Pharmacology
Mechanism of action
Rifampicin inhibits bacterial DNA-dependent RNA synthesis by inhibiting bacterial DNA-dependent RNA polymerase.Crystal structure data and biochemical data suggest that rifampicin binds to the pocket of the RNA polymerase β subunit within the DNA/RNA channel, but away from the active site. The inhibitor prevents RNA synthesis by physically blocking elongation, and thus preventing synthesis of host bacterial proteins. By this "steric-occlusion" mechanism, rifampicin blocks synthesis of the second or third phosphodiester bond between the nucleotides in the RNA backbone, preventing elongation of the 5 end of the RNA transcript past more than 2 or 3 nucleotides.In a recent study Rifampicin was shown to bind to cytochrome P450 reductase and alter its conformation as well as activity towards supporting metabolism of progesterone via CYP21A2. Mechanism of resistance
Resistance to rifampicin arises from mutations that alter residues of the rifampicin binding site on RNA polymerase, resulting in decreased affinity for rifampicin. Resistance mutations map to the rpoB gene, encoding the beta subunit of RNA polymerase. The majority of resistance mutations in E. coli are in 3 clusters on rpoB. Cluster I is amino acids 509 to 533, cluster II is amino acids 563 to 572, and cluster III is amino acid 687. When describing mutations in rpoB in other species, the corresponding amino acid number in E. coli is usually used. In Mycobacterium tuberculosis, the majority of mutations leading to rifampicin resistance are in cluster I, in a 81bp hotspot core region called RRDR for "rifampcin resistance determining region".
Osteochondropathy refers to a disease ("-pathy") of the bone and cartilage. However, it is more common to refer to these conditions as one of the following:

chondropathy (disease of the cartilage)
A bone disease is also called an "osteopathy", but because the term osteopathy is often used to describe a healthcare approach, use of the term can cause some confusion. See also
Osteochondrosis
Osteochondritis

References


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