Rifampin

Rifampicin is a bactericidal antibiotic drug of the rifamycin group.

The Effect of Single and Multiple Doses of Rifampin on the Pharmacokinetics of Doravirine in Healthy Subjects.[Pubmed:28353169]

Clin Drug Investig. 2017 Jul;37(7):659-667.

BACKGROUND AND OBJECTIVE: Doravirine is a novel, next-generation, non-nucleoside reverse transcriptase inhibitor in development for the treatment of human immunodeficiency virus-1 infection in combination with other antiretrovirals. Doravirine is a substrate for cytochrome P450 (CYP) 3A and P-glycoprotein. Rifampin (rifampicin) is used for treating tuberculosis in patients who are co-infected with human immunodeficiency virus. Rifampin demonstrates organic anion-transporting polypeptide 1B1 and P-glycoprotein inhibition after single-dose administration and CYP3A and P-glycoprotein induction after multiple-dose administration. The objective of this study was to evaluate the effects of co-administration of single and multiple doses of Rifampin on doravirine pharmacokinetics. METHODS: In period 1 of this open-label, two-period, fixed-sequence study in healthy adults, subjects received single-dose doravirine 100 mg; blood samples for measuring plasma concentration were collected pre-dose and up to 72 h post-dose. In period 2, following a 7-day washout, subjects received doravirine 100 mg and Rifampin 600 mg on day 1, Rifampin 600 mg daily on days 4-18, with doravirine 100 mg co-administered on day 17; blood samples were collected pre-dose and up to 72 h post-dose on day 1 and up to 48 h post-dose on day 17. Safety assessments included adverse events, physical examinations, vital signs, and clinical laboratory measurements. RESULTS: Ten subjects completed the study. Doravirine area under the concentration-time curve from time zero extrapolated to infinity and plasma concentration at 24 h post-dose were comparable in the presence and absence of single-dose Rifampin [geometric mean ratios (90% confidence intervals)] of 0.91 (0.78-1.06) and 0.90 (0.80-1.01), respectively. Doravirine maximum plasma concentration increased when co-administered with single-dose Rifampin vs. doravirine alone, geometric mean ratio (90% confidence interval): 1.40 (1.21-1.63). Reductions in doravirine geometric mean ratios (90% confidence interval), area under the concentration-time curve from time zero extrapolated to infinity: 0.12 (0.10-0.15), plasma concentration at 24 h post-dose: 0.03 (0.02-0.04), maximum plasma concentration: 0.43 (0.35-0.52), and apparent terminal half-life were observed when co-administered with multiple-dose Rifampin vs. doravirine administered alone. Doravirine was well tolerated. Adverse events were mild and resolved by study completion. CONCLUSIONS: Doravirine co-administration with single-dose Rifampin indicated that inhibition of organic anion-transporting polypeptide uptake transporters and P-glycoprotein has little impact on doravirine pharmacokinetics. Long-term co-administration of Rifampin or other strong CYP3A inducers with doravirine will likely reduce its efficacy.

CYP3A4 Induction by Rifampin: An Alternative Pathway for Vitamin D Inactivation in Patients With CYP24A1 Mutations.[Pubmed:28324001]

J Clin Endocrinol Metab. 2017 May 1;102(5):1440-1446.

Context: The P450 enzyme CYP24A1 is the principal inactivator of vitamin D metabolites. Biallelic loss-of-function mutations in CYP24A1 are associated with elevated serum levels of 1,25-dihydroxyvitamin D3 with consequent hypercalcemia and hypercalciuria and represent the most common form of idiopathic infantile hypercalcemia (IIH). Current management strategies for this condition include a low-calcium diet, reduced dietary vitamin D intake, and limited sunlight exposure. CYP3A4 is a P450 enzyme that inactivates many drugs and xenobiotics and may represent an alternative pathway for inactivation of vitamin D metabolites. Objective: Our goal was to determine if Rifampin, a potent inducer of CYP3A4, can normalize mineral metabolism in patients with IIH due to mutations in CYP24A1. Methods: We treated two patients with IIH with daily Rifampin (10 mg/kg/d, up to a maximum of 600 mg). Serum calcium, phosphorus, parathyroid hormone (PTH), liver, and adrenal function and vitamin D metabolites, as well as urinary calcium excretion, were monitored during treatment of up to 13 months. Results: Prior to treatment, both patients had hypercalcemia, hypercalciuria, and nephrocalcinosis with elevated serum 1,25-dihydroxyvitamin D3 and suppressed serum PTH. Daily treatment with Rifampin was well tolerated and led to normalization or improvement in all clinical and biochemical parameters. Conclusion: These observations suggest that Rifampin-induced overexpression of CYP3A4 provides an alternative pathway for inactivation of vitamin D metabolites in patients who lack CYP24A1 function.

Treatment completion for latent tuberculosis infection: a retrospective cohort study comparing 9 months of isoniazid, 4 months of rifampin and 3 months of isoniazid and rifapentine.[Pubmed:28196479]

BMC Infect Dis. 2017 Feb 14;17(1):146.

BACKGROUND: The U.S. Centers for Disease Control and Prevention (CDC) recommended a new regimen for treatment of latent tuberculosis (three months of weekly isoniazid and rifapentine) in late 2011. While completion rates of this regimen were reported to be higher than nine months of isoniazid, little is known about the completion rates of three months of isoniazid and rifapentine compared to nine months of isoniazid or four months of Rifampin in actual use scenarios. METHODS: We conducted a retrospective cohort study comparing treatment completion for latent tuberculosis (TB) infection in patients treated with nine months of isoniazid, three months of isoniazid and rifapentine or four months of Rifampin in outpatient clinics and a public health TB clinic in Seattle, Washington. The primary outcome of treatment completion was defined as 270 doses of isoniazid within 12 months, 120 doses of Rifampin within six months and 12 doses of isoniazid and rifapentine within four months. RESULTS: Three hundred ninety-three patients were included in the study. Patients were equally likely to complete three months of weekly isoniazid and rifapentine or four months of Rifampin (85% completion rate of both regimens), as compared to 52% in the nine months of isoniazid group (p < 0.001). These associations remained statistically significant even after adjusting for clinic location and type of monitoring. Monitoring type (weekly versus monthly versus less often than monthly) had less impact on treatment completion than the type of treatment offered. CONCLUSIONS: Patients were equally as likely to complete the three months of isoniazid and rifapentine as four months of Rifampin. Four months of Rifampin is similar in efficacy compared to placebo as isoniazid and rifapentine but does not require directly observed therapy (DOT), and is less expensive compared to combination therapy with isoniazid and rifapentine, and thus can be the optimal treatment regimen to achieve the maximal efficacy in a community setting.

Pregnane X receptor is SUMOylated to repress the inflammatory response.[Pubmed:20719936]

J Pharmacol Exp Ther. 2010 Nov;335(2):342-50.

Long-term treatment of patients with the macrolide antibiotic and prototypical activator of pregnane X receptor (PXR) rifampicin (Rif) inhibits the inflammatory response in liver. We show here that activation of the inflammatory response in hepatocytes strongly modulates SUMOylation of ligand-bound PXR. We provide evidence that the SUMOylated PXR contains SUMO3 chains, and feedback represses the immune response in hepatocytes. This information represents the first step in developing novel pharmaceutical strategies to treat inflammatory liver disease and prevent adverse drug reactions in patients experiencing acute or systemic inflammation. These studies also provide a molecular rationale for constructing a novel paradigm that uniquely defines the molecular basis of the interface between PXR-mediated gene activation, drug metabolism, and inflammation.

Allosteric modulation of the RNA polymerase catalytic reaction is an essential component of transcription control by rifamycins.[Pubmed:16096056]

Cell. 2005 Aug 12;122(3):351-63.

Rifamycins, the clinically important antibiotics, target bacterial RNA polymerase (RNAP). A proposed mechanism in which rifamycins sterically block the extension of nascent RNA beyond three nucleotides does not alone explain why certain RNAP mutations confer resistance to some but not other rifamycins. Here we show that unlike rifampicin and rifapentin, and contradictory to the steric model, rifabutin inhibits formation of the first and second phosphodiester bonds. We report 2.5 A resolution structures of rifabutin and rifapentin complexed with the Thermus thermophilus RNAP holoenzyme. The structures reveal functionally important distinct interactions of antibiotics with the initiation sigma factor. Strikingly, both complexes lack the catalytic Mg2+ ion observed in the apo-holoenzyme, whereas an increase in Mg2+ concentration confers resistance to rifamycins. We propose that a rifamycin-induced signal is transmitted over approximately 19 A to the RNAP active site to slow down catalysis. Based on structural predictions, we designed enzyme substitutions that apparently interrupt this allosteric signal.

Orphan nuclear receptors constitutive androstane receptor and pregnane X receptor share xenobiotic and steroid ligands.[Pubmed:10748001]

J Biol Chem. 2000 May 19;275(20):15122-7.

Xenobiotics induce the transcription of cytochromes P450 (CYPs) 2B and 3A through the constitutive androstane receptor (CAR; NR1I3) and pregnane X receptor (PXR; NR1I2), respectively. In this report, we have systematically compared a series of xenobiotics and natural steroids for their effects on mouse and human CAR and PXR. Our results demonstrate dual regulation of PXR and CAR by a subset of compounds that affect CYP expression. Moreover, there are marked pharmacological differences between the mouse (m) and human (h) orthologs of both CAR and PXR. For example, the planar hydrocarbon 1, 4-bis[2-(3,5-dichloropyridyl-oxy)]benzene activates mCAR and hPXR but has little or no activity on hCAR and mPXR. In contrast, the CAR deactivator androstanol activates both mouse and human PXR. Similarly, the PXR activator clotrimazole is a potent deactivator of hCAR. Using radioligand binding and fluorescence resonance energy transfer assays, we demonstrate that several of the compounds that regulate mouse and human CAR, including natural steroids, bind directly to the receptors. Our results suggest that CAR, like PXR, is a steroid receptor that is capable of recognizing structurally diverse compounds. Moreover, our findings underscore the complexity in the physiologic response to xenobiotics.

Rifampin: mechanisms of action and resistance.[Pubmed:6356275]

Rev Infect Dis. 1983 Jul-Aug;5 Suppl 3:S407-11.

Rifampin specifically inhibits bacterial RNA polymerase, the enzyme responsible for DNA transcription, by forming a stable drug-enzyme complex with a binding constant of 10(-9) M at 37 C. The corresponding mammalian enzymes are not affected by Rifampin. Bacterial resistance to Rifampin is caused by mutations leading to a change in the structure of the beta subunit of RNA polymerase. Such resistance is not an all-or-nothing phenomenon; rather, a large number of RNA polymerases with various degrees of sensitivity to Rifampin have been found. No strict correlation exists between enzyme sensitivity and MIC values, since inhibition of RNA synthesis does not always show up to the same extent in the two different test systems used for the determination of these values.

Rifampicin is a potent and broad spectrum antibiotic against bacterial pathogens. Rifampicin has anti-influenza virus activities.

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