Co-administration Of Rifampicin Research Articles

Effects of CYP Induction by Rifampicin on Tamoxifen Exposure

Tamoxifen undergoes biotransformation into several metabolites, including endoxifen. Differences in metabolism contribute to the interindividual variability in endoxifen concentrations, potentially affecting treatment efficacy. We evaluated the effects of cytochrome P450 (CYP) induction by rifampicin on the exposure levels of tamoxifen and its metabolites and found that coadministration of rifampicin resulted in markedly reduced (up to 86%, P ≤ 0.040) concentrations of tamoxifen and its metabolites. Given the extensive metabolism undergone by tamoxifen, several factors may have contributed to this effect. Similar drug-drug interactions may exist between tamoxifen and other strong CYP inducers.

Model-based approach to dose optimization of lopinavir/ritonavir when co-administered with rifampicin.

Rifampicin, a key component of antitubercular treatment, profoundly reduces lopinavir concentrations. The aim of this study was to develop an integrated population pharmacokinetic model accounting for the drug-drug interactions between lopinavir, ritonavir and rifampicin, and to evaluate optimal doses of lopinavir/ritonavir when co-administered with rifampicin. Steady-state pharmacokinetics of lopinavir and ritonavir were sequentially evaluated after the introduction of rifampicin and gradually escalating the dose in a cohort of 21 HIV-infected adults. Intensive pharmacokinetic sampling was performed after each dose adjustment following a morning dose administered after fasting overnight. A population pharmacokinetic analysis was conducted using NONMEM 7. A simultaneous integrated model was built. Rifampicin reduced the oral bioavailability of lopinavir and ritonavir by 20% and 45% respectively, and it increased their clearance by 71% and 36% respectively. With increasing concentrations of ritonavir, clearance of lopinavir decreased in an E(max) relationship. Bioavailability was 42% and 45% higher for evening doses compared with morning doses for lopinavir and ritonavir, respectively, while oral clearance of both drugs was 33% lower overnight. Simulations predicted that 99.5% of our patients receiving doubled doses of lopinavir/ritonavir achieve morning trough concentrations of lopinavir > 1 mg l(-1) during rifampicin co-administration, and 95% of those weighing less than 50 kg achieve this target already with 600/150 mg doses of lopinavir/ritonavir. The model describes the drug-drug interactions between lopinavir, ritonavir and rifampicin in adults. The higher trough concentrations observed in the morning were explained by both higher bioavailability with the evening meal and lower clearance overnight.

The Safety, Effectiveness and Concentrations of Adjusted Lopinavir/Ritonavir in HIV-Infected Adults on Rifampicin-Based Antitubercular Therapy

ObjectiveRifampicin co-administration dramatically reduces plasma lopinavir concentrations. Studies in healthy volunteers and HIV-infected patients showed that doubling the dose of lopinavir/ritonavir (LPV/r) or adding additional ritonavir offsets this interaction. However, high rates of hepatotoxicity were observed in healthy volunteers. We evaluated the safety, effectiveness and pre-dose concentrations of adjusted doses of LPV/r in HIV infected adults treated with rifampicin-based tuberculosis treatment.MethodsAdult patients on a LPV/r-based antiretroviral regimen and rifampicin-based tuberculosis therapy were enrolled. Doubled doses of LPV/r or an additional 300 mg of ritonavir were used to overcome the inducing effect of rifampicin. Steady-state lopinavir pre-dose concentrations were evaluated every second month.Results18 patients were enrolled with a total of 79 patient months of observation. 11/18 patients were followed up until tuberculosis treatment completion. During tuberculosis treatment, the median (IQR) pre-dose lopinavir concentration was 6.8 (1.1–9.2) mg/L and 36/47 (77%) were above the recommended trough concentration of 1 mg/L. Treatment was generally well tolerated with no grade 3 or 4 toxicity: 8 patients developed grade 1 or 2 transaminase elevation, 1 patient defaulted additional ritonavir due to nausea and 1 patient developed diarrhea requiring dose reduction. Viral loads after tuberculosis treatment were available for 11 patients and 10 were undetectable.ConclusionOnce established on treatment, adjusted doses of LPV/r co-administered with rifampicin-based tuberculosis treatment were tolerated and LPV pre-dose concentrations were adequate.

Damage of testicular cell macromolecules and reproductive capacity of male rats following co-administration of ethambutol, rifampicin, isoniazid and pyrazinamide.

The necessity to minimize adverse effects of tuberculosis chemotherapy requires a comprehensive evaluation of the effects of antituberculosis drugs on the reproductive system and testicular cell macromolecules. The epidemiological situation of tuberculosis in Central and Eastern Europe is getting worse. Data on adverse effects of antituberculosis drugs are scare concerning particularly their effects on the reproductive system. The aim of the present study was to investigate the potential effect of ethambutol, rifampicin, isoniazid and pyrazinamide co-administration on lipid peroxidation, glutathione content and protein SH-groups, DNA fragmentation levels, the reproductive capacity of Wistar male rats and the antenatal development of their posterity. The rats (150–170 g) were divided into two groups: group I – received antituberculosis drugs suspended in 1% starch gel per os: ethambutol – 155 mg/kg b.w./day, rifampicin – 74.4 mg/kg b.w./day, isoniazid – 62 mg/kg b.w./day, pyrazinamide – 217 mg/kg b.w./day, group II (control) – received only starch gel in corresponding volumes. The contents of TBA-active compounds, glutathione and protein SH-groups in testis and sperm were determined spectrophotometrically, the DNA-fragmentation was determined using an UV transilluminator (BIORAD, USA), reproductive system indices were measured by standard methods. The co-administration of therapeutic doses of ethambutol, isoniazid, rifampicin and pyrazinamide to male rats during the period of spermatogenesis caused an increase in the rate of thiobarbituric acid reactive substances formation in testis and sperm, decrease of testis glutathione and protein SH-group contents, significant changes in DNA fragmentation, fatal decrease of male fertilizing capacity and fertility, and increase of pre- and post-implantation embryo lethality. The changes in reproductive indices could be the result of direct or indirect effects of one or more drugs investigated.

Clarithromycin Is Absorbed by an Intestinal Uptake Mechanism That Is Sensitive to Major Inhibition by Rifampicin: Results of a Short-Term Drug Interaction Study in Foals

Pulmonary penetration of clarithromycin (CLR) in epithelial lining fluid (ELF) and bronchoalveolar lavage cells (BALCs) can be influenced by CYP3A4, by P-glycoprotein, and, according to our hypothesis, by a member of the organic anion-transporting protein (OATP) family, for which rifampicin (RIF) is inhibiting in single doses but inducing after long-term coadministration. To assess the partial inhibitory effect, we measured absorption and pulmonary distribution of CLR after short-term (2.5-day) coadministration of RIF, after which up-regulation is not expected. The drug interaction study was performed with five doses (12-h interval) of CLR (7.5 mg/kg) and RIF (10 mg/kg) in nine healthy foals; horse transporters are very similar in protein sequence and transcriptional regulation to the human analogs. RIF was equally distributed in ELF but reached half the plasma levels in BALCs. The deacetylated metabolite accumulated 1.4- to 6-fold in ELF and 8- to 60-fold in BALCs. CLR did not significantly influence the distribution of RIF. CLR and 14-hydroxyclarithromycin (14OH-CLR) accumulated approximately 20- to 40-fold and 1.5- to 4.5-fold in ELF and 300- to 1800-fold and 25- to 90-fold in BALCs, respectively. With RIF, plasma levels of CLR decreased by more than 70% without changes in 14OH-CLR formation, the half-lives of CLR and 14OH-CLR, and the 4β-hydroxycholesterol/cholesterol ratio (a surrogate for CYP3A4 induction). CLR was an inhibitor of OATP1B3 (IC(50) = 9.50 ± 3.50 μM), OATP1B1 (IC(50) = 46.0 ± 2.27 μM), OATP1A2 (IC(50) = 92.6 ± 1.49 μM), and OATP2B1 (IC(50) = 384 ± 5.30 μM) but was not a substrate for these transporters in transfected human embryonic kidney cells. In conclusion, despite having no significant inducing effects, RIF decreased plasma levels of CLR below the minimal inhibitory concentration required to inhibit 90% of growth of pathogenic bacteria, most likely through inhibition of an unknown intestinal uptake transporter.

Effect of Cytochrome P450 3A4 Inducers on the Pharmacokinetic, Pharmacodynamic and Safety Profiles of Bortezomib in Patients with Multiple Myeloma or Non-Hodgkinʼs Lymphoma

Bortezomib, an antineoplastic agent with proteasome inhibitory activity, is extensively metabolized by the hepatic microsomal cytochrome P450 (CYP) enzymes CYP3A4 and CYP2C19. Drugs that affect these enzymes may therefore have an impact on the pharmacological profile of bortezomib. This study evaluated the effects of co-administration of a potent CYP3A4 inducer (rifampicin [rifampin]) and a weak CYP3A4 inducer (dexamethasone) on the pharmacokinetic, pharmacodynamic and safety profiles of bortezomib. Patients aged ≥18 years with relapsed or refractory multiple myeloma or non-Hodgkin's lymphoma received intravenous bortezomib 1.3 mg/m2, administered on days 1, 4, 8 and 11 of a 21-day cycle, for 3 cycles. In stage 1, patients were randomized (1 : 1) to receive bortezomib alone or in combination with oral rifampicin 600 mg once daily on days 4-10 during cycle 3 only. If the mean area under the plasma concentration-time curve (AUC) of bortezomib was reduced by ≥30% during rifampicin co-administration, then stage 2 was initiated, in which patients received bortezomib with dexamethasone 40 mg once daily on days 1-4 and days 9-12 during cycle 3 only. Blood samples were collected on days 11 through 14 of cycles 2 and 3 before and after bortezomib administration, at prespecified time points, for pharmacokinetic and pharmacodynamic (proteasome inhibition) assessments. Twelve patients in the bortezomib-alone arm, six patients in the bortezomib plus rifampicin arm and seven patients in the bortezomib plus dexamethasone arm were included in the pharmacokinetics-evaluable set. Rifampicin reduced the mean AUC from 0 to 72 hours (AUC(72h)) of bortezomib by approximately 45% (223 ng · h/mL in cycle 2 vs 123 ng · h/mL in cycle 3), while dexamethasone had no effect (mean AUC(72h): 179 ng · h/mL in cycle 2 vs 170 ng · h/mL in cycle 3). Proteasome inhibition parameters in peripheral blood were unaffected by rifampicin or dexamethasone. Safety profiles were similar across the treatment arms and consistent with previous experience of bortezomib. In patients with multiple myeloma or non-Hodgkin's lymphoma, co-administration of rifampicin decreased the exposure to bortezomib but did not affect the proteasome inhibition or safety profiles; co-administration of dexamethasone did not affect the exposure to bortezomib, proteasome inhibition or safety profiles. Concomitant administration of bortezomib with strong CYP3A4 inducers such as rifampicin is not recommended, as it may result in a reduction of the clinical effect, whereas concomitant administration of weak CYP3A4 inducers such as dexamethasone does not affect the pharmacological profile of bortezomib.

Effect of rifampicin on the pharmacokinetics and pharmacodynamics of saxagliptin, a dipeptidyl peptidase‐4 inhibitor, in healthy subjects

To investigate the effect of co-administration of rifampicin, a potent inducer of cytochrome P450 (CYP) 3A4 enzymes, on the pharmacokinetics (PK) and pharmacodynamics (PD) of saxagliptin and 5-hydroxy saxagliptin in healthy subjects. Saxagliptin is metabolized by CYP3A4/3A5 to 5-hydroxy saxagliptin, its major pharmacologically active metabolite. In a non-randomized, open label, single sequence design, 14 healthy subjects received single oral doses of saxagliptin 5 mg with and without steady-state rifampicin (600 mg once daily for 6 days). PK (saxagliptin and 5-hydroxy saxagliptin) and PD (plasma DPP-4 activity) were measured for up to 24 h on days 1 and 7. Concomitant administration with rifampicin resulted in 53% (point estimate 0.47, 90% CI 0.38, 0.57) and 76% (point estimate 0.24, 90% CI 0.21, 0.27) decreases in the geometric mean C(max) and AUC values of saxagliptin, respectively, with a 39% (point estimate 1.39, 90% CI 1.23, 1.56) increase in the geometric mean C(max) and no change (point estimate 1.03, 90% CI 0.97, 1.09) in the AUC of 5-hydroxy saxagliptin. Similar maximum % inhibition and area under the % inhibition-time effect curve over 24 h for DPP-4 activity were observed when saxagliptin was administered alone or with rifampicin. The saxagliptin total active moieties exposure (AUC) decreased by 27% (point estimate 0.73, 90% CI 0.66, 0.81). Saxagliptin with or without rifampicin in this study was generally well tolerated. Lack of change of PD effect of saxagliptin is consistent with the observed 27% reduction in systemic exposure to the total active moieties, which is not considered clinically meaningful. Based on these findings, it is not necessary to adjust the saxagliptin dose when co-administered with rifampicin.

Clinical analysis of drug interaction between rifampicin and clarithromycin which are used for treating pulmonary Mycobacterium avium complex infection

We reviewed the interaction between rifampicin (RFP) and clarithromycin (CAM) during treatment of pulmonary Mycobacterium avium complex infection. The subjects were patients with pulmonary non-tuberculous acid-fast bacillus infection during the period from September 2004 to January 2006 who consented to this study. Drug blood concentrations were compared with the minimum inhibitory concentrations for M. avium isolated from sputum and blood levels of CAM were assessed when the time of administration was changed for RFP. The blood concentration of CAM showed a marked decrease in all cases (n = 6) when administered together with RFP, but there was no significant difference in the blood concentration of 14-R-hydroxy-clarithromycin (M-5), the active metabolite of CAM. However, the total blood concentration of CAM and M-5 showed a significant fall, similar to the blood concentration of CAM alone. When the blood concentration and bacterial MIC were compared for RFP, the blood concentration exceeded five MIC(s) in six samples as did the CAM+M-5 level in four out of six samples. There was no significant difference in the blood concentration of CAM (n = 5) when the time of RFP administration was altered. CONCLUSION; Because the total blood concentration of CAM+M-5 fell markedly by co-administration of RFP, this might have an influence on the antibacterial effect of CAM. In addition, examination of the administration of RFP and CAM at different times showed that the blood concentration of CAM did not increase and the influence of induction of hepatic drug-metabolizing enzymes by RFP could not be avoided.

Pharmacokinetics and Hepatic Uptake of Eltrombopag, a Novel Platelet-Increasing Agent

Eltrombopag (ELT) is a novel thrombopoietin receptor agonist for the treatment of idiopathic thrombocytopenic purpura. Previous reports indicate that ELT is mainly eliminated in the liver, although its pharmacokinetic profile has not yet been clarified in detail. The purpose of the present study is to investigate the overall elimination mechanism of ELT. After intravenous administration of ELT to rats, approximately 40% of unchanged ELT was excreted into the bile in 72 h, whereas less than 0.02% of the dose was excreted in urine, indicating that liver is the major elimination organ for ELT. The total clearance was much lower than the hepatic blood flow rate and comparable with hepatic uptake clearance obtained from integration plot analysis. Coadministration of rifampicin, an organic anion transporter inhibitor, reduced both total clearance and hepatic uptake clearance of ELT. These results suggest that hepatic uptake is the rate-limiting process in the overall elimination of ELT. To further characterize the uptake mechanism, uptake of ELT by freshly isolated mouse hepatocytes was examined. The ELT uptake showed concentration and energy dependence and was inhibited by various compounds, including not only organic anions but also organic cations. Hepatic uptake clearance in vivo was reduced by coadministration of an organic cation, tetrapentylammonium. Finally, uptake of ELT was observed in human embryonic kidney 293 cells transfected with human hepatic transporters organic anion-transporting polypeptide (OATP) 1B1 and OATP2B1 and organic cation transporter OCT1. These results suggest that multiple transporters, including organic anion transporters and organic cation transporters, are involved in hepatic ELT uptake.

In silico prediction of efavirenz and rifampicin drug–drug interaction considering weight and CYP2B6 phenotype

This study aimed to test whether a pharmacokinetic simulation model could extrapolate nonclinical drug data to predict human efavirenz exposure after single and continuous dosing as well as the effects of concomitant rifampicin and further to evaluate the weight-based dosage recommendations used to counteract the rifampicin-efavirenz interaction. Efavirenz pharmacokinetics were simulated using a physiologically based pharmacokinetic model implemented in the Simcyp™ population-based simulator. Physicochemical and metabolism data obtained from the literature were used as input for prediction of pharmacokinetic parameters. The model was used to simulate the effects of rifampicin on efavirenz pharmacokinetics in 400 virtual patients, taking into account bodyweight and CYP2B6 phenotype. Apart from the absorption phase, the simulation model predicted efavirenz concentration-time profiles reasonably well, with close agreement with clinical data. The simulated effects of rifampicin co-administration on efavirenz treatment showed only a minor decrease of 16% (95% confidence interval 13-19) in efavirenz area under the concentration-time curve, of the same magnitude as what has been clinically observed (22%). Efavirenz exposure depended on CYP2B6 phenotype and bodyweight. Increasing the efavirenz dose during concomitant rifampicin was predicted to be most successful in patients over 50 kg regardless of CYP2B6 status. Our findings, although based on a simulation approach using limited in vitro data, support the current recommendations for using a 50 kg bodyweight cut-off for efavirenz dose increment when co-treating with rifampicin.

慢性肺アスペルギルス症に対するイトラコナゾール注射薬と 高用量カプセル薬による維持療法の検討

Itraconazole (ITCZ) is a novel triazole antifungal with a broad spectrum including Aspergillus species. We conducted a three-month open, noncomparative multicenter study of the efficacy and safety of ITCZ injections and high dose capsules in chronic pulmonary aspergillosis. Patients with chronic pulmonary aspergillosis received intravenous injection of ITCZ (200mg) (twice a day for the first two days, then once a day for the following 3-12 days) prior to the oral administration of ITCZ capsules (200mg) twice a day. Radiologic findings by chest CT and clinical symptoms were evaluated at baseline and 12 weeks later. We also measured ITCZ plasma trough concentrations after two weeks and four weeks of the study. Twenty patients were included in the study, among which 14 patients presented with chronic necrotizing pulmonary aspergillosis (CNPA) and 6 presented with pulmonary aspergilloma. The efficacy evaluation was available in 17 patients (CNPA, 12 patients; aspergilloma, 5 patients). Radiological improvement was observed in nine (52.9%, 95%CI: 31.0%-73.8%) patients (CNPA, 7 patients; aspergilloma, 2 patients). One patient with aspergilloma showed deterioration. The clinical symptoms showed significant improvement on expectoration, bloody sputum, and pyrexia. Two patients had to stop treatment with ITCZ because of congestive heart failure. Other adverse effects were reported but did not lead to the discontinuation of treatment, as follows: hepatic dysfunction, two patients; hypokalemia, nine patients. In two patients who combined pulmonary Mycobacterium avium complex disease coadministration of ITCZ and rifampicin was done. Their ITCZ plasma concentrations were extremely low, and one of them was the only deterioration case in the primarily radiologic evaluation. Itraconazole injections and high dose capsules maintenance therapy is effective in treating chronic pulmonary aspergillosis.

Effects of Rifampicin (Rifampin) on the Pharmacokinetics and Safety of Ambrisentan in Healthy Subjects

Ambrisentan is a once-daily, endothelin (ET) type A receptor-selective antagonist approved for the treatment of pulmonary arterial hypertension. Ambrisentan is primarily metabolized by glucuronidation and undergoes cytochrome P450 (CYP)-mediated oxidation to a lesser extent. To assess the effects of rifampicin (rifampin), a potent inducer of CYP3A4 and inhibitor of organic anion transporter polypeptides (OATPs), on the steady-state pharmacokinetics, safety and tolerability of ambrisentan. This was a 14-day, single-sequence, open-label study that was conducted in 24 healthy adults. Subjects were administered oral doses of ambrisentan (10 mg) once daily on days 1 through 5 and were then co-administered ambrisentan (10 mg) plus rifampicin (600 mg) once daily on days 6 through 13. The steady-state pharmacokinetics of ambrisentan and its oxidative metabolite 4-hydroxymethyl ambrisentan were determined in the absence and presence of repeated administration of rifampicin. The main outcome measure was the analysis of ambrisentan pharmacokinetics (area under the plasma concentration-time curve during a dosage interval [AUC(τ)], maximum plasma drug concentration [C(max)] and minimum plasma drug concentration [C(min)]) for steady-state ambrisentan alone (day 5) as compared with steady-state ambrisentan plus steady-state rifampicin (day 13). Adverse events (AEs), ECG recordings, vital signs and clinical laboratory parameters were monitored throughout the study and at follow-up. A transient increase (+87% [95% CI 79, 95]) in ambrisentan steady-state systemic exposure (AUC(τ)) was observed during the first 2 days of rifampicin co-administration. However, in the presence of steady-state rifampicin, ambrisentan C(max) and AUC(τ) values were similar (+2% [95% CI -7, 12] and -4% [-9, 2], respectively) to those observed for ambrisentan alone. Relative systemic exposure of 4-hydroxymethyl ambrisentan was unaffected by either acute or steady-state rifampicin. No serious AEs or AEs leading to withdrawal were reported and there were no clinically significant changes in vital signs, ECG recordings or clinical laboratory parameters with co-administration of ambrisentan and rifampicin. Steady-state rifampicin had no clinically relevant effects on the steady-state pharmacokinetics of ambrisentan. The overall safety profile of ambrisentan was similar in the presence and absence of rifampicin. No dose adjustment of ambrisentan should be required when it is co-administered with rifampicin, a strong inducer of CYP3A4 activity and inhibitor of OATPs.

Effect of the Cytochrome P450 3A4 Inducers, Rifampicin and Dexamethasone, on the Pharmacokinetic, Pharmacodynamic and Safety Profile of Bortezomib In Patients with Multiple Myeloma (MM) and Non-Hodgkin's Lymphoma (NHL)

AbstractAbstract 3983Background: Bortezomib is primarily metabolized by cytochrome P450 (CYP) 3A4 and 2C19 enzymes. Effects of co-administration of rifampicin (a potent CYP3A4 inducer) and dexamethasone (weak CYP3A4 inducer) on the pharmacokinetic (PK), pharmacodynamic (PD) and safety profiles of bortezomib were evaluated. Methods: Patients with relapsed or refractory multiple myeloma (MM) or non-Hodgkin's lymphoma (NHL) were enrolled in this open-label, 2-stage, parallel-group study. In stage 1, patients were randomized (1:1) to receive 3 cycles of bortezomib (1.3 mg/m2) on d 1, 4, 8, and 11 q3wk either alone or in combination with rifampicin 600 mg once-daily on d 4 to 10 of cycle 3 only. Stage 2 patients received bortezomib at same dose and schedule in combination with dexamethasone 40 mg once-daily on d 1 to 4 and d 9 to 12 of cycle 3 only. Patients could continue with bortezomib monotherapy for up to 10 cycles in case of clinical benefit. For PK/PD, blood samples were collected before and through 72 hours following bortezomib administration on d 11 of cycles 2 and 3. PK was the primary endpoint, secondary endpoints included PD (proteasome inhibition) and safety. Results: 61 patients were enrolled (39 MM, 22 NHL) in the study. 13 were treated with bortezomib + rifampicin, 18 with bortezomib + dexamethasone, and 30 with bortezomib only. Co-administration of rifampicin reduced the mean bortezomib maximum plasma concentration (Cmax) by approximately 23% (118 vs 93 ng/mL) and the mean area under plasma concentration-time curve from 0 to 72 hours (AUC72) by approximately 45% (223 vs 123 ng.h/mL). Co-administration of dexamethasone had no effect on mean AUC72 (179 vs 170 ng.h/mL). The mean bortezomib Cmax was 20% lower after co-administration of dexamethasone (140 vs 119 ng/mL); however this difference in Cmax was within the observed variability in Cmax during cycle 2 (CV=38%) and cycle 3 (CV=45%). Mean (SD) maximum percent proteasome inhibition (Emax) and area under percent proteasome inhibition-time curve from 0 to 72 hours (AUE72h) were comparable for bortezomib alone and in combination with rifampicin (Emax: 61.9 [4.56] vs. 62.3 [3.81] and AUE72h: 836 [323] vs. 777 [358]). Co-administration of dexamethasone did not affect the Emax (66.7 [4.27] vs. 61.8 [6.69]) or AUE72h (1329 [638] vs. 1157 [381]). Safety profiles were consistent with prior bortezomib experience in this population. Drug-related serious adverse events and treatment discontinuations were reported in 7/30 (23%) and 8/30 (27%) in bortezomib-only, in 3/13 (23%) and 3/13 (23%) in bortezomib + rifampicin, and 3/18 (17%) and 5/18 (28%) in bortezomib + dexamethasone subgroups. Investigator-assessed responses (CR+PR) were observed in 13/17 MM and 6/13 NHL patients in bortezomib-only, in 6/9 MM and 3/4 NHL patients in bortezomib + rifampicin, and in 10/13 MM and 2/5 NHL patients in bortezomib + dexamethasone subgroups. Conclusions: Co-administration of dexamethasone did not affect the PK or PD profiles of bortezomib. Co-administration of rifampicin reduced bortezomib exposure (AUC) by approximately 45%. Patients receiving bortezomib concomitantly with strong CYP3A4 inducers, such as rifampicin, should be monitored for reduction in clinical effect, while concomitant administration of weak CYP3A4 inducers, such as dexamethasone, is not expected to affect the bortezomib pharmacologic profile. Disclosures:Off Label Use: Discussion of Velcade in NHL subtypes other than mantle cell lymphoma is included. Rule:Johnson & Johson: Consultancy, Speakers Bureau; Roche: Consultancy. Walewski:Johnson & Johnson: Honoraria, Research Funding; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen-Cilag: Investigators fee. Shpilberg:Johnson & Johnson: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Feng:Johnson & Johnson: Employment. van de Velde:Johnson & Johnson: Employment, Equity Ownership. Patel:Johnson & Johnson: Employment, Equity Ownership. Skee:Johnson & Johnson: Employment. Girgis:Johnson & Johnson: Employment. Louw:Janssen-Cilag: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Key Oncologics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers-Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees.

Protective effect of vitamin C and or vitamin E on micronuclei induction by rifampicin in mice

Rifampicin which is a known antituberculous agent has been reported to induce both chromosomal breakage and numerical chromosomal abnormalities. This study was carried out to determine the mutagenicity of rifampicin and more importantly to investigate the protective roles of antioxidants-vitamin C and E individually and in-combination therapy against rifampicin mutagenicity using micronucleus assay. Therapeutic concentrations of rifampicin alone (9mg/kg), rifampicin plus vitamin E (5mg/kg), rifampicin plus vitamin C (8mg/kg) and rifampicin plus vitamin C plus vitamin E were administered orally for 28 consecutive days using 6 mice in each group. The negative and positive control mice received same volume of distilled water and cyclophosphamide (40 mg/kg) intraperitoneally 6 hours before sacrifice, respectively. The results showed rifampicin alone treated group to demonstrate significant ( P P ≤0.05) in the proportion of MPCE to PCE was demonstrated in the rifampicin plus vitamin E; rifampicin plus vitamin C plus E and rifampicin plus vitamin C groups compared with cyclophosphamide treated group and rifampicin treated group. These findings suggest that rifampicin has damaging effects on the deoxyribonucleic acid (DNA). However, co-administration of rifampicin and antioxidants (vitamin C and E) has protective effect on the damaging potentials of rifampicin.

Lopinavir Exposure is Insufficient in Children Given Double Doses of Lopinavir/Ritonavir during Rifampicin-Based Treatment for Tuberculosis

Coadministration of rifampicin dramatically reduces the concentrations of protease inhibitors. A pharmacokinetic study in healthy adults showed that doubling the dose of coformulated lopinavir/ritonavir was able to overcome the inducing effect of rifampicin. We evaluated this strategy in children treated with rifampicin-based antituberculosis therapy attending antiretroviral clinics in South Africa. Plasma concentrations of lopinavir were measured in children (aged 0.64-2.43 years) established on antituberculosis treatment who commenced antiretroviral therapy comprising double the usual recommended dose of lopinavir/ritonavir oral solution (460/115 mg/m(2) twice daily) plus two nucleoside reverse transcriptase inhibitors. Control children (0.57-4.23 years old) without tuberculosis received standard doses of lopinavir/ritonavir (230/57.5 mg/m(2) twice daily). Pre-dose lopinavir concentrations were reduced by >80% in children with tuberculosis (median 0.7 mg/l, IQR 0.1-2.0) compared with controls (4.2 mg/l, IQR 3.4-8.1; P<0.001) and were below the minimum recommended concentration of 1 mg/l in 12 of 20 (60%) children with tuberculosis versus 2 of 24 (8%) controls (P<0.001). Double doses of coformulated lopinavir/ritonavir results in inadequate lopinavir concentrations in young children treated concurrently with rifampicin. Suitable regimens are urgently needed for treating young children with HIV-associated tuberculosis.

Effects of CYP2B6 G516T polymorphisms on plasma efavirenz and nevirapine levels when co-administered with rifampicin in HIV/TB co-infected Thai adults

BackgroundCytochrome P450 2B6 (CYP2B6) metabolizes efavirenz and nevirapine, the major core antiretroviral drugs for HIV in Thailand. Rifampicin, a critical component of tuberculosis (TB) therapy is a potent inducer of CYP enzyme activity. Polymorphisms of CYP2B6 and CYP3A4 are associated with altered activity of hepatic enzyme in the liver and pharmacokinetics resulting in treatment efficacy. This study aimed to investigate whether CYP2B6 or CYP3A4 polymorphisms had effects on plasma efavirenz and nevirapine concentrations when co-administered with rifampicin in HIV/TB co-infected Thai adults.ResultsWe studied 124 rifampicin recipients with concurrent HIV-1/TB coinfection, receiving efavirenz (600 mg/day) (n = 65) or nevirapine (400 mg/day) (n = 59) based antiretroviral therapy (ART). The frequencies of GG, GT and TT genotypes of CYP2B6-G516T were 38.46%, 47.69% and 13.85% in efavirenz group and 44.07%, 52.54% and 3.39% in nevirapine group, respectively. The mean 12-hour post-dose plasma efavirenz concentration in patients with TT genotype at weeks 6 and 12 of ART and 1 month after rifampicin discontinuation (10.97 ± 2.32, 13.62 ± 4.21 and 8.48 ± 1.30 mg/L, respectively) were significantly higher than those with GT (3.43 ± 0.29, 3.35 ± 0.27 and 3.21 ± 0.22 mg/L, respectively) (p < 0.0001) or GG genotypes (2.88 ± 0.33, 2.45 ± 0.26 and 2.08 ± 0.16 mg/L, respectively) (p < 0.0001). Likewise, the mean 12-hour post-dose plasma nevirapine concentration in patients carrying TT genotype at weeks 6 and 12 of ART and 1 month after rifampicin discontinuation (14.09 ± 9.49, 7.94 ± 2.76 and 9.44 ± 0.17 mg/L, respectively) tended to be higher than those carrying GT (5.65 ± 0.54, 5.58 ± 0.48 and 7.03 ± 0.64 mg/L, respectively) or GG genotypes (5.42 ± 0.48, 5.34 ± 0.50 and 6.43 ± 0.64 mg/L, respectively) (p = 0.003, p = 0.409 and p = 0.448, respectively). Compared with the effects of CYP2B6-516TT genotype, we could observe only small effects of rifampicin on plasma efavirenz and nevirapine levels. After 12 weeks of both drug regimens, there was a trend towards higher percentage of patients with CYP2B6-TT genotype who achieved HIV-1 RNA levels <50 copies/mL compared to those with GT or GG genotypes. This is the first report to demonstrate the effects of CYP2B6 G516T polymorphisms on plasma efavirenz and nevirapine concentrations when co-administered with rifampicin in HIV/TB co-infected Thai adults.ConclusionsCYP2B6-TT genotype had impact on plasma efavirenz and nevirapine concentrations, while rifampicin co-administration had only small effects.

The effects of ketoconazole and rifampicin on the pharmacokinetics of mirodenafil in healthy Korean male volunteers: An open-label, one-sequence, three-period, three-treatment crossover study

Background: Mirodenafil, a phosphodiesterase 5 inhibitor reported to be effective in the treatment of erectile dysfunction, is metabolized by cytochrome P450 (CYP) 3A4 to the active metabolite N-dehydroxyethyl mirodenafil. Mirodenafil may have drug-drug interactions with ketoconazole and/or rifampicin. Objective: The aim of this study was to investigate the effects of a potent inhibitor (ketoconazole) and inducer (rifampicin) of the CYP3A4 isozyme on the pharmacokinetics of mirodenafil to meet the regulatory requirements for the marketing of mirodenafil in Korea. Methods: An open-label, 1-sequence, 3-period, 3-treatment crossover study was conducted over 22 days in healthy Korean male volunteers. Each subject received 100 mg of mirodenafil in each of 3 study periods: mirodenafil alone (period 1); mirodenafil after pretreatment with ketoconazole 400 mg once daily for 3 days (period 2); and mirodenafil after pretreatment with rifampicin 600 mg once daily for 10 days (period 3). Serial blood samples were collected for pharmacokinetic analysis after the administration of mirodenafil in each study period. Plasma concentration-time data for mirodenafil and its major metabolite, N-dehydroxyethyl mirodenafil, were determined using LC-MS/MS and analyzed by a noncompartmental method. The results for mirodenafil coadministration with either ketoconazole or rifampicin were compared with those for mirodenafil alone. Adverse events (AEs) were identified by asking general health-related questions of the subjects, by physical examination, and by subject self-report throughout the study period. Results: Nineteen subjects were enrolled (mean [SD] age, 23.2 [2.76] years [range, 19–29 years]; weight, 69.3 [6.50] kg [range, 61.0–84.0 kg]; body mass index, 22.4 [1.77] kg/m 2 [range, 20.0–26.0 kg/m 2]) and 18 subjects completed the study. One subject discontinued the study due to protocol violation and was replaced. The AUC 0−∞) of mirodenafil increased 5.04-fold (90% CI, 3.78–6.72) and the metabolic ratio decreased 0.21-fold after pretreatment with ketoconazole compared with mirodenafil alone. After pretreatment with rifampicin, the AUC0-X) of mirodenafil decreased 0.03-fold (90% CI, 0.02–0.05) and the metabolic ratio increased 2.9-fold. Twelve cases of headache, 6 of nasal congestion, 2 of feeling hot, 2 of epistaxis, and 1 each of dizziness, nausea, and somnolence were considered to be related to administration of mirodenafil. Twenty-eight AEs were reported in period 2 (in 68.4% of subjects), during which systemic exposure to mirodenafil was highest, whereas 7 AEs were reported in period 1 (in 31.6% of subjects) and 5 AEs in period 3 (in 16.7% of subjects). Conclusion: In these healthy Korean male volunteers, the coadministration of ketoconazole and rifampicin resulted in significant changes in systemic exposure to mirodenafil.

Effects of rifampicin on the pharmacokinetics of roflumilast and roflumilast N‐oxide in healthy subjects

To evaluate the effect of co-administration of rifampicin, an inducer of cytochrome P450 (CYP)3A4, on the pharmacokinetics of roflumilast and roflumilast N-oxide. Roflumilast is an oral, once-daily phosphodiesterase 4 (PDE4) inhibitor, being developed for the treatment of chronic obstructive pulmonary disease. Roflumilast is metabolized by CYP3A4 and CYP1A2, with further involvement of CYP2C19 and extrahepatic CYP1A1. In vivo, roflumilast N-oxide contributes >90% to the total PDE4 inhibitory activity. Sixteen healthy male subjects were enrolled in an open-label, three-period, fixed-sequence study. They received a single oral dose of roflumilast 500 microg on days 1 and 12 and repeated oral doses of rifampicin 600 mg once daily on days 5-15. Plasma concentrations of roflumilast and roflumilast N-oxide were measured for up to 96 h. Test/Reference ratios and 90% confidence intervals (CIs) of geometric means for AUC and C(max) of roflumilast and roflumilast N-oxide and for oral apparent clearance (CL/F) of roflumilast were estimated. During the steady-state of rifampicin, the AUC(0-infinity) of roflumilast decreased by 80% (point estimate 0.21; 90% CI 0.16, 0.27); C(max) by 68% (0.32; CI 0.26, 0.39); for roflumilast N-oxide, the AUC(0-infinity) decreased by 56% (0.44; CI 0.36, 0.55); C(max) increased by 30% (1.30; 1.15, 1.48); total PDE4 inhibitory activity decreased by 58% (0.42; 0.38, 0.48). Co-administration of rifampicin and roflumilast led to a reduction in total PDE4 inhibitory activity of roflumilast by about 58%. The use of potent cytochrome P450 inducers may reduce the therapeutic effect of roflumilast.

LC–MS/TOF and UHPLC–MS/MS study of in vivo fate of rifamycin isonicotinyl hydrazone formed on oral co-administration of rifampicin and isoniazid

The formation and fate of 3-formylrifamycin isonicotinyl hydrazone (HYD) was investigated following oral co-administration of rifampicin (RIF) and isoniazid (INH) in Sprague–Dawley (SD) rats ( n = 5) using advanced analytical modalities. The study was carried out with 20 and 5 mg/kg doses of RIF and INH, respectively. The plasma, urine and faeces samples were collected at different time points up to 48 h, which were qualitatively and quantitatively evaluated for the presence of HYD after proper sample preparation. For the same, initially liquid chromatography–mass spectrometry/time-of-flight (LC–MS/TOF) method was developed in electrospray ionization (ESI) positive mode, wherein separation was achieved on a C18 column (4.6 mm × 250 mm, 5 μm), using a volatile mobile phase in a gradient mode. The presence of HYD was confirmed by accurate mass study, spiking with the standard and UV–visible spectra matching. For quantitative evaluation of HYD, a selective and sensitive ultra high-performance liquid chromatography tandem mass spectrometry (UHPLC–MS/MS) method was developed for all the three matrices. In this case, elution of HYD was achieved on a small C18 column (4.6 mm × 50 mm, 1.8 μm) using a short gradient method. The quantitation was done by selective reaction monitoring (SRM) in ESI positive mode. The validation parameters like linearity, accuracy, precision, selectivity, matrix effect, recovery and stability were assessed as per regulatory guidelines. The calibration range was established between 1 and 200 ng/ml, with r 2 > 0.99 in all the cases. The back calculated values for three quality control (QC) samples, and at lower limit of quantitation (LLOQ) were within 15 and 20%, respectively, of the nominal values. Similarly, the intra- and inter-day precisions were found within 15% at the four tested levels. The HYD was found to be stable for the duration of sample preparation and analysis in the controlled experimental conditions. The analysis of in vivo samples showed a significant extent of HYD in faeces, however, the interaction product was not found in plasma and urine. To verify the results, 5 mg/kg oral dose of HYD standard was given to rats separately, and its presence was studied in all the three matrices. Further, in vitro plasma stability of HYD was also carried out to explain its absence in plasma and urine, which showed ∼55% disappearance of HYD in 2 h.

Effects of a concomitant single oral dose of rifampicin on the pharmacokinetics of pravastatin in a two-phase, randomized, single-blind, placebo-controlled, crossover study in healthy Chinese male subjects

Background: Pravastatin is a potent cholesterol-lowering agent; ~34% of an oral dose of pravastatin is eliminated unchanged through biliary and urinary excretion. Rifampicin is an inducer of drug metabolism enzymes, and it affects the activities of transporters involved in pravastatin disposition. Drug-drug interaction between rifampicin and pravastatin is possible because of the effects of rifampicin on the activities of drug transporters. Objective: This study was designed to investigate the effects of a single oral dose of rifampicin on the pharmacokinetics of pravastatin. Methods: Healthy Chinese male volunteers were recruited for this 2-phase, single-blind, placebo-controlled, crossover study. The subjects were randomly divided into 2 groups to receive either rifam-picin or placebo concomitantly with pravastatin. All subjects received a 20-mg oral dose of pravastatin on days 1 and 9, separated by an 8-day washout period. Subjects in the rifampicin group received a single 600-mg oral dose of rifampicin on day 1 and placebo on day 9; those in the placebo group received placebo on day 1 and a single 600-mg oral dose of rifampicin on day 9. High-performance liquid chromatography-tandem mass spectrometry was used to determine plasma concentrations of pravastatin for up to 12 hours after administration. Results: Twelve volunteers participated in the study (6 per group). The mean (SD) age of the subjects was 20 (2) years (range, 18–25 years). The mean height of the subjects was 174 (4) cm (range, 168–180 cm), and the mean weight was 69.2 (3.7) kg (range, 65–77 kg). The mean pharmacokinetic parameters for pravastatin that changed significantly were as follows (rifampicin and placebo groups, respectively): C max (315.7 [227.2] and 115.8 [77.5] ng · mL −1 [ P = 0.009]); AUC 0–12 (604.8 [73.3] and 259.0 [133.4] ng · h · mL −1 [ P < 0.001]); AUC 0–∞) (623.3 [248.8] and 275.1 [58.5] ng · h · mL −1 [ P < 0.001]); and apparent oral clearance (CL/F) (0.52 [0.18] and 1.30 [0.58] L · h −1 · kg −1 [ P < 0.001]). No significant changes in the T max or t ½ of pravastatin were observed. All subjects tolerated pravastatin well during both phases of the study, with or without coadministration of rifampicin. None of the subjects withdrew from the study. Conclusion: Coadministration of a single oral dose of rifampicin significantly increased the plasma concentration of pravastatin in this group of healthy Chinese male subjects.