experience by their breastfed infants. One of 11 cephalexin-exposed infants reportedly developed diarrhea during maternal cephalexin therapy.[5] A woman received intravenous cephalothin 1 g every 6 hours for 3 days. Her breastfed infant had a green liquid stool, severe diarrhea, discomfort and crying. The mother's drug regimen was then changed to oral cephalexin 500 mg plus oral probenecid 500 mg 4 times daily for another 16 days. The infant continued to have diarrhea during this time. The authors rated the diarrhea as probably related to cephalexin in milk.[3] Antibiotics [contents] Amoxicillin Larotid, Amoxil Approved B L1 Aztreonam Azactam Approved B L2 Cefadroxil Ultracef, Duricef Approved B L1 Cefazolin Ancef, Kefzol Approved B L1 Cefotaxime Claforan Approved B L2 Cefoxitin Mefoxin Approved B L1 Cefprozil Cefzil Approved C L1 Ceftazidime Ceftazidime, Fortaz, Taxidime Approved B L1 Ceftriaxone Rocephin Approved B L2 Ciprofloxacin [more] Cipro Approved C L3 Clindamycin Cleocin Approved B L3 Erythromycin E-Mycin, Ery-tab, ERYC, Ilosone Approved B L1 L3 early postnatal Fleroxacin - Approved - NR Gentamicin Garamycin Approved C L2 Kanamycin Kebecil, Kantrex Approved D L2 Moxalactam Moxam Approved - NR Nitrofurantoin Macrobid Approved B L2 Ofloxacin Floxin Approved C L2 Penicillin - Approved B L1 Streptomycin Streptomycin Approved D L3 Sulbactam - Approved - NR Sulfisoxazole Gantrisin, Azo-Gantrisin Approved C L2 Tetracycline Achromycin, Sumycin, Terramycin Approved D L2 Ticarcillin Ticarcillin, Ticar, Timentin Approved B L1 Trimethoprim/sulfamethoxazole Proloprim, Trimpex Approved C L3"