Herramientas farmacométricas para antichagásicos, aplicadas a estudios fármaco y toxicocinéticos en contexto pediátrico / Pharmacometric tools for antihagasics, applied to drug and toxicokinetic studies in a pediatric context

La enfermedad de Chagas afecta aproximadamente a 10 millones de personas en Sudamérica y 1,5 millones en la Argentina. La transmisión congénita es la más importante en áreas urbanas. Existen dos drogas aprobadas para el tratamiento: nifurtimox (Laboratorios Bayer) y benznidazol (BNZ) (Laboratorios Roche, LAFEPE y Elea) que fueron desarrolladas hace más de 40 años y cuya farmacología y metabolismo en humanos han sido poco estudiados. La información disponible es virtualmente inexistente en niños y mujeres embarazadas. Se busca aportar estudios sistemáticos hacia una farmacoterapéutica racional en niños ya que empíricamente ha demostrado gran efectividad. Se desarrollaron métodos bioanalíticos aplicables a matrices biológicas como plasma, orina y leche materna para las drogas madres y la identificación de metabolitos en muestras de pacientes bajo terapéutica. La farmacocinética poblacional pediátrica descripta aquí para BNZ es concluyente respecto de sus diferencias con la farmacocinética en adultos. Se identificaron tres compuestos presentados como metabolitos del BNZ. La transferencia de dicho fármaco a la leche materna no supone riesgo para el lactante. Estos resultados brindan información para mejorar los protocolos de tratamiento existentes buscando una farmacoterapéutica adaptada a la edad y un uso más seguro de los fármacos en niños y eventualmente en adultos.

Chagas disease affects approximately 10 million people in South America and 1.5 million in Argentina. Congenital transmission is most important in urban areas. There are two drugs approved for treatment: nifurtimox (Bayer) and benznidazole (BNZ) (Roche, LAFEPE, Elea),developed more than 40 years ago. Their pharmacology and metabolism in humans have been seldom studied. The information available on children and pregnant women is virtually non-existent. The aim of this study is to provide systematic studies towards a rational pharmacotherapeutic sin children, which has been empirically proven to be highly effective. Bioanalytical methods were developed for plasma, urine and breast milk for parent drugs and for the identification of their metabolites in samples of patients under treatment. The pediatric population pharmacokinetics described here for BNZ is conclusive about their differences from adult pharmacokinetics. Three compounds presented as BNZ metabolites were identified. The transfer of this drug to the breast milk does not present a risk to the infant. These evidences offer information to improve the existing treatment protocols, seeking a pharmacotherapy adapted to the age and a safer use of the drugs in children and eventually in adults.

A doença de Chagas afeta aproximadamente 10 milhões de pessoas na América do Sul e 1,5 milhão na Argentina. A transmissão congênita é a mais importante em áreas urbanas. Existem dois medicamentos aprovados para o tratamento: nifurtimox (Laboratórios Bayer) e benznidazol (BNZ) (Laboratórios Roche, LAFEPE e Elea), desenvolvidas há mais de 40 anos, e sua farmacologia e seu metabolismo em humanos têm sido pouco estudados. A informação disponível é praticamente inexistente em crianças e mulheres grávidas. O objetivo é fornecer estudos sistemáticos para uma farmacoterapêutica racional em crianças visto que foram comprovadas empiricamente como sendo altamente eficazes. Métodos bioanalíticos aplicáveis a matrizes biológicas como plasma, urina e leite materno para fármacos-mãe e para a identificação de metabólitos em amostras de pacientes em tratamento terapêutico foram desenvolvidos. A farmacocinética da população pediátrica aqui descrita para BNZ é conclusiva em relação às suas diferenças com a farmacocinética de adultos. Três compostos apresentados como metabólitos do BNZ foram identificados. A transferência do referido medicamento para o leite materno não representa risco para o lactente. Essas evidências oferecem informações para melhorar os protocolos de tratamento existentes, buscando uma farmacoterapia adaptada à idade e um uso mais seguro dos medicamentos em crianças e eventualmente em adultos.

Pharmacokinetic and pharmacodynamic responses in adult patients with Chagas disease treated with a new formulation of benznidazole.

Pharmacological treatment of Chagas disease with benznidazole (BNZ) is effective in children in all stages, but it is controversial in chronically infected adults. We report the pharmacokinetics and pharmacodynamics in six adult patients with Chagas disease treated with the new BNZ formulation (ABARAX®) in doses between 2.5-5.5 mg/Kg/day. All but one patient had plasmatic BNZ concentrations within the expected range. All patients finalised treatment with nondetectable Trypanosoma cruzi quantitative polymerase chain reaction, which remained nondetectable at the six month follow-up. Our data suggests parasitological responses with the new BNZ and supports the hypothesis that treatment protocols with lower BNZ doses may be effective.

Pharmacokinetic and pharmacodynamic responses in adult patients with Chagas disease treated with a new formulation of benznidazole

Pharmacological treatment of Chagas disease with benznidazole (BNZ) is effective in children in all stages, but it is controversial in chronically infected adults. We report the pharmacokinetics and pharmacodynamics in six adult patients with Chagas disease treated with the new BNZ formulation (ABARAX®) in doses between 2.5-5.5 mg/Kg/day. All but one patient had plasmatic BNZ concentrations within the expected range. All patients finalised treatment with nondetectable Trypanosoma cruziquantitative polymerase chain reaction, which remained nondetectable at the six month follow-up. Our data suggests parasitological responses with the new BNZ and supports the hypothesis that treatment protocols with lower BNZ doses may be effective.

Limited infant exposure to benznidazole through breast milk during maternal treatment for Chagas disease.

BACKGROUND: Benznidazole (BNZ) is safe and effective for the treatment of paediatric Chagas disease. Treatment of adults is also effective in many cases, but discouraged in breastfeeding women because no information on BNZ transfer into breast milk is available. We aimed to evaluate the degree of BNZ transfer into breast milk in lactating women with Chagas disease. PATIENTS AND METHODS: Prospective cohort study of lactating women with Chagas disease treated with BNZ administered for 30 days. Patients and their breastfed infants were evaluated at admission, the 7th and 30th day of treatment (and monthly thereafter, for 6 months). BNZ was measured in plasma and milk by high performance liquid chromatography. The protocol was registered in ClinicalTrials.gov (#NCT01547533). RESULTS: 12 lactating women with chronic Chagas disease were enrolled (median age 28.5 years, range 20-34). Median BNZ dose was 5.65 mg/kg/day twice daily. Five mothers had adverse drug events (45%), but no adverse drug reactions or any untoward outcomes were observed in the breastfed infants. Median milk BNZ concentration was 3.8 mg/L (range 0.3-5.9) and 6.26 mg/L (range 0.3-12.6) in plasma. Median BNZ milk to plasma ratio was 0.52 (range 0.3-2.79). Median relative BNZ dose received by the infant (assuming a daily breast milk intake of 150 mL/kg/day) was 12.3% of the maternal dose per kg (range 5.5%-17%). CONCLUSIONS: The limited transference of BNZ into breast milk and the reassuring normal clinical evaluation of the breastfed babies suggest that maternal BNZ treatment for Chagas disease during breast feeding is unlikely to present a risk for the breastfed infant. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov NCT01547533.

Identification of N-benzylacetamide as a major component of human plasmatic metabolic profiling of benznidazole.

Chagas disease is an endemic infection in Latin America with a high health impact. Caused by the parasite Trypanosoma cruzi, it has expanded to non-endemic regions such as North America and European countries via immigration of infected people. This infectious disease has been rising in the ranking of international health priorities due to the growing migration flows from endemic to non-endemic areas. Benznidazole (BZN), a nitroheterocyclic drug, is one of the two trypanocidal drugs currently in clinical use, associated with significant adverse drug reactions (ADRs). Mammalian metabolism of BNZ has been poorly studied, including the potential role of metabolites on both toxicity and anti-parasitic activity. High-resolution UPLC/MS/MS was used to analyze three plasma samples obtained from pediatric patients under BNZ treatment in steady state. Spectroscopic and structural criteria were applied to identify BNZ and accompanying substances from chromatographic signals. From all detected species, two can be undoubtedly associated with the BNZ and N-benzylacetamide molecules, the second one being a fragment of the parent drug (BZN). From the obtained results, two hypotheses could be formulated. The first one is to relate the presence of N-benzyl acetamide with the hepatic metabolism of BNZ. The second hypothesis has to do with the possible trypanocidal activity of this metabolite, as well as its role in the development of side effects, associated with the pharmacotherapy. Complementary studies should be carried out to determine the possible association of this metabolite with the BNZ treatment stages, patient's clinical features, ADRs, and trypanocidal effectiveness.

Development of a LC-MS/MS methodology for the monitoring of the antichagasic drug benznidazole in human urine.

Monitoring the drug benznidazole in biological fluids is a powerful tool for clinical diagnostic and pharmacological studies in chagasic patients. However, research in this concern needs to be done. The accurate quantitation of this drug in complex matrices represents a highly challenging task complicated by the absence of sensitive analytical methods. It follows that sample processing strategies, preparation/cleanup procedures, and chromatographic/ionization/detection parameters, were evaluated for method optimization. The summation of this work generated a rapid, selective, sensitive methodology based on reversed-phase chromatography-tandem mass spectrometry for the analysis of benznidazole in urine samples. To the best of our knowledge, this is a first report of a LC-MS/MS platform employed for this application. Matrix effect was determined; a 90% of signal suppression was observed. The limits of detection and quantification were 0.75 and 4.85 µg L(-1); respectively. The latter allowed the method's application to the detection of benznidazole in clinical studies and pharmacological monitoring analysis.

Population pharmacokinetic study of benznidazole in pediatric Chagas disease suggests efficacy despite lower plasma concentrations than in adults.

INTRODUCTION: Chagas disease, caused by the parasite Trypanosoma cruzi, can lead to long term cardiac morbidity. Treatment of children with benznidazole is effective, but no pediatric pharmacokinetics data are available and clinical pharmacology information on the drug is scarce. PATIENTS AND METHODS: Prospective population pharmacokinetic (PK) cohort study in children 2-12 years old with Chagas disease treated with oral benznidazole 5-8 mg/kg/day BID for 60 days. (clinicaltrials.gov #NCT00699387). RESULTS: Forty children were enrolled in the study. Mean age was 7.3 years. A total of 117 samples were obtained from 38 patients for PK analysis. A one compartment model best fit the data. Weight-corrected clearance rate (CL/F) showed a good correlation with age, with younger patients having a significantly higher CL/F than older children and adults. Simulated median steady-state benznidazole concentrations, based on model parameters, were lower for children in our study than for adults and lowest for children under 7 years of age. Treatment was efficacious in the 37 patients who completed the treatment course, and well tolerated, with few, and mild, adverse drug reactions (ADRs). DISCUSSION: Observed benznidazole plasma concentrations in children were markedly lower than those previously reported in adults (treated with comparable mg/kg doses), possibly due to a higher CL/F in smaller children. These lower blood concentrations were nevertheless associated to a high therapeutic response in our cohort. Unlike adults, children have few adverse reactions to the drug, suggesting that there may be a direct correlation between drug concentrations and incidence of ADRs. Our results suggest that studies with lower doses in adults may be warranted. TRIAL REGISTRATION: ClinicalTrials.gov NCT00699387.

Development of UV/HPLC methods for quantitative analysis of benznidazole in human plasma and urine for application in pediatric clinical studies.

OBJECTIVE: Chagas disease constitutes a major public health problem in Latin America. Correctly designed pharmacokinetic, safety, and bioequivalence studies are desirable in order to fill the knowledge gaps that presently exist on available drugs. It is necessary to develop accurate, simple, reproducible, and sensitive high-performance liquid chromatography (HPLC)/UV methods for the quantization of benznidazole (BNZ) in human plasma and urine for clinical applications, specially in pediatric patients. METHODS: Quantization of BNZ in human plasma involved freeze-drying and re-suspension in organic solvent followed by reverse phase HPLC with UV detection. Analysis of BNZ in urine involved liquid/liquid extraction followed by reverse phase HPLC with UV detection. RESULTS: Limits of quantization (LOQ) were 0.32 µg/ml for plasma and 5.2 µg/ml for urine. No metabolite interferences were showed in both methods. CONCLUSION: The LOQ of methods seems appropriate in pediatric clinical contexts. Both procedures were applied with good results, to the quantization of BNZ in plasma and urine of patients treated for Chagas disease.