Pharmacological issues in the treatment of tuberculosis

Study of risk factors and clinical management of patients with clinical non-response due to low plasma levels of anti-tubercular drugs

This study was carried out to assess the role of therapeutic drug monitoring of crucial first-line anti-tubercular drugs: rifampicin (R) and isoniazid (H) among 75 non-responding proven drug-sensitive tuberculosis patients on treatment followed by intervention in field conditions. The intervention was done in the form of either an increase in the dosage of R and H in patients with minimally low drug levels or a modification of the regimen in a certain group of patients with significantly low drug levels by augmenting it with three or four second-line drugs in addition to standard first-line drugs. This study also aimed to determine the relationship between the measured plasma concentration of anti-tubercular drugs and various demographic, microbiological, radiological, and malabsorption factors and the presence of co-morbidities affecting them. The study also focused on the clinical impact of the intervention for low plasma levels of anti-TB drugs on TB treatment outcomes. In our study overall, 85.5% of patients had low levels of any drug. In 85.3% of patients, R levels were low, and in 39.1%, H levels were low. On univariate analysis, low body mass index (BMI), hypoalbuminemia, bilateral disease on chest X-rays, and the presence of cavities were found to be significantly associated with low drug levels, while none of the factors were independently significantly associated. Low BMI, pulmonary tuberculosis and disseminated tuberculosis, far-advanced disease and bilateral disease on chest X-ray, presence of cavities, and only low R levels were associated with unfavorable outcomes, with none of the factors found to be significant on multivariate analysis. In our study, it was seen that the treatment outcome was favorable in 59.6% of patients in whom this intervention was done by augmenting the treatment regimen with three/four second-line drugs along with increasing the dose of R and H. To conclude, various factors may be associated with low plasma levels of anti-tubercular drugs. If such patients show clinical non-response after >6 months of treatment and have significantly low drug levels, with an absence of drug resistance, their treatment regimen may need augmentation with three/four second-line drugs along with an increase in the dose of R and H, which may lead to a favorable outcome.

The Role of Therapeutic Drug Monitoring in Slow Response Extra-Pulmonary Tuberculosis Treatment: A Case Report

Tuberculosis is caused by an infectious bacterium and it has significant morbidity and mortality rates globally. It mostly affects the lungs, but it can also spread to other parts of the body, like the lymph nodes (tuberculous lymphadenitis). The most common way to treat it is with the RIPE regimen, which includes rifampin, isoniazid, pyrazinamide, and ethambutol. The drugs can be slowly or rapidly metabolized, resulting in either increased toxicity or subtherapeutic drug levels. In this paper, we discuss the case of a slow responder who was treated with increased rifampin and isoniazid doses and improved clinically and biochemically. It's the first case of a slow responder diagnosed with tuberculous lymphadenitis reported in the Gulf region.

Circadian gene variants and the skeletal muscle circadian clock contribute to the evolutionary divergence in longevity across Drosophila populations

Organisms use endogenous clocks to adapt to the rhythmicity of the environment and to synchronize social activities. Although the circadian cycle is implicated in aging, it is unknown whether natural variation in its function contributes to differences in lifespan between populations and whether the circadian clock of specific tissues is key for longevity. We have sequenced the genomes of Drosophila melanogaster strains with exceptional longevity that were obtained via multiple rounds of selection from a parental strain. Comparison of genomic, transcriptomic, and proteomic data revealed that changes in gene expression due to intergenic polymorphisms are associated with longevity and preservation of skeletal muscle function with aging in these strains. Analysis of transcription factors differentially modulated in long-lived versus parental strains indicates a possible role of circadian clock core components. Specifically, there is higher period and timeless and lower cycle expression in the muscle of strains with delayed aging compared to the parental strain. These changes in the levels of circadian clock transcription factors lead to changes in the muscle circadian transcriptome, which includes genes involved in metabolism, proteolysis, and xenobiotic detoxification. Moreover, a skeletal muscle-specific increase in timeless expression extends lifespan and recapitulates some of the transcriptional and circadian changes that differentiate the long-lived from the parental strains. Altogether, these findings indicate that the muscle circadian clock is important for longevity and that circadian gene variants contribute to the evolutionary divergence in longevity across populations.

Clinical response of tuberculosis patients, a prospective cohort study

Clinical response means a response to drug intake that can be detected and appreciated by a change in signs and symptoms. The objectives of this study were to assess time to clinical response, the incidence density for clinical response and determinants of clinical response of tuberculosis (TB) patients in the intensive phases of TB treatment. Prospective cohort study design was implemented. The target population for this study was all patients following the directly observed therapy. Baseline data has been collected during the start of the directly observed TB treatment strategy. We have been collected updated data after the seven days of the baseline data collection, then after every seven days updated data has been collected from each pulmonary and extra pulmonary TB patients. Kaplan Meier curve was used to estimate time to clinical response. Incidence density using person days was used to estimate incidence of clinical response. Cox proportional hazard model was used to identify the predictors of clinical responses. A total of 1608 TB patients were included with a response rate at 99.5%. The mean age of the respondents was 24.5 years [standard deviation (SD) 14.34 years]. The incidence density for clinical response was 1429/38529 person days. One fourth of the TB patients showed clinical response at day 14, 25% of at day 21 and 75% o at day 31. Predictors of clinical response for TB patients includes: age (AHR 1.007 [95% CI 1.003-1.011]), type of TB (AOR 2.3[95% CI 2.04-2.59]), Previous history of TB (AHR 0.18 [95% CI 0.11-0 .30]), Intestinal parasitic infection (AOR 0.22[95% CI 0.19-0.26]), hemoglobin (AOR 2.35 [95% CI 2.18-2.54]), weight gain (AOR 1.11 [95% CI 1.05-1.17]), Micronutrient supplementation (AOR 9.71 [95% CI 8.28-11.38]), male sex (AOR 0.87 [95% CI 0.79-0.97]).The clinical responses for extra-pulmonary TB patients were slower than pulmonary TB. Deworming and micronutrient supplementation should be considered as the additional TB treatment strategy for TB patients.

Adverse effects of oral second-line antituberculosis drugs in children

INTRODUCTION

Increasing numbers of children with drug-resistant tuberculosis are accessing second-line antituberculosis drugs; these are more toxic than first-line drugs. Little is known about the safety of new antituberculosis drugs in children. Knowledge of adverse effects, and how to assess and manage these, is important to ensure good adherence and treatment outcomes.

AREAS COVERED

A Pubmed search was performed to identify articles addressing adverse effects of second-line antituberculosis drugs; a general search was done for the new drugs delamanid and bedaquiline. This review discusses adverse effects associated with oral second-line antituberculosis drugs. The spectrum of adverse effects caused by antituberculosis drugs is wide; the majority are mild or moderate, but these are important to manage as it could lead to non-adherence to treatment. Adverse effects may be more common in HIV-infected than in HIV-uninfected children.

EXPERT OPINION

Although children may experience fewer adverse effects from oral second-line antituberculosis drugs than adults, evidence from prospective studies of the incidence of adverse events in children is limited. Higher doses of second-line drugs, new antituberculosis drugs, and new drug regimens are being evaluated in children: these call for strict pharmacovigilance in children treated in the near future, as adverse effect profiles may change.

Therapeutic drug monitoring: how to improve drug dosage and patient safety in tuberculosis treatment

In this article we describe the key role of tuberculosis (TB) treatment, the challenges (mainly the emergence of drug resistance), and the opportunities represented by the correct approach to drug dosage, based on the existing control and elimination strategies. In this context, the role and contribution of therapeutic drug monitoring (TDM) is discussed in detail. Treatment success in multidrug-resistant (MDR) TB cases is low (62%, with 7% failing or relapsing and 9% dying) and in extensively drug-resistant (XDR) TB cases is even lower (40%, with 22% failing or relapsing and 15% dying). The treatment of drug-resistant TB is also more expensive (exceeding €50,000 for MDR-TB and €160,000 for XDR-TB) and more toxic if compared to that prescribed for drug-susceptible TB. Appropriate dosing of first- and second-line anti-TB drugs can improve the patient's prognosis and lower treatment costs. TDM is based on the measurement of drug concentrations in blood samples collected at appropriate times and subsequent dose adjustment according to the target concentration. The 'dried blood spot' technique offers additional advantages, providing the rationale for discussions regarding a possible future network of selected, quality-controlled reference laboratories for the processing of dried blood spots of difficult-to-treat patients from reference TB clinics around the world.

New anti-tuberculosis drugs and regimens: 2015 update

Over 480 000 cases of multidrug-resistant (MDR) tuberculosis (TB) occur every year globally, 9% of them being affected by extensively drug-resistant (XDR) strains of Mycobacterium tuberculosis. The treatment of MDR/XDR-TB is unfortunately long, toxic and expensive, and the success rate largely unsatisfactory (<20% among cases with resistance patterns beyond XDR).

The aim of this review is to summarise the available evidence-based updated international recommendations to manage MDR/XDR-TB, and to update the reader on the role of newly developed drugs (delamanid, bedaquiline and pretomanid) as well as repurposed drugs (linezolid and meropenem clavulanate, among others) used to treat these conditions within new regimens.

A nonsystematic review based on historical trials results as well as on recent literature and World Health Organization (WHO) guidelines has been performed, with special focus on the approach to managing MDR/XDR-TB.

The new, innovative global public health interventions, recently approved by WHO and known as the “End TB Strategy”, support the vision of a TB-free world with zero death, disease and suffering due to TB. Adequate, universally accessed treatment is a pre-requisite to reach TB elimination. New shorter, cheap, safe and effective anti-TB regimens are necessary to boost TB elimination.

The new WHO post-2015 End TB Strategy will support the efforts that research on new drugs and regimens requireshttp://ow.ly/LnJER

Epigenetic mechanisms regulate placental c-myc and hTERT in normal and pathological pregnancies; c-myc as a novel fetal DNA epigenetic marker for pre-eclampsia

Placental development is known for its resemblance with tumor development, such as in the expression of oncogenes (c-myc) and telomerase (hTERT). The expression of c-myc and hTERT is up-regulated during early pregnancy and gestational trophoblastic diseases (GTDs). To determine the role of DNA methylation [via methylation-sensitive high resolution melting (MS-HRM)] and histone modifications [via chromatin immunoprecipitation (ChIP assay)] in regulating the differential expression of c-myc and hTERT during normal gestation and their dysregulation during placental disorders, we obtained placental samples from 135 pregnant women, in five groups: normal first, second and third trimester (n = 30 each), pre-eclamptic pregnancy (n = 30) and molar pregnancy (n = 15). Two placental cell lines (JEG-3 and HTR-8/SVneo) and isolated first-trimester cytotrophoblasts were also studied. Quantitative RT-PCR revealed decreased mRNA expression levels of c-myc and hTERT, which were associated with a higher level of H3K9me3 (1.5-fold, P < 0.05) and H3K27me3 (1.9-fold, P < 0.05), respectively, in third-trimester placental villi versus first-trimester villi. A significantly lower level of H3K27me3 in molar placenta was associated with a higher mRNA expression of c-myc and hTERT. The development of pre-eclampsia (PE) was associated with increased methylation (P < 0.001) and H3K27me3 (P < 0.01) at the c-myc promoter and reduced H3K9me3 (P < 0.01) and H3K27me3 (P < 0.05) at the hTERT promoter. Further, mRNA expression of c-myc and hTERT was strongly correlated in molar villi (r = 0.88, P < 0.01) and JEG-3 cells (r = 0.99, P < 0.02). Moreover, on the basis of methylation data, we demonstrate the potential of c-myc as a fetal DNA epigenetic marker for pre-eclamptic pregnancies. Thus we suggest a role for epigenetic mechanisms in regulating differential expression of c-myc and hTERT during placental development and use of the c-myc promoter region as a potential fetal DNA marker in the case of PE.

Inputs drive cell phenotype variability

What is the significance of the extensive variability observed in individual members of a single-cell phenotype? This question is particularly relevant to the highly differentiated organization of the brain. In this study, for the first time, we analyze the in vivo variability within a neuronal phenotype in terms of input type. We developed a large-scale gene-expression data set from several hundred single brainstem neurons selected on the basis of their specific synaptic input types. The results show a surprising organizational structure in which neuronal variability aligned with input type along a continuum of sub-phenotypes and corresponding gene regulatory modules. Correlations between these regulatory modules and specific cellular states were stratified by synaptic input type. Moreover, we found that the phenotype gradient and correlated regulatory modules were maintained across subjects. As these specific cellular states are a function of the inputs received, the stability of these states represents “attractor”-like states along a dynamic landscape that is influenced and shaped by inputs, enabling distinct state-dependent functional responses. We interpret the phenotype gradient as arising from analog tuning of underlying regulatory networks driven by distinct inputs to individual cells. Our results change the way we understand how a phenotypic population supports robust biological function by integrating the environmental experience of individual cells. Our results provide an explanation of the functional significance of the pervasive variability observed within a cell type and are broadly applicable to understanding the relationship between cellular input history and cell phenotype within all tissues.

Impact of food intake on the pharmacokinetics of first-line antituberculosis drugs in Taiwanese tuberculosis patients

BACKGROUND/PURPOSE

Under the directly observed treatment, short course (DOTS) program, antituberculosis (anti-TB) medications were possibly taken at random time, regardless of whether it was prior to or after meals. This study was to evaluate the impact of food intake on pharmacokinetic profiles of first-line TB drugs in Taiwanese TB patients, as well as the relationship between drug levels and pharmacogenetics.

METHODS

This open-label, randomized, cross-over study included newly diagnosed Taiwanese TB patients treated between January 2010 and February 2011 at Taipei Medical University-Wan Fang Hospital. Rifater [a fixed-dose combination formulation of isoniazid (INH), rifampicin (RIF), and pyrazinamide (PZA)] and ethambutol (EMB) were given according to national TB guidelines. Blood samples were collected prior to and 1 hour, 2 hours, 4 hours, 6 hours, and 10 hours after dosing under fasting or postprandial conditions. Pharmacokinetic parameters of the maximum serum concentration (Cmax), time to Cmax, and area under the serum concentration-time curve from the beginning to the 10(th) hour (AUC0-10) were calculated.

RESULTS

Sixteen TB patients were included and received anti-TB treatment under the DOTS program after discharge. The overall effects showed that food intake reduced the mean Cmax (INH: 40.6%, RIF: 40.2%, EMB 34.4%, PZA: 24.4%) and AUC0-10 (INH: 21.3%, RIF: 26.4%, EMB: 12.2%, PZA: 12.0%). Meanwhile, food increased the time to Cmax (INH: 78.1%, RIF: 151.3%, EMB: 41.4%, PZA: 148.9%).

CONCLUSION

Significantly lower serum drug concentrations were observed under postprandial conditions than fasting conditions for INH, RIF, and PZA. The impact of taking random anti-TB drugs under the DOTS program instead of taking drugs regularly prior to meals requires further study.

Low plasma levels of cholecalciferol and 13-cis-retinoic acid in tuberculosis: implications in host-based chemotherapy

OBJECTIVE

The aim of this study was to estimate the concentration of cholecalciferol and 13-cis-retinoic acid (RA) in the plasma and pleural fluid of patients with tuberculosis (TB) against controls.

METHODS

Plasma levels of cholecalciferol and 13-cis-RA were measured in 22 patients with TB and healthy controls and their pleural fluids levels were measured in 6 TB patients and diseased controls by established high-performance liquid chromatography-based procedure.

RESULTS

Cholecalciferol levels in plasma and pleural fluid of patients with TB and healthy controls were 67.45 (10.71) nmol/L and 21.40 (8.58) nmol/L compared with 117.43 (18.40) nmol/L (P < 0.001) and 94.73 (33.34) nmol/L (P = 0.0049), respectively. 13-cis-RA level in the plasma of patients with TB and healthy controls were 1.51 (0.72) nmol/L and 6.67 (0.81) nmol/L (P < 0.001), respectively. 13-cis-RA was not detectable in pleural fluid. The levels of both the agents were lower in patients with TB than in controls.

CONCLUSION

It was observed that in patients with TB there is a combined deficiency of cholecalciferol and 13-cis-RA compared with healthy volunteers. Because cholecalciferol and 13-cis-RA are in equilibrium with active ingredients of vitamins A and D, we feel that there is a combined deficiency of these vitamins in patients with TB. There is an evidence that concomitant vitamin A and D supplementation can kill intracellular Mycobacterium tuberculosis in vitro. Therefore, the observations made in this study can pave the path for a trial of combined supplementation of available formulations of vitamin A and D (cholecalciferol and 13-cis-RA) for novel anti-tubercular drug therapy. Because such an approach is host-based it has potential to treat even multidrug-resistant and extensively drug-resistant forms of TB.

Human chorionic gonadotropin (hCG) modulation of TIMP1 secretion by human endometrial stromal cells facilitates extravillous trophoblast invasion in vitro

STUDY QUESTION

Are secreted extracellular matrix (ECM) remodelling elements, relevant to embryo implantation and placentation, modified by hCG in endometrial stromal cells (ESCs)?

SUMMARY ANSWER

hCG decreases tissue inhibitor of metalloproteinase 1 (TIMP-1) secretion in ESCs, thereby facilitating extravillous trophoblast invasion in vitro.

WHAT IS KNOWN ALREADY

Successful embryo implantation and placentation depend on the appropriate invasion of the trophoblast into the maternal endometrial stroma. hCG is one of the earliest embryo-derived secreted signals in the endometrium which abundantly expresses hCG receptors. However, there is little data concerning the effects of hCG on endometrial ECM remodelling with respect to embryo implantation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This study was conducted in an academic research laboratory within a tertiary-care hospital. Samples were collected from 36 women undergoing benign gynaecological surgery during the mid-secretory phase. ESCs were isolated and stimulated with hCG (10 UI/ml) or vehicle. Conditioned media (CM) were analysed to determine changes in the secreted profile of nine matrix metalloproteinases (MMPs) and three tissue-specific inhibitors of MMPs (TIMPs) using an ELISA array. Data were confirmed by gelatine zymography, western blot and ELISA. The HTR8/SVneo cell line served as a model for trophoblast cells. The invasive potential of trophoblast cells was assessed using Transwell invasion assays under CM or co-culture conditions with ECS and the role of regulated molecules was examined by using immunoprecipitation in CM prior to the assessment of invasive potential.

MAIN RESULTS AND THE ROLE OF CHANCE

MMP-2 levels increased 30%, whereas TIMP-1 levels decreased 20% in CM from ESCs stimulated with hCG (P < 0.05). Gelatine zymography confirmed an increase in MMP-2 activity (P < 0.05). ELISA and western blotting also confirmed the reduction in TIMP-1 upon hCG treatment (P < 0.05). Invasion assays revealed a ∼50% increase in invading HTR8/SVneo cells in chambers with hCG-stimulated ESCs compared with the control (P < 0.05). Immunodepletion of TIMP-1 from control ESC-CM partially resembled the effect of CM from hCG-stimulated ESCs in the trophoblast invasion assays.

LIMITATIONS, REASONS FOR CAUTION

The assays were performed in vitro and ESCs were not decidualized, therefore they reflected the very early stages of embryo implantation or the advanced stages when decidualization fails.

WIDER IMPLICATIONS OF THE FINDINGS

Our data suggest that hCG induces endometrial stromal extracellular remodelling by modulating secreted MMP-2 and TIMP-1. This regulation may be physiologically relevant because it increases the invasive potential of trophoblast-derived cells. At present, few data exist concerning the implications of hCG and endometrial ECM remodelling in embryo implantation. Hence, our results should be confirmed by further in vivo studies.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by FONDECYT 11100443, PBCT-PSD51 (IDIMI) and FONDAP 15010006. None of the authors have any conflicts of interest to declare.

Immediate pain response to interlaminar lumbar epidural steroid administration: response characteristics and effects of anesthetic concentration

BACKGROUND AND PURPOSE

Interlaminar LESIs are commonly used to treat LBP or radiculopathy. Most studies focus on the long-term outcomes of LESI. The purpose of this study is to evaluate the immediate effects of fluoroscopically guided LESI on LBP/radiculopathy including low- or high-strength anesthetic response.

MATERIALS AND METHODS

The procedure notes, post-procedure records, and imaging records dedicated spine nurse assessments, and imaging records were retrospectively evaluated in 392 fluoroscopically guided LESIs performed in 276 patients (nonrandomized, nonblinded; 131 males, 145 females; average age, 56 years) with LBP/radiculopathy using either low- or high-strength anesthetic (80 mg of methylprednisilone mixed with bupivacaine [0.25% or 0.5%]). Post-procedure documentation of the patient's pre- and postprocedure VAS pain-scale level were tabulated.

RESULTS

Single LESI was performed in 199 patients, with multiple LESIs in 77 (193 injections). Low-strength bupivacaine (0.25%) was used in 237 injections, with high-strength (0.5%) in 155. Complete to near-complete immediate pain relief (<20% residual pain) was reported after 197 of 392 (50.3%) injections. No pain relief was reported after 60 (15.4%) injections (>80% residual), with partial relief in the remainder. No statistical difference was noted between low- and high-anesthetic strength or between single- and multiple-injection patients. In multiple-LESI patients, consistent pain relief response was noted in 39 of 77 (50.6%) patients, with improving LESI response in 20.8%, deteriorating LESI response in 19.5%, and variable response in 9.1%.

CONCLUSIONS

An immediate pain-extinction response is identified after LESI, which appears independent of anesthetic strength. This observation may relate to pain origin and/or pain nociceptor afferent pathway in an individual patient and potentially relate to treatment response.

Assessing the risk of birth defects associated with exposure to fixed-dose combined antituberculous agents during pregnancy in rats

Due to the risks of disease progression and transmission to the newborn, treatment of tuberculosis is often pursued during pregnancy and fixed-dose combined antituberculous agents have been found to be beneficial. Unfortunately, there is paucity of data on the safety of the fixed-dose combined antituberculous drugs during pregnancy. This study intends to assess the teratogenic effect of fixed-dose combined antituberculous drugs on the organogenesis stage of fetal development and also investigate the possible roles of vitamin C in modulating the teratogenic effects of these agents on the fetus using animal model. Pregnant rats were divided into 3 groups with 12 animals per group: group 1 received distilled water (10 mL/kg) orally; group 2 received 51.4 mg/kg/day of fixed-dose combined antituberculous agents orally; group 3 received 51.4 mg/kg/day of fixed-dose combined antituberculous agents plus vitamin C (10 mg/kg/day) orally. Six rats in each group were randomly selected and sacrificed on day 20 by cervical dislocation prior to day 21 of gestation, and the foetuses were harvested through abdominal incision for physical examination. Blood samples were collected from the 1st filial rats of the remaining six animals for biochemical and hematological examination. The liver, kidney, heart, and brain of all the sacrificed animals were used for histopathological examination. There were significant (P ≤ 0.05) low birth weights of the foetuses of the animals that were treated with fixed-dose combined antituberculous agents. The haematological parameters also revealed a reduction in the platelets counts and neutrophiles at the first filial generation. Significant (P ≤ 0.05) elevations in the levels of aspartate aminotransferase (AST) and alkaline phosphatase (ALP) in the foetuses of the animals treated with fixed-dose combined antituberculous agents were also observed. However, the combination of vitamin C with fixed-dose combined antituberculous agents significantly (P ≤ 0.05) reduced the level of AST. Fixed-dose combined antituberculous agents have teratogenic potential as shown in low birth weight and mild liver damage in the first filial of the treated animals. As much as it is imminent to treat TB patients in pregnancy, there is need to always exercise caution and clinically weigh the risk-benefit ratio.

Mutations in gidB confer low-level streptomycin resistance in Mycobacterium tuberculosis

The global threat posed by drug-resistant strains of Mycobacterium tuberculosis demands a greater understanding of the genetic basis and molecular mechanisms that govern how such strains develop resistance against various antituberculous drugs. In this report, we examine a new genetic basis for resistance to one of the oldest and most widely used second-line drugs employed in tuberculosis therapy, streptomycin (SM). This marker for SM resistance was first discovered on the basis of genomic data obtained from drug-resistant M. tuberculosis strains collected in Japan, wherein an association was observed between SM resistance and a mutation in gidB, a putative 16S rRNA methyltransferase. By evaluating an isogenic ΔgidB mutant strain constructed from strain H37Rv, we demonstrate the causal role of gidB in conferring a low-level SM-resistant phenotype in M. tuberculosis with a 16-fold increase in the MIC over the parent strain. Among clinical isolates, the modest increase in SM resistance conferred by a gidB mutation leads to an MIC distribution of gidB mutation-containing strains that spans the recommended SM breakpoint concentration currently used in drug susceptibility testing protocols. As such, some gidB mutation-containing isolates are found to be SM sensitive, while others are SM resistant. On the basis of a pharmacodynamic analysis and Monte Carlo simulation, those isolates that are found to be SM sensitive should still respond favorably to SM treatment, while nearly half of those found to be SM resistant will likely respond poorly. This report provides the first microbiological evidence for the contribution of gidB in streptomycin resistance and examines the clinical implications of mutations in the gidB gene.

Therapeutic drug monitoring for slow response to tuberculosis treatment in a state control program, Virginia, USA

TOC summary: Diabetes was associated with increased risk for slow response and low rifampin levels.

Therapeutic drug monitoring may be useful in tuberculosis management, but programmatic implementation is understudied. We performed a retrospective cohort study to determine prevalence of lower than expected levels of isoniazid, rifampin, ethambutol, and pyrazinamide measured at time of estimated peak serum concentration. Patients were tested for serum concentration at 2 hours after medication administration. When patients were tested, 22 had concentrations lower than expected range for rifampin, 23 of 39 patients had low levels of isoniazid, and 8 of 26 patients had low levels of ethambutol; all 20 patients tested for pyrazinamide were within expected range. Over 26 months, 42 patients met criteria for slow response. Diabetes was associated with slow response (p<0.001), and persons with diabetes were more likely than persons without diabetes to have low rifampin levels (p = 0.03). Dosage adjustment of rifampin was more likely to elevate serum concentration to the target range than adjustment of isoniazid given in daily doses (p = 0.01).

Chronic pelvic pain and endometriosis: translational evidence of the relationship and implications

BACKGROUND

Many clinicians and patients believe that endometriosis-associated pain is due to the lesions. Yet causality remains an enigma, because pain symptoms attributed to endometriosis occur in women without endometriosis and because pain symptoms and severity correlate poorly with lesion characteristics. Most research and reviews focus on the lesions, not the pain. This review starts with the recognition that the experience of pain is determined by the central nervous system (CNS) and focuses on the pain symptoms.

METHODS

Comprehensive searches of Pubmed, Medline and Embase were conducted for current basic and clinical research on chronic pelvic pain and endometriosis. The information was mutually interpreted by a basic scientist and a clinical researcher, both in the field of endometriosis. The goal was to develop new ways to conceptualize how endometriosis contributes to pain symptoms in the context of current treatments and the reproductive tract.

RESULTS

Endometriotic lesions can develop their own nerve supply, thereby creating a direct and two-way interaction between lesions and the CNS. This engagement provides a mechanism by which the dynamic and hormonally responsive nervous system is brought directly into play to produce a variety of individual differences in pain that can, in some women, become independent of the disease itself.

CONCLUSIONS

Major advances in improving understanding and alleviating pain in endometriosis will likely occur if the focus changes from lesions to pain. In turn, how endometriosis affects the CNS would be best examined in the context of mechanisms underlying other chronic pain conditions.

PA-824 exhibits time-dependent activity in a murine model of tuberculosis

PA-824 is one of two nitroimidazoles in phase II clinical trials to treat tuberculosis. In mice, it has dose-dependent early bactericidal and sterilizing activity. In humans with tuberculosis, PA-824 demonstrated early bactericidal activity (EBA) at doses ranging from 200 to 1,200 mg per day, but no dose-response effect was observed. To better understand the relationship between drug exposure and effect, we performed a dose fractionation study in mice. Dose-ranging pharmacokinetic data were used to simulate drug exposure profiles. Beginning 2 weeks after aerosol infection with Mycobacterium tuberculosis, total PA-824 doses from 144 to 4,608 mg/kg were administered as 3, 4, 8, 12, 24, or 48 divided doses over 24 days. Lung CFU counts after treatment were strongly correlated with the free drug T(>MIC) (R(2) = 0.87) and correlated with the free drug AUC/MIC (R(2) = 0.60), but not with the free drug C(max)/MIC (R(2) = 0.17), where T(>MIC) is the cumulative percentage of the dosing interval that the drug concentration exceeds the MIC under steady-state pharmacokinetic conditions and AUC is the area under the concentration-time curve. When the data set was limited to regimens with dosing intervals of ≤72 h, both the T(>MIC) and the AUC/MIC values fit the data well. Free drug T(>MIC) of 22, 48, and 77% were associated with bacteriostasis, a 1-log kill, and a 1.59-log kill (or 80% of the maximum observed effect), respectively. Human pharmacodynamic simulations based on phase I data predict 200 mg/day produces free drug T(>MIC) values near the target for maximal observed bactericidal effect. The results support the recently demonstrated an EBA of 200 mg/day and the lack of a dose-response between 200 and 1,200 mg/day. T(>MIC), in conjunction with AUC/MIC, is the parameter on which dose optimization of PA-824 should be based.

Clinical pharmacology and lesion penetrating properties of second- and third-line antituberculous agents used in the management of multidrug-resistant (MDR) and extensively-drug resistant (XDR) tuberculosis

Failure of first-line chemotherapy to cure tuberculosis (TB) patients occurs, in part, because of the development of resistance to isoniazid (INH) and rifampicin (RIF) the two most sterilizing agents in the four-drug regimen used to treat primary infections. Strains resistant to both INH and RIF are termed multidrug-resistant (MDR). Treatment options for MDR patients involve a complex array of twenty different drugs only two classes of which are considered to be highly effective (fluoroquinolones and aminoglycosides). Resistance to these two classes results in strains known as extensively drug-resistant (XDR) and these types of infections are becoming increasingly common. Many of the remaining agents have poorly defined pharmacology but nonetheless are widely used in the treatment of this disease. Several of these agents are known to have highly variable exposures in healthy volunteers and little is known in the patients in which they must be used. Therapeutic drug monitoring (TDM) is infrequently used in the management of MDR or XDR disease yet the clinical pharmacokinetic studies that have been done suggest this might have a large impact on disease outcome. We review what is known about the pharmacologic properties of each of the major classes of second- and third-line antituberculosis agents and suggest where judicious use of TDM would have the maximum possible impact. We summarize the state of knowledge of drug-drug interactions (DDI) in these classes of agents and those that are currently in clinical trials. Finally we consider what little is known about the ability of TB drugs to reach their ultimate site of action--the interior of a granuloma by penetrating the diseased lung area. Careful consideration of the pharmacology of these agents is essential if we are to avoid further fueling the growing epidemic of highly drug-resistant TB and critical in the development of new antituberculosis drugs.

The 5-lipoxygenase/leukotriene pathway in preclinical models of cardiovascular disease

Leukotrienes (LTs) derived from 5-lipoxygenase (5-LO) activity are most widely known for their actions during acute inflammation and asthma. 5-LO/LT pathway involvement in cardiovascular disease (CVD) pathogenesis has come to the forefront based on provocative human genetic/population and animal studies leading to the hypothesis that this pathway promotes atherosclerosis, abdominal aortic aneurysm, and myocardial infarction/reperfusion injury via increased leucocyte chemotaxis, vascular inflammation and enhanced permeability, and subsequent tissue/matrix degeneration. A series of pre-clinical studies have tested this hypothesis by means of genetic or pharmacological inhibition of either the LT biosynthesis axis (5-LO, 5-LO-activating protein, LTA(4) hydrolase, LTC(4) synthase) or the cognate LT receptors. Here, we summarize, compare, and analyse these animal studies and relate their findings to human disease pathogenesis. We draw a complex picture of 5-LO/LT participation in cardiovascular disorders, which is further complicated by marked differences between species. Moreover, we discuss how the cytokine footprint of the respective pathological conditions determines the expression level and hence, the contribution of components of the pathway to the overall disease state. Current knowledge implies a role for 5-LO and LTs during the early/acute phase of CVD, but our understanding of a putative 5-LO/LT involvement in more advanced stages of CVD is limited, thereby preventing simple extrapolation of findings from animal studies to humans.

Metastasis associated lung adenocarcinoma transcript 1 is up-regulated in placenta previa increta/percreta and strongly associated with trophoblast-like cell invasion in vitro

Placenta previa increta/percreta (I/P) is a severe form of invasive placentation associated with massive peripartum hemorrhage, which often requires Cesarean hysterectomy. The pathogenesis of invasive placentation is multidimensional, involving decidual deficiency, endomyometrial damage and excessively deep trophoblast invasion into the uterus. In this study, annealing control primer-polymerase chain reaction (ACP-PCR) was used to identify differentially expressed genes, which may impair placentation resulting in placenta previa I/P. Placental tissues from I/P and non-increta/percreta (non-I/P) sites were concomitantly collected from patients undergoing Cesarean hysterectomy. After ACP-PCR experiments (three patients), the differentially expressed bands, consistently showing up- or down-regulated trends between each of the I/P and non-I/P tissue pairs, were cloned and sequenced. Human non-protein coding metastasis associated lung adenocarcinoma transcript 1 (MALAT-1) gene was identified. Real-time quantitative PCR (10 patients) confirmed significant overexpression of MALAT-1 in I/P samples (P = 0.005). To investigate the role of MALAT-1 gene in the regulation of trophoblast cell invasion, targeting of MALAT-1 mRNA expression with short interfering RNA (siRNA) in trophoblast-like BeWo, JAR and JEG-3 choriocarcinoma cells was performed. The invasion ability of these cells was significantly suppressed after siRNA silencing (P < 0.001), and this was not correlated with abnormal MMP-2 and MMP-9 enzyme activities. Our results suggest that MALAT-1 expression in placenta previa I/P is increased and its down-regulation inhibits trophoblast-like cell invasion in vitro. MALAT-1 might be involved in regulating trophoblast invasion during the development of advanced invasive placentation.

Tuberculosis pharmacotherapy: strategies to optimize patient care

INTRODUCTION

The treatment of tuberculosis (TB) is a mature discipline, with more than 60 years of clinical experience accrued across the globe. The requisite Multi-drug treatment of drug-susceptible TB, however, lasts 6 months and has never been optimized according to current standards. Multi-drug resistant TB and TB in individuals coinfected with HIV present additional treatment challenges.

OBJECTIVE

This article reviews the role that existing drugs and new compounds could have in shortening or improving treatment for TB. The key to treatment shortening seems to be sterilizing activity, or the ability of drugs to kill mycobacteria that persist after the initial days of multi-drug treatment.

RESULTS

Among existing anti-TB drugs, the rifamycins hold the greatest potential for shortening treatment and improving outcomes, in both HIV-infected and HIV-uninfected populations, without dramatic increases in toxicity. Clinical studies underway or being planned, are supported by in vitro , animal and human evidence of increased sterilizing activity--without significant increases in toxicity--at elevated daily doses. Fluoroquinolones also seem to have significant sterilizing activity. At present, at least two class members are being evaluated for treatment shortening with different combinations of first-line drugs. However, in light of apparent rapid selection for fluoroquinolone-resistant mutants, relative frequency of serious adverse events and a perceived need to 'reserve' fluoroquinolones for the treatment of drug-resistant TB, their exact role in TB treatment remains to be determined. Other possible improvements may come from inhaled delivery or split dosing (linezolid) of anti-TB drugs for which toxicity (ethionamide) or lack of absorption (aminoglycosides and polypeptides) precludes delivery of maximally effective, oral doses, once daily. New classes of drugs with novel mechanisms of action, nitroimidazopyrans and a diarylquinoline, among others, may soon provide opportunities for improving treatment of drug-resistant TB or shortening treatment of drug-susceptible TB.

CONCLUSION

More potential options for improved TB treatment currently exist than at any other time in the last 30 years. The challenge in TB pharmacotherapy is to devise well-tolerated, efficacious, short-duration regimens that can be used successfully against drug-resistant and drug-resistant TB in a heterogeneous population of patients.

Role of activated endocannabinoid system in regulation of cellular cholesterol metabolism in macrophages

AIMS

Evidence from recent studies suggests that the endocannabinoid system participates in the regulation of lipid metabolism and body composition. We hypothesize that the system is activated by oxidized low-density lipoprotein (oxLDL) and regulates cellular cholesterol metabolism in macrophages.

METHODS AND RESULTS

Primary peritoneal macrophages isolated from Sprague-Dawley rats and RAW264.7 mice macrophages were cultured. A liquid chromatography/mass spectrometry (LC/MS) system was used to measure the endocannabinoid anandamide (AEA), 2-arachidonoylglycerol (2-AG), and cellular cholesterol levels in macrophages. The regulatory mechanisms of cellular cholesterol metabolism were also investigated by molecular biology methods. The results showed that the endocannabinoid system in macrophages was activated by oxLDL through elevation of the AEA and 2-AG levels and the up-regulation of the cannabinoid CB1 and CB2 receptor expression. Win55,212-2, a synthetic cannabinoid, promotes cellular cholesterol accumulation in macrophages, which was associated with an increase in the expression of CD36 and a decrease in the expression of ATP-binding cassette protein A1 (ABCA1) as mediated by an up-regulated peroxisome proliferator-activated receptor gamma (PPARgamma). AM251, a selective cannabinoid CB1 receptor antagonist, impaired the abilities of Win55,212-2-treated macrophages to accumulate cholesterol by down-regulating CD36 receptor expression and up-regulating ABCA1 expression.

CONCLUSION

We have demonstrated, for the first time, that the endocannabinoid system in macrophages is activated by oxLDL and that the activated endocannabinoid system promotes cellular cholesterol accumulation in macrophages. The results also indicate that selectively blocking the CB1 receptor can reduce oxLDL accumulation in macrophages, which might represent a promising therapeutic strategy for atherosclerosis.

Dickkopf-1 secreted by decidual cells promotes trophoblast cell invasion during murine placentation

Dickkopf-1 (Dkk1) is one of the secreted antagonists in the canonical Wnt signaling pathway. It plays important roles in diverse developmental processes. However, the role of Dkk1 in trophoblast cell invasion during placentation remains unclear. In this study, we found that Dkk1 was mainly expressed in maternal decidual tissue but trivially in ectoplacental cones (EPCs) in day 8 post coitum (p.c.) pregnant mouse uterus and that the efficiency of EPC attachment and outgrowth was increased when co-cultured with decidual cells, which secreted Dkk1, and this enhancement was abolished by pretreating decidual cells with Dkk1 blocking antibody before co-culture experiment. This indicates that Dkk1 secreted by decidual cells plays an important role in trophoblast cell invasion. Indeed, when recombinant mouse Dkk1 was added to EPCs in vitro, the efficiency of attachment and outgrowth was increased. Migration of EPCs toward the decidua was retarded when antisense Dkk1 oligonucleotide (ODN) was administered via intrauterine injection in vivo. Furthermore, the active beta-catenin nuclear location was lost when we treated cultured EPCs with recombinant mouse Dkk1, and the efficiency of EPCs attachment and outgrowth was obviously increased when we treated cultured EPCs with antisense beta-catenin ODN. Taken together, Dkk1 secreted by decidual cells may induce trophoblast cell invasion in the mouse and beta-catenin may be involved in such functions of Dkk1.

Pyrazinamide blood concentrations in children suffering from tuberculosis: a comparative study at two doses

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Pyrazinamide is recommended in doses varying from 15 to 40 mg kg(-1). The most commonly used average daily dose is 25 mg kg(-1). Its use is associated with dose dependent hepatotoxicity. Lower doses are not used because of lack of pharmacokinetic data especially in children. There is only one detailed study of pyrazinamide in children at a dose of 35 mg kg(-1).

WHAT THIS STUDY ADDS

This is the first study evaluating serum concentrations of pyrazinamide in children at a dose of 15 mg kg(-1) which is on the lower side of the recommended dose. The study also compared the serum concentrations and pharmacokinetics achieved with this dose with the widely used dose of 25 mg kg(-1) in children suffering from tuberculosis. The pharmacokinetics and pharmacodynamic indices of pyrazinamide were comparable with the 25 and 15 mg kg(-1) doses.

AIMS

To evaluate the pharmacokinetics and pharmacodynamic indices of pyrazinamide at doses of 15 and 25 mg kg(-1) in children suffering from tuberculosis.

METHODS

Twenty children with tuberculosis received pyrazinamide at a single dose of 25 mg kg(-1) (group I) and 15 mg kg(-1) (group II). Serial blood samples were collected and the drug concentrations were analyzed spectrophotometrically. The pharmacokinetic parameters were calculated and the duration of time for which pyrazinamide concentrations in serum remained above the pyrazinamide inhibitory concentrations of 20 microg ml(-1) and 25 microg ml(-1) was studied.

RESULTS

The mean peak serum concentration was 42.4 +/- 3.3 microg ml(-1) (95% CI +/- 6.5) and 38.6 +/- 3.9 microg ml(-1) (95% CI +/- 7.7) in groups I and II, respectively. The elimination half-life was 9.3 +/- 1.3 h and 10.5 +/- 2.3 h (P = 0.6) and clearance was 0.06 +/- 0.01 l h(-1) kg(-1) and 0.04 +/- 0.01 l h(-1) kg(-1) (P = 0.08) in groups I and II, respectively. Pharmacokinetic parameters and PKPD indices were comparable with both the doses.

CONCLUSIONS

The study indicates that comparable serum concentrations of pyrazinamide are attained with 25 mg kg(-1) and 15 mg kg(-1) doses in children. The elimination half-life was longer and volume of distribution greater in children than in the adult population.

The resumption of consumption -- a review on tuberculosis

Among all infectious diseases that afflict humans, tuberculosis (TB) remains the deadliest. At present, epidemiologists estimate that one-third of the world population is infected with tubercle bacilli, which is responsible for 8 to 10 million new cases of TB and 3 million deaths annually throughout the world. Approximately 95% of new cases and 98% of deaths occur in developing nations, generally due to the few resources available to ensure proper treatment and where human immunodeficiency virus (HIV) infections are common. In 1882, Dr Robert Koch identified an acid-fast bacterium, Mycobacterium tuberculosis, as the causative agent of TB. Thirty-nine years later, BCG vaccine was introduced for human use, and became the most widely used prophylactic strategy to fight TB in the world. The discovery of the properties of first-line antimycobacterial drugs in the past century yielded effective chemotherapies, which considerably decreased TB mortality rates worldwide. The later introduction of some additional drugs to the arsenal used to treat TB seemed to provide an adequate number of effective antimicrobial agents. The modern, standard short-course therapy for TB recommended by the World Health Organization is based on a four-drug regimen that must be strictly followed to prevent drug resistance acquisition, and relies on direct observation of patient compliance to ensure effective treatment. Mycobacteria show a high degree of intrinsic resistance to most antibiotics and chemotherapeutic agents due to the low permeability of its cell wall. Nevertheless, the cell wall barrier alone cannot produce significant levels of drug resistance. M. tuberculosis mutants resistant to any single drug are naturally present in any large bacterial population, irrespective of exposure to drugs. The frequency of mutants resistant to rifampicin and isoniazid, the two principal antimycobacterial drugs currently in use, is relatively high and, therefore, the large extra-cellular population of actively metabolizing and rapidly growing tubercle bacilli in cavitary lesions will contain organisms which are resistant to a single drug. Consequently, monotherapy or improperly administered two-drug therapies will select for drug-resistant mutants that may lead to drug resistance in the entire bacterial population. Thereby, despite the availability of effective chemotherapy and the moderately protective vaccine, new anti-TB agents are urgently needed to decrease the global incidence of TB. The resumption of TB, mainly caused by the emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains and HIV epidemics, led to an increased need to understand the molecular mechanisms of drug action and drug resistance, which should provide significant insight into the development of newer compounds. The latter should be effective to combat both drug-susceptible and MDR/XDR-TB.

Pharmacokinetics and tolerability of a higher rifampin dose versus the standard dose in pulmonary tuberculosis patients

Rifampin is a key drug for tuberculosis (TB) treatment. The available data suggest that the currently applied 10-mg/kg of body weight dose of rifampin may be too low and that increasing the dose may shorten the treatment duration. A double-blind randomized phase II clinical trial was performed to investigate the effect of a higher dose of rifampin in terms of pharmacokinetics and tolerability. Fifty newly diagnosed adult Indonesian TB patients were randomized to receive a standard (450-mg, i.e., 10-mg/kg in Indonesian patients) or higher (600-mg) dose of rifampin in addition to other TB drugs. A full pharmacokinetic curve for rifampin, pyrazinamide, and ethambutol was recorded after 6 weeks of daily TB treatment. Tolerability was assessed during the 6-month treatment period. The geometric means of exposure to rifampin (area under the concentration-time curve from 0 to 24 h [AUC(0-24)]) were increased by 65% (P < 0.001) in the higher-dose group (79.7 mg.h/liter) compared to the standard-dose group (48.5 mg.h/liter). Maximum rifampin concentrations (C(max)) were 15.6 mg/liter versus 10.5 mg/liter (49% increase; P < 0.001). The percentage of patients for whom the rifampin C(max) was > or =8 mg/liter was 96% versus 79% (P = 0.094). The pharmacokinetics of pyrazinamide and ethambutol were similar in both groups. Mild (grade 1 or 2) hepatotoxicity was more common in the higher-dose group (46 versus 20%; P = 0.054), but no patient developed severe hepatotoxicity. Increasing the rifampin dose was associated with a more than dose-proportional increase in the mean AUC(0-24) and C(max) of rifampin without affecting the incidence of serious adverse effects. Follow-up studies are warranted to assess whether high-dose rifampin may enable shortening of TB treatment.

Evaluating chronic pain impact among patients in primary care: further validation of a brief assessment instrument

OBJECTIVE

To evaluate the psychometric properties of the Profile of Chronic Pain: Screen (PCP:S) in primary care. The PCP:S is a brief assessment device designed to gauge pain severity, interference, and emotional burden.

DESIGN

Questionnaire survey with short-term reliability and validity follow-up.

METHODS

Two hundred and forty-four outpatients (52% female) with chronic pain recruited from five primary care settings completed the 15-item PCP:S at an initial testing session. Approximately 1 week later, two subgroups participated in a retest reliability and validity follow-up. The battery of follow-up questionnaires included a measure of social desirability response bias and several instruments designed to provide convergent validity for the PCP:S.

RESULTS

Retest reliability, internal consistency, factor structure, and social desirability bias were all found to be acceptable. Likewise, preliminary evidence suggests that, by virtue of its correlation with established measures of pain adjustment, the PCP:S is a valid pain assessment device.

CONCLUSIONS

Although the PCP:S was initially developed and validated using a national community sample of adults with chronic pain who provided data via telephone interviews, the present findings support its use as a brief and psychometrically sound paper-and-pencil measure for the assessment of three key components of chronic pain in primary care.

Serum concentrations of antimycobacterial drugs in patients with pulmonary tuberculosis in Botswana

BACKGROUND

We conducted a pharmacokinetic study of antimycobacterial drugs involving a cohort of patients with pulmonary tuberculosis (TB) in Gaborone, Botswana, to assess the prevalence of and risk factors for low drug concentrations in serum.

METHODS

Adults participated if they had a history of cough > or =2 weeks, had abnormal chest radiograph findings, consented to testing for human immunodeficiency virus (HIV), had sputum cultures positive for Mycobacterium tuberculosis, and were receiving antituberculous therapy for >7 days. Observed maximum serum concentrations were compared with published normal ranges. RESULTS. Of 91 patients enrolled, 89 (98%) were outpatients, and 59 (68%) of 87 patients tested had HIV infection. The following numbers of patients had low serum concentrations of the following drugs: isoniazid, 27 (30%) of 90; rifampin, 71 (78%) of 91; ethambutol, 37 (41%) of 91; and pyrazinamide, 1 (1%) of 91. Low serum concentrations of both isoniazid and rifampin occurred in 23 (26%) of 90 patients. Low serum concentrations of rifampin were found in both HIV-infected and non-HIV-infected patients, and such patients were less likely to have >4 weeks of symptoms, more likely to have lymphadenopathy, and more likely to have low serum albumin levels (P<.05 for all). The associations with noncavitary pulmonary disease (P=.12) and HIV infection (P=.07) did not reach statistical significance. Delayed absorption was most common with ethambutol, followed by rifampin.

CONCLUSIONS

These data, predominantly from HIV-infected patients with TB, suggest that low isoniazid, rifampin, and ethambutol concentrations are common in Botswana. In contrast, pyrazinamide usually is well absorbed.

Use of therapeutic drug monitoring for multidrug-resistant tuberculosis patients

STUDY OBJECTIVES

Therapeutic drug monitoring (TDM) is the process of obtaining the serum concentration of a medication and modifying the dose based on the results. Little is known about the application of TDM in the treatment of patients with multidrug-resistant (MDR) tuberculosis (TB) in clinical practice. This study characterized how TDM was applied in the management of MDR TB patients, and examined the clinical indications for ordering TDM, the process for obtaining drug concentrations, and the clinician response to the drug concentrations.

DESIGN

In a retrospective study, we compared the clinical and demographic characteristics of MDR TB patients who received TDM with those who did not. The clinical application of TDM also was described in patients who received TDM.

SETTING

A municipal TB control program.

PATIENTS OR PARTICIPANTS

Patients in whom TB was diagnosed that was caused by an isolate resistant to at least isoniazid and rifampin, and who received treatment for TB in one of the health department chest clinics between July 1, 1993, and August 31, 1997, were studied.

RESULTS

Forty-nine patients receiving TDM had a longer time to culture conversion and treatment duration, more pulmonary TB in combination with an extrapulmonary site, drug resistance, and visits to the health department clinics (p < 0.05) than the 60 patients without TDM. Of the 49 patients who had initial TDM, 73.5% of them had the reason for being tested specified. A total of 85.7% of initial TDM results were collected at the appropriate time of blood sampling. Clinician response to TDM results varied with the drug that was being tested.

CONCLUSIONS

The use of TDM depended largely on the patient's clinical presentation. Site-specific guidelines on the use of TDM for managing TB patients may maximize the benefit of TDM.

Pharmacokinetics-pharmacodynamics of rifampin in an aerosol infection model of tuberculosis

Limited information exists on the pharmacokinetic (PK)-pharmacodynamic (PD) relationships of drugs against Mycobacterium tuberculosis. Our aim was to identify the PK-PD parameter that best describes the efficacy of rifampin on the basis of in vitro and PK properties. Consistent with 83.8% protein binding by equilibrium dialysis, the rifampin MIC for M. tuberculosis strain H37Rv rose from 0.1 in a serum-free system to 1.0 mg/ml when it was tested in the presence of 50% serum. In time-kill studies, rifampin exhibited area under the concentration-time curve (AUC)-dependent killing in vitro, with maximal killing seen on all days and with the potency increasing steadily over a 9-day exposure period. MIC and time-kill studies performed with intracellular organisms in a macrophage monolayer model yielded similar results. By use of a murine aerosol infection model with dose ranging and dose fractionation over 6 days, the PD parameter that best correlated with a reduction in bacterial counts was found to be AUC/MIC (r(2) = 0.95), whereas the maximum concentration in serum/MIC (r(2) = 0.86) and the time that the concentration remained above the MIC (r(2) = 0.44) showed lesser degrees of correlation.

Therapeutic drug monitoring in the treatment of tuberculosis

Therapeutic drug monitoring (TDM) is a standard clinical technique used for many disease states, including many infectious diseases. As for these other conditions, the use of TDM in the setting of tuberculosis (TB) allows the clinician to make informed decisions regarding the timely adjustment of drug therapy. Such adjustments may not be required for otherwise healthy individuals who are responding to the standard, four-drug TB regimens. However, some patients are slow to respond to treatment, have drug-resistant TB, are at risk of drug-drug interactions or have concurrent disease states that significantly complicate the clinical situation. Such patients may benefit from TDM and early interventions may preclude the development of further drug resistance. It is not possible to collect multiple blood samples in the clinical setting for logistical and financial reasons. Therefore, one typically is limited to one or two time points. When only one sample can be obtained, the 2-hour post-dose concentrations of isoniazid, rifampin, pyrazinamide and ethambutol are usually most informative. Unfortunately, low 2-hour values do not distinguish between delayed absorption (late peak, close to normal range) and malabsorption (low concentrations at all time points). A second sample, often collected at 6-hour post-dose, can differentiate between these two scenarios. The second time point can also provide some information about clearance and half-life, assuming that drug absorption was nearly completed by 2 hours. TDM requires that samples are promptly centrifuged, and that the serum is promptly harvested and frozen. Isoniazid and ethionamide, in particular, are not stable in human serum at room temperature. Rifampin is stable for more than 6 hours under these conditions. During TB treatment, isoniazid causes the greatest early reduction in organisms and is considered to be one of the two most important TB drugs, along with rifampin. Although isoniazid is highly active against TB, low isoniazid concentrations were associated with poorer clinical and bacteriological outcomes in US Public Health Services (USPHS) TB Trial 22. Several earlier trials showed a clear dose-response for rifampin and pyrazinamide, so low concentrations for those two drugs also may correlate with poorer treatment outcomes. At least in USPHS TB Trial 22, the rifampin pharmacokinetic parameters were not predictive of the outcome variables. In contrast, low concentrations of unbound rifapentine may have been responsible, in part, for the worse-than-anticipated performance of this drug in clinical trials. The 'second-line' TB drugs, including p-aminosalicylic acid, cycloserine and ethionamide, are relatively weak TB drugs. Under the best conditions, treatment with these drugs takes over 2 years, as opposed to 6 to 9 months with isoniazid- and rifampin-containing regimens. Therefore, TB centres such as National Jewish Medical and Research Center in Denver, CO, USA, measure serum concentrations of the 'second-line' TB drugs early in the course of treatment. That way, poor drug absorption can be dealt with in a timely manner. This helps to minimise the time that patients are sputum smear- and culture-positive with multidrug-resistant TB, and may prevent the need for even longer treatment durations. Patients with HIV are at particular risk for drug-drug interactions. Because the published guidelines typically reflect interactions only between two drugs, these guidelines are of limited value when the patient is treated with three or more interacting drugs. Under such complicated circumstances, TDM often is the best available tool for sorting out these interactions and placing the patient the necessary doses that they require. TDM is only one part of the care of patients with TB. In isolation, it is of limited value. However, combined with clinical and bacteriological data, it can be a decisive tool, allowing the clinician to successfully treat even the most complicated TB patients.

Treatment of multidrug-resistant tuberculosis during pregnancy: a report of 7 cases

Multidrug-resistant tuberculosis (MDR-TB) is a global public health problem affecting women of childbearing age. Little is known, however, about the safety of the drugs used to treat MDR-TB during pregnancy. We describe 7 patients who were treated for MDR-TB during pregnancy. These patients had chronic tuberculosis that had caused extensive parenchymal damage and had high-grade resistance to antituberculous drugs. All patients received individualized antituberculous therapy prior to delivery of healthy term infants. Neither obstetrical complications nor perinatal transmission of MDB-TB was observed. One patient experienced treatment failure, and another abandoned therapy. The other 5 patients are currently cured or in treatment and have culture-negative status. In each of these 7 cases, excellent treatment outcomes were obtained for the women and their children. Under certain circumstances, MDR-TB can be successfully treated during pregnancy.

Different age-specific demographic profiles are generated in the same normal-lived Drosophila strain by different longevity stimuli

We review the empirical data obtained with our normal-lived Ra control strain of Drosophila and show that this one genome is capable of invoking at least three different responses to external stimuli that induce the animal to express one of three different extended longevity phenotypes, each of which arises from one of three different antagonistic molecular mechanisms of stress resistance. The phenotypes are distinguished by different age-specific mortality patterns. Depending on the selected mechanism, the genome may respond by expressing a delayed onset of senescence (type 1), an increased early survival (type 2), or an increased late survival (type 3) phenotype, suggesting their different demographic effects. We suggest that the different demographic effects stem in part from the differential ability of each selection regime to reallocate the organism's energy from reproduction to somatic maintenance. These data document the complexity of the aging process and argue for a relationship between molecular mechanisms and longevity phenotypes.