Function and expression of N-acetyltransferases 1 and 2 are altered in lymphocytes in type 2 diabetes and obesity.

The cytosolic enzymes N-Acetyl Transferases 1 and 2 (NATs) transfer an acetyl group from acetyl-CoA to a xenobiotic substrate. NATs are regulated at the genetic and epigenetic levels by deacetylase enzymes such as sirtuins. The enzymatic expression of NAT1, NAT2, and SIRT1 was evaluated by flow cytometry, as well as the enzymatic activity of NATs by cell culture and HPLC analysis. Six SNPs were determined through genotyping. T2D patients (n = 29) and healthy subjects (n = 25) with a median age of 57 and 50, respectively, were recruited. An increased enzyme expression and a diminished NAT2 enzymatic activity were found in cells of T2D patients compared to the control group, while NAT1 was negatively correlated with body fat percentage and BMI. In contrast, Sirtuin inhibition increased NAT2 activity, while Sirtuin agonism decreased its activity in both groups. The analysis of NAT2 SNPs showed a higher frequency of rapid acetylation haplotypes in T2D patients compared to the control group, possibly associated as a risk factor for diabetes. The enzymatic expression of CD3+NAT2+ cells was higher in the rapid acetylators group compared to the slow acetylators group. The levels and activity of NAT1 were associated with total cholesterol and triglycerides. Meanwhile, CD3+NAT2+ cells and NAT2 activity levels were associated with HbA1c and glucose levels. The results indicate that NAT2 could be involved in metabolic processes related to the development of T2D, due to its association with glucose levels, HbA1c, and the altered SIRT-NAT axis. NAT1 may be involved with dyslipidaemias in people who are overweight or obese.

Model-informed precision dosing of antimicrobial drugs in pediatrics: experiences from a pilot scale program.

Antibiotics are among the most utilized drugs in pediatrics. Nonetheless, there is a lack in pharmacokinetics information for this population, and dosing criteria may vary between healthcare centers. Physiological variability associated with maturation in pediatrics makes it challenging to reach a consensus on adequate dosing, which is further accentuated in more vulnerable groups, such as critically ill or oncology patients. Model-informed precision dosing is a useful practice that allows dose optimization and attainment of antibiotic-specific pharmacokinetic/pharmacodynamic targets. The aim of this study was to evaluate the needs of model-informed precision dosing of antibiotics in a pediatrics unit, at a pilot scale. Pediatric patients under antibiotic treatment were monitored with either a pharmacokinetic/pharmacodynamic optimized sampling scheme or through opportunistic sampling. Clindamycin, fluconazole, linezolid, meropenem, metronidazole, piperacillin, and vancomycin plasma concentrations were quantified through a liquid chromatography coupled to mass spectrometry method. Pharmacokinetic parameters were estimated using a Bayesian approach to verify pharmacokinetic/pharmacodynamic target attainment. A total of 23 pediatric patients aged 2 to 16 years were included, and 43 dosing regimens were evaluated; 27 (63%) of them required adjustments as follows: 14 patients were underdosed, 4 were overdosed, and 9 patients needed infusion rate adjustments. Infusion rate adjustments were mostly recommended for piperacillin and meropenem; daily doses were augmented for vancomycin and metronidazole, meanwhile linezolid was adjusted for under- and overdosing. Clindamycin and fluconazole regimens were not adjusted at all.  Conclusion: Results showcase a lack of antibiotic pharmacokinetic/pharmacodynamic target attainment (particularly for linezolid, vancomycin, meropenem, and piperacillin), and the need for model-informed precision dosing in pediatrics. This study provides pharmacokinetic evidence which can further improve antibiotic dosing practices. What is Known: • Model-informed precision dosing is performed in pediatrics to optimize the treatment of antimicrobial drugs such as vancomycin and aminoglycosides, while its usefulness is debated for other groups (beta-lactams, macrolides, etc.). What is New: • Vulnerable pediatric subpopulations, such as critically ill or oncology patients, can benefit the most from model-informed precision dosing of antibiotics. • Model-informed precision dosing of linezolid, meropenem, piperacillin, and vancomycin is particularly useful in pediatrics, and further research may improve dosing practices altogether.

Standardization and validation of a novel UPLC-MS/MS method to quantify first line anti-tuberculosis drugs in plasma and dried blood spots.

Tuberculosis (TB) is a high-burden infectious disease with high prevalence and mortality rates. The first-line anti-TB drugs include isoniazid (INH), rifampicin (RMP), pyrazinamide (PZA), and ethambutol (EMB). At present, the standard method of blood sampling for therapeutic drug monitoring (TDM) analysis is venipuncture. Dried blood spots (DBS) are a minimally invasive method for collecting small quantities of whole blood from fingertips. The aim of the current study was to develop an ultrahigh-performance liquid chromatography technique coupled to tandem mass spectrometry (UPLC-MS/MS) for simultaneous quantification of the first-line anti-TB drugs in human plasma and DBS as a sampling alternative. The separation and detection conditions were optimized to quantify INH, RMP, PZA, and EMB in both matrices in an ACQUITY UPLC H Class system coupled to a XEVO TQD detector. Chromatographic separation was performed through an Acquity HSS T3 column (2.1 × 100 mm, 1.8 µm) with 0.1% formic acid in water and acetonitrile as the mobile phase. The total run time was 7 min for both methods, with retention time in plasma of 0.85, 1.22, 3.16, and 4.04 min and 0.74, 0.87, 0.97, and 4.16 min for EMB, INH, PZA, and RMP in DBS, respectively. The bioanalytical methods developed were proved selective, linear, precise, and accurate (inter- and intra-assay); the matrix effect was demonstrated to be within the established limits. Short- and long-term stability, freeze-thaw cycles for plasma, and short-term stability for DBS were established. A total of 15 patients with 46 ± 17 (mean ± SD) years old were included, and anti-TB drug concentrations were quantified on plasma and DBS as proof of concept. Based on RMP and INH plasma concentrations (Cp), and Bayesian estimation of individual pharmacokinetic parameters, a dose adjustment was necessary for 93% of patients. The slopes of the correlation lines between plasma and DBS concentrations of RMP, EMB, INH, and PZA were 0.5321, 0.8125, 0.5680, and 0.6791, respectively. Finally, significant correlations (p < 0.05) were observed between DBS and plasma concentrations for RMP (r2 = 0.6961), EMB (r2 = 0.4369), INH (r2 = 0.8675) and PZA (r2 = 0.7363). A simple, fast, and reliable UPLC-MS/MS method was developed to quantify first-line anti-TB drugs in plasma and DBS, which provides an easy sampling and storage to be applied as a new strategy for TDM in patients with TB.

Urinary phthalate metabolite and BPA concentrations in women with cervical cancer.

Environmental pollutants are involved in the development and progression of numerous cancers, including cervical cancer (CC). One possible explanation for this is the ability of several pollutants to mimic natural hormones. This study aimed to evaluate the urinary concentrations of monoesters of phthalates and bisphenol A (BPA) in women with CC. A total of 45 women were included: 15 in the control group, 12 with CC diagnosis classified in early stages IA-IIB, and 18 in late stages III-IV. Urine samples were analyzed for BPA, mono-isobutyl phthalate (MiBP), mono-n-butyl phthalate (MBP), monobenzyl phthalate (MBzP), and mono 2-ethylhexyl phthalate (MEHP) using high-performance liquid chromatography coupled to a tandem mass detector. The detection rate of environmental pollutants was 100%, with a median concentration in the control group and early-, and late-stage groups of 10.4, 9.2, 4.3, 38.4, and 12.9 µg L-1; 3.1, 3.1, 151.1, 54.5, and 30.4 µg L-1 and 1.9, 92.8, 3.6, 31.0, and 9.3 µg L-1 for BPA, MEHP, MBzP, MBP, and MiBP, respectively This study reveals high levels of phthalates, particularly MEHP, in urine samples of women with CC associated with human papillomavirus (HPV) infection. Further studies are needed to evaluate the possible role of phthalates in synergy with HPV in progression to CC.

A comparison of pharmacokinetics software for therapeutic drug monitoring of piperacillin in patients with severe infections.

OBJECTIVE: To evaluate the predictive performance of population pharmacokinetic models for piperacillin (PIP) available in the software MwPharm, TDMx and ID-ODs for initial dosing selection and therapeutic drug monitoring (TDM) purposes. METHODS: This is a prospective observational study in adult patients with severe infections receiving PIP treatment. Plasma concentrations were quantified by ultra-high performance liquid chromatography coupled to tandem mass spectrometry. The differences between predicted and observed PIP concentrations were evaluated with Bland-Altman plots; additionally, the relative and absolute bias and precision of the models were determined. RESULTS: A total of 145 PIP plasma concentrations from 42 patients were analysed. For population prediction, MwPharm showed the best predictive performance with a mean relative difference of 34.68% (95% CI -197% to 266%) and a root mean square error (RMSE) of 60.42 µg/mL; meanwhile TDMx and ID-ODs under-predicted PIP concentrations. For individual prediction, the TDMx model was found to be the most precise with a mean relative difference of 7.61% (95% CI -57.63 to 72.86%), and RMSE of 17.86 µg/mL. CONCLUSION: Current software for TDM is a valuable tool, but it may also include different population pharmacokinetic models in patients with severe infections, and should be evaluated before performing a model-based TDM in clinical practice. Considering the heterogeneous characteristics of patients with severe infections, this study demonstrates the need for therapy personalisation for PIP to improve pharmacokinetic/pharmacodynamic target attainment.

Disease activity and therapeutic drug monitoring of polyglutamates of methotrexate after daily or weekly administration of low-dose methotrexate in patients recently diagnosed with rheumatoid arthritis.

Low-dose methotrexate can be challenging to treat rheumatoid arthritis due to side effects, lack of adherence and risk of medication errors. The aim of this study was to explore the safety and efficacy of low-dose methotrexate administered daily or weekly in patients with rheumatoid arthritis. Patients were randomized according to a total oral dose of 12.5 mg of methotrexate administered: (A) divided in 5 days/week and (B) once per week. Patients were assessed along 24 weeks after starting treatment. Polyglutamates of methotrexate were quantified by ultrahigh-performance liquid chromatography coupled to tandem mass spectrometer. Patients from groups A and B showed a good response to methotrexate treatment in 29% and 25.5%, respectively, and a global frequency of adverse events of 37%. Methotrexate polyglutamate 3 concentrations were higher in normal weight (body mass index 18.5-24.9 kg/m2 ) than in obese (body mass index 30 kg/m2 ) patients with a median (interquartile range) of 28 (17.95-45.15) and 10.35 (5.22-30.88) nM without differences between dosage groups. Daily dosage regimen represents a therapeutic alternative without compromising the efficacy and safety of methotrexate treatment and with similar adherence patterns than weekly dosage regimen; further, methotrexate polyglutamate 3 concentrations could be a useful tool for therapeutic drug monitoring purposes.

Factors associated with fluoxetine and norfluoxetine plasma concentrations and clinical response in Mexican patients with mental disorders.

Over the last few years, fluoxetine has been one of the most prescribed medications for the treatment of diverse psychiatric conditions in Mexico. Fluoxetine therapeutic effect is consequence of the joint action of the parent drug and its active metabolite, norfluoxetine. However, the clinical efficacy of fluoxetine, can be affected due to diverse factors, such as drug-drug interactions and the large interindividual variability in the pharmacokinetics of this drug. The aim of this study was to determine the factors associated with variability in plasma concentrations of fluoxetine and norfluoxetine and its association with the therapeutic response. Fluoxetine and norfluoxetine plasma concentrations were quantified by liquid chromatography in 81 Mexican patients with mental disorders; 25% of the patients had no medication adherence and 40% were below the reference range of fluoxetine plus norfluoxetine plasma concentrations. The results showed that concentrations can be affected by fluoxetine metabolism caused by CYP2D6 phenotype and the concomitant administration of olanzapine. Furthermore, CYP3A5 and CYP2C19 phenotype were associated with lower anxiety and depression control during treatment with fluoxetine. This study can be a starting point to elucidate the causes of fluoxetine variable response in Mexican patients with mental disorders, as well as to detect and support medication adherence.

Quantification of pyrazinamide, isoniazid, acetyl-isoniazid, and rifampicin by a high-performance liquid chromatography method in human plasma from patients with tuberculosis.

The aim of this study was to establish and validate an alternative high-performance liquid chromatography method for simultaneous quantification of pyrazinamide, isoniazid, acetyl-isoniazid and rifampicin in plasma of patients under treatment for tuberculosis. The performed method was lineal (r2  > 0.99) in the range of 2.00-50.00 µg/mL for pyrazinamide, 0.50-20.00 µg/mL for both acetyl-isoniazid and isoniazid, and 1.20-25.00 µg/mL for rifampicin. Precision and trueness were demonstrated with coefficient of variation < 15% and deviations < 15%, respectively, for quality controls samples. The lower limits of quantification were 2.00, 0.50, 0.50, and 1.20 µg/mL for pyrazinamide, isoniazid, acetyl-isoniazid and rifampicin, respectively. The method was applied for the analysis of plasma from patients with tuberculosis. This method allowed ensuring reliable quantification of the target compounds and their pharmacokinetics parameters. In general, the mean values of maximum concentration of each antituberculosis drug were located within their respective reference therapeutic ranges. However, patients with sub-therapeutic plasma concentrations of isoniazid and rifampicin were detected. This is the first analytical technique that simultaneously quantifies isoniazid, acetyl-isoniazid, rifampicin, and pyrazinamide concentrations from plasma samples by high-performance liquid chromatography with ultraviolet/visible. The proposed method could be applied for therapeutic drug monitoring and pharmacokinetics studies of the four compounds throughout the treatment of tuberculosis patients.

A population approach of rifampicin pharmacogenetics and pharmacokinetics in Mexican patients with tuberculosis.

The aim of this study was to develop a population pharmacokinetic model of rifampicin (RMP) in Mexican patients with tuberculosis (TB) to evaluate the influence of anthropometric and clinical covariates, as well as genotypic variants associated with MDR1 and OATP1B1 transporters. A prospective study approved by Research Ethics Committee was performed at Hospital Central in San Luis Potosí, Mexico. TB patients under DOTS scheme and who signed informed consent were consecutively included. Anthropometric and clinical information was retrieved from medical records. Single nucleotide polymorphisms in MDR1 (C3435T) and SLCO1B1 (A388G and T521C) genes were evaluated. RMP plasma concentrations and time data were assessed with NONMEM software. A total of 71 Mexican TB patients from 18 to 72 years old were included for RMP quantification from 0.3 to 12 h after dose; 329 and 97 plasma concentrations were available for model development and validation, respectively. Sequential process includes a typical lag time of 0.25 h prior to absorption start with a Ka of 1.24 h-1 and a zero-order absorption of 0.62 h to characterize the gradual increase in RMP plasma concentrations. Final model includes total body weight in volume of distribution (0.7 L/kg, CV = 26.8%) and a total clearance of 5.96 L/h (CV = 38.5%). Bioavailability was modified according to time under treatment and generic formulation administration. In conclusion, a population pharmacokinetic model was developed to describe the variability in RMP plasma concentrations in Mexican TB patients. Genetic variants evaluated did not showed significant influence on pharmacokinetic parameters. Final model will allow therapeutic drug monitoring at early stages.

Population pharmacokinetics of isoniazid and dose recommendations in Mexican patients with tuberculosis.

Background The standardized doses of isoniazid in therapy against tuberculosis are determined based on total body weight, without considering genetic polymorphisms of the metabolic enzyme N-acetyltransferase-2 that contribute to the wide pharmacokinetic variability of isoniazid. Objective The aim of this work was to build a population pharmacokinetic model of isoniazid in Mexican patients with tuberculosis to characterize typical estimates of pharmacokinetics, as well as inter-individual and residual variability of isoniazid considering the genetic factors associated with the N-acetyltransferase-2 enzyme. Setting A prospective study was conducted at the Department of Internal Medicine in Hospital Central, San Luis Potosí, México. Methods Plasma concentrations of isoniazid were measured by high performance liquid chromatography. The acetylator phenotype was predicted through single nucleotide polymorphisms in the N-acetyltransferase-2 gene. Genetic, anthropometric and clinical covariates were used to develop a pharmacokinetic model. Main outcome measure Isoniazid plasma concentration. Results A total of 69 patients with tuberculosis were included. Blood samples were drawn from 20 min to 12 h post dose to determinate the isoniazid plasma concentration. Typical pharmacokinetics parameters were characterized through two-compartment open model with first-order absorption and linear elimination. Clearance was different for each predicted N-acetyltransferase-2 phenotype being 11.4, 19.2 and 27.4 L/h for slow, intermediate and rapid acetylators, respectively. Central volume of distribution was determined as 1.5 * body mass index (L). Through the application of the model, external validation was performed and initial dose regimen of isoniazid is proposed based on stochastic simulations. Conclusion A validated population pharmacokinetic model of isoniazid was developed in Mexican patients with tuberculosis. Through the application of the final model, initial dose recommendations were provided considering body mass index and N-acetyltransferase-2 phenotype.

Dosing Recommendations Based on Population Pharmacokinetics of Lamotrigine in Mexican Adult Patients With Epilepsy.

Dose individualization is essential in epilepsy treatment, especially in antiepileptic drugs that present high interindividual variability such as lamotrigine. We aimed an observational study to develop a population pharmacokinetic model for quantitative evaluation of the factors that influence lamotrigine pharmacokinetics in Mexican adults with epilepsy. Patients on stable treatment with lamotrigine therapy were included, plasma concentrations were analyzed by a high-performance liquid chromatography method and UGT2B7-161C > T polymorphism was determined. The data were analyzed by NONMEM® 7.3, model validation was performed using bootstrap approach and visual predictive check. Finally, stochastic simulations were carried out to propose dosage regimens. A total of 73 lamotrigine plasma concentrations from 2 h after last dose and up to 0.5 h prior to next administration were fitted to a one-compartment open model. The final population pharmacokinetic model for lamotrigine indicates that concomitant treatment with valproic acid and carbamazepine should be considered to individualize epilepsy treatment with this drug. Based on this model, we proposed dosage regimens to achieve trough lamotrigine concentrations within reference interval (2.5-15 mg/L). These results provide clinical useful data to give more rational anticonvulsant therapy in our population.

Population pharmacokinetics of mycophenolic acid in Mexican patients with lupus nephritis.

BACKGROUND: Mycophenolic acid (MPA) is an effective oral immunosuppressive drug used to treat lupus nephritis (LN), which exhibits large pharmacokinetic variability. This study aimed to characterize MPA pharmacokinetic behaviour in Mexican LN patients and to develop a population pharmacokinetic model which identified factors that influence MPA pharmacokinetic variability. METHODS: Blood samples from LN patients treated with mycophenolate mofetil (MMF) were collected pre dose and up to six hours post dose. MPA concentrations were determined by a validated ultra-performance liquid chromatography tandem mass spectrometry technique. Patients were genotyped for polymorphisms in enzymes (UGT1A8, 1A9 and 2B7) and transporters (ABCC2 and SLCO1B3). The anthropometric, clinical, genetic and co-medication characteristics of each patient were considered as potential covariates to explain the variability. RESULTS: A total of 294 MPA concentrations from 40 LN patients were included in the development of the model. The data were analysed using NONMEM software and were best described by a two-compartment linear model. MPA CL, Vc, Vp, Ka and Q were 15.4 L/h, 22.86 L, 768 L, 1.28 h-1 and 20.3 L/h, respectively. Creatinine clearance and prednisone co-administration proved to have influence on clearance, while body weight influenced Vc. The model was internally validated, proving to be stable. MMF dosing guidelines were obtained through stochastic simulations performed with the final model. CONCLUSIONS: This is the first MPA population pharmacokinetic model to have found that co-administration of prednisone results in a considerable increase on clearance. Therefore, this and the other covariates should be taken into account when prescribing MMF in order to optimize the immunosuppressant therapy in patients with LN.

Population pharmacokinetics of mycophenolic acid in adult kidney transplant patients under prednisone and tacrolimus regimen.

Mycophenolate mofetil (MMF) is typically used in combination with prednisone and tacrolimus to avoid graft rejection in kidney transplant patients. The aim of this study was to develop and validate a population pharmacokinetic model of mycophenolic acid (MPA) in kidney transplant patients to investigate the influence of clinical and genetic covariates and to propose a dosage regimen based on the final model. Adult kidney transplant patients (>18 years old) receiving combination of MMF, prednisone and tacrolimus regimen were included. The population pharmacokinetic model was built using a two-compartment model and First Order Conditional Estimation method with Interaction (FOCEI though NONMEM v.7.4.). A total of 343 MPA concentrations at steady state from 77 kidney transplant patients were included in the analysis. MPA CL/F, V1/F, Q/F, V2/F, and Ka were 12.4 L/h, 45.6 L, 29.9 L/h, 658 L, and 1.67 h-1, respectively. It was found that CL/F increases with serum creatinine and uric acid levels and V1/F is modified by blood urea nitrogen and the UGT1A9 genotype. In the final model the interindividual variabilities associated to CL/F and V1/F were 56.5% and 105.8%, respectively. The residual variability was 41.8%. Evaluation by bootstrapping showed that the final model was stable. The predictive performance was evaluated by goodness-of-fit plots and visual predictive check. Dosage regimens for MMF were proposed based on the final model and would be appropriate for a prospective evaluation. In conclusion, it was built a population pharmacokinetic model for MPA in kidney transplant patients, which include clinical and genetic covariates.

Population Pharmacokinetics and Dosing Recommendations of Levetiracetam in Adult and Elderly Patients With Epilepsy.

The objective was to develop and externally validate a population pharmacokinetic model of levetiracetam in adult and elderly patients with epilepsy, and to perform dosing simulations to propose individualized dosing regimens more likely to achieve therapeutic concentrations. This prospective study included 367 plasma samples from 107 patients receiving oral levetiracetam. Samples were analyzed by HPLC-UV. Pharmacokinetic data, as well as patient demographic, clinical characteristics, other drug therapy, and the use of innovator or generic products of levetiracetam, were collected. Population modeling was performed with NONMEM and included internal and external validations of the final model. Simulations were used to propose optimized dosing regimens. The pharmacokinetics of levetiracetam was described by a one-compartment model with first-order absorption and linear elimination. Body surface area had a significant effect on the apparent volume of distribution, as did creatinine clearance (CrCL) over the drug clearance (p < 0.01). The final model performed adequately during external validation testing. The final model showed a better predictive performance. Dosing simulations support 1000 mg 12-hourly dosing of levetiracetam for patients with CrCL ~60-75 mL/min with higher dose needed for higher values (1500 mg 12-hourly for CrCL ~93-111 mL/min). Dosing regimens should be personalized to the patient's CrCL to maximize the likelihood of therapeutic concentrations.

Population pharmacokinetics of methotrexate in Mexican pediatric patients with acute lymphoblastic leukemia.

PURPOSE: To develop and validate a population pharmacokinetic model of Methotrexate (MTX) in Mexican children with acute lymphoblastic leukemia (ALL) for the design of personalized dosage regimens based on the anthropometric and physiological characteristics of each patient. METHODS: A prospective study was developed in 50 children (1-15 years old) with ALL diagnosis attended at Pediatric Hemato-Oncology Service from Hospital Central "Dr. Ignacio Morones Prieto" and under treatment with high doses of MTX administered in 24-h continuous intravenous infusion. Plasma concentrations of MTX were determined in blood samples collected at 24, 36, 42 or 48 h post-infusion, by means of the CMIA immunoassay. The development of the population pharmacokinetic model was performed using the NONMEM® software evaluating the covariates that influence in clearance (CL), intercompartmental clearance (Q), central (Vc) and peripheral (Vp) volume of distribution of MTX. RESULTS: A two-compartment open model was selected to describe concentration-time data and body surface area (BSA) was the covariate that influences on MTX total CL. The population pharmacokinetic model obtained was: CL (L/h) = 6.5 × BSA0.62, Vc (L) = 0.36 × Weight, Q (L/h) = 0.41 and Vp (L) = 3.2. Internal validation was performed by bootstrap and visual predictive check. Predictive performance of final model was evaluated by external validation in a different group of patients. Initial MTX dosing regimens were established by stochastic simulation with final population pharmacokinetic model. CONCLUSIONS: The establishment of MTX dosing criteria in children with ALL should be adjusted based on the BSA of each patient to optimize oncological therapy and reduce the development of adverse effects. Therapeutic drug monitoring is an essential tool to individualize MTX doses to reduce toxicity and improve patients' outcomes.

Determination of mycophenolic acid in human plasma by ultra-performance liquid chromatography-tandem mass spectrometry and its pharmacokinetic application in kidney transplant patients.

To implement and validate an analytical method by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC MS/MS) to quantify mycophenolic acid (MPA) in kidney transplant patients. Quantification of MPA was performed in an ACQUITY UPLC H Class system coupled to a Xevo TQD detector and it was extracted from plasma samples by protein precipitation. The chromatographic separation was achieved through an ACQUITY HSS C18 SB column with 0.1% formic acid and acetonitrile (60:40 vol/vol) as mobile phase. The pharmacokinetic parameters were calculated by non-compartmental analysis of MPA plasma concentrations from 10 kidney transplant patients. The linear range for MPA quantification was 0.2-30 mg/L with a limit of detection of 0.07 mg/L; the mean extraction recovery was 99.99%. The mean intra- and inter-day variability were 2.98% and 3.4% with a percentage of deviation of 8.4% and 6.6%, respectively. Mean maximal concentration of 10 mg/L at 1.5 h, area under the concentration-time curve of 36.8 mg·h/L, elimination half-life of 3.9 h, clearance of 0.32 L/h/kg and volume of distribution of 1.65 L/kg were obtained from MPA pharmacokinetics profiles. A simple, fast and reliable UPLC-MS/MS method to quantify MPA in plasma was validated and has been applied for pharmacokinetic analysis in kidney transplant patients.

Anthropometric and Genetic Factors Associated With the Exposure of Rifampicin and Isoniazid in Mexican Patients With Tuberculosis.

BACKGROUND: Tuberculosis (TB) remains a critical infectious, contagious disease worldwide with high prevalence and mortality rate. The directly observed treatment short-course therapy includes rifampicin (RMP) and isoniazid (INH) for at least 6 months. The purposes of this scheme are to interrupt the transmissibility of the Mycobacterium tuberculosis complex and to avoid secondary complications. Low plasma concentrations of these anti-TB drugs have been associated with extended treatment duration, therapeutic failure, and relapse. The determination of anthropometric, genetic, and clinical variables that may affect plasma concentrations of RMP and INH might facilitate the detection of patients at increased risk of therapeutic failure. METHODS: A prospective observational study was performed in patients with TB diagnosis. A fixed-dose combined formulation was administered following clinical guidelines, and 12 venous blood samples were collected within 24 hours after dose for the quantification of plasma levels of RMP and INH by high-performance liquid chromatography-ultraviolet. The plasma concentrations versus time for each drug in each patient were assessed by a noncompartmental approach to obtain Cmax, and the area under the concentration-time curve to the last observation point (AUC0-24 h) was calculated by the linear trapezoidal rule. Genetic polymorphisms of the enzyme involved in INH metabolism (NAT2) and proteins involved in RMP transport (glycoprotein-P and OATP1B1) were determined. RESULTS: A total of 34 patients aged between 18 and 72 years with the diagnosis of TB were included in the current study. A multivariate analysis was performed to determine the anthropometric and genetic characteristics that modified the Cmax and AUC0-24 h of RMP and INH. Results indicated that RMP Cmax and AUC0-24 h were affected by sex, dose/weight, and single nucleotide polymorphism of MDR1. In addition, age, body mass index, and NAT2 acetylator genotype were shown to determine the Cmax and AUC0-24 h for INH. CONCLUSIONS: Anthropometric, genetic, and dosage characteristics of Mexican patients with TB are an important source of risk for subtherapeutic plasma concentrations of anti-TB drugs. Factors such as lower-than-recommended RMP dose, male patients with TB, and MDR1 3435 genotype, in addition to age group, body mass index, and INH acetylator phenotype based on NAT2 genotype, should be considered during treatment.

Dosing recommendations based on population pharmacokinetics of tacrolimus in Mexican adult patients with kidney transplant.

The aim of this study was to perform a population pharmacokinetic analysis of tacrolimus in Mexican adult kidney transplant patients to analyse the influence of clinical and genetic covariates to propose a dosage regimen. Kidney transplant patients (>18 years old) receiving oral tacrolimus treatment were included in the current study. The population pharmacokinetic model was built using a one-compartment model and the First Order Conditional Estimation method with Interaction (FOCEI via NONMEM v.7.3.). A total of 600 tacrolimus trough blood concentrations from 52 kidney transplant patients were analysed. Tacrolimus clearances were 26, 18.8 and 12.3 L/h, for patients with genetic polymorphisms CYP3A5*1*1, *1*3 and *3*3, respectively. The influence of haematocrit was inversely related to tacrolimus clearance, following an allometric power function. Total volume of distribution was 604 L. Interindividual variability associated with tacrolimus clearance and distribution volume for the final model was 33 and 63%, respectively, with a residual error of 2.5 ng/mL. Relative bioavailability was calculated between generic formulations A (0.53) and B (1) of tacrolimus. Internal validation was performed through bootstrap analysis to evaluate the stability of the final model; external validation was performed in a new group of patients (n = 13) to estimate residual errors on basic (57.8%) and final (34.8%) models. Finally, stochastic simulations were performed to propose a dosage regimen based on haematocrit, CYP3A5 genotype and generic formulation of tacrolimus. A stable and predictive population pharmacokinetic model of tacrolimus was developed for Mexican adult kidney transplant patients; additionally, the proposed dosage regimen of tacrolimus should be prospectively validated.

Genetic polymorphisms of arylamine N-acetyltransferases 1 and 2 and the likelihood of developing pediatric acute lymphoblastic leukemia.

Acute lymphoblastic leukemia (ALL) is one of the main causes of death in children and is associated with both genetic susceptibility and environmental factors. Genes encoding the arylamine N-acetyltransferases 1 and 2 (NAT1 and NAT2) isoenzymes are highly polymorphic among populations. Single-nucleotide polymorphism analysis was performed by real-time polymerase chain reaction from the genomic DNA of 225 healthy subjects and 57 children with ALL diagnoses. Significant associations were found between the development of ALL and the presence of the haplotypes NAT1*3 (Odds ratio [OR], 2.1), NAT1*4 (OR, 1.92), NAT2*6B (OR, 3.30), NAT2*6J (OR, 3.25) and NAT2*7A (OR, 2.45) and the NAT1 rapid (OR, 6.69) and NAT2 slow phenotypes (OR, 2.95). Our results indicate that haplotypes that provide rapid NAT1 and slow NAT2 acetylating phenotypes may influence the development of ALL in children.

Pharmacokinetics of rifampicin in Mexican patients with tuberculosis and healthy volunteers.

OBJECTIVE: The aim of this study was to compare the pharmacokinetics (PK) of rifampicin (RIF) between healthy volunteers and patients with tuberculosis (TB). METHODS: RIF was administered as a single 600-mg dose to 24 healthy volunteers and 24 TB patients, followed by serial blood sampling. Plasma concentrations were analysed using a chromatographic method, and the PK parameters were estimated using WinNonlin software. KEY FINDINGS: Peak plasma concentration ranged from 6.4 to 19.9 mg/l, which was subtherapeutic for 15% of the study participants in both groups, mostly in men (71.4%). The mean area under the concentration-time curve (AUC0-24h ) did not show differences between these groups (P > 0.05). The absorption rate was slower in TB patients and the volume of distribution normalized by total body weight (Vd/kg) was greater than healthy volunteers (P < 0.05). A greater Vd and clearance were found in male subjects. The lag time (tlag) and the time before reach Cmax (Tmax) were longer for female TB patients (P < 0.05). CONCLUSION: The main differences in PK parameters of RIF between Mexican TB patients and healthy volunteers were demonstrated in absorption and distribution processes. In addition, differences in PK parameters observed by sex should be considered for further dosing recommendations.