Rifampicin (other name: rifampin) is a semisynthetic rifamycin antibiotic, which is chemically synthesized from rifamycin, which is isolated from a strain of the actinomycete Amycolatopsis mediterranei. Rifampicin has activity against a wide variety of organisms, including tuberculosis germs and Staphylococcus aureus, as well as in vitro activity against penicillin-resistant Streptococcus pneumoniae, and many Gram-negative bacteria. Rifampicin inhibits bacterial DNA-dependent RNA synthesis by inhibiting bacterial DNA-dependent RNA polymerase, which is responsible for DNA transcription. In contrast, the corresponding mammalian enzymes are not affected by rifampicin. Bacterial resistance to rifampicin is caused by mutations leading to a change in the structure of the β subunit of RNA polymerase. Rifampicin acts as a cytochrome P450 3A4 (CYP3A4) inducer, which increase the activity of CYP3A4. Thus, rifampicin can cause drug interaction with other medications.