The naphthoquinonic chromophore gives rifampicin its characteristic red-orange crystalline color.The critical functional groups of rifampicin in its inhibitory binding of bacterial RNA polymerase are the four critical hydroxyl groups of the ansa bridge and the naphthol ring, which form hydrogen bonds with amino acid residues on the protein.Rifampicin is the 3-(4-methyl-1-piperazinyl)-iminomethyl derivative of rifamycin SV. Interactions
Rifampicin is the most powerful known inducer of the hepatic cytochrome P450 enzyme system, including isoenzymes CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP3A4, CYP3A5, and CYP3A7. It increases metabolism of many drugs and as a consequence, can make them less effective, or even ineffective, by decreasing their levels. For instance, patients undergoing long-term anticoagulation therapy with warfarin have to increase their dosage of warfarin and have their clotting time checked frequently because failure to do so could lead to inadequate anticoagulation, resulting in serious consequences of thromboembolism.Rifampicin can reduce the efficacy of birth control pills or other hormonal contraception by its induction of the cytochrome P450 system, to the extent that unintended pregnancies have occurred in women who use oral contraceptives and took rifampicin even for very short courses (for example, as prophylaxis against exposure to bacterial meningitis).Other interactions include decreased levels and less effectiveness of antiretroviral agents, everolimus, atorvastatin, rosiglitazone, pioglitazone, celecoxib, clarithromycin, caspofungin, voriconazole, and lorazepam.Rifampicin is antagonistic to the microbiologic effects of the antibiotics gentamicin and amikacin. The activity of rifampicin against some species of mycobacteria can be potentiated by isoniazid (through inhibiting mycolate synthesis) and ambroxol (through host directed effects in autophagy and pharmacokinetics).
Facial palsy is considered severe if the person is unable to close the affected eye completely or the face is asymmetric even at rest. Corticosteroids initiated within three days of Bells palsy onset have been found to increase chances of recovery, reduce time to recovery, and reduce residual symptoms in case of incomplete recovery. However, for facial palsy caused by Lyme disease, corticosteroids have been found in some studies to harm outcomes. Other studies have found antivirals to possibly improve outcomes relative to corticosteroids alone for severe Bells palsy. In those whose blinking is disrupted by the facial palsy, frequent use of artificial tears while awake is recommended, along with ointment and a patch or taping the eye closed when sleeping. References


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