Does Keflex have an interaction with oral contraceptives?

Patient : I had unprotective sex this morning and now I need to begin an antibiotic regiment using Keflex tomorrow for a cellulitis infection. Should I wait to take Keflex in order to avoid any possibility of pregnancy, or will Keflex not interfere with birth control pills?
Doctor :   Thank you for your question. Although Cephalexin (keflex) does have a rare, but existing interaction with oral hormone c ontraceptives, which can reduce their efficacy. We recommend that start your keflex as prescribed, but also use barrier protection, such as condoms, while taking your antibiotics, and up to 7 days after completing your course of antibiotics. Thank you for choosing

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