Rifampicin, also known as rifampin, is an ansamycin antibiotic used to treat several types of bacterial infections, including tuberculosis (TB), Mycobacterium avium complex, leprosy, and Legionnaires' disease.

[3] It is almost always used together with other antibiotics with two notable exceptions: when given as a "preferred treatment that is strongly recommended"[4] for latent TB infection; and when used as post-exposure prophylaxis to prevent Haemophilus influenzae type b and meningococcal disease in people who have been exposed to those bacteria.

[13][14] Rifampicin can be used alone in patients with latent tuberculosis infections to prevent or delay the development of active disease because only small numbers of bacteria are present.

[18] With multidrug therapy used as the standard treatment of Hansen's disease, rifampicin is always used in combination with dapsone and clofazimine to avoid causing drug resistance.

[21] A meta-analysis concluded that adding adjunctive rifampicin to a β-lactam or vancomycin may improve outcomes in staphylococcus aureus bacteremia.

[citation needed] It has been used with amphotericin B in largely unsuccessful attempts to treat primary amoebic meningoencephalitis caused by Naegleria fowleri.

[26] Rifampicin is relatively ineffective against spirochetes, which has led to its use as a selective agent capable of isolating them in materials being cultured in laboratories.

Taking rifampicin usually causes certain bodily fluids, such as urine, sweat, and tears, to become orange-red in color, a benign side effect that nonetheless can be frightening if it is not expected.

[citation needed] Other adverse effects include: Rifampicin is a polyketide belonging to the chemical class of compounds termed ansamycins, so named because of their heterocyclic structure containing a naphthoquinone core spanned by an aliphatic ansa chain.

[citation needed] Other interactions include decreased levels and less effectiveness of antiretroviral agents, everolimus, atorvastatin, rosiglitazone, pioglitazone, celecoxib, clarithromycin, caspofungin, voriconazole, and lorazepam.

The activity of rifampicin against some species of mycobacteria can be potentiated by isoniazid (through inhibiting mycolate synthesis)[47] and ambroxol (through host directed effects in autophagy and pharmacokinetics).

[40][50] 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.

With the assistance of the enzyme Arr produced by the pathogen Mycobacterium smegmatis, ADP-ribose is added to rifampicin at one of its ansa chain hydroxy groups, thereby inactivating the drug.

[54] Traditional methods of detecting resistance involve mycobacterial culture and drug susceptibility testing, results of which could take up to 6 weeks.

[citation needed] Rifampicin is easily absorbed from the gastrointestinal (GI) tract; its ester functional group is quickly hydrolyzed in bile, and it is catalyzed by a high pH and substrate-specific esterases.

[57] The decrease in rifampicin absorption with food is sometimes enough to noticeably affect urine color, which can be used as a marker for whether or not a dose of the drug has been effectively absorbed.

Since the substance itself is red, this high distribution is the reason for the orange-red color of the saliva, tears, sweat, urine, and feces.

[citation needed] In 1957, a soil sample from a pine forest on the French Riviera was brought for analysis to the Lepetit Pharmaceuticals research lab in Milan, Italy.

There, a research group headed by Piero Sensi[59] and Maria Teresa Timbal discovered a new bacterium, Nocardia mediterranei.

Because Sensi, Timbal and the researchers were particularly fond of the French crime story Rififi (about a jewel heist and rival gangs),[60] they decided to call these compounds rifamycins.

Derivatives of one molecule, rifamycin B, which itself possess minimal antibiotic activity yielded several highly active antibiotics, one of the earliest which was used as a medicine being rifamycin SV, which was introduced in some countries for the parenteral and topical treatment of infections due to gram-positive bacteria and infections of the biliary tract.

[61] After two years of attempts to obtain more stable semisynthetic products, a new molecule with high efficacy and good tolerability was produced in 1965 and was named rifampicin.

[62] The FDA and manufacturers are investigating the origin of these impurities in rifampin, and the agency is developing testing methods for regulators and industry to detect the 1-methyl-4-nitrosopiperazine (MNP).