Will taking Keflex affect the working of Implanon?

Dear Ask The Doctor: I was prescribed Keflex 500 mg and I am currently using the Implanon as a form of birth control. Would the antibiotic effect the Implanon at all? I have had unprotected sex.

Dear Caroline: It is completely safe to take Keflex (Cephalosporin) when you are using Implanon ( a subdermal contraceptive implant). There is no evidence that would suggest that the antibiotic reduces the efficacy of Implanon, so you need not be worried.