AntibioticsRifampicin-like medicines are the only types of antibiotic that can make hormonal contraception less effective. This includes:rifampicinrifabutinThese types of medicine can increase the enzymes in your body. This is known as enzyme-inducing and can affect hormonal contraception.Enzymes are proteins that control your body’s chemical reactions. Enzyme-inducing antibiotics speed up the processing of some contraceptive hormones and therefore reduce the levels of these hormones in your bloodstream. This makes the contraceptive less effective.Apart from those mentioned above, all other antibiotics are not enzyme-inducing.