Doses Of Rifampin Research Articles

125. Dynamic PET facilitated Pharmacokinetic Modeling and High-dose Rifampin Regimens for Staphylococcus aureus Orthopedic Implant Associated Infections: Bench to Bedside

125. Dynamic PET facilitated Pharmacokinetic Modeling and High-dose Rifampin Regimens for <i>Staphylococcus aureus</i> Orthopedic Implant Associated Infections: Bench to Bedside

Pharmacodynamic biomarkers for quantifying the mycobacterial effect of high doses of rifampin in patients with rifampin-susceptible pulmonary tuberculosis.

BackgroundSuboptimal drug exposure in patients with drug-susceptible tuberculosis (DS-TB) can drive treatment failure. Pharmacodynamics (PD) biomarkers such as the plasma TB drug-activity (TDA) assay may guide dose finding studies and predict microbiological outcomes differently than conventional indices.MethodsA study was nested from phase 2b randomized double-blind controlled trial of Tanzanian patients who received a 600 mg, 900 mg, or 1200 mg with a standard dose for DS-TB. Serum at 6 weeks collected over 24-h at 2-h intervals was collected for rifampin area under the concentration–time curve relative to minimum inhibitory concentration (AUC0-24/MIC) or peak concentration and MIC (Cmax/MIC). TDA was the ratio of time-to-positive growth of the patient’s Mycobacterium tuberculosis isolates with and without coculture of patient’s plasma collected at Cmax. Spearman’s rank correlation (r) between PD parameters and culture convention on both liquid and solid culture media.ResultsAmong 10 patients, 600 mg (3), 900 mg (3), and 1200 mg (4) of rifampin dosages. The mean ± standard deviation (SD) of AUC0-24/MIC for patients on 600 mg was 168 ± 159 mg·h/L, on 900 mg was 169 ± 166 mg·h/L, and on 1200 mg was 308 ± 238 mg·h/L. The mean-TDA (SD) was 2.56 (±0.75), 1.5 (±0.59), and 2.29 (±1.08) for patients on 600 mg, 900 mg, and 1200 mg rifampin doses, respectively. Higher TDA values correlated with faster time to culture convention on both liquid (r =–0.55, P = 0.099) and solid media (r =–0.65, P = 0.04).ConclusionsTDA and rifampin AUC0-24/MIC did not trend as expected with rifampin dose, but TDA better predicted the time to sputum culture conversion. TDA may provide additional discrimination in predicting treatment response for some regimens distinct from plasma exposure relative to MIC or mg/kg dose.

Population Pharmacokinetics and Significant Under-Dosing of Anti-Tuberculosis Medications in People with HIV and Critical Illness

Critical illness from tuberculosis (TB) bloodstream infection results in a high case fatality rate for people living with human immunodeficiency virus (HIV). Critical illness can lead to altered pharmacokinetics and suboptimal drug exposures. We enrolled adults living with HIV and hospitalized with sepsis, with and without meningitis, in Mbarara, Uganda that were starting first-line anti-TB therapy. Serum was collected two weeks after enrollment at 1-, 2-, 4-, and 6-h post-dose and drug concentrations quantified by validated LC-MS/MS methods. Non-compartmental analyses were used to determine total drug exposure, and population pharmacokinetic modeling and simulations were performed to determine optimal dosages. Eighty-one participants were enrolled. Forty-nine completed pharmacokinetic testing: 18 (22%) died prior to testing, 13 (16%) were lost to follow-up and one had incomplete testing. Isoniazid had the lowest serum attainment, with only 4.1% achieving a target exposure over 24 h (AUC0–24) of 52 mg·h/L despite appropriate weight-based dosing. Simulations to reach target AUC0–24 found necessary doses of rifampin of 1800 mg, pyrazinamide of 2500–3000 mg, and for isoniazid 900 mg or higher. Given the high case fatality ratio of TB-related critical illness in this population, an early higher dose anti-TB therapy should be trialed.

Pharmacokinetics of oral antimycobacterials and dosing guidance for Mycobacterium avium complex treatment in cystic fibrosis

BackgroundTreatment failure of Mycobacterium avium complex (MAC) pulmonary disease occurs in about 30% of people with cystic fibrosis (CF) and may be a result of abnormal drug concentrations. MethodsProspective, cross-over, single-dose PK study of 20 pancreatic insufficient individuals with CF and 10 healthy controls (HC). CF subjects received simultaneous doses of oral azithromycin, ethambutol, and rifampin in the fasting state and with food and pancreatic enzymes, separated by two weeks. HC received fasting doses only. A non-compartmental model was used to estimate PK parameters of drugs and metabolites. ResultsAzithromycin maximum concentration (Cmax ) was higher and rifampin Cmax was lower in fasting CF subjects compared to HC, while other PK measures, including those for ethambutol, were similar. Addition of food and enzymes did not improve the Cmax of the antimycobacterial drugs. Nineteen of 20 CF subjects had one or more abnormal Cmax z-scores in either the fasting or fed state (or both), when compared to HC. ConclusionPK profiles of azithromycin and ethambutol were similar between CF and HC, except azithromycin Cmax was slightly higher in people with CF after a single dose. Rifampin PK parameters were altered in persons with CF. Addition of food and enzymes in CF subjects did not improve PK parameters. Standard dosing guidelines should be used as a starting point for people with CF initiating MAC therapy and therapeutic drug monitoring should be routinely performed to prevent the possibility of treatment failure due to abnormal drug concentrations. Clinical trial registrationClinicalTrials.gov Identifier: NCT02372383Prior abstract publication:1. Martiniano S, Wagner B, Brennan L, Wempe M, Anderson P, Nick J, Sagel S. Pharmacokinetics of oral MAC antibiotics in cystic fibrosis. Am J Resp Crit Care Med A4842-A4842, 2017.2. Martiniano SL, Wagner BD, Brennan L, Wempe MF, Anderson PL, Nick JA, Sagel SD. Pharmacokinetics of oral MAC antibiotics in cystic fibrosis. J Cyst Fibros 16: S52–53, 2017.

Liver Toxicity Observed With Lorlatinib When Combined With Strong CYP3A Inducers: Evaluation of Cynomolgus Monkey as a Nonclinical Model for Assessing the Mechanism of Combinational Toxicity.

Lorlatinib is a potent small-molecule anaplastic lymphoma kinase inhibitor approved for the treatment of patients with nonsmall cell lung cancer. In a drug-drug interaction study in healthy human participants, liver enzyme elevations were observed when a single 100 mg dose of lorlatinib was administered after multiple doses of rifampin, a strong cytochrome P450 (CYP) 3A inducer and a pregnane X receptor (PXR) agonist. A series of in vitro and in vivo studies were conducted to evaluate potential mechanisms for the observed clinical toxicity. To investigate the involvement of CYP3A and/or PXR in the observed liver toxicity, studies were conducted in cynomolgus monkeys administered lorlatinib alone or with coadministration of multiple doses of known CYP3A inducers that are predominantly PXR agonists (rifampin, St. John's wort) or predominantly constitutive androstane receptor agonists (carbamazepine, phenytoin) and a net CYP3A inhibitory PXR agonist (ritonavir). Results from the investigative studies identified cynomolgus monkeys as a pharmacologically relevant nonclinical model, which recapitulated the elevated liver function test results observed in humans. Furthermore, liver toxicity was only observed in this model when lorlatinib was coadministered with strong CYP3A inducers, and the effects were not restricted to, or exclusively dependent upon, a PXR activation mechanism. These results generated mechanistic insights on the liver enzyme elevations observed in the clinical drug-drug interaction study and provided guidance on appropriate product safety label for lorlatinib.

If, When, and How to Use Rifampin in Acute Staphylococcal Periprosthetic Joint Infections, a Multicentre Observational Study.

BackgroundRifampin is generally advised in the treatment of acute staphylococcal periprosthetic joint infections (PJI). However, if, when, and how to use rifampin remains a matter of debate. We evaluated the outcome of patients treated with and without rifampin, and analyzed the influence of timing, dose and co-antibiotic.MethodsAcute staphylococcal PJIs treated with surgical debridement between 1999 and 2017, and a minimal follow-up of 1 year were evaluated. Treatment failure was defined as the need for any further surgical procedure related to infection, PJI-related death or the need for suppressive antimicrobial treatment.ResultsA total of 669 patients were analyzed. Treatment failure was 32.2% (131/407) in patients treated with rifampin and 54.2% (142/262) in whom rifampin was withheld (P < .001). The most prominent effect of rifampin was observed in knees (treatment failure 28.6% versus 63.9%, respectively, P < .001). The use of rifampin was an independent predictor of treatment success in the multi-variate analysis (OR 0.30, 95% CI 0.20 – 0.45). In the rifampin group, the use of a co-antibiotic other than a fluoroquinolone or clindamycin (OR 10.1, 95% CI 5.65 – 18.2) and the start of rifampin within 5 days after surgical debridement (OR 1.96, 95% CI 1.08 – 3.65) were predictors of treatment failure. The dosing of rifampin had no effect on outcome.ConclusionsOur data supports the use of rifampin in acute staphylococcal PJIs treated with surgical debridement, particularly in knees. Immediate start of rifampin after surgical debridement should probably be discouraged, but requires further investigation.

The Development and Validation of a Novel "Dual Cocktail" Probe for Cytochrome P450s and Transporter Functions to Evaluate Pharmacokinetic Drug-Drug and Herb-Drug Interactions.

This study was designed to develop and validate a 10 probe drug cocktail named “Dual Cocktail”, composed of caffeine (Cyp1a2 in rat and CYP1A2 in human, 1 mg/kg), diclofenac (Cyp2c11 in rat and CYP2C9 in human, 2 mg/kg), omeprazole (Cyp2c11 in rat and CYP2C19 in human, 2 mg/kg), dextromethorphan (Cyp2d2 in rat and CYP2D6 in human, 10 mg/kg), nifedipine (Cyp3a1 in rat and CYP3A4 in human, 0.5 mg/kg), metformin (Oct1/2 in rat and OCT1/2 in human, 0.5 mg/kg), furosemide (Oat1/3 in rat and OAT1/3 in human, 0.1 mg/kg), valsartan (Oatp2 in rat and OATP1B1/1B3 in human, 0.2 mg/kg), digoxin (P-gp in rat and human, 2 mg/kg), and methotrexate (Mrp2 in rat and MRP2 in human, 0.5 mg/kg), for the evaluation of pharmacokinetic drug–drug and herb-drug interactions through the modulation of a representative panel of CYP enzymes or transporters in rats. To ensure no interaction among the ten probe substrates, we developed a 2-step evaluation protocol. In the first step, the pharmacokinetic properties of five individual CYP probe substrates and five individual transporter substrates were compared with the pharmacokinetics of five CYP cocktail or five transporters cocktails in two groups of randomly assigned rats. Next, a pharmacokinetic comparison was conducted between the CYP or transporter cocktail group and the dual cocktail group, respectively. None of the ten comparison groups was found to be statistically significant, indicating the CYP and transporter substrate sets or dual cocktail set could be concomitantly administered in rats. The “Dual Cocktail” was further validated by assessing the metabolism of nifedipine and omeprazole, which was significantly reduced by a single oral dose of ketoconazole (10 mg/kg); however, no changes were observed in the pharmacokinetic parameters of other probe substrates. Additionally, multiple oral doses of rifampin (20 mg/kg) reduced the plasma concentrations of nifedipine and digoxin, although not any of the other substrates. In conclusion, the dual cocktail can be used to characterize potential pharmacokinetic drug–drug interactions by simultaneously monitoring the activity of multiple CYP isoforms and transporters.

Post-exposure prophylaxis (PEP) efficacy of rifampin, rifapentine, moxifloxacin, minocycline, and clarithromycin in a susceptible-subclinical model of leprosy.

BackgroundSubclinical infection with Mycobacterium leprae is one potential source of leprosy transmission, and post-exposure prophylaxis (PEP) regimens have been proposed to control this source. Because PEP trials require considerable investment, we applied a sensitive variation of the kinetic mouse footpad (MFP) screening assay to aid in the choice of drugs and regimens for clinical trials.Methodology/Principal findingsAthymic nude mice were inoculated in the footpad (FP) with 6 x 103 viable M. leprae and treated by gastric gavage with a single dose of Rifampin (SDR), Rifampin + Ofloxacin + Minocycline (SD-ROM), or Rifapentine + Minocycline + Moxifloxacin (SD-PMM) or with the proposed PEP++ regimen of three once-monthly doses of Rifampin + Moxifloxacin (RM), Rifampin + Clarithromycin (RC), Rifapentine + Moxifloxacin (PM), or Rifapentine + Clarithromycin (PC). At various times post-treatment, DNA was purified from the FP, and M. leprae were enumerated by RLEP quantitative PCR. A regression analysis was calculated to determine the expected RLEP value if 99.9% of the bacilli were killed after the administration of each regimen. SDR and SD-ROM induced little growth delay in this highly susceptible murine model of subclinical infection. In contrast, SD-PMM delayed measurable M. leprae growth above the inoculum by 8 months. The four multi-dose regimens delayed bacterial growth for >9months post-treatment cessation.Conclusions/SignificanceThe delay in discernable M. leprae growth post-treatment was an excellent indicator of drug efficacy for both early (3–4 months) and late (8–9 months) drug efficacy. Our data indicates that multi-dose PEP may be required to control infection in highly susceptible individuals with subclinical leprosy to prevent disease and decrease transmission.

Single-Dose Pharmacokinetics of Ozanimod and its Major Active Metabolites Alone and in Combination with Gemfibrozil, Itraconazole, or Rifampin in Healthy Subjects: A Randomized, Parallel-Group, Open-Label Study.

The aims of this study were to characterize the single-dose pharmacokinetics (PK) of the major active metabolites of ozanimod, CC112273 and CC1084037, and to evaluate the effect of gemfibrozil (a strong inhibitor of cytochrome P450 [CYP] 2C8), itraconazole (a strong inhibitor of CYP3A and P-glycoprotein [P-gp]), and rifampin (a strong inducer of CYP3A/P-gp and moderate inducer of CYP2C8) on the single-dose PK of ozanimod and its major active metabolites in healthy subjects. This was a phase1, randomized, parallel-group, open-label study with two parts. In part1, 40 subjects were randomized to receive a single oral dose of ozanimod 0.46mg (groupA, n = 20) or oral doses of gemfibrozil 600mg twice daily for 17days with a single oral dose of ozanimod 0.46mg on day4 (groupB, n = 20). In part2, 60 subjects were randomized to receive a single oral dose of ozanimod 0.92mg (groupC, n = 20), oral doses of itraconazole 200mg once daily for 17days with a single oral dose of ozanimod 0.92mg on day4 (groupD, n = 20), or oral doses of rifampin 600mg once daily for 21days with a single oral dose of ozanimod 0.92mg on day8 (groupE, n = 20). Plasma PK parameters for ozanimod, CC112273, and CC1084037 were estimated using noncompartmental methods. Dose-proportional increases in maximum observed concentration (Cmax) and area under the concentration-time curve (AUC) were observed for ozanimod, CC112273, and CC1084037. The mean terminal elimination half-life (t1/2) for ozanimod was approximately 20-22h while the mean t1/2 for CC112273 and CC1084037 were approximately 10days. CC112273 and CC1084037 exposures were highly correlated with or without interacting drugs. Itraconazole increased ozanimod AUC by approximately 13% while rifampin reduced ozanimod AUC by approximately 24%, suggesting a minor role of CYP3A and P-gp in the overall disposition of ozanimod. Gemfibrozil increased the AUC for CC112273 and CC1084037 by approximately 47% and 69%, respectively. Rifampin reduced the AUC for CC112273 and CC1084037, primarily via CYP2C8 induction, by approximately 60% and 55%, respectively. Ozanimod's major active metabolites, CC112273 and CC1084037, exhibited similar single-dose PK properties and their exposures were highly correlated. CYP2C8 is one of the important enzymes in the overall disposition of CC112273 and subsequently its direct metabolite CC1084037. Clinical trial: NCT03624959.

Absence of OATP1B (Organic Anion-Transporting Polypeptide) Induction by Rifampin in Cynomolgus Monkeys: Determination Using the Endogenous OATP1B Marker Coproporphyrin and Tissue Gene Expression.

Organic anion-transporting polypeptide (OATP) 1B induction is an evolving mechanism of drug disposition and interaction. However, there are contradictory reports describing OATP1B expression in hepatocytes and liver biopsies after administration of an inducer. This study investigated the in vivo effects of the common inducer rifampin (RIF) on the activity and expression of cynomolgus monkey OATP1B1 and OATP1B3 transporters, which are structurally and functionally similar their human OATP1B counterparts. Multiple doses of oral RIF (15 mg/kg) resulted in a steady 3.9-fold increase of CYP3A biomarker, 4β-hydroxycholesterol (4βHC), in the plasma samples collected before each RIF dose during the treatment period (i.e., predose). In contrast, the predose plasma levels of OATP1B biomarkers coproporphyrin (CP) I and CPIII did not change when compared with RIF treatment. The trough concentration, area under plasma concentration-time curve (AUC), and half-life of RIF decreased markedly during RIF treatment, suggesting that RIF induced its own clearance. Consequently, RIF treatment increased CPI and CPIII AUCs substantially after a single administration and, to a lesser extent, after multiple administrations compared with preadministration AUCs. In addition, OATP1B1 and OATP1B3 mRNA expressions were not modulated by RIF treatment (0.85-1.3-fold), whereas CYP3A8 expression was increased 3.7-5.0-fold, which correlated well with the predose levels of CP and 4βHC. Rifampin treatment showed 2.0-3.3-fold increases in P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and multidrug resistance-associated protein 2 (MRP2) expression in the small intestine. Collectively, these findings indicate that monkey OATP1B and OATP1B3 are not induced by RIF, and further investigation of OATP1B induction by RIF and other nuclear receptor activators in humans is warranted. SIGNIFICANCE STATEMENT: In this study, combined endogenous biomarker and gene expression data suggested that RIF did not induce OATP1B in cynomolgus monkeys. For the first time, the study determines transporter gene expression in the nonhuman primate liver, gut, and kidney tissues after administration of RIF for 7 days, leading to a better understanding of the induction of OATP1B and other major drug transporters. Finally, it provides evidence to strengthen the claim that coproporphyrin is a suitable endogenous probe of OATP1B activity.

Validation of a Drug Transporter Probe Cocktail Using the Prototypical Inhibitors Rifampin, Probenecid, Verapamil, and Cimetidine.

Background and ObjectiveA novel cocktail containing four substrates of key drug transporters was previously optimized to eliminate mutual drug–drug interactions between the probes digoxin (P-glycoprotein substrate), furosemide (organic anion transporter 1/3), metformin (organic cation transporter 2, multidrug and toxin extrusion protein 1/2-K), and rosuvastatin (organic anion transporting polypeptide 1B1/3, breast cancer resistance protein). This clinical trial investigated the effects of four commonly employed drug transporter inhibitors on cocktail drug pharmacokinetics.MethodsIn a randomized open-label crossover trial in 45 healthy male subjects, treatment groups received the cocktail with or without single oral doses of rifampin, verapamil, cimetidine or probenecid. Concentrations of the probe drugs in serial plasma samples and urine fractions were measured by validated liquid chromatography-tandem mass spectrometry assays to assess systemic exposure.ResultsThe results were generally in accordance with known in vitro and/or clinical drug–drug interaction data. Single-dose rifampin increased rosuvastatin area under the plasma concentration–time curve up to the last quantifiable concentration (AUC0–tz) by 248% and maximum plasma concentration (Cmax) by 1025%. Probenecid increased furosemide AUC0–tz by 172% and Cmax by 23%. Cimetidine reduced metformin renal clearance by 26%. The effect of single-dose verapamil on digoxin systemic exposure was less than expected from multiple-dose studies (AUC0–tz unaltered, Cmax + 22%).ConclusionsTaking all the interaction results together, the transporter cocktail is considered to be validated as a sensitive and specific tool for evaluating transporter-mediated drug–drug interactions in drug development.Clinical Trial RegistrationEudraCT number 2017-001549-29.Electronic supplementary materialThe online version of this article (10.1007/s40262-020-00907-w) contains supplementary material, which is available to authorized users.

In pursuit of the triple crown: mechanism-based pharmacodynamic modelling for the optimization of three-drug combinations against KPC-producing Klebsiella pneumoniae

ObjectivesOptimal combination therapy for Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-Kp) is unknown. The present study sought to characterize the pharmacodynamics (PD) of polymyxin B (PMB), meropenem (MEM) and rifampin (RIF) alone and in combination using a hollow fibre infection model (HFIM) coupled with mechanism-based modelling (MBM). MethodsA 10-day HFIM was utilized to simulate human pharmacokinetics (PK) of various PMB, MEM and RIF dosing regimens against a clinical KPC-Kp isolate, with total and resistant subpopulations quantified to capture PD response. A MBM was developed to characterize bacterial subpopulations and synergy between agents. Simulations using the MBM and published population PK models were employed to forecast the bacterial time course and the extent of its variability in infected patients for three-drug regimens. ResultsIn the HFIM, a PMB single-dose (‘burst’) regimen of 5.53 mg/kg combined with MEM 8 g using a 3-hr prolonged infusion every 8 hr and RIF 600 mg every 24 hr resulted in bacterial counts below the quantitative limit within 24 hr and remained undetectable throughout the 10-day experiment. The final MBM consisted of two bacterial subpopulations of differing PMB and MEM joint susceptibility and the ability to form a non-replicating, tolerant subpopulation. Synergistic interactions between PMB, MEM and RIF were well quantified, with the MBM providing adequate capture of the observed data. DiscussionAn in vitro–in silico approach answers questions related to PD optimization as well as overall feasibility of combination therapy against KPC-Kp, offering crucial insights in the absence of clinical trials.

A Clinical Study To Assess The Magnitude, Time‐course And Variability Of CYP3A4 Induction By Rifampin In Healthy Volunteers

IntroductionConsistent with its important role in human drug metabolism, CYP3A4 has an exceptionally broad substrate specificity. Consequently, CYP3A4 is highly susceptible to metabolic‐drug drug interactions (mDDI’s) that induce activity, which are an important source of between‐subject variability (BSV) in drug exposure. Failure to account for BSV is a common underlying cause of attrition in early clinical drug development. An understanding of CYP3A4 induction will hence improve the accuracy of clinical mDDI prediction. No prescriptive dosing guidance exists for clinical DDI studies that use the prototypical CYP3A4 inducer rifampin to assess the clinical mDDI victim risk of drugs metabolised by CYP3A4. Recent simulation data indicate dosing rifampin for less than 10 days is likely to underestimate the magnitude of induction.AimsThis study sought to assess CYP3A4 activity at baseline (Day 1) and following 7 and 14 days administration of rifampin (600 mg PO/daily) in a cohort of healthy males and females and to assess CYP3A4 activity at baseline and following 7 days administration of rifampin (300 mg PO/daily) in a cohort of healthy males. The impact of rifampin dose (mg) was assessed as a trial characteristic effecting the magnitude of CYP3A4 induction. The performance of a personalised PBPK model with respect to estimating exposure to oral midazolam was also evaluated.MethodsThe study was a single centre, open label, single sequence metabolic phenotyping clinical trial. Healthy volunteers were dosed with midazolam (1 mg PO on Day 1, 8, 15) and timed blood samples (8mL) were collected pre‐dose, and up to 6 hr post‐dose. Participants self‐administered up to a 14‐day course of rifampin (300 or 600 mg PO daily). Midazolam exposure was measured prior the first rifampin dose (Day 1), following seven doses of rifampin (Day 8) and 16 hours after completing the 14‐day course rifampin (Day 15). Baseline CYP3A4 activity was compared with activity following administration of rifampin for 7 and 14 days. A verified Simcyp® model describing rifampin‐mediated CYP3A4 induction was used to compare personalised PBPK simulations to observed oral midazolam exposure at baseline and following rifampin administration.ResultsThe mean observed midazolam AUC ratio following dosing of rifampin (300 mg) for 7 days was 0.32, the mean midazolam AUC ratio following dosing of rifampin (600 mg) for 7 days was 0.21. No significant difference in AUC ratio was observed between 7 and 14 days rifampin dosing (600 mg). Simulated midazolam PK parameters for Day 1 (baseline) was within 2‐fold of the observed parameter (i.e. MFE 0.62 to 1.61) for all participants. Simulated parameters for Day 7 and Day 14 ranged from 3‐fold lower to 6.5‐fold higher than the observed parameter (i.e. MFE 0.33 to 6.40).DiscussionConsistent with prior studies greater CYP3A4 induction was achieved using 600 mg rifampin. Contrary to simulations suggesting a minimum of 10 days rifampin dosing is required to achieve maximal induction of hepatic CYP3A4, data indicate 7 days dosing is sufficient to produce maximal change in midazolam exposure. Robust concordance of individual participant simulated and observed oral midazolam PK parameters at baseline (Day 1) was observed, however concordance was variable and typically poor following rifampicin administration.Support or Funding InformationNHMRC

Duration of rifampin therapy is a key determinant of improved outcomes in early-onset acute prosthetic joint infection due to Staphylococcus treated with a debridement, antibiotics and implant retention (DAIR): a retrospective multicenter study in France.

Introduction: In patients undergoing a « debridement, antibiotics, and implant retention » (DAIR) procedure for acute staphylococcal prosthetic joint infection (PJI), post-operative treatment with rifampin has been associated with a higher probability of success.(1,2) However, it is not known whether it is the total dose, delay of introduction or length of therapy with rifampin that is most strongly associated with the observed improved outcomes.Methods: A multicentric, retrospective cohort study of patients with acute staphylococcal hip and knee PJI treated with DAIR between January 2011 and December 2016. Failure of the DAIR procedure was defined as persistent infection, need for another surgery or death. We fitted logistic and Cox regression multivariate models to identify predictors of DAIR failure. We compared Kaplan-Meier estimates of failure probability in different levels of the 3 variables of interest - total dose, delay of introduction or length of therapy with rifampin - with the log-rank test.Results: 79 patients included (median age 71 years [63.5-81]; 55 men [70%]), including 54 (68%) DAIR successes and 25 (32%) DAIR failures. Patients observed for a median of 435 days [IQR 107.5-834]. Median ASA score significantly lower in DAIR successes than in DAIR failures (2 vs. 3, respectively p = 0.011). Bacterial cultures revealed 65 (82.3%) S. aureus and 16 (20.3%) coagulase negative staphylococci, with 2 patients being infected simultaneously with S. aureus and CNS. Among S. aureus isolates, 7 (10.8%) resistant to methicillin; 2 (3.1 %) resistant to rifampin. Median duration of antimicrobial therapy was 85 days [IQR 28.5-97.8]. Fifty-eight patients (73.4%) received rifampin at a median dose of 14.6 mg/kg/day |IQR 13-16.7], started at a median delay of 8.5 days [IQR, 4-7.5] after debridement surgery. Twenty-one patients (26.6%) developed a drug-related adverse event, leading to rifampin interruption in 6 of them (7.6% of total cohort). Determinants of DAIR failure were rifampin use (HR 0.17, IC [0.06, 0.45], p-value <0.001), association of rifampin with a fluoroquinolone (HR 0.19, IC [0.07, 0.53], p-value = 0.002) and duration of rifampin therapy (HR 0.97, IC [0.95, 1], p-value = 0.022). We did not observe a significant difference between DAIR successes and failures in rifampin use, dose and delay of introduction. In a multivariate Cox model, only duration of rifampin therapy was significantly associated with DAIR failure. Kaplan Meier estimate of DAIR failure probability was significantly higher in patients receiving less than 14 days of rifampin in comparison with those receiving more than 14 days of rifampin (p = 0.0017).Conclusion: Duration of rifampin therapy is a key determinant of improved outcomes in early-onset acute prosthetic joint infection due to Staphylococcus treated with DAIR.

Effects of paroxetine, ketoconazole, and rifampin on the metabolism of eliglustat, an oral substrate reduction therapy for Gaucher disease type 1

Eliglustat is an oral glucosylceramide synthase inhibitor indicated for the long-term treatment of adults with Gaucher disease type 1 and CYP2D6 extensive, intermediate, or poor metabolizer phenotypes. Eliglustat is metabolized primarily by CYP2D6 and to a lesser extent by CYP3A4 and is a substrate of P-glycoprotein (P-gp). Three studies evaluated the effects of paroxetine (strong CYP2D6 inhibitor), ketoconazole (strong CYP3A4 and P-gp inhibitor), and rifampin (strong CYP3A4/P-gp inducer; OATP inhibitor) on the pharmacokinetics of orally administered eliglustat in healthy adults. An 8.9-fold increase in eliglustat exposure following co-administration of multiple-dose eliglustat and paroxetine is attributed to inhibition of CYP2D6-mediated metabolism of eliglustat by paroxetine. A 4.3-fold increase in eliglustat exposure following co-administration of multiple-dose eliglustat and ketoconazole is attributed to inhibition of CYP3A4-mediated metabolism and/or P-gp-mediated transport of eliglustat by ketoconazole. Co-administration of eliglustat with oral doses of rifampin reduced eliglustat exposure by >85% due to induction of CYP3A4/P-gp by rifampin, while a single intravenous dose of rifampin had no effect on eliglustat, confirming that eliglustat is not an OATP substrate. Depending on CYP2D6 metabolizer phenotype, co-administration of eliglustat with CYP2D6 and/or CYP3A inhibitors or CYP3A inducers may alter eliglustat exposure, warrant dosage adjustment or use with caution, or be contraindicated.

The Effect of Rifampin on the Pharmacokinetics and Safety of Lorlatinib: Results of a Phase One, Open-Label, Crossover Study in Healthy Participants

Lorlatinib is a third-generation tyrosine kinase inhibitor approved for the treatment of anaplastic lymphoma kinase (ALK)-positive metastatic non-small cell lung cancer; cytochrome P450 (CYP) 3A plays an important role in the metabolism of lorlatinib. This phase 1, open-label, two-period, crossover study estimated the effect of oral rifampin (a strong CYP3A inducer) on the pharmacokinetics and safety of oral lorlatinib (NCT02804399). Healthy participants received single-dose lorlatinib 100mg in period 1 followed by rifampin 600mg/day (days 1-12) and single-dose lorlatinib 100mg (day 8) in period 2. Blood samples were collected for 120h after each dose of lorlatinib. When a single dose of lorlatinib was administered during daily dosing with rifampin (period 2), the area under the plasma concentration-time profile extrapolated to infinity (AUCinf) and maximum plasma concentration (Cmax) of lorlatinib were 14.74% [90% confidence interval (CI) 12.78%, 17.01%] and 23.88% (90% CI 21.58%, 26.43%), respectively, of those in period 1 (lorlatinib alone). A single dose of lorlatinib was well tolerated in period 1, but elevations in transaminase values were observed in all participants (grade 2-4 in 11 participants) within 1-3days after a single dose of lorlatinib was administered with ongoing rifampin in period 2. Rifampin dosing was therefore halted. Transaminase levels subsequently returned to normal (median time to recovery: 15days). No elevations in bilirubin were observed. The addition of a single dose of lorlatinib to daily dosing with rifampin significantly reduced lorlatinib plasma exposure relative to a single dose of lorlatinib administered alone and was associated with severe but self-limiting transaminase elevations in all healthy participants. These observations support the contraindication in the product label against concomitant use of lorlatinib with all strong CYP3A inducers. ClinicalTrials.gov identifier, NCT02804399.

Population Pharmacokinetics of Rifampicin on Pulmonary Tuberculosis Patients

Abstract: This study aimed to establish a reasonable population pharmacokinetic model for rifampicin taken orally by patients with pulmonary tuberculosis, estimate pharmacokinetic parameters as well as influencing covariates. Blood samples of patients were collected at day 10 – 14 after commencing treatment. Time – concentration data were handled using non-linear mixed-effect model with Monolix 2018. An one-compartment, linear elimination, absorption with transit compartments model was found to be the most suitable for rifampicin. Volume of distribution (33,5 L) and clearance (9,62 L) were found to be influenced by fat-free mass (calculated using Janmahasatian’s method). Absorption-related parameters (Ktr, mean transit time and Ka) were found to have high inter-individual variability.&#x0D; Keywords&#x0D; Rifampicin, population pharmacokinetics, pulmonary tuberculosis.&#x0D; References&#x0D; [1] Christian Lienhardt et al, Target regimen profiles for treatment of tuberculosis: a WHO document (2017).[2] J.G. Pasipanodya et al, Serum drug concentrations predictive of pulmonary tuberculosis outcomes, The Journal of infectious diseases 208(9) (2013) 1464-1473. https://doi.org/10.1093/infdis/jit352[3] Jonathan Reynolds, Scott K Heysell (2014), Understanding pharmacokinetics to improve tuberculosis treatment outcome, Expert opinion on drug metabolism &amp; toxicology 10(6) (2014) 813-823. https://doi.org/10.1517/17425255.2014.895813[4] E.F. Egelund, A.B. Barth, C.A. Peloquin (2011), Population pharmacokinetics and its role in anti-tuberculosis drug development and optimization of treatment, Current pharmaceutical design 17(27) (2017) 2889-2899. https://doi.org/10.2174/138161211797470246.[5] J.F. Murray, D.E. Schraufnagel, P.C. Hopewell, Treatment of tuberculosis. A historical perspective, Annals of the American Thoracic Society 12(12) (2015) 1749-1759. https://doi.org/10.1513/AnnalsATS.201509-632PS[6] K.E. Stott, et al, Pharmacokinetics of rifampicin in adult TB patients and healthy volunteers: a systematic review and meta-analysis, Journal of Antimicrobial Chemotherapy 73(9) (2018) 2305-2313. https://doi.org/10.1093/jac/dky152.[7] Le Thi Luyen, Ta Manh Hung et al, Simultaneous Determination of Pyrazinamide, Rifampicin, Ethambutol, Isoniazid and Acetyl Isoniazid in Human Plasma by LC-MS/MS Method, Journal of Applied Pharmaceutical Science 8(09) (2018) 061-073. https://doi.org/ 10.7324/JAPS.2018.8910.[8] M.T. Chirehwa et al, Model-based evaluation of higher doses of rifampin using a semimechanistic model incorporating autoinduction and saturation of hepatic extraction, Antimicrobial agents and chemotherapy 60(1) (2016) 487-494. https://doi.org/10.1128/AAC.01830-15.[9] Paolo Denti et al, A population pharmacokinetic model for rifampicin auto-induction, The 3rd international workshop on clinical pharmacology of TB drugs (2010).[10] Y. Jing et al, Population pharmacokinetics of rifampicin in Chinese patients with pulmonary tuberculosis, The Journal of Clinical Pharmacology 56(5) (2016) 622-627. https://doi.org/10.1002/jcph.643.[11] S.R.C. Milán et al, Population pharmacokinetics of rifampicin in Mexican patients with tuberculosis, Journal of clinical pharmacy and therapeutics 38(1) (2013) 56-61. https://doi.org/10.1111/jcpt.12016.[12] Anushka Naidoo et al, Effects of genetic variability on rifampicin and isoniazid pharmacokinetics in South African patients with recurrent tuberculosis, Pharmacogenomics(00) (2013). https://doi.org/10.2217/pgs-2018-0166.[13] Neesha Rockwood et al, HIV-1 coinfection does not reduce exposure to rifampin, isoniazid, and pyrazinamide in South African tuberculosis outpatients, Antimicrobial agents and chemotherapy 60(10) (2016) 6050-6059. https://doi.org/10.1128/AAC.00480-16.[14] Alessandro Schipani et al, A simultaneous population pharmacokinetic analysis of rifampicin in Malawian adults and children, British Journal of Clinical Pharmacology 81(4) (2016) 679-687. https://doi.org/10.1111/bcp.12848.[15] Kok-Yong Seng et al, Population pharmacokinetics of rifampicin and 25-deacetyl-rifampicin in healthy Asian adults, Journal of Antimicrobial Chemotherapy 70(12) (2015) 3298-3306. https://doi.org/10.1093/jac/dkv268.[16] J.J. Wilkins et al, Population pharmacokinetics of rifampin in pulmonary tuberculosis patients, including a semimechanistic model to describe variable absorption, Antimicrobial agents and chemotherapy 52(6) (2008)2138-2148. https://dx.doi.org/10.1128%2FAAC.00461-07.[17] Sylvain Goutelle et al, Population modeling and Monte Carlo simulation study of the pharmacokinetics and antituberculosis pharmacodynamics of rifampin in lungs, Antimicrobial agents and chemotherapy 53(7) (2009) 2974-2981. https://doi.org/10.1128/AAC.01520-08.[18] R.M. Savic et al, Implementation of a transit compartment model for describing drug absorption in pharmacokinetic studies, Journal of pharmacokinetics and pharmacodynamics 34(5) (2007) 711-726. https://doi.org/10.1007/s10928-007-9066-0.[19] B.J. Anderson, N.H.G. Holford, Mechanism-based concepts of size and maturity in pharmacokinetics, Annu. Rev. Pharmacol. Toxicol 48 (2008) 303-332. https://doi.org/10.1146/annurev.pharmtox.48.113006.094708.[20] Kok-Yong Seng et al, Population pharmacokinetic analysis of isoniazid, acetyl-isoniazid and isonicotinic acid in healthy volunteers, Antimicrobial agents and chemotherapy, pp. AAC. (2015) 01244-15. https://doi.org/10.1128/AAC.01244-15.[21] Sarayut Janmahasatian et al, Quantification of lean bodyweight, Clinical pharmacokinetics 44(10), (2005) 1051-1065. https://doi.org/10.2165/00003088-200544100-00004.[22] Kidola Jeremiah et al, Nutritional supplementation increases rifampin exposure among tuberculosis patients coinfected with HIV, Antimicrobial agents and chemotherapy 58(6) (2014) 3468-3474. https://doi.org/10.1128/AAC.02307-13&#x0D;

3178 Augmentin-Induced Liver Injury in a Patient With Progressive Familial Intrahepatic Hepatic Cholestasis (PFIC)

INTRODUCTION: We are reporting a case of drug induced liver injury (DILI) within 48 hours of Augmentin administration in a patient with progressive familial intrahepatic cholestasis. CASE DESCRIPTION/METHODS: 27-yo female with PMH of severe ATP8B1 protein deficiency, PFIC S/P hepatojejunostomy with external biliary diversion, not a transplant candidate due to psychosocial issues, presented with epigastric pain, vomiting and constipation. Home meds included hydroxyzine, questran and rifampin. On admission vitals were BP: 110/59, pulse: 107, temp: 98.3, O2 sat: 100% on RA. Physical exam was unremarkable except icteric sclera. Labs showed WBCs: 19.1, H&amp;H: 14.1/41.4, PLT: 187, Total Billi: 17.9, AST/ALT/ALP of 566/398/172, normal BMP except Bicarb: 15. INR: 1.8, lipase 25, UA negative for infection. CT Abd/pelvis W/contrast did not show any acute hepatobiliary pathology, except endometrial prominence with some fluid. Rifampin was stopped, aggressive bowel regimen, IV hydration and IV antibiotics including Unasyn and doxycycline were started. Fuid from endometrial cavity was cultured. Pt's abdominal pain improved as constipation resolved. Antibiotics were switched to Augmentin for presumed endometrial infection. LFTs started rising within 48 hrs of augmentin administration. Peak LFTs were T.Billi/AST/ALT/ALP:21.5/762/528/132. Complete laboratory evaluation included negative serologies for hepatitis, A, B, C, EBV, CMV and negative assays for ANA, AMA, ASMA. Augmentin was stopped. Two weeks after discontinuation of Augmentin, patient's LFTs started to improve. DISCUSSION: DILI is a well-recognized complication of Augmentin use and multiple cases have been reported. Associated mortality can be as high as 10%, and thus prompt recognition and removal of the offending agent is of critical importance. In our patient, while systemic infection and rifampin use were other possibilities for liver injury however, worsening and improvement in LFTs correlated with Augmentin administration and discontinuation. Moreover, dose of rifampin was not changed for over a year. Several risk factors have been identified for DILI including older age, genetic determinants, preexisting liver disease and properties of certain medications. Our patient had PFIC and Augmentin use caused liver injury within 48 hrs of administration as compared to other case reports where latent period of Augmentin induced liver injury varied from days to weeks. In both DILI and PFIC, treatment options are very limited thus Augmentin should be avoided.

Rifampin pharmacokinetics in tuberculosis-diabetes mellitus patients: a pilot study from Baja California, Mexico.

BACKGROUND: Worldwide, there has been an increase in type 2 diabetes mellitus (DM2) as a comorbidity of tuberculosis (TB), which is characterized by alterations in the pharmacokinetics of drugs used for TB treatment.OBJECTIVE: To characterize the pharmacokinetics of rifampin in patients with TB and TB-DM2.METHODS: Blood samples were collected in two hospitals in Baja California, Mexico from March through December 2017. Sampling was not random and included 14 patients with TB and 16 with TB-DM2. High-performance liquid chromatographic (HPLC) was carried out to determine the concentration of rifampin in human serum.RESULTS: On average, the highest concentration of rifampin for both groups was registered at 2.5 h after ingestion (3.5 ± 2.64 μg/ml). The maximum difference in concentration (Cmax) of rifampin between TB and TB-DM2 group was not significant (P > 0.05). Importantly however, the analysis showed suboptimal levels of Cmax in a high proportion of both groups of patients studied.CONCLUSION: The study suggests that under the currently recommended rifampin dose, suboptimal Cmax levels are reached in a high proportion of patients, regardless of whether they have diabetes or not. It may therefore be necessary to use higher doses of rifampin and perform routine monitoring of serum levels. However, further work is needed to confirm these findings.

Study to Evaluate the Effect of Multiple Doses of Itraconazole and Rifampin on the Single-Dose Pharmacokinetics of Mitapivat Sulfate (AG-348) in Healthy Adult Participants

Study to Evaluate the Effect of Multiple Doses of Itraconazole and Rifampin on the Single-Dose Pharmacokinetics of Mitapivat Sulfate (AG-348) in Healthy Adult Participants