Rifabutin

Rifabutin is a naphthalenic ansamycin that derives from rifamycin S and has the activity to against mycobacteria infection with MICs ranged from 0.125 to 0.25 µg/ml [1].
TB (tuberculosis) is a chronic infectious disease caused by Mycobacterium tuberculosis infection. TB can invade to human organs whole body, but mainly affects the lung which is called pulmonary tuberculosis. About 2 billion people has been infected with TB all around the word and the emergence of new infected TB patients is about 8-10 million every year. Rifabutin is an anti-TB medicine used to treat TB infected patients with fewer side effects [1].
Rifabutin is a potent antimycobacterial medicine and has lower toxic than rifampicin. When tested with the mimic human-bacterial plasma membranes, Rifabutin showed high affinity for the bacterial membrane mediated by electrostatic interactions with the phospholipid head groups [2]. In patients with organ transplant, Rifabutin was an excellent medicine to reduce the incidence of TB (tuberculosis) infection [3]. When tested 34 isolates of clinical drug resistant M.tuberculosis with Rifabutin, they showed sensitive to Rifabutin compared with rifampicin treatment [1].
In mice model with TB infected, intravenous administration of Rifabutin reduced bacterial loads in spleen, liver and lung [4].
References:
[1].    Pham, D.D., E. Fattal, and N. Tsapis, Pulmonary drug delivery systems for tuberculosis treatment. Int J Pharm, 2014. 478(2): p. 517-529.
[2].    Pinheiro, M., et al., Differential interactions of rifabutin with human and bacterial membranes: implication for its therapeutic and toxic effects. J Med Chem, 2013. 56(2): p. 417-26.
[3].    Tabarsi, P., et al., Mycobacterial infection and the impact of rifabutin treatment in organ transplant recipients: A single-center study. Saudi J Kidney Dis Transpl, 2015. 26(1): p. 6-11.
[4].    Gaspar, M.M., et al., Rifabutin encapsulated in liposomes exhibits increased therapeutic activity in a model of disseminated tuberculosis. Int J Antimicrob Agents, 2008. 31(1): p. 37-45.

Effect of a 150 mg dose of rifabutin on serum itraconazole levels in patients with coexisting chronic pulmonary aspergillosis and Mycobacterium avium complex lung disease.[Pubmed:28284662]

J Infect Chemother. 2017 Sep;23(9):658-660.

Patients with coexisting chronic pulmonary aspergillosis and nontuberculous mycobacterial lung disease may undergo treatment with both the antifungal itraconazole and the antimycobacterial rifamycin. However, rifamycins interact with itraconazole. We examined the effects of a 150 mg dose of Rifabutin on serum itraconazole levels and found significantly lower levels in 28 patients receiving itraconazole with Rifabutin (median, 0.65 mug/ml) compared with 65 patients receiving itraconazole alone (median 3.45 mug/ml, P < 0.001). One-third of patients receiving itraconazole and Rifabutin reached the therapeutic range of serum itraconazole concentration. Therapeutic drug monitoring is strongly recommended during concomitant use of Rifabutin and itraconazole.

Simultaneous determination of rifabutin and human serum albumin in pharmaceutical formulations by capillary electrophoresis.[Pubmed:28137656]

J Pharmacol Toxicol Methods. 2017 May - Jun;85:55-60.

Capillary zone electrophoresis (CZE) was used for determination of Rifabutin (RFB), an anti-tuberculosis antibiotic drug, in various pharmaceutical formulations. Apart from that, simultaneous determination of RFB and human serum albumin (HSA) was performed. Electrophoretic behaviour of RFB was examined at various pH levels. CE conditions: a quartz capillary tube (internal diameter 75mm, effective length 50cm, total length 60cm), the capillary temperature was 25 degrees capital ES, Cyrillic, the voltage applied to the capillary tube was +20kV, the UV detection wavelength was 214nm, hydrodynamic injection of the sample was performed at 30mbar for 5s, tetraborate buffer solution (0.01capital EM, Cyrillic, small er, Cyrilliccapital EN, Cyrillic9.2). The obtained results are characterized by high efficiency (number of theoretical plates up to 260,000) and sufficient sensitivity (LOQ starting from 0.02mug/ml for RFB). The obtained data are in good accord with both HPLC results (for RFB) and spectrophotometry (for HSA).

Simultaneous LC-MS-MS Determination of Lopinavir and Rifabutin in Human Plasma.[Pubmed:28334925]

J Chromatogr Sci. 2017 Jul 1;55(6):617-624.

Tuberculosis (TB) with human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome represents the most common infectious diseases worldwide. Anti-TB drugs are used concurrently with antiretroviral drug for treatment of TB-HIV co-morbidities. Due to lower risk of interaction with protease inhibitors, Rifabutin is preferred over rifampicin in treatment of HIV and TB co-morbidity. A simple and specific liquid chromatography tandem mass spectrometry method was developed for quantification of Rifabutin (RBT) and lopinavir (LPV) simultaneously in human plasma. Following extraction using 60% n-hexane in ethyl acetate, the processed samples were chromatographed on a Discovery HS C18 column (5 mum, 50 x 4.6 mm, id) using mobile phase [85% acetonitrile in ammonium acetate buffer (10 mM, pH 4.5)] at a flow rate of 0.7 mL/min. Mass spectrometric detection was performed in positive electrospray ionization mode using multiple reaction monitoring (RBT, m/z 847.7 --> 815.4; LPV, m/z 629.6 --> 447.4). Raloxifene and phenacetin were used as internal standards for RBT and LPV, respectively. Linearity was established in the range of 1-1,000 ng/mL and 0.5-10 microg/mL (R2 >/= 0.99) for RBT and LPV, respectively. The recovery of LPV and RBT were always >90 and >50%, respectively. The precisions and accuracies were well within the acceptable limits of variation.

Rifabutin-based Fourth and Fifth-line Rescue Therapy in Patients with for Helicobacter pylori Eradication Failure.[Pubmed:28239079]

Korean J Gastroenterol. 2017 Feb 25;69(2):109-118.

Background/Aims: Optimized regimen has not yet been established for failures of multiple Helicobacter pylori (H. pylori) eradication. Hence, we aimed to evaluate the efficacy of Rifabutin-based rescue therapy, at least after three eradication failures. Methods: Twelve patients, who failed in the treatment for H. pylori eradication at least three times, were consecutively enrolled between 2007 and 2015 at Seoul National University Bundang Hospital. The Rifabutin-based rescue regimen was consisted of proton pump inhibitor (PPI), Rifabutin (150 mg b.i.d.), and amoxicillin (1 g b.i.d.), given for 7 or 14 days. MIC concentration test by the agar dilution method was performed on six patients prior to Rifabutin-based rescue therapy. Results: One patient did not take this regimen, and per-protocol (PP) analysis was performed in 11 patients. The overall eradication rate by intention-to-treat and PP analysis with Rifabutin-based rescue therapy was 50.0% (6/12 patients) and 54.5% (6/11 patients), respectively. There was no difference of the eradication rate depending on the underlying disease, smoking, alcohol, number of previous eradication failures, and CYP2C19 genotype. All of the six patients were susceptible to Rifabutin, but only three of them succeeded in eradicating with H. pylori. Side effects occurred in two patients (18.2%), and compliance was 90.9%. Conclusions: Even the eradication rate of Rifabutin-based rescue therapy was not very good. Rifabutin-based rescue therapy could be considered as a rescue therapy, perhaps as the fourth or the fifth-line treatment option. No correlation of Rifabutin sensitivity with eradication success rate of H. pylori suggests that frequent administration of high dose PPI and amoxicillin might be important.

Rifabutin (Ansamycin) is a semisynthetic ansamycin antibiotic with potent antimycobacterial properties. Rifabutin inhibits DNA-dependent RNA polymerase.

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