Understanding hemoglobin contribution to high-dose methotrexate disposition-population pharmacokinetics in pediatric patients with hematological malignancies.

PURPOSE: The aim of the present study was to develop a population pharmacokinetic model for methotrexate (MTX) during high-dose treatment (HDMTX) in pediatric patients with acute lymphoblastic leukemia (ALL) and non-Hodgkin's lymphoma (NHL) and to describe the influence of variability factors. METHODS: The study included 50 patients of both sexes (aged 1-18 years) who received 3 or 5 g/m2 of HDMTX. A nonlinear mixed effect modeling approach was applied for data analysis. Parameter estimation was performed by first-order conditional estimation method with interaction (FOCEI), whereas stepwise covariate modeling was used to assess variability factors. RESULTS: The final model is a two-compartment model that incorporates the effect of body surface area and the influence of hemoglobin and serum creatinine on MTX clearance (CL). Population pharmacokinetic values for a typical subject were estimated at 5.75 L/h/m2 for clearance (CL), 21.3 L/m2 for volume of the central compartment (V1), 8.2 L/m2 for volume of the peripheral compartment (V2), and 0.087 L/h/m2 for intercompartmental clearance (Q). According to the final model, MTX CL decreases with increasing serum creatinine, whereas a positive effect was captured for hemoglobin. A difference of almost 32% in MTX CL was observed among patients' hemoglobin values reported in the study. CONCLUSION: The developed population pharmacokinetic model can contribute to the therapy optimization during HDMTX in pediatric patients with ALL and NHL. In addition to renal function and body weight, it describes the influence of hemoglobin on CL, allowing better understanding of its contribution to the disposition of HDMTX.

Association of clozapine and norclozapine levels with patient and therapy characteristics-focus on interaction with valproic acid.

PURPOSE: The goal of the study was to examine clozapine (CLZ) and norclozapine (NCLZ) therapeutic drug monitoring (TDM) data and associated sources of pharmacokinetic variability, particularly the impact of valproic acid (VPA) use. METHODS: This study included 126 patients with psychiatric disorders on mono- or co-therapy with CLZ. Patients' data during routine TDM were collected retrospectively from clinical records. The descriptive and statistical analysis was computed using IBM SPSS Statistics software (version 22, NY, USA). Multiple linear regression, based on the last observations, was used to assess correlation between demographic characteristics, life habits and co-therapy with dose-corrected serum levels (C/D) of CLZ and NCLZ, as well as CLZ/NCLZ. RESULTS: A total of 295 CLZ concentrations were measured in 126 patients, with a mean of 275.5 ± 174.4 µg/L, while 124 NCLZ concentrations were determined in 74 patients, with a mean of 194.6 ± 149.8 µg/L. A statistically significant effect on ln-transformed CLZ C/D was confirmed for sex and smoking, whereas sex, smoking and VPA therapy were associated with ln-transformed NCLZ C/D. According to the final models, lower values of NCLZ C/D for about 45.9% can be expected in patients receiving VPA. Concomitant use of VPA was the only factor detected to contribute in CLZ/NCLZ variability. CONCLUSION: The results of this study may help clinicians interpret TDM data and optimize CLZ dosing regimens, especially in patients concomitantly treated with VPA. Our results show that VPA primarily decreases NCLZ levels, while alteration of the parent drug is not statistically significant.

Pharmacokinetic characterization, benefits and barriers of subcutaneous administration of monoclonal antibodies in oncology.

OBJECTIVE: Therapeutic monoclonal antibodies in oncology are slowly becoming the dominant treatment option for many different cancer types. The main route of administration, infusion, requires extensive product preparations, patient hospitalization and close monitoring. Patient comfort improvement, staff workload reduction and cost savings dictated the development of subcutaneous formulations. The aim of this review is to present pharmacokinetic characteristics of subcutaneous products, discuss the differences between intravenous and subcutaneous routes and to point out the advantages as well as challenges of administration route shift from the formulation development and pharmacometric angle. DATA SOURCES: Food and Drug administration's Purple book database and electronic medicines compendium were used to identify monoclonal antibodies in oncology approved as subcutaneous forms. Using keywords subcutaneous, monoclonal antibodies, pharmacokinetics, model, as well as specific drugs previously identified, both PubMed and ScienceDirect databases were researched. DATA SUMMARY: There are currently six approved subcutaneous onco-monoclonal antibodies on the market. For each of them, exposure to the drug was similar in relation to infusion, treatment effectiveness was the same, administration was well tolerated by the patients and costs of the medical service were reduced. CONCLUSION: Development of subcutaneous forms for existing and emerging new monoclonal antibodies for cancer treatment as well as shifting from administration via infusion should be encouraged due to patient preference, lower costs and overall lack of substantial differences in efficacy and safety between the two routes.

Methotrexate concentrations and associated variability factors in high dose therapy of children with acute lymphoblastic leukemia and non-Hodgkin lymphoma.

Monitoring and optimization procedures improved high dose methotrexate (HDMTX) treatment outcomes. However, there are still some concerns regarding unexplained concentration variability. The objective of this study was to evaluate drug concentrations and associated variability factors in pediatric patients with acute lymphoblastic leukemia (ALL) and non-Hodgkin lymphoma (NHL) on HDMTX. Fifty patients (aged 1-18 years), receiving in total 184 HDMTX cycles of 3 or 5 g/m2/24 h infusion, were included in the study. Comparisons of MTX concentrations and concentrations to dose ratio between two dosing groups were conducted by Mann-Whitney U test. Regression analysis was performed with transformed data to assess relationship between MTX concentration to dose ratio and patient characteristics, biochemical analysis and therapy data. Statistically significant difference in concentrations between 3 and 5 g/m2 dosing groups was detected only at 24 h after the start of infusion (p < 0.001), but not at 48 and 72 h (p > 0.05). There was no difference between dose-normalized concentrations. Regression analysis showed that 73.9% of variability in dependent variable can be explained by included variables: time since dose, creatinine clearance (CrCl), hemoglobin and certain concomitant therapy. Our results highlight the importance of not only renal function and concomitant therapy, but also hemoglobin in reducing the variation in MTX concentrations. Therefore, monitoring of aforementioned biochemical parameters during HDMTX is important not only to assess toxicity, but also in predicting their impact on drug level.

Impact of pharmacist's intervention on decreasing erlotinib interactions in the treatment of lung cancer patients in low resource settings.

BACKGROUND: This study aimed to demonstrate that having clinical pharmacist as a member of oncology team in low and middle income countries might lead to significant reduction in the number of erlotinib interactions in the treatment of non-small cell lung cancer patients. METHODS: A group of 44 patients was labeled as intervention group and they were analyzed prospectively in the period from 1 January 2017 to 1 May 2018 during clinical pharmacist's participation in regular weekly multidisciplinary oncology team meetings. The control group consisted of 44 out of 110 patients treated with erlotinib before the involvement of a clinical pharmacist in oncology team, match paired with 44 patients in intervention group. RESULTS: Clinically significant interactions were identified in two-thirds of studied patients (57 out of 88). Most drug interactions, 38%, potentially result in decrease of serum concentration of erlotinib. Clinical pharmacist provided therapy modification suggestions for 32 out of 44 (72.72%) patients in the intervention group, most of which were accepted by doctors. In the intervention group, there were significantly less clinically significant interactions compared to the control group (10 versus 24, p = 0.002). Progression-free survival was significantly longer in the pharmacist's intervention group (p = 0.001). CONCLUSIONS: Clinical pharmacist's intervention led to significant decrease in erlotinib interactions which may result in treatment optimization of lung cancer patients.

Understanding variability in the pharmacokinetics of atypical antipsychotics - focus on clozapine, olanzapine and aripiprazole population models.

Antipsychotic medicines are widely used for the management of psychotic symptoms regardless of the underlying diagnosis. Most atypical antipsychotics undergo extensive metabolism prior to excretion. Various factors may influence their pharmacokinetics, particularly elimination, leading to highly variable drug concentrations between individual patients following the same dosing regimen. Population pharmacokinetic approach, based on nonlinear mixed effects modeling, is a useful tool to identify covariates explaining pharmacokinetic variability, as well as to characterize and distinguish unexplained residual and between-subject (interindividual) variability. In addition, this approach allows the use of both sparsely and intensively sampled data. In this paper, we reviewed the pharmacokinetic characteristics of clozapine, olanzapine and aripiprazole, focusing on a population modeling approach. In particular, models based on a nonlinear mixed effects approach performed by NONMEM® software in order to identify and quantify sources of pharmacokinetic variability are presented. Population models were identified through systematic searches of PubMed and sixteen studies were selected. Some of the factors identified that significantly contribute to variability in elimination among clozapine, olanzapine, and aripiprazole are demographic characteristics, body weight, genetic polymorphism, smoking and in some cases drug interactions. Scientific research based on pharmacometric modeling is useful to further characterize sources of variability and their combined effect.

Adjusted indirect comparisons to assess bioequivalence between generic clopidogrel products in Serbia.

AIMS: Generic products can be regarded as therapeutically equivalent and switchable with the reference product. However, switchability between generics is unknown, as direct comparisons between generics are not performed. The aim of this study was to investigate the bioequivalence between generic clopidogrel products by means of adjusted indirect comparisons (AICs). METHODS: AICs were conducted to assess bioequivalence between 4 generic clopidogrel products that are authorised in Serbia. Generics are considered equivalent to the reference if the 90% confidence intervals (CIs) for the ratios test/reference of the maximum concentration (Cmax ) and area under the curve up to the last measurable concentration (AUC0-t ) fall within the acceptance range 80.00-125.00%. However, for AICs between generics, the Canadian acceptance criterion for Cmax was employed, where only the point estimate of Cmax needs to be within 80.00-125.00%. RESULTS: The 90% CIs of the AICs demonstrated bioequivalence within 80.00-125.00% for all AUC0-t comparisons. The point estimates of Cmax in all AICs were also within this range. CONCLUSION: This study demonstrates that the bioavailability of these 4 generic clopidogrel products authorised in Serbia is very similar. Despite the limited power of AICs, bioequivalence was demonstrated for all 90% CIs of AUC0-t and all 90% CIs of Cmax comparisons were within or very close to the acceptance range, being able to comply with the acceptance criterion employed in Canada for Cmax . Therefore, these 4 generic clopidogrel products authorised in Serbia can be considered switchable with each other in clinical practice based on the adjusted indirect comparisons.

A Simple Index for Nonalcoholic Steatohepatitis-HUFA-Based on Routinely Performed Blood Tests.

Background and objectives: Data suggests that nearly 30% of the general population have steatosis and up to 5% of this population develops nonalcoholic steatohepatitis (NASH). Liver biopsy is still considered to be the gold standard for the diagnosis of NASH. Great effort is being made toward the identification of sensitive diagnostic tests that do not involve invasive procedures to address a common concern in patients with the nonalcoholic fatty liver disease-whether they have NASH or simple steatosis. We aimed to investigate the independent predictors and develop a non-invasive, easy-to-perform, low-cost set of parameters that may be used in clinical practice to differentiate simple steatosis from NASH. Methods: А cross-sectional study of nonalcoholic fatty liver disease (NAFLD) patients divided into two groups: group I-simple steatosis (SS) and group II-biopsy-proven NASH. Strict inclusion criteria and stepwise analysis allowed the evaluation of a vast number of measured/estimated parameters. Results: One hundred and eleven patients were included-82 with simple steatosis and 29 with biopsy-proven NASH. The probability of NASH was the highest when homeostatic model assessment of insulin resistance (HOMA-IR) was above 2.5, uric acid above 380 µmol/L, ferritin above 100 µg/L and ALT above 45 U/L. An acronym of using first letters was created and named the HUFA index. This combined model resulted in an area under the receiver operator characteristic curve (AUROC) of 0.94, provided sensitivity, specificity, positive predictive value and a negative predictive value for NASH of 70.3%, 95.1%, 83.1% and 90.0%, respectively. Conclusion: We suggest a simple non-invasive predictive index HUFA that encompasses four easily available parameters (HOMA-IR, uric acid, ferritin and ALT) to identify patients with NASH, which may reduce the need for a liver biopsy on a routine basis in patients with NAFLD.

Investigation of factors influencing radioiodine (131I) biokinetics in patients with benign thyroid disease using nonlinear mixed effects approach.

PURPOSE: Radioiodine (131I) therapy is the common treatment option for benign thyroid diseases. The objective of this study was to characterize 131I biokinetics in patients with benign thyroid disease and to investigate and quantify the influence of patients' demographic and clinical characteristics on intra-thyroidal 131I kinetics by developing a population model. METHODS: Population pharmacokinetic analysis was performed using a nonlinear mixed effects approach. Data sets of 345 adult patients with benign thyroid disease, retrospectively collected from patients' medical records, were evaluated in the analysis. The two-compartment model of 131I biokinetics representing the blood compartment and thyroid gland was used as the structural model. RESULTS: Results of the study indicate that the rate constant of the uptake of 131I into the thyroid (ktu) is significantly influenced by clinical diagnosis, age, functional thyroid volume, free thyroxine in plasma (fT4), use of anti-thyroid drugs, and time of discontinuation of therapy before administration of the radioiodine (THDT), while the effective half-life of 131I is affected by the age of the patients. Inclusion of the covariates in the base model resulted in a decrease of the between subject variability for ktu from 91 (3.9) to 53.9 (4.5)%. CONCLUSIONS: This is the first population model that accounts for the influence of fT4 and THDT on radioiodine kinetics. The model could be used for further investigations into the correlation between thyroidal exposure to 131I and the outcome of radioiodine therapy of benign thyroid disease as well as the development of dosing recommendations.

Association between Adverse Effects and Parental Beliefs about Antiepileptic Medicines.

Background and Aim: Adverse effects are common in children treated with antiepileptic medications and may affect parental beliefs about treatment. The aim of the study was to investigate the relationship between adverse effects and parental beliefs about antiepileptic drugs used for the treatment of their children. Methods: The study was performed at the University Children's Hospital, Belgrade, Serbia from 2013⁻2015. Parents of children treated with valproic acid, carbamazepine or lamotrigine, were eligible. They were asked to fill in the Beliefs about Medications Questionnaire (BMQ) and The Liverpool Adverse Events Profile (LAEP). Results: Parents of 127 children (average age 9.88 ± 4.16 years) of whom 111 had epilepsy (67 generalized, 44 focal) and 16 with febrile seizures participated in the study. Nervousness and/or agitation, weight gain, restlessness, headache, difficulty in concentrating, feeling of aggression and upset stomach were most frequent adverse effects, reported in 37% of the population. BMQ-specific necessity scores significantly correlated with parental education; parents with elementary school showed lower scores than those with higher education. The presence of difficulty in concentrating of their child was associated with higher BMQ concern scores (20.73 ± 4.25 vs. 18.99 ± 3.60, p = 0.043) as well as necessity scores (18.42 ± 3.31 vs. 16.40 ± 2.73, p = 0.017). Higher scores of BMQ-general overuse were reported in the presence of a headache (8.79 ± 2.81 vs. 7.64 ± 2.72, p = 0.027). Conclusions: The main finding of our study is that parental beliefs about antiepileptic drugs were associated with the presence of adverse effects. Understanding this relationship could allow physicians and pharmacists to structure better educational programs for parents of children treated with antiepileptic drugs. Education should be more focused towards understanding the adverse effects of antiepileptics which could alleviate parental concerns and strengthen their beliefs about the necessity of medication use in their children.

The prevalence and preventability of potentially relevant drug-drug interactions in patients admitted for cardiovascular diseases: A cross-sectional study.

AIM: The aim was to describe the type and prevalence of potentially relevant drug-drug interactions (pDDIs) in a population of patients admitted for cardiovascular diseases (CVD), and management strategies for reducing the occurrence of pDDIs. METHODS: A retrospective cross-sectional study was performed on Cardiology ward of University Clinical Hospital Center in Belgrade, Serbia. A total of 527 patients, with more than one prescription during hospital stay, were enrolled in this study. Data were obtained from medical records. LexiInteract was used as the screening tool. RESULTS: At least one potentially relevant pDDI was identified in 83.9% of patients. Occurrence was significantly more prevalent in patients with higher number of drugs, multimorbidity, longer length of stay, arrhythmia, heart failure, infectious and respiratory disease. About 13% of pDDIs exposures were accompanied with concurrent renal or liver disease, as an additional risk for DDI manifestation. Among CVD, patients with a history of myocardial infarction possessed the highest additional risk. The most common potential clinical outcome was the effect on cardiovascular system 48.5%, renal function and/or potassium 22.3%, bleeding 9.5%, impaired glucose control 6.8% and digoxin toxicity 4.6%. Main management strategies to avoid X or D class included using paracetamol instead of NSAID or alternative NSAID (38%), alternative antibiotic or antifungal (20.4%), H2 receptor antagonist instead of PPI (8.3%), avoiding therapeutic duplication (7.3%), and alternative HMG-CoA reductase inhibitor (7%). Heart rate, blood pressure, electrolytes/potassium and blood glucose could have been employed in monitoring for potential consequence of 72.2% C class pDDIs. CONCLUSIONS: Use of drug interaction screening tools can be beneficial risk mitigation strategy for potentially relevant pDDIs in CVD patients. DDI screening software could be linked to the patient's laboratory results or clinical data regarding renal or liver function, as an approach to reinforce DDIs alert quality.

THE POSOLOGY AND TROUGH CONCENTRATIONS OF DIGOXIN IN ADULT AND ELDERLY PATIENTS.

Being a narrow therapeutic index drug, digoxin may cause harm if dosed without regular measurements of serum levels. Due to various limitations in its dosing, different challenges still exist in clinical practice. This study aimed to assess digoxin though concentrations after different regimens in adult and elderly patients, and to identify predictor variables for the ratio of given dose and digoxin trough level. This was prospective open-label study. Digoxin was administered per os as 0.125 or 0.25 mg during different continuous and interrupted dosage regimens. Study protocol allowed an additional therapy according to contemporary guidelines. Digoxin concentrations were determined using Abbott AxSYM Digoxin II assay in trough samples (1-3 per patient) after 3-4 weeks stable regimen. In total, 191 concentrations (104 patients) were analyzed. Digoxin weekly dose was in range 0.375-1.75 mg. On average, we observed slightly lower digoxin levels in HF patients. Results showed that in patients receiving digoxin with interrupted dosage regimen post- pause digoxin level was statistically significantly lower than pre-pause (p < 0.05). Based on multi- ple linear regression, the ratio of given dose and trough concentration was mainly predicted by clearance creatinine, and to lesser extent by patient's ideal body weight. Interrupted dosing schedule shows greater variability in drug levels comparing to continuous dosing, and it additionally causes difficulties in reaching and maintaining steady trough levels between doses. Hence, individualization of dosing regimen should be carefully guided based on target levels and not solely on clinical signs and symptoms.

Nonlinear mixed effects modelling approach in investigating phenobarbital pharmacokinetic interactions in epileptic patients.

PURPOSE: The present study aimed to establish population pharmacokinetic model for phenobarbital (PB), examining and quantifying the magnitude of PB interactions with other antiepileptic drugs concomitantly used and to demonstrate its use for individualization of PB dosing regimen in adult epileptic patients. METHODS: In total 205 PB concentrations were obtained during routine clinical monitoring of 136 adult epilepsy patients. PB steady state concentrations were measured by homogeneous enzyme immunoassay. Nonlinear mixed effects modelling (NONMEM) was applied for data analyses and evaluation of the final model. RESULTS: According to the final population model, significant determinant of apparent PB clearance (CL/F) was daily dose of concomitantly given valproic acid (VPA). Typical value of PB CL/F for final model was estimated at 0.314 l/h. Based on the final model, co-therapy with usual VPA dose of 1000 mg/day, resulted in PB CL/F average decrease of about 25 %, while 2000 mg/day leads to an average 50 % decrease in PB CL/F. CONCLUSIONS: Developed population PB model may be used in estimating individual CL/F for adult epileptic patients and could be applied for individualizing dosing regimen taking into account dose-dependent effect of concomitantly given VPA.

Application of Counter-propagation Artificial Neural Networks in Prediction of Topiramate Concentration in Patients with Epilepsy.

PURPOSE: The application of artificial neural networks in the pharmaceutical sciences is broad, ranging from drug discovery to clinical pharmacy. In this study, we explored the applicability of counter-propagation artificial neural networks (CPANNs), combined with genetic algorithm (GA) for prediction of topiramate (TPM) serum levels based on identified factors important for its prediction. METHODS: The study was performed on 118 TPM measurements obtained from 78 adult epileptic patients. Patients were on stable TPM dosing regimen for at least 7 days; therefore, steady-state was assumed. TPM serum concentration was determined by high performance liquid chromatography with fluorescence detection. The influence of demographic, biochemical parameters and therapy characteristics of the patients on TPM levels were tested. Data analysis was performed by CPANNs. GA was used for optimal CPANN parameters, variable selection and adjustment of relative importance. RESULTS: Data for training included 88 measured TPM concentrations, while remaining were used for validation. Among all factors tested, TPM dose, renal function (eGFR) and carbamazepine dose significantly influenced TPM level and their relative importance were 0.7500, 0.2813, 0.0625, respectively. Relative error and root mean squared relative error (%) and their corresponding 95% confidence intervals for training set were 2.14 [(-2.41) - 6.70] and 21.5 [18.5 - 24.1]; and for test set were -6.21 [(-21.2) - 8.77] and 39.9 [31.7 - 46.7], respectively. CONCLUSIONS: Statistical parameters showed acceptable predictive performance. Results indicate the feasibility of CPANNs combined with GA to predict TPM concentrations and to adjust relative importance of identified variability factors in population of adult epileptic patients.

Pharmacokinetic variability of amikacin after once-daily and twice-daily dosing regimen in full-term neonates.

The purpose of the study was to compare peak (Cpeak) and trough (Ctrough) amikacin levels after twice-daily (TD) or once-daily dosing (OD) in full-term neonates. Additionally, the study aimed to address amikacin pharmacokinetics and its variability. Data included 31 patients born on term. Amikacin daily dose was 15 or 20 mg/kg depending on the neonate's age. Patients randomly received amikacin every 12 or 24 h. In all patients corresponding Cpeak and Ctrough were taken. Volume of distribution (Vd), clearance (CL) and half-life (t1/2) were calculated. Mean Cpeak of 21.79 µg/ml in the TD group was statistically different from Cpeak of 36.39 µg/ml in the OD group. Average Ctrough in TD (5.67 µg/ml) was statistically different from the corresponding 3.99 µg/ml in the OD group. Mean amikacin Vd, CL, and t1/2 were 0.78 ± 0.38 l/kg, 86.99 ± 48.22 ml/h∙kg, and 6.81 ± 2.51 h, respectively. High interindividual pharmacokinetic variability was observed. Further analysis showed that neonatal age contributed to the pharmacokinetic parameters' values. Statistically significant difference in CL and t1/2 was observed between patients age ≤ 2 and > 2 days on therapy initiation. As expected, amikacin given OD achieved higher Cpeak and lower Ctrough than TD. Based on the results, observed variability in amikacin pharmacokinetics was possibly due to the renal maturation process.

Effect of Long-term Topiramate Therapy on Serum Bicarbonate and Potassium Levels in Adult Epileptic Patients.

BACKGROUND: Topiramate (TPM) is a sulfamate-substituted monosaccharide that is structurally different from other antiepileptic drugs. TPM inhibits carbonic anhydrase activity, which is associated with loss of bicarbonate from the kidney and consequently metabolic acidosis or electrolyte imbalance. OBJECTIVE: The objectives of the study were to investigate the influence of TPM therapy on bicarbonate and potassium levels in adult epileptic patients. METHODS: Data were collected from 59 adult patients on monotherapy or co-therapy of TPM and other antiepileptic drugs. Serum bicarbonate and potassium levels were available from all patients. Steady-state TPM trough concentrations were determined in blood samples by high-performance liquid chromatography. Data analysis was performed by SPSS software (version 17, Chicago, IL). RESULTS: Patients were divided into group A (duration of therapy shorter than or equal to 5 years) and group B (duration of therapy longer than 5 years). Significant difference (P < 0.05) in serum bicarbonate levels was observed between these 2 groups. Bicarbonate levels were linearly related to the TPM therapy duration. No correlation was found between the TPM dose or patient age and bicarbonate or potassium levels, as well as between therapy duration and potassium level. Linear regression analysis showed no significant association among 54 available TPM trough concentrations and bicarbonate or potassium levels. CONCLUSIONS: Results highlight the frequent occurrence of lower bicarbonate level associated with prolonged TPM therapy. Monitoring bicarbonate levels in patients on long-term TPM therapy might be useful.

Pharmacokinetics of lamotrigine in paediatric and young adult epileptic patients--nonlinear mixed effects modelling approach.

PURPOSE: The purpose of the study was to examine and describe adjunctive lamotrigine (LTG) pharmacokinetics in paediatric and young adult patients using a nonlinear mixed effects modelling (NONMEM) approach. METHODS: The study included 53 patients (age range 3-35 years) who were concomitantly treated with carbamazepine (CBZ) and/or valproic acid (VPA). A total of 70 blood samples corresponding to trough levels were available for analysis. Data were modelled, and the final model was evaluated using NONMEM and auxiliary software tools. RESULTS: The final LTG population model included the effects of concomitant drugs and patient's weight (WT) which stratified the population into three groups: ≤25 kg, >25 to <60 kg and ≥60 kg. Based on the final model, the estimated LTG oral clearance (CL/F) for a typical patient weighing ≤25 kg, >25 to <60 kg or ≥60 kg who was concomitantly treated with CBZ was estimated to be 3.28, 4.23, or 7.15 l/h, respectively. If a patient was concomitantly treated with CBZ + VPA, the CL/F decreased on average by 69.5 % relative to LTG + CBZ co-therapy. VPA was found to decrease the LTG CL/F by 87.6 % compared to co-therapy with only CBZ. CONCLUSION: The LTG population pharmacokinetic model developed in this study may be a reliable method for individualising the LTG dosing regimen in paediatric and young adult patients on combination therapy during therapeutic drug monitoring.

Hepatotoxicity of newer antiseizure medications in children: an overview and disproportionality analysis of VigiBase.

BACKGROUND: We aimed to characterize newer antiseizure medications (ASMs)-induced hepatotoxicity in children and identify signals of disproportionate reporting of hepatotoxicity-related adverse drug events (ADEs). RESEARCH DESIGN AND METHODS: Case reports reported to VigiBase were accessed using Empirica™ Signal software. To summarize characteristics of the retrieved cases, descriptive statistics were used. A disproportionality analysis was conducted using the Multi-item Gamma Poisson Shrinker algorithm, which calculates Empirical Bayesian Geometric Mean value and its lower and upper 95% confidence limits (EB05 and EB95, respectively). EB05 > 2, N > 0 was considered a signal. RESULTS: Based on 870 analyzed cases, a higher proportion of cases was reported in girls than in boys and in patients aged 2-11 years than in other age groups. Most cases were serious. In 25 cases, hepatotoxicity resulted in death. A high proportion of patients (n = 275, 31.61%) experienced hypersensitivity reactions, mostly due to lamotrigine. The disproportionality analysis yielded 17 signals concerning felbamate, lamotrigine, levetiracetam, oxcarbazepine, stiripentol, and topiramate. Four signals were for severe liver injury and concerned felbamate, lamotrigine, levetiracetam, and topiramate. Gender-biased reporting frequency was detected for four ASM-ADE combinations. CONCLUSION: Our results should serve to raise clinicians' awareness about the potential association between several newer ASMs and drug-induced liver injury in children.

Integrating Clopidogrel's First-Pass Effect in a Joint Semi-Physiological Population Pharmacokinetic Model of the Drug and Its Inactive Carboxylic Acid Metabolite.

Clopidogrel (CLO), a pro-drug for preventing thrombotic events, undergoes rapid absorption and extensive metabolism, with approximately 85-90% converted to an inactive carboxylic acid metabolite (CLO-CA) and the remaining to an active thiol (CLO-TH). Few pharmacokinetic models for the drug and its metabolites exist, with most focusing on CLO-TH. Although CLO-CA is inactive, its predominant (compared to its parent drug and metabolites) presence in plasma underscores the importance of characterizing its formation and pharmacokinetic profile. This study aimed to characterize the process of the absorption of CLO and its conversion to CLO-CA via developing a population pharmacokinetic model. Individual participants' data from two bioequivalence studies were utilized. Extensive blood samples were collected at predetermined intervals, including 841 concentrations of CLO and 1149 of CLO-CA. A nonlinear, mixed-effects modelling approach using NONMEM® software (v 7.5) was applied. A one-compartment model was chosen for CLO, while a two-compartment proved optimal for CLO-CA. Absorption from the depot compartment was modeled via two transit compartments, incorporating transit rate constants (Ktr). A semi-physiological model explained the first-pass effect of CLO, integrating a liver compartment. The estimated mean transit times (MTTs) for the studies were 0.470 and 0.410 h, respectively. The relative bioavailability for each study's generic medicine compared to the reference were 1.08 and 0.960, respectively. Based on the estimated parameters, the fractions metabolized to inactive metabolites (FiaM_st1 and FiaM_st2) were determined to be 87.27% and 86.87% for the two studies, respectively. The appropriateness of the final model was confirmed. Our model offers a robust framework for elucidating the pharmacokinetic profiles of CLO and CLO-CA.

The Role of a Clinical Pharmacist in the Identification of Potentially Inadequate Drugs Prescribed to the Geriatric Population in Low-Resource Settings Using the Beers Criteria: A Pilot Study.

Population aging is a global phenomenon. Each country in the world faces an increased number of older persons in the total population. With aging, a high prevalence of multiple chronic diseases occurs, leading to the use of complex therapeutic regimens and often to polypharmacy. Potentially inappropriate medication (PIM) is a medicine prescribed to a patient for whom the risks outweigh the benefits. Today, several tools are used to evaluate the use of pharmacotherapy in older adults, one of them is the 2019 AGS Beers Criteria. In this prospective, pilot study, we aimed to investigate if the number of PIMs in elderly patients would be significantly reduced if a clinical pharmacist performed a pharmacotherapy review. The study included 66 patients over 65 years of age who were hospitalized at the 1200-bed university hospital. The intervention was conducted by a clinical pharmacist who reviewed the patients' pharmacotherapy and provided written suggestions to physicians. The pharmacotherapy was again reviewed at the patients' discharge from the hospital. A total number of 204 PIMs were identified in the pharmacotherapy of the study population. At discharge, the number of PIMs decreased to 67. A total of 67% of the pharmacist's suggestions were accepted by the physicians. The pharmacist's intervention led to significant decrease in the number of PIMs on patients' discharge letters.