Pharmacokinetic study of an anti-trypanosome agent with different formulations and administration routes in mice by HPLC-MS/MS.

Previously compound 12 showed great anti-trypanosome activity without toxicity in an in vivo study. In the current study, a sensitive and rapid high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed and validated to investigate its pharmacokinetics in mouse plasma. A protein precipitation method was applied to extract the compound, and it was then separated using a Kinetex C18 column with mobile phase consisting of acetonitrile-0.1% formic acid water (50:50, v/v) at a flow rate of 300 µl/min. The analytes were detected with the multiple reaction monitoring in negative electrospray ionization source for quantitative response of the compounds. Compound 12 was detected at m/z 477.0 → 367.2, while the internal standard compound 14 was detected at m/z 499.2 → 268.2. Inter- and intra-day precision was <5.22 and 2.79% respectively, while the accuracy range was within ±9.65%. The method was successfully applied to evaluate the pharmacokinetics of compound 12 in mouse plasma with two formulations (20% Cremophor EL or sesame oil) and drug administration routes (oral and intraperitoneal injection). We observed a better drug serum concentration with the Cremophor formulation, and the two different drug administration routes did not show significant differences from the drug distribution.

IL-17A, a possible biomarker for the evaluation of treatment response in Trypanosoma cruzi infected children: A 12-months follow-up study in Bolivia.

BACKGROUND: The National Program for Chagas disease was implemented in Bolivia in 2006, and it greatly decreased the number of infections through vector control. Subsequently, a treatment regimen of benznidazole (BNZ) was started in seropositive school-age children living in certified vector control areas. METHODS AND FINDINGS: We conducted a 12-month follow-up study and seven blood samples were taken during and after the treatment. Serology, conventional diagnostic PCR (cPCR) and quantitative Real-time PCR (qPCR) were performed. Plasma Th1/Th2/Th17 cytokines levels were also determined. Approximately 73 of 103 seropositive children complied with BNZ, with three interruptions due to side effects. To evaluate each individual's treatment efficacy, the cPCR and qPCR values during the final 6 months of the follow-up period were observed. Among 57 children who completed follow-up, 6 individuals (11%) showed both cPCR(+) and qPCR(+) (non reactive), 24 (42%) cPCR(-) but qPCR(+) (ambiguous) and 27 (47%) cPCR(-) and qPCR(-) (reactive). Within 14 Th1/Th2/Th17 cytokines, IL-17A showed significantly higher levels in seropositive children before the treatment compared to age-matched seronegative children and significantly decreased to the normal level one-year after. Moreover, throughout the follow-up study, IL-17A levels were positively co-related to parasite counts detected by qPCR. At the 12 months' time point, IL-17A levels of non-reactive subjects were significantly higher than either those of reactive or ambiguous subjects suggesting that IL-17A might be useful to determine the reactivity to BNZ treatment. CONCLUSIONS: Plasma levels of IL-17A might be a bio-marker for detecting persistent infection of T. cruzi and its chronic inflammation.

Determination of Benznidazole in Human Dried Blood Spots by Liquid Chromatography-Mass Spectrometry to Monitor Adherence to Trypanosoma cruzi Infection Treatment in Infants and Children.

Medication adherence is critical to the effectiveness of benznidazole (BZ) therapy for the treatment of Chagas disease. Assessing BZ adherence using traditional plasma sampling methods presents numerous challenges in resource-limited settings. Dried blood spot (DBS) sampling of BZ can be used to overcome logistical barriers and provides a less invasive method for assessing BZ levels. A BZ DBS assay using liquid chromatography-tandem mass spectrometry was developed and applied to a clinical study of infants and children being treated with BZ for Trypanosoma cruzi infection in Argentina. The assay was validated over a concentration range of 9.8-5,000 ng/mL. Inter-assay and intra-assay measures ranged from -2.9% to 2.7% and 0.5% to 8.3% for accuracy and from 3.5% to 12% and 1.6% to 13.6% for precision, respectively. The mean recovery of BZ was greater than 91%. Partitioning ratios for DBSs/plasma ranged from 0.95 to 1.02. A cohort of 10 infants and six children with T. cruzi infection being treated with BZ had median BZ concentrations of 1.2 (IQR 0.29, 2.14) µg/mL with seven of 65 (11%) samples above the BZ treatment goal of 3 µg/mL for adults. The reported DBS assay is a simple and accurate method for the quantitative measurement of BZ that can be applied to facilitate urgently needed clinical studies of BZ for the treatment of Chagas disease and assess BZ adherence in resource-limited settings.

Pharmacokinetics and Tissue Distribution of Benznidazole after Oral Administration in Mice.

Specific chemotherapy using benznidazole (BNZ) for Chagas disease during the chronic stage is controversial due to its limited efficacy and toxic effects. Although BNZ has been used to treat Chagas disease since the 1970s, few studies about the biodistribution of this drug exist. In this study, BNZ tissue biodistribution in a murine model and its pharmacokinetic profile in plasma were monitored. A bioanalytical high-performance liquid chromatography method with a UV detector (HPLC-UV) was developed and validated according to the European Medicines Agency for quantification of BNZ in organs and plasma samples prepared by liquid-liquid extraction using ethyl acetate. The developed method was linear in the BNZ concentration, which ranged from 0.1 to 100.0 µg/ml for plasma, spleen, brain, colon, heart, lung, and kidney and from 0.2 to 100.0 µg/ml for liver. Validation assays demonstrated good stability for BNZ under all conditions evaluated. Pharmacokinetic parameters confirmed rapid, but low, absorption of BNZ after oral administration. Biodistribution assays demonstrated different maximum concentrations in organs and similar times to maximum concentration and mean residence times, with means of 40 min and 2.5 h, respectively. Therefore, the biodistribution of BNZ is extensive, reaching organs such as the heart and colon, which are the most relevant organs affected by Trypanosoma cruzi infection, and also the spleen, brain, liver, lungs, and kidneys. Simultaneous analyses of tissues and plasma indicated high BNZ metabolism in the liver. Our results suggest that low bioavailability, instead of inadequate biodistribution, could be responsible for therapeutic failure during the chronic phase of Chagas disease.

Pharmacokinetics of Benznidazole in Healthy Volunteers and Implications in Future Clinical Trials.

Despite its toxicity and low efficacy in the chronic phase, benznidazole is the drug of choice in Chagas disease. Scarce information about pharmacokinetics and pharmacodynamics of benznidazole has been published. We performed a phase I, open-label, nonrandomized pharmacokinetic study of benznidazole (Abarax) conducted with 8 healthy adult volunteers at the Infectious Diseases Department of the Vall d'Hebron University Hospital (Barcelona, Spain). The separation and detection of benznidazole were performed on a Waters Acquity ultraperformance liquid chromatography system (UPLC) coupled with a Waters Xevo TQ MS triple quadrupole mass spectrometer. The pharmacokinetic parameters were calculated based on a noncompartmental body model using Phoenix WinNonlin version 6.3 software. Furthermore, computational simulations were calculated for the multiple-dose administration at two dose regimens: 100 mg of benznidazole administered every 8 h and 150 mg of benznidazole administered every 12 h. After benznidazole administration, the median area under the concentration-time curve from time zero to time t (AUC0-t ) and extrapolated to infinity (AUC0-∞) were about 46.4 µg · h/ml and 48.4 µg · h/ml, respectively. Plasma benznidazole concentrations peaked at 3.5 h, with maximal concentrations of 2.2 µg/ml, and benznidazole exhibited a terminal half-life of 12.1 h. The median maximum concentration (Cmax) of benznidazole was lower in men than in women (1.6 versus 2.9 µg/ml), and median volume of distribution (V) as a function of bioavailability (F) was higher in men than in women (125.9 versus 88.6 liters). In conclusion, dose regimens (150 mg/12 h or 100 mg/8 h) reached a steady-state range concentration above of the minimum experimental therapeutic dose. Sex differences in the benznidazole pharmacokinetics were observed; mainly, men had lower Cmax and higher V/F than women.

A DBS method for quantitation of the new oral trypanocidal drug fexinidazole and its active metabolites.

AIM: Fexinidazole (FEX) is a nitroimidazole being developed as a new trypanocide treatment for human African trypanosomiasis/sleeping sickness. Its main metabolites, fexinidazole sulfoxide (M1) and fexinidazole sulfone (M2), show the same in vitro pharmacological activity as FEX. METHODS & RESULTS: An LC-MS/MS assay was developed for quantitation of FEX in DBS, collected via finger-prick from healthy subjects. The DBS assay was specific, accurate and reproducible for FEX, M1 and M2 when validated against the current plasma assay. DBS samples were stable for 24 h at 37°C with 95% relative humidity, and 58 weeks desiccated at room temperature. CONCLUSION: DBS finger-prick sampling offers a simple, practical method for determining FEX, M1 and M2 concentrations in clinical studies in Africa.

Systematic Review and Meta-analysis of the Pharmacokinetics of Benznidazole in the Treatment of Chagas Disease.

Chagas disease is a neglected parasitic illness affecting approximately 8 million people, predominantly in Latin America. Benznidazole is the drug of choice for treatment, although its availability has been limited. A paucity of knowledge of the pharmacokinetic properties of this drug has contributed to its limited availability in several jurisdictions. The objective of this study was to conduct a systematic literature review and a Bayesian meta-analysis of pharmacokinetic studies to improve estimates of the basic pharmacokinetic properties of benznidazole. A systematic search of the Embase, Medline, LILACS, and SciELO (Scientific Electronic Library Online) databases was conducted. Eligible studies reported patient-level data from single-100-mg-dose pharmacokinetic evaluations of benznidazole in adults or otherwise provided data relevant to the estimation of pharmacokinetic parameters which could be derived from such studies. A Bayesian hierarchical model was used for analysis. Secondary data (i.e., data from studies that did not include patient-level, single-100-mg-dose data) were used for the generation of empirical priors for the Bayesian analysis. The systematic search identified nine studies for inclusion. Nine pharmacokinetic parameters were estimated, including the area under the concentration-time curve (AUC), the maximum concentration of drug in plasma (Cmax), the time to Cmax, the elimination rate constant (kel), the absorption rate constant (Ka), the absorption and elimination half-lives, the apparent oral clearance, and the apparent oral volume of distribution. The results showed consistency across studies. AUC and Cmax were 51.31 mg · h/liter (95% credible interval [CrI], 45.01, 60.28 mg · h/liter) and 2.19 mg/liter (95% CrI, 2.06, 2.33 mg/liter), respectively. Ka and kel were 1.16 h-1 (95% CrI, 0.59, 1.76 h-1) and 0.052 h-1 (95% CrI, 0.045, 0.059 h-1), respectively, with the corresponding absorption and elimination half-lives being 0.60 h (95% CrI, 0.38, 1.11 h) and 13.27 h (95% CrI, 11.79, 15.42 h), respectively. The oral clearance and volume of distribution were 2.04 liters/h (95% CrI, 1.77, 2.32 liters/h) and 39.19 liters (95% CrI, 36.58, 42.17 liters), respectively. A Bayesian meta-analysis was used to improve the estimates of the standard pharmacokinetic parameters of benznidazole. These data can inform clinicians and policy makers as access to this drug increases.

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.

Applicability of a novel immunoassay based on surface plasmon resonance for the diagnosis of Chagas disease.

BACKGROUND: We defined the methodological criteria for the interpretation of the results provided by a novel immunoassay based on surface plasmon resonance (SPR) to detect antibodies anti-Trypanosoma cruzi in human sera (SPRCruzi). Then, we evaluated its applicability as a diagnostic tool for Chagas disease. METHODS: To define the cut-off point and serum dilution factor, 57 samples were analyzed at SPRCruzi and the obtained values of SPR angle displacement (ΔθSPR) were submitted to statistical analysis. Adopting the indicated criteria, its performance was evaluated into a wide panel of samples, being 99 Chagas disease patients, 30 non-infected subjects and 42 with other parasitic/infectious diseases. In parallel, these samples were also analyzed by ELISA. RESULTS: Our data demonstrated that 1:320 dilution and cut-off point at ∆θSPR=17.2 m° provided the best results. Global performance analysis demonstrated satisfactory sensitivity (100%), specificity (97.2%), positive predictive value (98%), negative predictive value (100%) and global accuracy (99.6%). ELISA and SPRCruzi showed almost perfect agreement, mainly between chagasic and non-infected individuals. However, the new immunoassay was better in discriminate Chagas disease from other diseases. CONCLUSION: This work demonstrated the applicability of SPRCruzi as a feasible, real time, label free, sensible and specific methodology for the diagnosis of Chagas disease.

Determination of nifurtimox in dog plasma by stable-isotope dilution LC-MS/MS.

BACKGROUND: Nifurtimox is a 5-nitrofuran derived antiprotozoal drug used to treat diseases caused by trypanosomes including Chagas' disease and sleeping sickness (African trypanosomiasis). Available methods for the determination of nifurtimox in plasma are tedious and of low sensitivity. For the first time, an isotope dilution HPLC/MS/MS method for the sensitive quantitation of nifurtimox down to 10.0 µg/l in plasma is described. RESULTS: Protein precipitation was used for sample preparation. Samples were analyzed on a standard triple quadrupole tandem mass spectrometer. The validated concentration range covers 10.0 µg/l (LLOQ) to 5000 µg/l. Interassay accuracy and precision (%CV) ranged from 98.4 to 101%, and 2.61 to 10.1%, respectively. CONCLUSION: The method consists of very simple sample preparation and provides unmatched sensitivity, high reproducibility and robustness enabling analysis of large sample numbers. Method performance met current guidelines on bioanalytical method validation.

HPLC-MS-MS Method Development and Validation of Antileishmanial Agent, S010-0269, in Hamster Serum.

A rapid, sensitive and simple high-performance liquid chromatography-tandem mass spectrometry method was developed and validated for the quantification of the antileishmanial agent, S010-0269, in hamster serum. A Discovery HS C-18 column (5 µm, 50 × 4.6 mm) maintained at 40°C was utilized for chromatographic separation with mobile phase [acetonitrile: aqueous ammonium acetate (0.01 M) buffer (85:15, v/v)] at a flow rate of 0.6 mL/min. The method requires low serum volume (20 µL) with a run time of 3.5 min. Excellent linear relationships (r ≥ 0.99) were obtained between the measured and added concentration over a range of 1-200 ng/mL. Validation parameters (accuracy, specificity, precision, recovery, matrix effect and stability) were assessed as per FDA guidelines. The precision and accuracy were acceptable as indicated by relative standard deviation ranging from 2.3 to 13.6% and bias values ranging from 1.5 to 6.5%, respectively. Moreover, the compound was found stable in hamster serum even after 30 days of storage at -80°C and being subjected to two freeze-thaw cycles. The validated method was successfully applied to the pharmacokinetic study after 10 mg/kg oral dose of S010-0269 in hamsters.

Rapid and sensitive ultra-high-pressure liquid chromatography method for quantification of antichagasic benznidazole in plasma: application in a preclinical pharmacokinetic study.

Benznidazole (BNZ) and nifurtimox are the only drugs available for treating Chagas disease. In this work, we validated a bioanalytical method for the quantification of BNZ in plasma aimed at improving sensitivity and time of analysis compared with the assays already published. Furthermore, we demonstrated the application of the method in a preclinical pharmacokinetic study after administration of a single oral dose of BNZ in Wistar rats. A Waters® Acquity UHPLC system equipped with a UV-vis detector was employed. The method was established using an Acquity® UHPLC HSS SB C18 protected by an Acquity® UHPLC HSS SB C18 VanGuard guard column and detection at 324 nm. The mobile phase consisted of ultrapure water-acetonitrile (65:35), and elution was isocratic. The mobile phase flow rate was 0.55 mL/min, the volume of injection was 1 µL, and the run time was just 2 min. The samples were kept at 25°C until injection and the column at 45°C for the chromatographic separation. The sample preparation was performed by a rapid protein precipitation with acetonitrile. The linear concentration range was 0.15-20 µg/mL. The pharmacokinetic parameters of BNZ in rats were determined and the method was considered sensitive, fast and suitable for application in pharmacokinetic studies.

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.

Cathepsin-L can resist lysis by human serum in Trypanosoma brucei brucei.

Closely related African trypanosomes cause lethal diseases but display distinct host ranges. Specifically, Trypanosoma brucei brucei causes nagana in livestock but fails to infect humans, while Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense cause sleeping sickness in humans. T. b. brucei fails to infect humans because it is sensitive to innate immune complexes found in normal human serum known as trypanolytic factor (TLF) 1 and 2; the lytic component is apolipoprotein-L1 in both TLFs. TLF resistance mechanisms of T. b. gambiense and T. b. rhodesiense are now known to arise through either gain or loss-of-function, but our understanding of factors that render T. b. brucei susceptible to lysis by human serum remains incomplete. We conducted a genome-scale RNA interference (RNAi) library screen for reduced sensitivity to human serum. Among only four high-confidence 'hits' were all three genes previously shown to sensitize T. b. brucei to human serum, the haptoglobin-haemoglobin receptor (HpHbR), inhibitor of cysteine peptidase (ICP) and the lysosomal protein, p67, thereby demonstrating the pivotal roles these factors play. The fourth gene identified encodes a predicted protein with eleven trans-membrane domains. Using chemical and genetic approaches, we show that ICP sensitizes T. b. brucei to human serum by modulating the essential cathepsin, CATL, a lysosomal cysteine peptidase. A second cathepsin, CATB, likely to be dispensable for growth in in vitro culture, has little or no impact on human-serum sensitivity. Our findings reveal major and novel determinants of human-serum sensitivity in T. b. brucei. They also shed light on the lysosomal protein-protein interactions that render T. b. brucei exquisitely sensitive to lytic factors in human serum, and indicate that CATL, an important potential drug target, has the capacity to resist these factors.

Dimeric flavonoids from Arrabidaea brachypoda and assessment of their anti-Trypanosoma cruzi activity.

The nonpolar fraction of an aqueous ethanol extract of the roots of Arrabidaea brachypoda, a Brazilian medicinal plant, demonstrated significant in vitro activity against Trypanosoma cruzi, the parasite responsible for Chagas disease. Targeted isolation of the active constituents led to the isolation of three new dimeric flavonoids (1-3), and their structures were elucidated using UV, NMR, and HRMS analysis, as well as by chemical derivatization. The anti-T. cruzi activity and cytotoxicity toward mammalian cells were determined for these substances. Compound 1 exhibited no activity toward T. cruzi, while flavonoids 2 and 3 exhibited selective activity against these trypomastigotes. Compounds 2 and 3 inhibited the parasite invasion process and its intracellular development in host cells with similar potencies to benznidazole. In addition, compound 2 reduced the blood parasitemia of T. cruzi-infected mice. This study has revealed that these two dimeric flavonoids represent potential anti-T. cruzi lead compounds for further drug development.

Pharmacokinetics and pharmacodynamics utilizing unbound target tissue exposure as part of a disposition-based rationale for lead optimization of benzoxaboroles in the treatment of Stage 2 Human African Trypanosomiasis.

SUMMARY This review presents a progression strategy for the discovery of new anti-parasitic drugs that uses in vitro susceptibility, time-kill and reversibility measures to define the therapeutically relevant exposure required in target tissues of animal infection models. The strategy is exemplified by the discovery of SCYX-7158 as a potential oral treatment for stage 2 (CNS) Human African Trypanosomiasis (HAT). A critique of current treatments for stage 2 HAT is included to provide context for the challenges of achieving target tissue disposition and the need for establishing pharmacokinetic-pharmacodynamic (PK-PD) measures early in the discovery paradigm. The strategy comprises 3 stages. Initially, compounds demonstrating promising in vitro activity and selectivity for the target organism over mammalian cells are advanced to in vitro metabolic stability, barrier permeability and tissue binding assays to establish that they will likely achieve and maintain therapeutic concentrations during in-life efficacy studies. Secondly, in vitro time-kill and reversibility kinetics are employed to correlate exposure (based on unbound concentrations) with in vitro activity, and to identify pharmacodynamic measures that would best predict efficacy. Lastly, this information is used to design dosing regimens for pivotal pharmacokinetic-pharmacodyamic studies in animal infection models.

Determination of the trypanocidal drug melarsoprol and its conversion products in biological fluids with HPLC-ICPMS/ESMS.

Although melarsoprol, an organoarsenic compound, is widely used for the treatment of trypanosomiasis (human African sleeping sickness), very little is known about its fate in the human body, its active metabolites passing the blood-brain barrier and the mode of action. Previous pharmacological studies based on the determination of melarsoprol by HPLC-UV or by a bioassay method produced different results. We report a HPLC-ICPMS method suitable for determining melarsoprol and its metabolites in biological fluids. The arsenic selective capability of the method allowed the quantitative measurement of melarsoprol and two arsenic-containing conversion products produced when melarsoprol was incubated with human serum and blood. The major product was identified as melarsen [4-[(4,6-diamino-1,3,5-triazin-2-yl)amino]phenyl]arsonic acid by HPLC/electrospray MS, and by accurate mass measurements. Investigations about the stability of melarsoprol in serum showed that within 30 h about 10% of melarsoprol is converted to melarsen. In blood, however, most of the melarsoprol was bound to proteins and only 1% was converted to melarsen after 30 hours. The limit of detection for melarsoprol and its conversion products were in the range of 1 µg AsL(-1) (13 nmol As L(-1)) based on signal to noise ratio of 3 with a 10 µL injection volume allowing direct determination of the compounds in blood and serum (after protein precipitation) at therapeutically realistic concentrations.

Pharmacokinetics of hydroxymethylnitrofurazone, a promising new prodrug for Chagas' disease treatment.

Hydroxymethylnitrofurazone (NFOH) is a trypanocidal prodrug of nitrofurazone (NF), devoid of mutagenic toxicity. The purpose of this work was to study the chemical conversion of NFOH into NF in sodium acetate buffer (pH 1.2 and 7.4) and in human plasma and to determine preclinical pharmacokinetic parameters in rats. At pH 1.2, the NFOH was totally transformed into NF, the parent drug, after 48 h, while at pH 7.4, after the same period, the hydrolysis rate was 20%. In human plasma, 50% of NFOH was hydrolyzed after 24 h. In the investigation of kinetic disposition, the concentration of drug in serum versus time curve was used to calculate the pharmacokinetic parameters after a single-dose regimen. NFOH showed a time to maximum concentration of drug in serum (Tmax) as 1 h, suggesting faster absorption than NF (4 h). The most important results observed were the volume of distribution (V) of NFOH through the tissues, which showed a rate that is 20-fold higher (337.5 liters/kg of body weight) than that of NF (17.64 liters/kg), and the concentration of NF obtained by in vivo metabolism of NFOH, which was about four times lower (maximum concentration of drug in serum [Cmax] = 0.83 µg/ml; area under the concentration-time curve from 0 to 12 h [AUC0-12] = 5.683 µg/ml · h) than observed for administered NF (Cmax = 2.78 µg/ml; AUC0-12 = 54.49 µg/ml · h). These findings can explain the superior activity and lower toxicity of the prodrug NFOH in relation to its parent drug and confirm NFOH as a promising anti-Chagas' disease drug candidate.

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.