Pyridoxal-5-phosphate plasma concentrations in children receiving tuberculosis chemotherapy including isoniazid

Perinatal tuberculosis-An approach to an under-recognized diagnosis

Tuberculosis (TB) in young infants (<3 months of age), often referred to as perinatal TB, is underdiagnosed, leading to severe morbidity and high mortality. Perinatal TB includes both congenital and postnatal transmission of Mycobacterium tuberculosis. We aimed to increase an awareness of TB in neonates and young infants and to provide guidance on the assessment and management when in contact with mothers with TB during or soon after pregnancy. Approximately 217,000 pregnant women develop TB annually; if they are not diagnosed and treated during pregnancy, their infants are at high risk of adverse birth outcomes and TB disease. Although safe and effective antituberculosis treatment regimens are available during pregnancy, the diagnosis of TB is challenging. Infants born to mothers newly diagnosed with TB, not receiving any effective treatment or with cultures not yet negative, should be assessed for TB disease or M. tuberculosis infection. TB preventive therapy should be instituted if the infant is clinically well but exposed to TB, while prompt initiation of TB treatment is essential if TB disease is presumed. HIV status of mother and infant should be considered as this will affect the management. Further research is needed for the diagnosis and prevention of TB during pregnancy, an early diagnosis of TB in infants, and antituberculosis drug pharmacokinetics in young infants.

Chronological Metabolic Response to Intensive Phase TB Therapy in Patients with Cured and Failed Treatment Outcomes

Despite the arguable success of the standardized tuberculosis (TB) treatment regime, a significant number of patients still present with treatment failure. To improve on current TB treatment strategies, we sought to gain a better understanding of the hosts' response to TB therapy. A targeted metabolomics approach was used to compare the urinary acylcarnitine and amino acid profiles of eventually cured TB patients with those of patients presenting with a failed treatment outcome, comparing these patient groups at the time of diagnosis and at weeks 1, 2, and 4 of treatment. Among the significant metabolites identified were histidine, isoleucine, leucine, methionine, valine, proline, tyrosine, alanine, serine, and γ-aminobutyric acid. In general, metabolite fluctuations in time followed a similar pattern for both groups for most compounds but with a delayed onset or shift of the pattern in the successfully treated patient group. These time-trends detected in both groups could potentially be ascribed to a vitamin B6 deficiency and fluctuations in the oxidative stress levels and urea cycle intermediates, linked to the drug-induced inhibition and stimulation of various enzymes. The earlier onset of observed trends in the failed patients is proposed to relate to genotypic and phenotypic variations in drug metabolizing enzymes, subsequently leading to a poor treatment efficiency either due to the rise of adverse drug reactions or to insufficient concentrations of the active drug metabolites. This study emphasizes the need for a more personalized TB treatment approach, by including enzyme phenotyping and the monitoring of oxidative stress and vitamin B6 levels, for example.

Toxicoproteomic Profiling of hPXR Transgenic Mice Treated with Rifampicin and Isoniazid

Tuberculosis is a global health threat that affects millions of people every year, and treatment-limiting toxicity remains a considerable source of treatment failure. Recent reports have characterized the nature of hPXR-mediated hepatotoxicity and the systemic toxicity of antitubercular drugs. The antitubercular drug isoniazid plays a role in such pathologic states as acute intermittent porphyria, anemia, hepatotoxicity, hypercoagulable states (deep vein thrombosis, pulmonary embolism, or ischemic stroke), pellagra (vitamin B₃ deficiency), peripheral neuropathy, and vitamin B₆ deficiency. However, the mechanisms by which isoniazid administration leads to these states are unclear. To elucidate the mechanism of rifampicin- and isoniazid-induced liver and systemic injury, we performed tandem mass tag mass spectrometry-based proteomic screening of mPxr^-/- and hPXR mice treated with combinations of rifampicin and isoniazid. Proteomic profiling analysis suggested that the hPXR liver proteome is affected by antitubercular therapy to disrupt [Fe-S] cluster assembly machinery, [2Fe-2S] cluster-containing proteins, cytochrome P450 enzymes, heme biosynthesis, homocysteine catabolism, oxidative stress responses, vitamin B₃ metabolism, and vitamin B₆ metabolism. These novel findings provide insight into the etiology of some of these processes and potential targets for subsequent investigations. Data are available via ProteomeXchange with identifier PXD019505.

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

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Monitoring of liver function tests is very important in patient receiving DOT therapy.

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There was no significance difference reported in the differential leucocytes count.

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We define mechanisms underlying the adverse drug reactions observed following DOTS.

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The plasma INH concentration was reported to be high in slow acetylation.

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Plasma INH concentration greater than the antimode are slow acetylator.

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

The Isoniazid Metabolites Hydrazine and Pyridoxal Isonicotinoyl Hydrazone Modulate Heme Biosynthesis

In a mouse model, rifampicin and isoniazid combination treatment results in cholestatic liver injury that is associated with an increase in protoporphyrin IX, the penultimate heme precursor. Both ferrochelatase (FECH/Fech) and aminolevulinic acid synthase 1 (ALAS1/Alas1) are crucial enzymes in regulating heme biosynthesis. Isoniazid has recently been reported to upregulate Alas1 but downregulate Fech protein levels in mice; however, the mechanism by which isoniazid mediates disruption of heme synthesis has been unclear. Two metabolites of isoniazid, pyridoxal isonicotinoyl hydrazone (PIH, the isoniazid-vitamin B6 conjugate) and hydrazine, have been detected in the urine of humans treated with isoniazid. Here we show that, in primary human hepatocytes and the human hepatocellular carcinoma cell line HepG2/C3A, (1) isoniazid treatment increases Alas1 protein levels but decreases Fech levels; (2) hydrazine treatment upregulates Alas1 protein and Alas1 mRNA levels; (3) PIH treatment decreases Fech protein levels, but not Fech mRNA levels; and (4) PIH is detected after isoniazid treatment, with levels increasing further when exogenous vitamin B6 analogs are coadministered. In addition, the PIH-mediated downregulation of human FECH is associated with iron chelation. Together, these data demonstrate that hydrazine upregulates ALAS1, whereas PIH downregulates FECH, suggesting that the metabolites of isoniazid mediate its disruption of heme biosynthesis by contributing to protoporphyrin IX accumulation.

Treatment of tuberculosis infection in children

INTRODUCTION

Identifying and treating children with tuberculosis (TB) infection in both low and high-TB burden settings will decrease the incidence of TB disease worldwide. Areas covered: This review covers each of the available TB infection treatment options for children based on effectiveness, safety, tolerability and treatment completion rates. Six to 9 months of daily administered isoniazid is no longer the treatment of choice for many children with TB infection. Shorter, rifamycin based, TB infection treatment regimens are effective, safe and easier for children to complete. Fluroquinolone-based regimens are recommended for the treatment of children infected by a source case with drug-resistant TB. Directly observed therapy (DOT) programs improve childhood TB infection treatment completion rates. Expert commentary: As shorter, rifamycin-based, TB infection treatment regimens offer superior treatment success rate in both adults and children; the widespread use of these regimens has huge potential to decrease the burden of TB disease worldwide. The implementation of these programs will involve improving patient access to the medications, decreasing their cost to the patient, and the use of novel electronic methods to document patient treatment completion.

Isoniazid metabolism and hepatotoxicity

Isoniazid (INH) is highly effective for the management of tuberculosis. However, it can cause liver injury and even liver failure. INH metabolism has been thought to be associated with INH-induced liver injury. This review summarized the metabolic pathways of INH and discussed their associations with INH-induced liver injury.

Impact of the Increased Recommended Dosage of Isoniazid on Pyridoxine Levels in Children and Adolescents

Isoniazid exposure causes dose-dependent pyridoxine deficiency. Recently, the recommended dosage of isoniazid in children was increased from 5 (4-6) to 10 (10-15) mg/kg/day. We aimed to analyze longitudinally pyridoxine levels in a cohort of previously healthy children and adolescents treated with isoniazid. Mild symptom-free pyridoxine deficiency was observed in 4/75 (5.6%) and 3/40 (7.5%) at baseline and at 3-month follow-up, respectively. Classical age-related risk factors identified patients at risk of pyridoxine deficiency. Our preliminary results support current recommendations regarding pyridoxine supplementation in healthy children.

Severe acute malnutrition and infection

Severe acute malnutrition (SAM) is associated with increased severity of common infectious diseases, and death amongst children with SAM is almost always as a result of infection. The diagnosis and management of infection are often different in malnourished versus well-nourished children. The objectives of this brief are to outline the evidence underpinning important practical questions relating to the management of infectious diseases in children with SAM and to highlight research gaps. Overall, the evidence base for many aspects covered in this brief is very poor. The brief addresses antimicrobials; antipyretics; tuberculosis; HIV; malaria; pneumonia; diarrhoea; sepsis; measles; urinary tract infection; nosocomial Infections; soil transmitted helminths; skin infections and pharmacology in the context of SAM. The brief is structured into sets of clinical questions, which we hope will maximise the relevance to contemporary practice.

Drug-resistant tuberculosis: pediatric guidelines

The World Health Organization estimates that there are 650,000 prevalent cases of multidrug-resistant (MDR) tuberculosis (TB) globally, and since children (<15 years of age) constitute up to 20 % of the TB caseload in high-burden settings, the number of children with drug-resistant (DR) TB is likely to be substantial. Because bacterial burden at the site of disease is often low, diagnosis involves collection of multiple specimens and a laboratory capable of performing culture, although the Xpert MTB/RIF assay has improved sensitivity over smear examination. The basic principles of treatment for children are the same as those for adults with MDR-TB; however, the treatment regimen is often empiric and based on the drug susceptibility pattern of the source case, if available, or on past history of treatment. Additional challenges arise when MDR-TB is diagnosed and managed in the context of HIV coinfection. HIV-infected children are also treated with antiretroviral therapy medications, which have the potential to interact with second-line anti-TB drugs. Lack of pediatric formulations of second-line drugs and paucity of pharmacokinetic data make dosage challenging. However, when treated appropriately, children with DR TB have good outcomes.

Outcomes of comprehensive care for children empirically treated for multidrug-resistant tuberculosis in a setting of high HIV prevalence

BACKGROUND

Few studies have examined outcomes for children treated for multidrug-resistant tuberculosis (MDR-TB), including those receiving concomitant treatment for MDR-TB and HIV co-infection. In Lesotho, where the adult HIV seroprevalence is estimated to be 24%, we sought to measure outcomes and adverse events in a cohort of children treated for MDR-TB using a community-based treatment delivery model.

METHODS

We reviewed retrospectively the clinical charts of children ≤15 years of age treated for culture-confirmed or suspected MDR-TB between July 2007 and January 2011.

RESULTS

Nineteen children, ages two to 15, received treatment. At baseline, 74% of patients were co-infected with HIV, 63% were malnourished, 84% had severe radiographic findings, and 21% had extrapulmonary disease. Five (26%) children had culture-confirmed MDR-TB, ten (53%) did not have culture results available, and four (21%) subsequently had results indicating drug-susceptible TB. All children with HIV co-infection who were not already on antiretroviral therapy (ART) were initiated on ART a median of two weeks after the start of the MDR-TB regimen. Among the 17 patients with final outcomes, 15 (88%) patients were cured or completed treatment, two (12%) patients died, and none defaulted or were lost to follow-up. The majority of patients (95%) experienced adverse events; only two required permanent discontinuation of the offending agent, and only one required suspension of MDR-TB treatment for more than one week.

CONCLUSIONS

Pediatric MDR-TB and MDR-TB/HIV co-infection can be successfully treated using a combination of social support, close monitoring by community health workers and clinicians, and inpatient care when needed. In this cohort, adverse events were well tolerated and treatment outcomes were comparable to those reported in children with drug-susceptible TB and no HIV infection.

Nutritional status and its response to treatment of children, with and without HIV infection, hospitalized for the management of tuberculosis

BACKGROUND

The association of childhood tuberculosis (TB) and malnutrition is known, but treatment response, the influence of the acute-phase response (APR) and concomitant HIV infection are not well documented.

AIM

To evaluate the nutritional response and APR in HIV-infected and uninfected children hospitalised for the treatment of TB and receiving standard anti-tuberculosis chemotherapy.

METHODS

During a study of the pharmacokinetics of standard anti-tuberculosis agents, anthropometric parameters were measured and blood concentrations of nutrients and C-reactive protein (CRP) determined at 1 and 4 months after initiation of chemotherapy.

RESULTS

24 HIV-infected and 34 HIV-uninfected children were studied. On enrollment, 31.6% of HIV-infected and 2.9% of HIV-uninfected children were underweight, and 31.6% and 14.7%, respectively, were stunted. Mean values of weight, height/length, head circumference and mid-upper-arm circumference on enrollment and at 4-month assessment in HIV-infected and uninfected children did not differ. Mean triceps skinfold (TSF) (8.17 and 9.73 cm) and subscapular skinfold (SSF) thicknesses (5.75 and 7.5 cm) on enrollment differed significantly (P = 0.03 and P = 0.003); by 4 months, TSF had declined to 5.97 cm (P<0.001) and 8.87 cm (P = 0.05), respectively, and SSF to 5.57 cm (P = 0.79) and 6.73 cm (P = 0.04); the arm muscle area (AMA) was low in a majority of children on enrollment and remained so at the second assessment. CRP was raised in 66.6% and 53.3% of HIV-infected and -uninfected children on enrollment, but at 4-month assessment was raised in 63.2% and 15.2%, respectively. Other micronutrient and haematological findings probably reflect an APR, but no children had sub-normal zinc or magnesium values; most selenium and vitamin C and E values were normal. An elevated platelet count (> 420 × 10(9)/L) was significantly more common in HIV-uninfected children, and was still raised in 39% at 4 months.

CONCLUSION

A majority of HIV-infected and uninfected children had an APR but it had resolved by 4 months in most HIV-uninfected children. In both groups, low and declining skinfolds and a persistently low AMA indicate a persistent disturbance of fat and protein metabolism, despite successful chemotherapy.

Drug-resistant tuberculosis: pediatric guidelines

Drug-resistant Mycobacterium tuberculosis (TB) infection represents a serious and growing problem. For patients infected or suspected of being infected with multidrug or extensively drug-resistant TB, several medications have to be given simultaneously for prolonged periods. Here, we review the literature on treatment and monitoring of adverse effects of pediatric drug-resistant TB therapy in a high resource, low TB burden setting.

Management of multidrug-resistant tuberculosis in children: a survival guide for paediatricians

WHO estimated that of 9.4 million cases of tuberculosis (TB) worldwide in 2008, 440,000 (3.6%) had multidrug-resistant (MDR)-TB. Childhood TB is estimated at 10-15% of the total burden, but little is known about the burden of MDR-TB in children. Children in close contact with MDR-TB cases are likely to become infected with the same resistant strains and are vulnerable to develop disease. Although MDR-TB is a microbiological diagnosis, children should be treated empirically according to the drug susceptibility result of the likely source case, as often cultures cannot be obtained from the child. MDR-TB treatment in children is guided by the same principles, using the same second-line drugs as in adults, with careful monitoring for adverse effects. Co-infection with HIV poses particular challenges and requires early initiation of antiretroviral therapy. Preventive therapy for high-risk MDR-TB contacts is necessary, but no consensus guidance exists on how best to manage these cases. Pragmatic and effective Infection control measures are essential to limit the spread of MDR-TB.

Tuberculosis at extremes of age

ABSTRACT Although tuberculosis (TB) has its highest burden among young adults, especially since the advent of HIV infection, two other groups with low immunity, the very young (<1 year) with immature immunity and the elderly (>65 years) with waning immunity, are vulnerable groups not to be forgotten. This review describes the epidemiology, clinical aspects, public health aspects and outcome of TB in patients at the extremes of age. The epidemiology differs therein that TB in infants occurs in developing countries with high incidences of TB and HIV, while TB in the elderly occurs in developed countries with ageing populations. The clinical presentation may be non-specific, history of contact with TB is often not known and TB is often not considered at these age extremes, and when the diagnosis is considered, disease progression may already be advanced. Anti-TB treatment regimens are the same as in other age groups, but drug dosages may need adjustment according to weight, renal function, liver function and other potentially complicating factors. Adverse events are more difficult to observe and both the young and the elderly are reliant on others for adherence to treatment. Mortality at both age extremes is higher than in the general TB population. For all the above reasons, public health measures to: prevent transmission of infection; identify those infected and providing preventive therapy; high index of suspicion in order to make an early diagnosis; and timely initiation of treatment are important in both the very young and the elderly.