Pharmacokinetics of rifampicin, isoniazid & pyrazinamide during daily & intermittent dosing: A preliminary study.

Background & objectives: The National Tuberculosis (TB) Control Programme has transitioned from thrice-weekly to daily drug treatment regimens in India. This preliminary study was conceived to compare the pharmacokinetics of rifampicin (RMP), isoniazid (INH) and pyrazinamide (PZA) in TB patients being treated with daily and thrice weekly anti-TB treatment (ATT). Methods: This prospective observational study was undertaken in 49 newly diagnosed adult TB patients receiving either daily ATT (n=22) or thrice-weekly ATT (n=27). Plasma RMP, INH and PZA were estimated by high-performance liquid chromatography. Results: The peak concentration (Cmax) of RMP was significantly higher (RMP: 8.5 µg/ml vs. 5.5 µg/ml; P=0.003) and Cmax of INH was significantly lower (INH: 4.8 µg/ml vs. 10.9 µg/ml; P<0.001) in case of daily dosing compared to thrice-weekly ATT. Cmax of drugs and doses was significantly correlated. A higher proportion of patients had subtherapeutic RMP Cmax (8.0 µg/ml) during thrice-weekly compared to daily ATT (78% vs. 36%; P=0.004). Multiple linear regression analysis showed that Cmax of RMP was significantly influenced by the dosing rhythm, pulmonary TB and Cmax of INH and PZA by the mg/kg doses. Interpretation & conclusions: RMP concentrations were higher and INH concentrations were lower during daily ATT, suggesting that INH doses may need to be increased in case of a daily regimen. Larger studies are, however, required using higher INH doses when monitoring for adverse drug reactions and treatment outcomes.

Global estimates and determinants of antituberculosis drug pharmacokinetics in children and adolescents: a systematic review and individual patient data meta-analysis.

BACKGROUND: Suboptimal exposure to antituberculosis (anti-TB) drugs has been associated with unfavourable treatment outcomes. We aimed to investigate estimates and determinants of first-line anti-TB drug pharmacokinetics in children and adolescents at a global level. METHODS: We systematically searched MEDLINE, Embase and Web of Science (1990-2021) for pharmacokinetic studies of first-line anti-TB drugs in children and adolescents. Individual patient data were obtained from authors of eligible studies. Summary estimates of total/extrapolated area under the plasma concentration-time curve from 0 to 24 h post-dose (AUC0-24) and peak plasma concentration (C max) were assessed with random-effects models, normalised with current World Health Organization-recommended paediatric doses. Determinants of AUC0-24 and C max were assessed with linear mixed-effects models. RESULTS: Of 55 eligible studies, individual patient data were available for 39 (71%), including 1628 participants from 12 countries. Geometric means of steady-state AUC0-24 were summarised for isoniazid (18.7 (95% CI 15.5-22.6) h·mg·L-1), rifampicin (34.4 (95% CI 29.4-40.3) h·mg·L-1), pyrazinamide (375.0 (95% CI 339.9-413.7) h·mg·L-1) and ethambutol (8.0 (95% CI 6.4-10.0) h·mg·L-1). Our multivariate models indicated that younger age (especially <2 years) and HIV-positive status were associated with lower AUC0-24 for all first-line anti-TB drugs, while severe malnutrition was associated with lower AUC0-24 for isoniazid and pyrazinamide. N-acetyltransferase 2 rapid acetylators had lower isoniazid AUC0-24 and slow acetylators had higher isoniazid AUC0-24 than intermediate acetylators. Determinants of C max were generally similar to those for AUC0-24. CONCLUSIONS: This study provides the most comprehensive estimates of plasma exposures to first-line anti-TB drugs in children and adolescents. Key determinants of drug exposures were identified. These may be relevant for population-specific dose adjustment or individualised therapeutic drug monitoring.

Discovery of a highly potent novel rifampicin analog by preparing a hybrid of the precursors of the antibiotic drugs rifampicin and clofazimine.

Tuberculosis (TB) is an infectious disease caused by the bacillus Mycobacterium tuberculosis (Mtb). The present work reports the design and synthesis of a hybrid of the precursors of rifampicin and clofazimine, which led to the discovery of a novel Rifaphenazine (RPZ) molecule with potent anti-TB activity. In addition, the efficacy of RPZ was evaluated in-vitro using the reference strain Mtb H37Rv. Herein, 2,3 diamino phenazine, a precursor of an anti-TB drug clofazimine, was tethered to the rifampicin core. This 2,3 diamino phenazine did not have an inherent anti-TB activity even at a concentration of up to 2 µg/mL, while rifampicin did not exhibit any activity against Mtb at a concentration of 0.1 µg/mL. However, the synthesized novel Rifaphenzine (RPZ) inhibited 78% of the Mtb colonies at a drug concentration of 0.1 µg/mL, while 93% of the bacterial colonies were killed at 0.5 µg/mL of the drug. Furthermore, the Minimum Inhibitory Concentration (MIC) value for RPZ was 1 µg/mL. Time-kill studies revealed that all bacterial colonies were killed within a period of 24 h. The synthesized novel molecule was characterized using high-resolution mass spectroscopy and NMR spectroscopy. Cytotoxicity studies (IC50) were performed on human monocytic cell line THP-1, and the determined IC50 value was 96 µg/mL, which is non-cytotoxic.

Explaining Differences in the Acceptability of 99DOTS, a Cell Phone-Based Strategy for Monitoring Adherence to Tuberculosis Medications: Qualitative Study of Patients and Health Care Providers.

BACKGROUND: 99DOTS is a cell phone-based strategy for monitoring tuberculosis (TB) medication adherence that has been rolled out to more than 150,000 patients in India's public health sector. A considerable proportion of patients stop using 99DOTS during therapy. OBJECTIVE: This study aims to understand reasons for variability in the acceptance and use of 99DOTS by TB patients and health care providers (HCPs). METHODS: We conducted qualitative interviews with individuals taking TB therapy in the government program in Chennai and Vellore (HIV-coinfected patients) and Mumbai (HIV-uninfected patients) across intensive and continuation treatment phases. We conducted interviews with HCPs who provide TB care, all of whom were involved in implementing 99DOTS. Interviews were transcribed, coded using a deductive approach, and analyzed with Dedoose 8.0.35 software (SocioCultural Research Consultants, LLC). The findings of the study were interpreted using the unified theory of acceptance and use of technology, which highlights 4 constructs associated with technology acceptance: performance expectancy, effort expectancy, social influences, and facilitating conditions. RESULTS: We conducted 62 interviews with patients with TB, of whom 30 (48%) were HIV coinfected, and 31 interviews with HCPs. Acceptance of 99DOTS by patients was variable. Greater patient acceptance was related to perceptions of improved patient-HCP relationships from increased phone communication, TB pill-taking habit formation due to SMS text messaging reminders, and reduced need to visit health facilities (performance expectancy); improved family involvement in TB care (social influences); and from 99DOTS leading HCPs to engage positively in patients' care through increased outreach (facilitating conditions). Lower patient acceptance was related to perceptions of reduced face-to-face contact with HCPs (performance expectancy); problems with cell phone access, literacy, cellular signal, or technology fatigue (effort expectancy); high TB- and HIV-related stigma within the family (social influences); and poor counseling in 99DOTS by HCPs or perceptions that HCPs were not acting upon adherence data (facilitating conditions). Acceptance of 99DOTS by HCPs was generally high and related to perceptions that the 99DOTS adherence dashboard and patient-related SMS text messaging alerts improve quality of care, the efficiency of care, and the patient-HCP relationship (performance expectancy); that the dashboard is easy to use (effort expectancy); and that 99DOTS leads to better coordination among HCPs (social influences). However, HCPs described suboptimal facilitating conditions, including inadequate training of HCPs in 99DOTS, unequal changes in workload, and shortages of 99DOTS medication envelopes. CONCLUSIONS: In India's government TB program, 99DOTS had high acceptance by HCPs but variable acceptance by patients. Although some factors contributing to suboptimal patient acceptance are modifiable, other factors such as TB- and HIV-related stigma and poor cell phone accessibility, cellular signal, and literacy are more difficult to address. Screening for these barriers may facilitate targeting of 99DOTS to patients more likely to use this technology.

Wild-Type MIC Distribution for Re-evaluating the Critical Concentration of Anti-TB Drugs and Pharmacodynamics Among Tuberculosis Patients From South India.

The World Health Organization (WHO) has developed specific guidelines for critical concentrations (CCs) of antibiotics used for tuberculosis (TB) treatment, which is universally followed for drug susceptibility testing (DST) of clinical specimens. However, the CC of drugs can differ significantly among the mycobacterial species based on the population, geographic location, and the prevalence of the infecting strain in a particular area. The association between CC and the minimal inhibitory concentration (MIC) of anti-TB drugs is poorly understood. In this study, we assessed the MICs of anti-TB drugs, including isoniazid (INH), rifampicin (RMP), moxifloxacin (MXF), ethambutol (ETH), and p-aminosalicylic acid (PAS) on drug-sensitive Mtb isolates from pulmonary TB patients in South India. The MIC assays performed using solid- and liquid-growth media showed changes in the CC of a few of the tested antibiotics compared with the WHO-recommended levels. Our observation suggests that the WHO guidelines could potentially lead to overdiagnosis of drug-resistant cases, which can result in inappropriate therapeutic decisions. To evaluate the correlation between drug-resistance and CC, we performed the whole-genome sequencing for 16 mycobacterial isolates, including two wild-type and 14 resistant isolates. Our results showed that two of the isolates belonged to the W-Beijing lineage, while the rest were of the East-African-Indian type. We identified a total of 74 mutations, including five novel mutations, which are known to be associated with resistance to anti-TB drugs in these isolates. In our previous study, we determined the serum levels of INH and RMP among the same patients recruited in the current study and estimated the MICs of the corresponding infected isolates in these cases. Using these data and the CCs for INH and RMP from the present study, we performed pharmacodynamics (PD) evaluation. The results show that the PD of RMP was subtherapeutic. Together, these observations emphasize the need for optimizing the drug dosage based on the PD of large-scale studies conducted in different geographical settings.

Pharmacokinetics of isoniazid in children with tuberculosis-A comparative study at two doses.

AIM: To compare the pharmacokinetics of isoniazid (INH) at doses 5 and 10 mg/kg/day. METHODS: INH concentrations were estimated by high-performance liquid chromatography in 24 Indian children aged 1 to 15 years on antituberculosis therapy. Blood samples were collected at 0, 2, 4, 6, 8 hours after administration of INH. Patients were randomly given INH at 5 or 10 mg/kg/day and maximum concentrations (Cmax ) and area under the curve (AUC(0-8) ) were determined in each group. The 2-hour concentration of INH was used as Cmax for this study. RESULTS: Mean (standard deviation) Cmax was reached in 2 hours and was 2.68 ± 1.19 µg/mL in 5 mg/kg/day group and 8.86 ± 3.94 µg/mL in 10 mg/kg/day group (P < .05). The normal therapeutic range at 2-hour concentrations for INH in adults achieving good clinical response is between 3 and 5 µg/mL. Among 5 mg/kg/day, only 4 (33%) patients had INH concentrations within the 2-hour concentrations therapeutic range whereas in 10 mg/kg/day group, 11 (91%) patients achieved Cmax higher than the 2-hour concentrations therapeutic range and 1 (9%) patient had Cmax within the 2-hour concentrations therapeutic range. The mean AUC(0-8) in 5 mg/kg/day group was 10.04 ± 6.12 and 35.93 ± 25.37 µg·h/mL in 10 mg/kg/day group (P = .0001). CONCLUSION: Children on daily INH 10 mg/kg/day have higher AUC and Cmax than the required therapeutic range whereas over 65% of children with daily 5 mg/kg/day INH therapy failed to achieve the optimal therapeutic range.

4-month moxifloxacin containing regimens in the treatment of patients with sputum-positive pulmonary tuberculosis in South India - a randomised clinical trial.

BACKGROUND: Shortening tuberculosis (TB) treatment duration is a research priority. We tested the efficacy and safety of 3- and 4-month regimens containing moxifloxacin in a randomised clinical trial in pulmonary TB (PTB) patients in South India. METHODS: New, sputum-positive, adult, HIV-negative, non-diabetic PTB patients were randomised to 3- or 4-month moxifloxacin regimens [moxifloxacin (M), isoniazid (H), rifampicin (R), pyrazinamide (Z) and ethambutol (E)] or to a control regimen (2H3 R3 Z3 E3 /4R3 H3 ) [C]. The 4 test regimens were 3R7 H7 Z7 E7 M7 [M3], 2R7 H7 Z7 E7 M7 /2R7 H7 M7 [M4], 2R7 H7 Z7 E7 M7 /2R3 H3 M3 [M4-I] or 2R7 H7 Z7 E7 M7 /2R3 H3 E3 M3 [M4-IE]. Treatment was directly observed. Clinical and bacteriological assessments were done monthly during treatment and for 24 months post-treatment. The primary end point was TB recurrence post-treatment. RESULTS: Of 1371 patients, randomised, modified intention-to-treat (ITT) analysis was done in 1329 and per-protocol (PP) analysis in 1223 patients. Regimen M3 was terminated due to high TB recurrence rates. 'Favourable' response at end of treatment was 96-100% in the moxifloxacin regimens and 93% in the control  regimen. Among these, the TB recurrence occurred in 4.1% in the M4 regimen and in 4.5% in the control regimen and demonstrated equivalence within a 5% margin (95% CI -3.68, 4.55). Similar findings were observed in modified ITT analysis. The TB recurrence rates in the M4-I and M4-IE regimens did not show equivalence with the control regimen. Sixteen (1.4%) of 1087 patients in the moxifloxacin regimens required treatment modification. CONCLUSION: The 4-month daily moxifloxacin regimen [M4] was found to be equivalent and as safe as the 6-month thrice-weekly control regimen.

CONTEXTE: La réduction de la durée du traitement de la tuberculose (TB) est une priorité de recherche. Nous avons testé l'efficacité et la sécurité de schémas thérapeutiques contenant de la moxifloxacine pendant 3 et 4 mois dans un essai clinique randomisé chez des patients atteints de TB pulmonaire (PTB) dans le sud de l'Inde. MÉTHODES: De nouveaux patients PTB, adultes, non diabétiques, positifs pour les expectorations, VIH négatifs ont été randomisés pour des schémas thérapeutiques contenant de la moxifloxacine pendant 3 mois ou 4 mois [moxifloxacine (M), isoniazide (H), rifampicine (R), pyrazinamide (Z), l'éthambutol (E)] ou pour un régime témoin (2H3 R3 Z3 E3 /4R3 H3 ) [C]. Les 4 régimes de l'essai étaient 3R7 H7 Z7 E7 M7 [M3], 2R7 H7 Z7 E7 M7 /2R7 H7 M7 [M4], 2R7 H7 Z7 E7 M7 /2R3 H3 M3 [M4-I] ou 2R7 H7 Z7 E7 M7 /2R3 H3 E3 M3 [M4-IE]. Le traitement a été directement observé. Les évaluations cliniques et bactériologiques ont été effectuées mensuellement au cours du traitement et durant 24 mois après le traitement. Le critère d'évaluation principal était la récidive de la TB après le traitement. RÉSULTATS: Des 1.371 patients randomisés, une analyse en intention de traiter (ITT) modifiée a été effectuée sur 1.329 et une analyse par protocole (PP) sur 1.223 patients. Le régime M3 a été interrompu en raison de taux élevés de récidive de la TB. La réponse «favorable¼ à la fin du traitement était de 96 à 100% dans les bras moxifloxacine et 93% dans le bras témoin. Parmi ceux-ci, la récidive de la TB est survenue chez 4,1% dans le schéma M4 et chez 4,5% dans le schéma témoin et a démontré une équivalence dans une marge de 5% (IC95%: −3,68, 4,55). Des résultats similaires ont été observés dans l'analyse ITT modifiée. Les taux de récidive de la TB dans les schémas M4-I et M4-IE n'ont pas montré d'équivalence avec le schéma témoin. 16 (1,4%) des 1.087 patients dans les régimes à moxifloxacine ont nécessité une modification du traitement. CONCLUSION: Le régime quotidien de moxifloxacine pendant 4 mois [M4] s'est avéré équivalent et aussi sûr que le régime témoin de trois fois par semaine pendant 6 mois.

Subtherapeutic Rifampicin Concentration Is Associated With Unfavorable Tuberculosis Treatment Outcomes.

BACKGROUND: The relationships between first-line drug concentrations and clinically important outcomes among patients with tuberculosis (TB) remain poorly understood. METHODS: We enrolled a prospective cohort of patients with new pulmonary TB receiving thrice-weekly treatment in India. The maximum plasma concentration of each drug was determined at months 1 and 5 using blood samples drawn 2 hours postdose. Subtherapeutic cutoffs were: rifampicin <8 µg/mL, isoniazid <3 µg/mL, and pyrazinamide <20 µg/mL. Factors associated with lower log-transformed drug concentrations, unfavorable outcomes (composite of treatment failure, all-cause mortality, and recurrence), and individual outcomes were examined using Poisson regression models. RESULTS: Among 404 participants, rifampicin, isoniazid, and pyrazinamide concentrations were subtherapeutic in 85%, 29%, and 13%, respectively, at month 1 (with similar results for rifampicin and isoniazid at month 5). Rifampicin concentrations were lower with human immunodeficiency virus coinfection (median, 1.6 vs 4.6 µg/mL; P = .015). Unfavorable outcome was observed in 19%; a 1-µg/mL decrease in rifampicin concentration was independently associated with unfavorable outcome (adjusted incidence rate ratio [aIRR], 1.21 [95% confidence interval {CI}, 1.01-1.47]) and treatment failure (aIRR, 1.16 [95% CI, 1.05-1.28]). A 1-µg/mL decrease in pyrazinamide concentration was associated with recurrence (aIRR, 1.05 [95% CI, 1.01-1.11]). CONCLUSIONS: Rifampicin concentrations were subtherapeutic in most Indian patients taking a thrice-weekly TB regimen, and low rifampicin and pyrazinamide concentrations were associated with poor outcomes. Higher or more frequent dosing is needed to improve TB treatment outcomes in India.

Differential Culturability of Mycobacterium tuberculosis in Culture-Negative Sputum of Patients With Pulmonary Tuberculosis and in a Simulated Model of Dormancy.

Tuberculosis (TB) remains a leading killer among infectious diseases of humans worldwide. Delayed diagnosis is a crucial problem in global TB control programs. Bacteriological methods currently used to diagnose TB in endemic countries take up to 8 weeks, which poses a significant delay in starting antibiotic therapy. The presence of a heterogeneous population of Mycobacterium tuberculosis, the causative agent of TB, is among the reasons for delayed diagnosis by bacteriological methods. Previously, it has been shown that mycobacterial resuscitation-promoting factors (RPFs), a family of proteins secreted by actively growing bacteria into the media, are capable of activating the growth of dormant bacteria, thus enhancing the detection of bacilli in the sputum of confirmed TB cases. However, the variability in bacterial resuscitation by RPF in the sputum of suspected pulmonary TB cases that showed differential smear and/or culture positivity during diagnosis has not been fully explored. Here, we report the presence of non-replicating bacteria in the sputum of suspected TB cases that show differential growth response to RPF treatment. Using crude and recombinant RPF treatment, we show improved sensitivity and reduced time to detect bacilli in the sputum samples of smear-positive/culture-negative or smear-negative/culture-negative cases. We also report the phenotypic heterogeneity in the RPF responsiveness among Mtb strains using an in vitro dormancy model. Our findings have implications for improving the bacteriological diagnostic modalities currently used to diagnose TB in endemic countries.

Pharmacokinetics of Second-Line Anti-Tubercular Drugs.

Multidrug-resistant tuberculosis (MDR TB) has become a major global health concern and is also an issue in children. Children with MDR TB need longer duration of treatment with multiple drugs. The MDR TB treatment regimen usually comprises of a fluoroquinolone, an aminoglycoside, ethionamide, cycloserine, pyrazinamide and ethambutol. In the absence of pediatric friendly tablets/formulations, in most cases the adult tablets are either crushed or broken. This is likely to lead to inaccurate dosing. Very limited information is available on the pharmacokinetics of second-line anti-TB drugs in children with MDR TB, except for few studies from South Africa and one from India. Drugs such as linezolid, clofazimine are also being considered for the treatment of MDR TB in children. However, their pharmacokinetics is not known in the pediatric population. It is important to generate pharmacokinetic studies of drugs used to treat MDR TB in children in different settings, which would provide useful information on the adequacy of drug doses.

Pharmacokinetics of rifabutin during atazanavir/ritonavir co-administration in HIV-infected TB patients.

BACKGROUND & OBJECTIVE: Rifabutin (RBT) is the rifamycin that is recommended to treat tuberculosis (TB) in HIV-infected individuals during combination antiretroviral therapy (ART) containing HIV protease inhibitors (PIs). We studied the pharmacokinetics of rifabutin at doses of 300 mg thrice weekly and 150 mg daily during concomitant atazanavir/ritonavir (ATZ/r) administration in adult HIV-infected TB patients treated in the Revised National TB Control Programme (RNTCP) in India. METHODS: This was a multi-centric study conducted in 45 adult HIV-infected TB patients, who were being treated for TB with a RBT-containing regimen and an antiretroviral treatment regimen with ATZ/r, at doses of 300 mg thrice-weekly (n = 36) or 150 mg daily (n = 9). Serial blood draws at pre-dosing and at 1, 2, 4, 6, 8, 12 and 24 hours after drug administration were done. Plasma RBT was estimated by high pressure liquid chromatography (HPLC). RESULTS: The peak concentration (Cmax) of both doses were within the therapeutic range (0.45-0.90 µg/ml) of RBT. Proportion of patients having Cmax above or below the therapeutic range and trough concentration (Cmin) below the minimum inhibitory concentration of RBT did not significantly differ between the two doses. TB treatment outcomes were also similar at both doses. CONCLUSIONS: This is the first and only study from India reporting on the pharmacokinetics of RBT at 300 mg thrice weekly and 150 mg daily doses. Both doses yielded similar plasma RBT concentrations, outcomes and were well tolerated. RBT can be administered at either doses during ATZ/r co-administration in HIV-infected patients with TB.

A Systematic Review on the Effect of HIV Infection on the Pharmacokinetics of First-Line Tuberculosis Drugs.

INTRODUCTION: Contrasting findings have been published regarding the effect of human immunodeficiency virus (HIV) on tuberculosis (TB) drug pharmacokinetics (PK). OBJECTIVES: The aim of this systematic review was to investigate the effect of HIV infection on the PK of the first-line TB drugs (FLDs) rifampicin, isoniazid, pyrazinamide and ethambutol by assessing all published literature. METHODS: Searches were performed in MEDLINE (through PubMed) and EMBASE to find original studies evaluating the effect of HIV infection on the PK of FLDs. The included studies were assessed for bias and clinical relevance. PK data were extracted to provide insight into the difference of FLD PK between HIV-positive and HIV-negative TB patients. This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement and its protocol was registered at PROSPERO (registration number CRD42017067250). RESULTS: Overall, 27 studies were eligible for inclusion. The available studies provide a heterogeneous dataset from which consistent results could not be obtained. In both HIV-positive and HIV-negative TB groups, rifampicin (13 of 15) and ethambutol (4 of 8) peak concentration (Cmax) often did not achieve the minimum reference values. More than half of the studies (11 of 20) that included both HIV-positive and HIV-negative TB groups showed statistically significantly altered FLD area under the concentration-time curve and/or Cmax for at least one FLD. CONCLUSIONS: HIV infection may be one of several factors that reduce FLD exposure. We could not make general recommendations with respect to the role of dosing. There is a need for consistent and homogeneous studies to be conducted.

Effect of Diabetes Mellitus on the Pharmacokinetics and Pharmacodynamics of Tuberculosis Treatment.

Diabetes mellitus (DM) and tuberculosis (TB) are two common diseases with increasing geographic overlap and clinical interactions. The effect of DM and hemoglobin A1c (HbA1c) values on the pharmacokinetics (PK) and pharmacodynamics (PD) of anti-TB drugs remains poorly characterized. Newly diagnosed TB patients with and without DM starting fixed-dose, thrice-weekly treatment underwent sampling for PK assessments (predose and 0.5, 2, and 6 h postdose) during the intensive and continuation phases of treatment. The effect of DM and HbA1c values on the maximum concentration (Cmax) of rifampin, isoniazid, and pyrazinamide and the association between drug concentrations and microbiologic and clinical outcomes were assessed. Of 243 patients, 101 had DM. Univariate analysis showed significant reductions in the Cmax of pyrazinamide and isoniazid (but not rifampin) with DM or increasing HbA1c values. After adjusting for age, sex, and weight, DM was associated only with reduced pyrazinamide concentrations (adjusted geometric mean ratio = 0.74, P = 0.03). In adjusted Cox models, female gender (adjusted hazards ratio [aHR] = 1.75, P = 0.001), a lower smear grade with the Xpert assay (aHR = 1.40, P < 0.001), and the pyrazinamide Cmax (aHR = 0.99, P = 0.006) were independent predictors of sputum culture conversion to negative. Higher isoniazid or rifampin concentrations were associated with a faster time to culture conversion in patients with DM only. A pyrazinamide Cmax above the therapeutic target was associated with higher unfavorable outcomes (treatment failure, relapse, death) (odds ratio = 1.92, P = 0.04). DM and higher HbA1c values increased the risk of not achieving therapeutic targets for pyrazinamide (but not rifampin or isoniazid). Higher pyrazinamide concentrations, though, were associated with worse microbiologic and clinical outcomes. DM status also appeared to influence PK-PD relationships for isoniazid and rifampin.

Intrapatient variability in plasma rifampicin & isoniazid in tuberculosis patients.

Background & objectives: Large variability in anti-tuberculosis (TB) drug concentrations between patients is known to exist. However, limited information is available on intrapatient drug levels during the course of anti-TB treatment (ATT). This study was conducted to evaluate intrapatient variability in plasma rifampicin (RMP) and isoniazid (INH) concentrations during ATT at start of the treatment, at the end of intensive phase (IP) of ATT and at the end of ATT in adult TB patients being treated in the Revised National TB Control Programme (RNTCP). Methods: Adult TB patients (n=485), receiving thrice-weekly ATT in the RNTCP, were studied. Two-hour post-dosing concentrations of RMP and INH were determined at month 1, end of IP and end of ATT, after directly observed drug administration. Drug concentrations were estimated by high-performance liquid chromatography. Results: The median (inter-quartile range) RMP concentrations during the first month, at end of IP and end of ATT were 2.1 (0.4-5.0), 2.4 (0.6-5.5) and 2.2 (0.5-5.3) µg/ml, respectively. The corresponding INH concentrations were 7.1 (4.2-9.9), 7.2 (3.9-10.9) and 6.7 (3.9-9.5) µg/ml. None of the differences in drug concentrations obtained at different time points during ATT were significant. RMP and INH concentrations at different time points were significantly correlated. Age and body mass index caused significant variability in drug concentrations. Interpretation & conclusions: Plasma RMP and INH estimations in adult TB patients at two hours after drug administration remained unaltered during ATT. Clinicians can consider testing drug concentrations at any time point during ATT. These findings may assume significance in the context of therapeutic drug monitoring of anti-TB drug concentrations.

Pharmacokinetic study of isoniazid and pyrazinamide in children: impact of age and nutritional status.

OBJECTIVES: To evaluate pharmacokinetics of first-line antitubercular drugs, isoniazid (INH) and pyrazinamide (PZA), with revised WHO dosages and to assess its adequacy in relation to age and nutritional status. DESIGN: Observational study. SETTING: This study was conducted at Sarojini Naidu Medical College, Agra, and National Institute for Research in Tuberculosis, Chennai. PATIENTS: 40 subjects diagnosed with tuberculosis were registered in the study and started on daily first-line antitubercular regimen based on the revised WHO guidelines. INTERVENTIONS: Blood samples were collected at 0, 2, 4, 6 and 8 hours from these subjects after 15 days of treatment for drug estimations. MAIN OUTCOME MEASURE: The measurement of drug concentrations (maximum peak concentration (Cmax) and area under the time -concentration curve (AUC0-8 hours)) for INH and PZA. Appropriate statistical methods were used to evaluate the impact of age and nutritional status on pharmacokinetic variables. RESULTS: For INH, the difference in drug exposures in children <3 years (Cmax 3.18 µg/mL and AUC0-8 hours15.76 µg/mL hour) and children >3 years (Cmax3.05 µg/mL and AUC0-8 hours 14.37 µg/mL hour) was not significant (P=0.94, P=0.81, respectively). The drug levels in children with low body mass index (BMI) (Cmax3.08 µg/mL; AUC0-8 hours14.81 µg/mL hour) were also comparable with their normal counterparts (Cmax3.09 µg/mL, P=0.99; AUC0-8 hours 14.69 µg/mL hour, P=0.82). PZA drug exposures obtained in children less than 3 years (Cmax29.22 µg/mL, AUC0-8 hours 155.45 µg/mL hour) were significantly lower compared with drug levels in children above 3 years (Cmax 37.12 µg/mL, P=0.03; AUC 202.63 µg/mL hour, P value=0.01). Children with low BMI had significantly lower drug concentrations (Cmax 31.90 µg/mL, AUC0-8 hours167.64 µg/mL hour) when compared with normal counterparts (Cmax 37.60 µg/mL, P=0.02; AUC0-8 hours 208.77 µg/mL hour, P=0.01). CONCLUSIONS: The revised WHO drug dosages were found to be adequate for INH with respect to age and nutritional status, whereas PZA showed significantly lower drug levels in children <3 years and in malnourished children.

A selective and sensitive high performance liquid chromatography assay for the determination of cycloserine in human plasma.

BACKGROUND: Cycloserine (CYC) is a second line antitubercular drug that is used for the treatment of multidrug resistant tuberculosis (MDR-TB) along with other antitubercular agents and is often used in developing countries. Monitoring CYC levels in plasma could be useful in the clinical management of patients with MDR-TB. A high performance liquid chromatography method for the determination of CYC in human plasma was developed. METHODS: The method involved extraction of the sample using solid phase extraction cartridges and analysis of the extracted sample using a reverse phase T3 column (150mm) and detection at 240nm with Photo Diode Array (PDA) detector. The chromatogram was run for 15min at a flow rate of 0.4ml/min at 30°C. RESULTS AND CONCLUSION: The assay was specific for CYC and linear from 5.0 to 50.0µg/ml. The relative standard deviations of within- and between-day assays were less than 10%. Recovery of CYC ranged from 102% to 109%. The interference of other second line anti-TB drugs in the assay of CYC was ruled out. The assay spans the concentration range of clinical interest. The specificity and sensitivity of this assay makes it highly suitable for pharmacokinetic studies.

Pharmacokinetics of Second-Line Antituberculosis Drugs in Children with Multidrug-Resistant Tuberculosis in India.

We studied the pharmacokinetics of levofloxacin (LFX), pyrazinamide (PZA), ethionamide (ETH), and cycloserine (CS) in children with multidrug-resistant tuberculosis (MDR-TB) who were being treated according to the Revised National TB Control Programme (RNTCP) guidelines in India. This observational, pharmacokinetic study was conducted in 25 children with MDR-TB at the Sarojini Naidu Medical College, Agra, India, who were being treated with a 24-month daily regimen. Serial blood samples were collected after directly observed administration of drugs. Estimations of plasma LFX, PZA, ETH, and CS were undertaken according to validated methods by high-performance liquid chromatography. Adverse events were noted at 6 months of treatment. The peak concentration (Cmax) of LFX was significantly higher in female than male children (11.5 µg/ml versus 7.3 µg/ml; P = 0.017). Children below 12 years of age had significantly higher ETH exposure (area under the concentration-time curve from 0 to 8 h [AUC0-8]) than those above 12 years of age (17.5 µg/ml · h versus 9.4 µg/ml; P = 0.030). Multiple linear regression analysis showed significant influence of gender on Cmax of ETH and age on Cmax and AUC0-8 of CS. This is the first and only study from India reporting on the pharmacokinetics of LFX, ETH, PZA, and CS in children with MDR-TB treated in the Government of India program. More studies on the safety and pharmacokinetics of second-line anti-TB drugs in children with MDR-TB from different settings are required.

High Prevalence of Lipid Abnormalities and Insulin Resistance Among Antiretroviral Naïve HIV-infected Children in India.

BACKGROUND: As large numbers of children are accessing antiretroviral therapy (ART) in India, we evaluated the dietary intake, growth pattern and risk of metabolic complications like dyslipidemia and insulin resistance among ART-naïve HIV-infected children (CLHIV). METHODS: CLHIV 2-12 years of age, at the time of initiating ART in Chennai and Bangalore, were assessed for their dietary intake, anthropometry, blood CD4 cell count, HIV-1 viral load, fasting serum lipids, glucose and insulin. Homeostatic model assessment-insulin resistance was derived. RESULTS: Three hundred and ninety CLHIV (mean age [SD]: 8 [3] yrs; median viral load: 141,000 [25,876-436,000] copies/mL) were started on non-nucleoside reverse transcriptase inhibitor-based ART. Perinatal infection was documented among 97%. Sixty percent of children were in stage 3 or 4 of World Health Organization clinical staging of HIV/AIDS. Food insecurity was seen in 40% of households. A total of 204 children (52.4%) were stunted and 224 (57.6%) were underweight. Stunting seemed to be more prevalent with increasing age (0-4 years: 48%; >9 years: 60%). Mean intakes of calories, iron, folate and calcium were significantly less than recommended dietary allowances across all age groups. Dyslipidemia, in terms of any abnormal triglycerides or total cholesterol or low-density lipoprotein cholesterol (excluding high-density lipoprotein cholesterol), was seen in approximately 40% of children; insulin resistance in 17%; and C-reactive protein in risk range of metabolic syndrome in 24% of children. CONCLUSIONS: In the background of high food insecurity and malnutrition, cardiometabolic abnormalities were seen in 20%-35% of ART-naïve CLHIV in India emphasizing close monitoring of these children for long-term cardiovascular morbidities after initiation of ART.

Suboptimal Antituberculosis Drug Concentrations and Outcomes in Small and HIV-Coinfected Children in India: Recommendations for Dose Modifications.

This work aimed to evaluate the once-daily antituberculosis treatment as recommended by the new Indian pediatric guidelines. Isoniazid, rifampin, and pyrazinamide concentration-time profiles and treatment outcome were obtained from 161 Indian children with drug-sensitive tuberculosis undergoing thrice-weekly dosing as per previous Indian pediatric guidelines. The exposure-response relationships were established using a population pharmacokinetic-pharmacodynamic approach. Rifampin exposure was identified as the unique predictor of treatment outcome. Consequently, children with low body weight (4-7 kg) and/or HIV infection, who displayed the lowest rifampin exposure, were associated with the highest probability of unfavorable treatment (therapy failure, death) outcome (Punfavorable ). Model-based simulation of optimized (Punfavorable ≤ 5%) rifampin once-daily doses were suggested per treatment weight band and HIV coinfection status (33% and 190% dose increase, respectively, from the new Indian guidelines). The established dose-exposure-response relationship could be pivotal in the development of future pediatric tuberculosis treatment guidelines.