Im have nexoplanon. got imfentigo from my son and was perscribed keflex. does keflex interact with the nexoplanon?

May be: some antibiotics would decrease hormonal contraceptive effect, you may want to use an alternative method of contraception while on antibiotics, such as barrier method, till done with the antibiotic course and for a day after, just to make sure it's out of your system, good that you asked, better exercise caution when on multiple medications

Drug interactions: You can use a drug interaction checker whenever you have questions about drug-drug interactions or drug - food interactions. Here is 1 option (Drugs.Com): https://www.drugs.com/drug_interactions.php Your pharmacist is also a good source of info.