Plasma Concentrations Of Isoniazid Research Articles

Effect of NAT2, GSTM1 and CYP2E1 genetic polymorphisms on plasma concentration of isoniazid and its metabolites in patients with tuberculosis, and the assessment of exposure-response relationships.

Objectives: Isoniazid is a key drug in the chemotherapy of tuberculosis (TB), however, interindividual variability in pharmacokinetic parameters and drug plasma levels may affect drug responses including drug induced hepatotoxicity. The current study investigated the relationships between isoniazid exposure and isoniazid metabolism-related genetic factors in the context of occurrence of drug induced hepatotoxicity and TB treatment outcomes. Methods: Demographic characteristics and clinical information were collected in a prospective TB cohort study in Latvia (N = 34). Time to sputum culture conversion (tSCC) was used as a treatment response marker. Blood plasma concentrations of isoniazid (INH) and its metabolites acetylisoniazid (AcINH) and isonicotinic acid (INA) were determined at three time points (pre-dose (0h), 2h and 6h after drug intake) using liquid chromatography-tandem mass spectrometry. Genetic variations of three key INH-metabolizing enzymes (NAT2, CYP2E1, and GSTM1) were investigated by application PCR- and Next-generation sequencing-based methods. Depending on variables, group comparisons were performed by Student's t-test, one-way ANOVA, Mann-Whitney-Wilcoxon, and Kruskal-Wallis tests. Pearson correlation coefficient was calculated for the pairs of normally distributed variables; model with rank transformations were used for non-normally distributed variables. Time-to-event analysis was performed to analyze the tSCC data. The cumulative probability of tSCC was obtained using Kaplan-Meier estimators. Cox proportional hazards models were fitted to estimate hazard rate ratios of successful tSCC. Results: High TB treatment success rate (94.1%) was achieved despite the variability in INH exposure. Clinical and demographic factors were not associated with either tSCC, hepatotoxicity, or INH pharmacokinetics parameters. Correlations between plasma concentrations of INH and its metabolites were NAT2 phenotype-dependent, while GSTM1 genetic variants did not showed any effects. CYP2E1*6 (T > A) allelic variant was associated with INH pharmacokinetic parameters. Decreased level of AcINH was associated with hepatotoxicity, while decreased values of INA/INH and AcINH/INH were associated with month two sputum culture positivity. Conclusion: Our findings suggest that CYP2E1, but not GSTM1, significantly affects the INH pharmacokinetics along with NAT2. AcINH plasma level could serve as a biomarker for INH-related hepatotoxicity, and the inclusion of INH metabolite screening in TB therapeutic drug monitoring could be beneficial in clinical studies for determination of optimal dosing strategies.

Effect of Metformin on Plasma Exposure of Rifampicin, Isoniazid, and Pyrazinamide in Patients on Treatment for Pulmonary Tuberculosis.

To evaluate the effect of metformin on the plasma levels of rifampicin, isoniazid, and pyrazinamide in patients with drug-sensitive pulmonary tuberculosis being treated with first-line antituberculosis treatment (ATT) and to assess the influence of gene polymorphisms on the metabolic pathway of metformin and plasma levels of antitubercular drugs. Nondiabetic adults aged 18-60 years with pulmonary tuberculosis were randomized to either the standard ATT (ATT group) or ATT plus metformin (METRIF group) groups in a phase IIB clinical trial. An intensive pharmacokinetic study with blood collection at 0 hour (predosing), followed by 1, 2, 4, 6, 8, and 12 hours after dosing was conducted during the first month of treatment in a subset of 60 study participants after a minimum of 14 doses. Plasma concentrations of rifampicin, isoniazid, pyrazinamide, and metformin were measured by high-performance liquid chromatography using validated methods, and pharmacokinetic parameters and OCT1 and MATE1 gene polymorphisms were compared between the groups. Significant increases in the clearance of rifampicin, isoniazid, and pyrazinamide were observed in patients in the METRIF group (n = 29) compared with those in the ATT group (n = 31). The AA genotypes of the single-nucleotide polymorphism of rs2289669 ( MATE1 ) in the METRIF group showed a significantly decreased area under the concentration-time curve to the last observation point and increased clearance of rifampicin. Metformin altered rifampicin and isoniazid plasma concentrations in patients receiving antituberculosis treatment for pulmonary tuberculosis with little effect on sputum conversion at the end of treatment. Studies with larger sample sizes are needed to understand host drug-drug interactions.

Correlation of N-acetyltransferase 2 genotype and acetylation status with plasma isoniazid concentration and its metabolic ratio in ethiopian tuberculosis patients

Unfavorable treatment outcomes for tuberculosis (TB) treatment might result from altered plasma exposure to antitubercular drugs in TB patients. The present study investigated the distribution of the N-Acetyltransferase 2 (NAT2) genotype, isoniazid acetylation status, genotype–phenotype concordance of NAT2, and isoniazid plasma exposure among Ethiopian tuberculosis patients. Blood samples were collected from newly diagnosed TB patients receiving a fixed dose combination of first-line antitubercular drugs daily. Genotyping of NAT2 was done using TaqMan drug metabolism assay. Isoniazid and its metabolite concentration were determined using validated liquid chromatography-tandem mass spectrometry (LC–MS/MS). A total of 120 patients (63 male and 57 female) were enrolled in this study. The mean daily dose of isoniazid was 4.71 mg/kg. The frequency of slow, intermediate, and fast NAT2 acetylators genotypes were 74.2%, 22.4%, and 3.3% respectively. The overall median isoniazid maximum plasma concentration (Cmax) was 4.77 µg/mL and the AUC0–7 h was 11.21 µg.h/mL. The median Cmax in slow, intermediate, and fast acetylators were 5.65, 3.44, and 2.47 μg/mL, respectively. The median AUC0–7 h hour in slow, intermediate, and fast acetylators were 13.1, 6.086, and 3.73 mg•h/L, respectively. The majority (87.5%) of the study participants achieved isoniazid Cmax of above 3 µg/mL, which is considered a lower limit for a favorable treatment outcome. There is 85% concordance between the NAT2 genotype and acetylation phenotypes. NAT2 genotype, female sex, and dose were independent predictors of Cmax and AUC0–7 h (p < 0.001). Our finding revealed that there is a high frequency of slow NAT2 genotypes. The plasma Cmax of isoniazid was higher in the female and slow acetylators genotype group. The overall target plasma isoniazid concentrations in Ethiopian tuberculosis patients were achieved in the majority of the patients. Therefore, it is important to monitor adverse drug reactions and the use of a higher dose of isoniazid should be closely monitored.

Pharmacokinetics of isoniazid in Wistar rats exposed to ethanol

Tuberculosis treatment consists of a drug combination, where isoniazid is the core drug and alcoholism is a factor highly related to poor patient compliance with the therapy. CYP2E1 is an enzyme involved both in the metabolism of ethanol and in the formation of hepatotoxic compounds during the metabolism of isoniazid. The shared metabolism pathway accounts for the possibility of pharmacokinetic interaction in cases of concomitant alcohol use during tuberculosis treatment. The aim of this study was to evaluate the effect of repeated exposure of Wistar rats (males, 250 g, n=6) to ethanol on the pharmacokinetics of a single dose of isoniazid in combination with pyrazinamide and rifampicin (100 mg/kg, 350 mg/kg and 100 mg/kg, respectively). An animal group received the combination of drugs and ethanol and was compared to a control group, which received the combination of drugs without exposure to ethanol. The plasma concentrations of isoniazid were determined by a UHPLC/UV bioanalytical method that was previously validated. Biochemical markers of liver function were measured to assess potential damage. A lower elimination half-life of isoniazid was observed in the ethanol group than in the control group (t1/2 0.91 h versus 1.34 h). There was no evidence of hepatotoxicity through the biomarker enzymes evaluated. The results allow us to infer that although there are no biochemical changes related to liver damage, there is a slight influence of ethanol exposure on the pharmacokinetic profile of isoniazid. This change may have a relevant impact on the efficacy of isoniazid in the outcome of tuberculosis treatment.

Pharmacokinetics and safety/tolerability of isoniazid, rifampicin and pyrazinamide in children and adolescents treated for tuberculous meningitis

ObjectiveTo assess the pharmacokinetics and safety/tolerability of isoniazid, rifampicin and pyrazinamide in children and adolescents with tuberculous meningitis (TBM).DesignProspective observational pharmacokinetic study with an exploratory pharmacokinetic/pharmacodynamic analysis.SettingHasan Sadikin Hospital, Bandung,...

Plasma drug concentrations of 4-drug fixed-dose combination regimen and its efficacy for treatment of pulmonary tuberculosis under National Tuberculosis Elimination Programme: A prospective pilot study

BackgroundThe thrice weekly dosing regimen of DOTS has shown low rifampicin plasma concentrations as an independent risk factor for unfavourable tuberculosis (TB) outcome. With introduction of daily regimen using fixed dose combinations (FDC) under National Tuberculosis Elimination Programme (NTEP) the existence of suboptimal plasma levels of first-line antitubercular drugs and its clinical significance remain poorly understood. MethodWe included a prospective cohort of newly diagnosed pulmonary tuberculosis (PTB) patients receiving 4-FDC daily regimen under NTEP. Plasma concentration at 2 hours (C2h) of each drug was determined after two weeks of treatment using liquid chromatography (LCMS/MS) developed by us. TB card and laboratory reports were reviewed for baseline characteristics and clinical status at 2, 4 and 6 months after the initiation of treatment. At a 1 year follow-up, therapy failure was defined as death or a relapse of tuberculosis. ResultsAmong 40 PTB patients, the C2h post dose plasma concentrations of H, R and E were suboptimal in 25%, 60% and 10% respectively. The C2h of H, R, Z and E were respectively 4.2 ± 2.0, 7.3 ± 2.8, 39.2 ± 8.8 and 3.5 ± 1.2 μg/ml; 60% of the patients had suboptimal plasma concentrations and commonly it was observed with H and R. C2h were lower than expected for at least two drugs i.e. H and R in 25% (10/40) of the patients. Plasma concentration of isoniazid and rifampicin has always been considered important for microbiological response and treatment outcome and low concentrations has been associated with poor treatment response. These patients may require a two year follow up and critical evaluation for prevention of MDR-TB. However, all the TB patients were cured and none of them had recurrence within one year follow up. ConclusionsAll the pulmonary TB patients administering 4-FDC daily regimen under programmatic settings were cured despite the suboptimal levels of isoniaizd and rifampicin. All the patients achieved pyrazinamide plasma levels and probably this could be the reason behind favourable outcome. Further study is required on large sample size with various subset of population to understand the need of therapeutic drug monitoring.

Quantification of pyrazinamide, isoniazid, acetyl-isoniazid, and rifampicin by a high-performance liquid chromatography method in human plasma from patients with tuberculosis.

The aim of this study was to establish and validate an alternative high-performance liquid chromatography method for simultaneous quantification of pyrazinamide, isoniazid, acetyl-isoniazid and rifampicin in plasma of patients under treatment for tuberculosis. The performed method was lineal (r2 >0.99) in the range of 2.00-50.00μg/mL for pyrazinamide, 0.50-20.00μg/mL for both acetyl-isoniazid and isoniazid, and 1.20-25.00μg/mL for rifampicin. Precision and trueness were demonstrated with coefficient of variation<15% and deviations<15%, respectively, for quality controls samples. The lower limits of quantification were 2.00, 0.50, 0.50, and 1.20μg/mL for pyrazinamide, isoniazid, acetyl-isoniazid and rifampicin, respectively. The method was applied for the analysis of plasma from patients with tuberculosis. This method allowed ensuring reliable quantification of the target compounds and their pharmacokinetics parameters. In general, the mean values of maximum concentration of each antituberculosis drug were located within their respective reference therapeutic ranges. However, patients with sub-therapeutic plasma concentrations of isoniazid and rifampicin were detected. This is the first analytical technique that simultaneously quantifies isoniazid, acetyl-isoniazid, rifampicin, and pyrazinamide concentrations from plasma samples by high-performance liquid chromatography with ultraviolet/visible. The proposed method could be applied for therapeutic drug monitoring and pharmacokinetics studies of the four compounds throughout the treatment of tuberculosis patients.

A pilot study to investigate the utility of NAT2 genotype-guided isoniazid monotherapy regimens in NAT2 slow acetylators.

Isoniazid is a therapeutic agent for the treatment of latent tuberculosis infection. Genetic variants in the N-acetyltransferase 2 (NAT2) are associated with the safety and pharmacokinetics of isoniazid. The study aimed to evaluate the safety and pharmacokinetics of a NAT2 genotype-guided regimen of isoniazid monotherapy. A randomized, open-label, parallel-group and multiple-dosing study was performed in healthy subjects. The subjects received isoniazid for 29 days. The NAT2 slow acetylators (NAT2*5/*5, -*5/*6, -*5/*7, -*6/*6, -*6/*7, -*7/*7) randomly received standard dose (300 mg, standard-treatment group) or reduced dose (200 mg, PGx-treatment group) of isoniazid. Also, all the NAT2 rapid acetylators (NAT2*4/*4) received isoniazid 300 mg (reference group). The safety and pharmacokinetics were evaluated during the study. The PGx-treatment group showed a more stable serum liver enzyme profile and a lower incidence of adverse drug reactions (ADRs) than the standard-treatment group. The emergence rates of ADRs were 12.5, 60 and 33.3% in the reference, standard-treatment and PGx-treatment groups, respectively. The PGx-treatment group showed higher plasma isoniazid concentrations than the reference group, although the PGx-treatment group received a reduced dose of isoniazid. Our results showed that a NAT2 genotype-guided regimen may reduce ADRs during isoniazid monotherapy without concern over insufficient drug exposure.

Population pharmacokinetics of isoniazid and dose recommendations in Mexican patients with tuberculosis.

Background The standardized doses of isoniazid in therapy against tuberculosis are determined based on total body weight, without considering genetic polymorphisms of the metabolic enzyme N-acetyltransferase-2 that contribute to the wide pharmacokinetic variability of isoniazid. Objective The aim of this work was to build a population pharmacokinetic model of isoniazid in Mexican patients with tuberculosis to characterize typical estimates of pharmacokinetics, as well as inter-individual and residual variability of isoniazid considering the genetic factors associated with the N-acetyltransferase-2 enzyme. Setting A prospective study was conducted at the Department of Internal Medicine in Hospital Central, San Luis Potosí, México. Methods Plasma concentrations of isoniazid were measured by high performance liquid chromatography. The acetylator phenotype was predicted through single nucleotide polymorphisms in the N-acetyltransferase-2 gene. Genetic, anthropometric and clinical covariates were used to develop a pharmacokinetic model. Main outcome measure Isoniazid plasma concentration. Results A total of 69 patients with tuberculosis were included. Blood samples were drawn from 20min to 12h post dose to determinate the isoniazid plasma concentration. Typical pharmacokinetics parameters were characterized through two-compartment open model with first-order absorption and linear elimination. Clearance was different for each predicted N-acetyltransferase-2 phenotype being 11.4, 19.2 and 27.4L/h for slow, intermediate and rapid acetylators, respectively. Central volume of distribution was determined as 1.5*body mass index (L). Through the application of the model, external validation was performed and initial dose regimen of isoniazid is proposed based on stochastic simulations. Conclusion A validated population pharmacokinetic model of isoniazid was developed in Mexican patients with tuberculosis. Through the application of the final model, initial dose recommendations were provided considering body mass index and N-acetyltransferase-2 phenotype.

Determination of isoniazid acetylation patterns in tuberculosis patients receiving DOT therapy under the Revised National tuberculosis Control Program (RNTCP) in India

Isoniazid is the most commonly used drug for treatment of tuberculosis, and is administered individually or in combination with other drugs as standard first line therapy. Offsetting its efficacy, severe adverse effects, especially peripheral neuropathy and hepatotoxicity, are associated with isoniazid therapy, limiting its use in tuberculosis. Isoniazid is acetylated in vivo producing hydrazine and acetyl hydrazine, which are responsible for hepatotoxicity. Marked pharmacogenetic differences in acetylation have been reported among different population across the globe. This study evaluates isoniazid acetylation patterns in tuberculosis patients receiving DOT therapy under the Revised National Tuberculosis Control Program (RNTCP) in a specialized tuberculosis hospital in north India. Of 351 patients from whom samples were taken for biochemical analysis of adverse events, 36 were assessed for acetylation patterns. Blood samples were taken 1 h after administration of a 600 mg dose of isoniazid, and plasma concentrations of isoniazid were determined using a validated HPLC method. Of these 36 patients, 20 (55.56%) were slow acetylators and 16 (44.44%) were fast acetylators. Our results are consistent with those of an earlier study conducted in a different region of India. Most biochemical changes produced during long-term isoniazid therapy resolve after therapy is terminated.

Plasma Concentration of Isoniazid and Single-Nucleotide Polymorphisms of N-Acetyltransferase 2 Predict Risk of Systemic Drug Reactions During Weekly Rifapentine and Isoniazid Therapy for Latent Tuberculosis Infection: A Prospective Observational Cohort Study

Background: Weekly rifapentine and isoniazid therapy (known as 3HP) for latent tuberculosis infection (LTBI) is increasingly used, but systemic drug reactions (SDR) remain a major concern. Little, however, is known regarding the predictors of 3HP-related SDRs. Methods: We prospectively recruited 2 LTBI cohorts who received the 3HP regimen. In the single-nucleotide polymorphism (SNP) cohort, we collected clinical information of SDRs and examined the NAT2, CYP2E1, and AADAC SNPs. In the pharmacokinetic (PK) cohort, we measured plasma drug and metabolite levels at 6 and 24 hours after 3HP administration. The generalised estimating equation model was used to identify the factors associated with SDRs. Candidate SNPs predicting SDRs were validated in the PK cohort. Findings: A total of 177 participants were recruited into the SNP cohort and 129 into the PK cohort, with 14 (8%) and 13 (10%) in these two cohorts developing SDRs, respectively. In the SNP cohort, NAT2 rs1041983 (TT vs CC CT, odds ratio [OR] [95% CI]: 7.38 [2.17-25.1]) and CYP2E1 rs2070673 (AA vs TT TA, OR [95% CI]: 3.49 [1.02-12.0]) were associated with SDR development. In the PK cohort, isoniazid level 24 hours after 3HP administration (OR [95% CI]: 1.61 [1.15-2.25]) was associated with SDRs. Additionally, the association between the NAT2 SNP and SDRs was validated in the PK cohort (rs1041983 TT vs CC CT, OR [95% CI]: 4.14 [1.24-13.8]). Interpretations: Isoniazid played a role in the development of 3HP-related SDRs. This could provide insight for further design of a more optimal regimen for latent TB infection. Funding: The study was supported by grants from the Ministry of Health and Welfare (MOHW106-CDC-C-11400104 and MOHW107-CDC-C-114-000105) and the Ministry of Science and Technology (MOST106-2314-B-002-055, MOST107-2314-B-002-191 and MOST107-2314-B-037-106-MY3). Declaration of Interest: The authors have no conflicts of interest to declare. Ethical Approval: The study was approved by the institutional ethics committees of both medical centres (NTUH REC 201609044RINB and KMUHIRB-G[II]-20170033).

Isoniazid and rifampicin concentrations in children with tuberculosis with either a daily or intermittent regimen: implications for the revised RNTCP 2012 doses in India

Suboptimal plasma drug concentrations in antitubercular therapy (ATT) may lead to delayed treatment response and the emergence of acquired drug resistance. This study aimed (i) to determine and compare plasma concentrations of isoniazid (INH) and rifampicin (RIF) in children treated for tuberculosis receiving a daily or intermittent ATT regimen and (ii) to study the effect of INH and RIF exposure on clinical outcome at the end of therapy (EOT). A total of 41 children aged 2–16 years initiated on either a daily or three-times weekly (intermittent) ATT regimen were recruited into the study. Towards the end of the intensive phase, blood specimens were collected pre-dose and at 0.5, 1, 1.5, 2, 2.5, 4 and 6 h post-dose. Concentrations of INH and RIF were analysed using validated liquid chromatography–tandem mass spectrometry and high-performance liquid chromatography assays, respectively. The maximum plasma concentration (Cmax), the area under the concentration–time curve from 0–6 h (AUC0–6h) and treatment outcome were determined. Ninety-two percent of patients had an INH Cmax > 3 µg/mL. Seventy-seven percent of patients had a RIF Cmax < 8 µg/mL and 28% of patients had a RIF AUC0–24h < 13 mg ⋅ h/L. INH and RIF exposure did not differ between daily and intermittent ATT regimens on the day of administration. All children had a favourable outcome at EOT. Since 77% of children had low RIF exposure, we recommend routine use of therapeutic drug monitoring to prevent relapse and to support implementation of the revised RNTCP 2012 doses.

Isoniazid concentrations in hair and plasma area-under-the-curve exposure among children with tuberculosis.

We measured hair and plasma concentrations of isoniazid among sixteen children with tuberculosis who underwent personal or video-assisted directly observed therapy and thus had 100% adherence. This study therefore defined typical isoniazid exposure parameters after two months of treatment among fully-adherent patients in both hair and plasma (plasma area under the concentration-time curve, AUC, estimated using pharmacokinetic data collected 0, 2, 4, and 6 hours after drug administration). We found that INH levels in hair among highly-adherent individuals did not correlate well with plasma AUC or trough concentrations, suggesting that each measure may provide incremental and complementary information regarding drug exposure in the context of TB treatment.

Limited sampling strategies for determining the area under the plasma concentration–time curve for isoniazid might be a valuable approach for optimizing treatment in adult patients with tuberculosis

This study aimed to develop clinically feasible models of limited sampling strategy (LSS) for estimation of the area under the concentration–time curve (AUC24h) for isoniazid, that could be applied easily in daily clinical practice for dosage adjustment in adult patients with tuberculosis. Isoniazid plasma concentrations (n = 1665) from 185 adult tuberculous patients were used for the development and validation of LSS models to estimate AUC24h following administration of the standard 5 mg/kg dose of isoniazid. Population pharmacokinetic analysis for appropriate estimation of isoniazid pharmacokinetic parameters was performed in a modelling group (n = 100). The Bayesian estimates of AUC24h (AUCref) obtained for each individual were used as the dependent variable in the regression analysis for the development of various LSS models. The LSS models were validated in a separate cohort (n = 85). Several three and four time point LSS models were built and tested. Model H (AUC24h = −1.88 + 1.05 × C1 + 0.78 × C2 + 9.44 × C5) and Model I (AUC24h = −0.65 + 1.00 × C1 + 1.94 × C2 + 15.45 × C9) had the best performances [adj-R2 = 0.93, median prediction error (MPE) = −0.20, root median squared prediction error (RMSE) = 4.65 for Model H; adj-R2 = 0.96, MPE = −0.05 RMSE = 3.56 for Model I]. The very high R2 values (≥0.94) of these regression equations in the validation cohort confirmed their high reliability. These LSS models could be applied in the context of therapeutic drug monitoring programmes aiming to personalize isoniazid dosing regimens for adult patients with tuberculosis.

N-acetyltransferase gene polymorphisms & plasma isoniazid concentrations in patients with tuberculosis.

Background & objectives:Variations in the N-acetyltransferase (NAT2) gene among different populations could affect the metabolism and disposition of isoniazid (INH). This study was performed to genotype NAT2 gene polymorphisms in tuberculosis (TB) patients from Chennai, India, and compare plasma INH concentrations among the different genotypes.Methods:Adult patients with TB treated in the Revised National TB Control Programme (RNTCP) in Chennai, Tamil Nadu, were genotyped for NAT2 gene polymorphism, and two-hour post-dosing INH concentrations were compared between the different genotypes. Plasma INH was determined by high-performance liquid chromatography. Genotyping of the NAT2 gene polymorphism was performed by real-time polymerase chain reaction method.Results:Among the 326 patients genotyped, there were 189 (58%), 114 (35%) and 23 (7%) slow, intermediate and fast acetylators, respectively. The median two-hour INH concentrations in slow, intermediate and fast acetylators were 10.2, 8.1 and 4.1 μg/ml, respectively. The differences in INH concentrations among the three genotypes were significant (P<0.001).Interpretation & conclusions:Genotyping of TB patients from south India for NAT2 gene polymorphism revealed that 58 per cent of the study population comprised slow acetylators. Two-hour INH concentrations differed significantly among the three genotypes.

Rifampicin and isoniazid plasma concentrations in relation to adverse reactions in tuberculosis patients: a retrospective analysis.

High concentrations of antituberculosis (anti-TB) drugs can be associated with many adverse drug reactions (ADRs). The objective of this study was to examine the plasma concentrations of rifampicin (RMP) and isoniazid (INH) in patients with and without ADRs. Concentration monitoring data of patients treated with anti-TB drugs were retrospectively analyzed from 2009 to 2011. RMP and INH plasma concentrations were measured 2 and 3 h after drug administration respectively using high-performance liquid chromatography. A total of 54 out of 120 patients have experienced ADRs to anti-TB drugs. The median concentrations [interquartile range (IQR)] obtained in patients with and without ADRs were 6.7 mg/l (3.7-9.9) and 5.6 mg/l (2.9-8.6) (p = 0.56) for RMP and 4.3 mg/l (2.3-5.3) and 3.1 mg/l (1.7-4.8) (p = 0.04) for INH, respectively. Related median doses (IQR) were 8.7 mg/kg (8.0-10.0) and 8.6 mg/kg (6.5-9.9) (p = 0.42) for RMP and 4.8 mg/kg (4.3-5.0) and 4.0 mg/kg (2.8-5) (p < 0.01) for INH, respectively. Concentrations above the expected range in patients with and without ADRs were not reached for RMP, but were 76% and 65% for INH, respectively. Correlation between concentrations and doses has not been established for RMP or INH. In addition, high INH concentrations showed no association with sex, age, liver injury or renal or diabetes. High INH concentrations were common in patients with and without ADRs whereas RMP concentrations were low or within the normal range in most patients. Further studies are required to assess the association between high INH concentrations and the occurrence of ADRs.

Suivi Thérapeutique Pharmacologique Des Antituberculeux : Quinze Ans d’Expérience

Tuberculosis is a world public health problem. Its treatment is based on a set of drugs that can cause many side effects. Liver toxicity remains one of the most common and severe side effect causing treatment failure. The objective of this study is to demonstrate the interest of therapeutic drug monitoring in the treatment of tuberculosis through the experience of the Laboratory of Toxicology and Pharmacology of the Anti Poison Center. This retrospective study involved 1152 patients who had benefited from a determination of plasma levels of first line antitubureculosis drugs (isoniasid, pyrazinamid, rifampicin) during 15 years. 135 patients had developed hepatotoxicity. The study showed that at therapeutic dose, 71.2% of TB patients had plasma concentrations lower than the therapeutic range, and 57.8% of patients had isoniazid plasma concentrations above the therapeutic range. This interindividual variability justifies the need for therapeutic drug monitoring to assess an inadequate response to tuberculosis treatment and prevent the development of hepatotoxicity.

The effect of renal replacement therapy on the plasma concentration of antituberculosis drugs

To explore the effect of renal replacement therapy (RRT) on the plasma drug concentration of first-line antituberculosis drugs. Thirty patients treated with continuous RRT and who were complicated with pulmonary tuberculosis from 2009 September to 2013 September were enrolled in the study. There were 19 males and 11 females, aged 18-75 years. They received RRT 3 times a week, 4 h each. The patients took isoniazid 300 mg and rifampin 450 mg one time every day, and pyrazinamide 40 mg · kg(-1) · d (-1) one time 24 h before RRT, 3 times every week. The plasma concentration of the drugs were monitored before and after each RRT for 4 weeks. Taken before RRT, the plasma concentration of isoniazid before RRP was (1.62 ± 0.44), (1.67 ± 0.38), (1.63 ± 0.41), (1.48 ± 0.38) mg/L respectively for 1-4 weeks; while that after RRT was (0.57 ± 0.22), (0.60 ± 0.24), (0.56 ± 0.20), (0.56 ± 0.15) mg/L (all P < 0.05). Taken before RRT, the plasma concentration of pyrazinamide before RRT was (16.08 ± 4.95), (16.32 ± 5.73), (14.89 ± 4.53), (13.81 ± 5.83) mg/L respectively for 1-4 weeks, while that after RRT was (3.73 ± 1.57), (3.57 ± 1.53), (3.22 ± 1.00), (2.81 ± 1.34) mg/L (all P < 0.05). Taken after RRT at once, the plasma concentration of pyrazinamide before RRT was (15.57 ± 3.47), (14.10 ± 2.27), (14.73 ± 2.36), (15.9 ± 3.02) mg/L respectively for 1-4 weeks, while that after RRT was (2.45 ± 1.14), (2.19 ± 1.07), (1.87 ± 1.52), (2.33 ± 1.30)mg/L. Taken before RRT, the plasma concentration of rifampin was (3.44 ± 1.17), (3.72 ± 1.24), (3.68 ± 1.16), (3.44 ± 1.22) mg/L respectively for 1-4 weeks (all P < 0.05), while that after RRT was (2.96 ± 1.10), (3.28 ± 1.04), (3.17 ± 1.02), (2.96 ± 1.05) mg/L (all P > 0.05). Continuous RRT has different effects on the plasma drug concentration of isoniazid and pyrazinamide. It almost has no effect on rifampin. To achieve the best plasma concentration and better anti-tuberculosis results, isoniazid and pyrazinamide should be taken after RRT, but rifampin before RRT.

Pharmacokinetics of isoniazid, rifampicin, pyrazinamide and ethambutol in Indian children.

BackgroundThe available pharmacokinetic data on anti-tubercular drugs in children raises the concern of suboptimal plasma concentrations attained when doses extrapolated from adult studies are used. Also, there is lack of consensus regarding the effect of malnutrition on pharmacokinetics of anti-tubercular drugs in children. We conducted this study with the aims of determining the plasma concentrations of isoniazid, rifampicin, pyrazinamide and ethambutol achieved with different dosage of the anti-tubercular drugs so as to provide supportive evidence to the revised dosages and to evaluate the effects of malnutrition on the pharmacokinetics of these drugs in children. We also attempted to correlate the plasma concentrations of these drugs with clinical outcome of therapy.MethodProspective drug estimation study was conducted in two groups of children, age 6 months to 15 years, with tuberculosis, with or without severe malnutrition, receiving different dosage of daily anti- tubercular therapy. The dosage (range) of isoniazid was 5 (4-6) and 10 (7-15) mg/kg in the two groups, respectively, that of rifampicin-10 (8–12) and 15 (10–12) mg/kg, respectively, both the groups received same dose of pyrazinamide (30–35 mg/kg) and ethambutol (20–25 mg/kg). All four drugs were simultaneously estimated by liquid chromatography-mass spectrometry (LC-MS/MS).Results and conclusionThe median (IQR) Cmax of isoniazid increased significantly from 0.6 (0.3,1.2) μg/mL to 3.4 (1.8, 5.0) μg/mL with increase in the dose. Plasma rifampicin concentrations increased only marginally on increasing the dose [median (IQR) Cmax: 10.4 (7.2, 13.9) μg/mL vs. 12.0 (6.1, 24.3) μg/mL, p = 0.08]. For ethambutol, 55.9% of the children had inadequate 2-hour concentrations. Two-hour plasma concentrations of at least one drug were low in 59 (92.2%) and 54 (85.7%) children in the two dosing regimen, respectively. We did not observe any effect of malnutrition on pharmacokinetic parameters of the drugs studied. We did not observe an association between low plasma drug concentrations and poor outcome. We may have to be cautious while increasing the doses and strive to asses other factors influencing the drug concentrations and treatment outcomes in children.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-015-0862-7) contains supplementary material, which is available to authorized users.

Clinical significance of 2 h plasma concentrations of first-line anti-tuberculosis drugs: a prospective observational study.

To study 2 h plasma concentrations of the first-line tuberculosis drugs isoniazid, rifampicin, ethambutol and pyrazinamide in a cohort of patients with tuberculosis in Denmark and to determine the relationship between the concentrations and the clinical outcome. After 6-207 days of treatment (median 34 days) 2 h blood samples were collected from 32 patients with active tuberculosis and from three patients receiving prophylactic treatment. Plasma concentrations were determined using LC-MS/MS. Normal ranges were obtained from the literature. Clinical charts were reviewed for baseline characteristics and clinical status at 2, 4 and 6 months after the initiation of treatment. At a 1 year follow-up, therapy failure was defined as death or a relapse of tuberculosis. Plasma concentrations below the normal ranges were frequently observed: isoniazid in 71%, rifampicin in 58%, ethambutol in 46%, pyrazinamide in 10% and both isoniazid and rifampicin in 45% of the patients. The plasma concentrations of isoniazid correlated inversely with the C-reactive protein level at the time of sampling (P = 0.001). During 1 year of follow-up, therapy failure occurred in five patients. Therapy failure occurred more frequently when the concentrations of isoniazid and rifampicin were both below the normal ranges (P = 0.013) and even more frequently when they were below the median 2 h drug concentrations obtained in the study (P = 0.005). At 2 h, plasma concentrations of isoniazid and rifampicin below the normal ranges were frequently observed. The inverse correlation between the plasma concentrations of isoniazid and C-reactive protein indicate a suboptimal treatment effect at standard dosing regimens. Dichotomization based on median 2 h drug concentrations was more predictive of outcome than dichotomization based on normal ranges.