Total Drug Concentration Research Articles

Pharmacokinetic Study of Cefazolin in Short Daily Hemodialysis.

A number of centers across the world offer short daily hemodialysis (SDHD) treatments. To date, cefazolin pharmacokinetics have not been described in patients undergoing SDHD. The purpose of this study was to investigate the effect of SDHD on the pharmacokinetics of cefazolin. This was a prospective, open-label, pharmacokinetic study of cefazolin during SDHD in 10 noninfected patients. Participants received a 1-g intravenous (IV) infusion of cefazolin after SDHD on study day 1 and a second dose after SDHD on study day 2. To determine the concentration of cefazolin, 6 blood samples were drawn at 0, 1, 2, 2.3, 4, and 24 hours after initiation of dialysis on day 2, and 2 dialysate samples were drawn at 1 and 2 hours after initiation of dialysis on day 2. Samples were analyzed using high-performance liquid chromatography, and pharmacokinetic parameters were determined. Median interdialysis clearance was 0.16 L/h (interquartile range [IQR]: 0.11-0.21 L/h), and median intradialysis clearance was 1.95 L/h (IQR: 1.66-2.45 L/h). Median interdialysis half-life was 28.2 hours (IQR: 23.5-59.3 hours) as compared with a median intradialysis half-life of 2.3 hours (IQR: 1.7-2.7 hours). The median percentage removal of cefazolin during dialysis was 41% (IQR: 35%-53%). Conclusion and Relevance: Estimated cefazolin dialysis clearance is similar to previous estimates with conventional thrice-weekly regimens. Current dosing recommendations of 1 g IV post-SDHD achieve total serum drug concentrations greater than 40 mg/L in all patients, which is the total drug concentration required for bactericidal activity against Staphylococcus species.

Identification differential behavior of Gd@C82(OH)22 upon interaction with serum albumin using spectroscopic analysis

The interaction between Gd@C82(OH)22 and serum albumin (HSA and BSA) were investigated by spectroscopic analysis. From the characteristic feature of fluorescence quenching spectra at different temperatures, the inherent binding information including quenching mechanism, association constants, number of binding site, fraction of initial fluorescence and basic thermodynamic parameters were calculated. The binding of Gd@C82(OH)22 to serum albumin caused strong quenching of protein intrinsic fluorescence and the structural changes of serum albumin. At lower concentrations, Gd@C82(OH)22 was likely to rise fluorescence quenching of serum albumin through individual static quenching process by forming a ground-state complex, while dynamic and static coexisting quenching mechanism occurred in high concentration. Bimolecular quenching (Kq) value is twice the diffusion-controlled quenching constant (2.0 × 1010 L mol−1 s−1); binding sites of BSA were slightly more than those of HAS, and all of them reached to 1; the distance r between donor and acceptor was found to be 3.1494 nm and 3.6479 nm for HSA and BSA, respectively, both of which were fewer than 7 nm. It is confirmed that binding interaction for proteins in the presence of drugs was strong, the binding ratio was 1:1, and non-radiative energy transfer from protein to drug was extremely high probability in lower density. Binding process of Gd@C82(OH)22-HSA was driven mainly through van der Waals forces and hydrogen bonding formation, however more likely to be electrostatic interaction involved in the Gd@C82(OH)22-BSA binding process; Binding sites of Gd@C82(OH)22 to serum albumin were near tryprophan (HSA) and tyrosine residues (BSA), respectively. Moreover, a theoretical model of predicting the binding rate of drug to serum albumin was estimated, further analyzed that the binding rate was dynamically altered in various dose of protein and drug. Overall, these results provide potentially significant information for elucidating the distribution, transportation, the apparent relationship between pharmacologic activity and total plasma drug concentration as well as anti-carcinogenic activity and mechanisms in vivo.

Melanin targeting for intracellular drug delivery: Quantification of bound and free drug in retinal pigment epithelial cells

Melanin binding affects drug distribution and retention in pigmented ocular tissues, thereby affecting drug response, duration of activity and toxicity. Therefore, it is a promising possibility for drug targeting and controlled release in the pigmented cells and tissues. Intracellular unbound drug concentrations determine pharmacological and toxicological actions, but analyses of unbound vs. total drug concentrations in pigmented cells are lacking. We studied intracellular binding and cellular drug uptake in pigmented retinal pigment epithelial cells and in non-pigmented ARPE-19 cells with five model drugs (chloroquine, propranolol, timolol, diclofenac, methotrexate). The unbound drug fractions in pigmented cells were 0.00016–0.73 and in non-pigmented cells 0.017–1.0. Cellular uptake (i.e. distribution ratio Kp), ranged from 1.3 to 6300 in pigmented cells and from 1.0 to 25 in non-pigmented cells. Values for intracellular bioavailability, Fic, were similar in both cells types (although larger variation in pigmented cells). In vitro melanin binding parameters were used to predict intracellular unbound drug fraction and cell uptake. Comparison of predictions with experimental data indicates that other factors (e.g. ion-trapping, lipophilicity-related binding to other cell components) also play a role. Melanin binding is a major factor that leads to cellular uptake and unbound drug fractions of a range of 3–4 orders of magnitude indicating that large reservoirs of melanin bound drug can be generated in the cells. Understanding melanin binding has important implications on retinal drug targeting, efficacy and toxicity.

Pregnancy- Associated Changes in Pharmacokinetics and their Clinical Implications.

To critically review pregnancy-induced pharmacokinetic changes and their clinical application. Structured review of Pubmed, MBASE and published books. For many drugs, advanced pregnancy is associated with lower maternal serum concentrations. As most drug concentrations are not measured routinely, such changes are not evident to the clinician. Moreover, even for drug concentrations measured clinically, one cannot interpret lower total drug levels as evidence of lower fraction of free drug, which is the pharmacologically- active component, due to lower protein binding of many drugs in late pregnancy. Higher fractions of free drug will lead to higher rate of hepatic metabolism, especially for high extraction medications, leading to lower total drug concentrations.. Pregnancy- induced larger volume of distribution will lead to lower peak of drugs and hence may impact the achievement therapeutic levels. To further complicate matters, the adherence of many women decreases during pregnancy, mostly due to fears of adverse fetal effects. These dynamic and complex processes make changes in recommendations for dose schedule very challenging and in many cases not practical. Indeed, there are presently no pregnancy- targeted dose schedules, similar to existing dose changes, for example, in renal failure. Similar to the recent increased attention given to pharmacokinetic changes in pregnancy, well designed studies should compare dose-effect relationships in women receiving medications in different stages of pregnancy, to women receiving the same drug before, and/or after pregnancy. Whenever possible, women with chronic conditions can serve as their own controls and decrease the uncertainty created by inter- patient variability. Measuring drug effects in parallel to drug concentrations, will allow pharmacokinetic- pharmacodynamic modelling, leading to evidence-based decisions regarding changes in dose schedules during gestation.

Moxifloxacin target site concentrations in patients with pulmonary TB utilizing microdialysis: a clinical pharmacokinetic study.

Moxifloxacin is a second-line anti-TB drug that is useful in the treatment of drug-resistant TB. However, little is known about its target site pharmacokinetics. Lower drug concentrations at the infection site (i.e. in severe lung lesions including cavitary lesions) may lead to development and amplification of drug resistance. Improved knowledge regarding tissue penetration of anti-TB drugs will help guide drug development and optimize drug dosing. Patients with culture-confirmed drug-resistant pulmonary TB scheduled to undergo adjunctive surgical lung resection were enrolled in Tbilisi, Georgia. Five serum samples per patient were collected at different timepoints including at the time of surgical resection (approximately at Tmax). Microdialysis was performed in the ex vivo tissue immediately after resection. Non-compartmental analysis was performed and a tissue/serum concentration ratio was calculated. Among the seven patients enrolled, the median moxifloxacin dose given was 7.7 mg/kg, the median age was 25.2 years, 57% were male and the median creatinine clearance was 95.4 mL/min. Most patients (71%) had suboptimal steady-state serum Cmax (total drug) concentrations. The median free moxifloxacin serum concentration at time of surgical resection was 1.23 μg/mL (range = 0.12-1.80) and the median free lung tissue concentration was 3.37 μg/mL (range = 0.81-5.76). The median free-tissue/free-serum concentration ratio was 3.20 (range = 0.66-28.08). Moxifloxacin showed excellent penetration into diseased lung tissue (including cavitary lesions) among patients with pulmonary TB. Moxifloxacin lung tissue concentrations were higher than those seen in serum. Our findings highlight the importance of moxifloxacin in the treatment of MDR-TB and potentially any patient with pulmonary TB and severe lung lesions.

Differences in combinations and concentrations of drugs of abuse in fatal intoxication and driving under the influence cases

BackgroundIn toxicology, international classification systems focus on single intoxicants as the cause of death. It is, however, well known that very few drug related deaths are caused by a single substance and that information concerning the drug concentrations as well as the combinations of drugs are essential in order to ascertain the cause of death. The aim of the study was to assess whether those prone to fatal intoxications differ significantly from chronic drug users – in terms of demographics and drug exposure patterns. Material and methodsFatal psychoactive drug intoxications in Norway during 2012, where a forensic autopsy including toxicological analysis were performed, were included. Analytical findings in blood were compared with concentrations in blood from apprehended drivers under the influence of drugs and ethanol (DUID) during the same time period. The opioid and benzodiazepine concentrations were assessed as morphine and diazepam equivalents, respectively, in order to compare concentrations across the different groups. ResultsA total of 194 autopsy cases and 4811 DUID cases were included. Opioids were detected in around 90% of the drug intoxication cases, but in only 16% of the DUID cases. The number of substances detected in fatal intoxications was 4.9 compared to 2.6 in the DUID cases. The total opioid concentrations were significantly higher in the fatal intoxication cases compared to DUID cases (229ng/mL versus 56.9ng/mL morphine equivalents, respectively). Benzodiazepines were detected in 90% of the fatal cases. Only one fatal opioid mono-intoxication was found; a case with a very high methadone concentration (1238ng/mL). DiscussionMono-intoxication with heroin was not seen in any of the fatal intoxications in Norway, and single drug intoxications were rare (1.5%). Fatal intoxications were caused by a combination of drugs with significantly more substances as well as higher total drug concentrations among the fatal cases compared to the DUID cases. The combination of opioids and benzodiazepines seemed to represent an increased risk of death. ConclusionThe total load of drugs influence the degree of intoxication and the total concentration level must be considered, including the total number of substances. Our findings imply that international statistics regarding an opioid being the main intoxicant should have a shift in focus towards combinations of drugs (especially opioids and benzodiazepines) as a major risk factor for fatal drug overdoses.

Determination of total and unbound docetaxel in plasma by ultrafiltration and UPLC-MS/MS: application to pharmacokinetic studies

A sensitive and specific liquid chromatographic/tandem mass spectrometric (LC-MS/MS) method was developed and validated for quantifying total and unbound docetaxel drug concentrations in plasma. Calibration curves for unbound and total docetaxel were linear over the respective ranges of 0.108~10.8 and 0.54~216 ng/mL. The intra- and interday assay accuracy and precision did not exceed 15%. The methods were validated to show the standard range linearity, sensitivity, selectivity, accuracy, precision, and stability of docetaxel in the matrices tested. In addition, this method is fast and simple with a short run time of 4.5 min and a small plasma sample volume (500 µL). The validated method was successfully applied to a pharmacokinetic study of a docetaxel micelle formulation in rat plasma after intravenous administration at a dose of 10 mg/kg. Docetaxel micelles slowly released their drug payload, and protein-bound, unbound, and micellar drug pools existed simultaneously. These various forms in plasma pools were also measured in the study. We confirmed that most of the docetaxel in plasma was micelle-associated (96.52% at 24 h and 83.14% at 72 h) after micellar docetaxel administration, as a result of sequestration of the drug in long-circulating micelles.

Modeling the Dynamics of Heterogeneity of Solid Tumors in Response to Chemotherapy.

In this paper, we extend the model of the dynamics of drug resistance in a solid tumor that was introduced by Lorz et al. (Bull Math Biol 77:1-22, 2015). Similarly to the original, radially symmetric model, the quantities we follow depend on a phenotype variable that corresponds to the level of drug resistance. The original model is modified in three ways: (i) We consider a more general growth term that takes into account the sensitivity of resistance level to high drug dosage. (ii) We add a diffusion term in space for the cancer cells and adjust all diffusion terms (for the nutrients and for the drugs) so that the permeability of the resource and drug is limited by the cell concentration. (iii) We add a mutation term with a mutation kernel that corresponds to mutations that occur regularly or rarely. We study the dynamics of the emerging resistance of the cancer cells under continuous infusion and on-off infusion of cytotoxic and cytostatic drugs. While the original Lorz model has an asymptotic profile in which the cancer cells are either fully resistant or fully sensitive, our model allows the emergence of partial resistance levels. We show that increased drug concentrations are correlated with delayed relapse. However, when the cancer relapses, more resistant traits are selected. We further show that an on-off drug infusion also selects for more resistant traits when compared with a continuous drug infusion of identical total drug concentrations. Under certain conditions, our model predicts the emergence of a heterogeneous tumor in which cancer cells of different resistance levels coexist in different areas in space.

Sensitive and selective quantification of total and free itraconazole and hydroxyitraconazole in human plasma using ultra-performance liquid chromatography coupled to tandem mass spectrometry

ObjectivesProtein-free (unbound) drug concentrations have been reported to be better biomarker of pharmacodynamics compared with total drug concentrations. In this study, we developed and validated an assay for the quantification of total and free itraconazole and hydroxyitraconazole, a main metabolite with antifungal activity, in human plasma using ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). Design & methodsPlasma sample was ultra-filtrated for the measurement of free itraconazole and hydroxyitraconazole concentrations. The samples were prepared by solid phase extraction, and then subject to UPLC-MS/MS quantification. ResultsThe assay fulfilled the requirements of the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) guidelines for assay validation, with a lower limit of quantification of 10ng/mL for total itraconazole and hydroxyitraconazole, and 0.1 and 0.5ng/mL for free itraconazole and hydroxyitraconazole, respectively. Recovery rates of total itraconazole and hydroxyitraconazole from whole plasma ranged from 53.3% to 64.0%, and recovery rates of free itraconazole and hydroxyitraconazole from ultrafiltrated plasma ranged from 81.6% to 98.7%. Matrix effect varied between 79.1% and 109.4% for total itraconazole and hydroxyitraconazole, and between 81.3% and 99.7% for free itraconazole and hydroxyitraconazole. The assay was successfully applied to therapeutic drug monitoring of itraconazole in three patients with chronic progressive pulmonary aspergillosis or invasive pulmonary aspergillosis. Plasma free hydroxyitraconazole concentrations were 8.1-, 23.3-, and 51.1-fold higher than plasma free itraconazole concentrations in the three patients. ConclusionsA method for sensitive and selective quantification of plasma total and free itraconazole and hydroxyitraconazole concentrations was developed using UPLC-MS/MS. Free hydroxyitraconazole concentration may be most important in therapeutic drug monitoring of itraconazole.

049 Investigation of protein binding in skin with dermal Open Flow Microperfusion (dOFM)

Quantification of the drug concentration at the site of action is of major importance during drug development. In dermatology, this site is located in the dermis, where the pharmacological effect of the drug is also influenced by protein binding. Dermal open flow microperfusion dOFM allows direct access to the ISF in skin and can be used to assess the rate and extent to which a topical drug becomes available in the dermis. The aim of the study was to develop a dOFM method for in-vivo sampling of undiluted ISF in dermal tissue and subsequently quantify total, bound and unbound drug concentrations. Two dOFM strategies, namely recirculation and suction were evaluated to sample undiluted ISF from the skin of anesthetized pigs (n = 5). Albumin concentration determined with BioTek Reader was used to compare undiluted ISF, lymph and plasma. Two pigs received an intravenous infusion of diclofenac and lidocaine followed by sampling of undiluted ISF, lymph and plasma. Equilibrium dialysis was performed with all body fluids. Total, bound and unbound concentrations were determined by HPLC in all samples. Recirculation resulted in an ISF with an ISF-to-plasma ratio of 0.42 ± 0.12. Suction resulted in an ISF with an ISF-to-plasma ratio of 0.40 ± 0.11. Lymph showed a significantly higher albumin concentration than ISF with a lymph-to-plasma ratio of 0.67 ± 0.22. Diclofenac reached 30% and lidocaine reached 50% of the plasma levels in the dermis. For both drugs, protein binding was reduced in dermis (Diclofenac: Plasma 100% - ISF 98 ± 0,5%. Lidocain: Plasma 67 ± 2% - ISF 35 ± 9%). Both dOFM strategies successfully sampled ISF from the dermis of anesthetized pigs. Undiluted ISF had a significantly lower albumin concentration than lymph, indicating that lymph may not be an appropriate ISF representative. Protein binding analysis revealed difference in protein binding between plasma and dermal ISF, demonstrating the value of the herein established dOFM strategies.

Heterogeneous Binding and Central Nervous System Distribution of the Multitargeted Kinase Inhibitor Ponatinib Restrict Orthotopic Efficacy in a Patient-Derived Xenograft Model of Glioblastoma.

This study investigated how differences in drug distribution and free fraction at different tumor and tissue sites influence the efficacy of the multikinase inhibitor ponatinib in a patient-derived xenograft model of glioblastoma (GBM). Efficacy studies in GBM6 flank (heterotopic) and intracranial (orthotopic) models showed that ponatinib is effective in the flank but not in the intracranial model, despite a relatively high brain-to-plasma ratio. In vitro binding studies indicated that flank tumor had a higher free (unbound) drug fraction than normal brain. The total and free drug concentrations, along with the tissue-to-plasma ratio (Kp) and its unbound derivative (Kp,uu), were consistently higher in the flank tumor than the normal brain at 1 and 6 hours after a single dose in GBM6 flank xenografts. In the orthotopic xenografts, the intracranial tumor core displayed higher Kp and Kp,uu values compared with the brain-around-tumor (BAT). The free fractions and the total drug concentrations, hence free drug concentrations, were consistently higher in the core than in the BAT at 1 and 6 hours postdose. The delivery disadvantages in the brain and BAT were further evidenced by the low total drug concentrations in these areas that did not consistently exceed the in vitro cytotoxic concentration (IC50). Taken together, the regional differences in free drug exposure across the intracranial tumor may be responsible for compromising efficacy of ponatinib in orthotopic GBM6.

Measurement and Mathematical Characterization of Cell-Level Pharmacokinetics of Antibody-Drug Conjugates: A Case Study with Trastuzumab-vc-MMAE.

The main objective of this work was to understand and mathematically characterize the cellular disposition of a tool antibody-drug conjugate (ADC), trastuzumab-valine-citrulline-monomethyl auristatin E (T-vc-MMAE). Toward this goal, three different analytical methods were developed to measure the concentrations of different ADC-related analytes in the media and cell lysate. A liquid chromatography-tandem mass spectrometry method was developed to quantify unconjugated drug (i.e., MMAE) concentrations, a forced deconjugation method was developed to quantify total drug concentrations, and an enzyme-linked immunosorbent assay method was developed to quantify total antibody (i.e., trastuzumab) concentrations. Cellular disposition studies were conducted in low-HER2-(GFP-MCF7) and high-HER2-expressing (N87) cell lines, following continuous or 2-hour exposure to MMAE and T-vc-MMAE. Similar intracellular accumulation of MMAE was observed between two cell lines following incubation with plain MMAE. However, when incubated with T-vc-MMAE, much higher intracellular exposures of unconjugated drug, total drug, and total antibody were observed in N87 cells compared with GFP-MCF7 cells. A novel single-cell disposition model was developed to simultaneously characterize in vitro pharmacokinetics of all three analytes of the ADC in the media and cellular space. The model was able to characterize all the data well and provided robust estimates of MMAE influx rate, MMAE efflux rate, and intracellular degradation rate for T-vc-MMAE. ADC internalization and degradation rates, HER2 expression, and MMAE efflux rate were found to be the key parameters responsible for intracellular exposure to MMAE, on the basis of a global sensitivity analysis. The single-cell pharmacokinetics model for ADCs presented here is expected to provide a better framework for characterizing bystander effect of ADCs.

Abstract LB-039: Translational research in a phase I proof-of-concept study supports that DCC-2618 is a pan-KIT inhibitor

Abstract Background: DCC-2618 is a potent switch control inhibitor of KIT and PDGFRα kinases maintains potent inhibition of mutant forms across all exon regions in preclinical models. Gastrointestinal stromal tumor (GIST) is an important disease to achieve a proof-of-concept due to the heterogeneity of resistance mutations in KIT which emerge on treatment with approved KIT inhibitors. In later lines of therapy resistance mechanisms independent of the KIT gene have also been described. Methods: The ongoing phase 1, PK-guided dose escalation study of DCC-2618 given orally BID [28-day cycle] tested doses from 20 mg to 200 mg in patients (pts) with advanced solid tumors including GIST (NCT02571036). We report preliminary longitudinal results of plasma cell free (cf) DNA sequencing by Guardant 360 collected throughout the study and levels of circulating tumor cells (CTCs) based on a viral telomerase promoter-driven GFP expression assay. Results: To date, 24 out of 31 enrolled pts had metastatic KITm GIST refractory to standard therapy. A high, total mean exposure of DCC-2618 and its active metabolite was achieved at 100 and 150 mg BID, affording steady state Cmax >5 µM in Cycle 1. Starting with 50 mg BID dose level, concentrations of total drug exceeding IC90 of the most resistant mutations to DCC-2618 were achieved. Next-generation sequencing of plasma cfDNA revealed a total of 40 KIT mutations in 16 of 18 GIST pts at baseline. DCC-2618 led to rapid decrease and/or clearance of the heterogeneous array of KIT mutations from plasma cfDNA including exons 9, 11, 13, 14, 17, and 18. Independent of suppressed KIT mutation burden, longitudinal monitoring of cfDNA revealed changes in non-KIT oncogenic mutations which may contribute to heterogenous mechanisms of resistance. KIT mutation burden will be correlated with metabolic response assessment by PET scans and exposure to DCC-2618. CTCs have been detected in blood from all GIST patients at baseline using a non-biased assay capable of identifying sarcoma cells. Preliminary result show that CTCs with immunofluorescent detection of KIT or PDGFRα, corresponding to their respective mutational status, show 1 of 3 patterns when compared to radiologic response: most pts show relatively stable low levels at stable disease (SD), a minority of pts with prolonged SD a decline in CTCs and 2 pts with progressive disease had significant increase in KIT positive CTCs. Conclusions: DCC-2618 and its active metabolite achieved high plasma concentrations sufficient to inhibit the most resistant KIT mutations at well-tolerated exposures. Monitoring of cfDNA KIT mutation frequency demonstrates rapid clearance of a broad spectrum of KIT mutations in this heavily pretreated GIST patient population and suggests candidate resistance genes that are independent of KIT. Our data provide a first signal that CTC monitoring might represent a potential marker for tumor control in KIT mutant GIST. Citation Format: Filip Janku, Albi Razak, Michael Gordon, David Brooks, Daniel Flynn, Anu Gupta, Michael Kaufman, Cynthia Leary, Bryan Smith, Deb Westwood, Neeta Somaiah, Elena Helman, Eric Gerstenberger, Oliver Rosen, Suzanne George. Translational research in a phase I proof-of-concept study supports that DCC-2618 is a pan-KIT inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-039. doi:10.1158/1538-7445.AM2017-LB-039

EVALUATION OF SODIUM VALPROATE LEVELS IN MALNOURISHED CHILDHOOD EPILEPSY AND ITS CONSEQUENCES

Objectives. To measure and compare free fraction of serum levels of VPA (valproic acid) between non-malnourished and malnourished epileptic children and to evaluate the adverse effects (myopathy, hepatotoxicity). Material and methods. It is a prospective comparative observational case control study in which forty epileptic children (malnourished: 18 male/8 female, age 8.3±2.5, non-malnourished: 8 male/6 female, age 8.1±2.1) who fulfilled the inclusion criteria were recruited as study group and twenty children as control group (12male/8 female, age 6.0±2.8). Outcome measures monitored are serum VPA levels (total and free fraction of serum VPA), serum CK (creatinine kinase), SGOT (serum glutamic oxaloacetic transaminase) and SGPT (serum glutamic pyruvic-transaminase). Using screening tool for the assessment of malnutrition in pediatrics (STAMP©), subjects are categorized into mild, moderate, severe malnourished as -1SD, -2SD, -3SD respectively Outcomes. There is an elevation in mean free fraction of VPA is 17.3±6.4 μg/ml whereas in non-malnourished group it was found to be 8.7±4.2 μg/ml with P= <0.001. While mean total drug concentration in malnourished and non-malnourished was found to be 88.6±49.9 μg/ml, 70.8±33.9 μg/ml respectively. Mean CK, SGOT, SGPT in control is 29.3±9.9IU/L, 28.5±5.4 IU/L,24.5±4.2 IU/L respectively. whereas mean CK, SGOT, SGPT in malnourished subjects is 16.9±9.1 IU/L, 28.8±8.5 IU/L,25.9±9.1 IU/L Correspondingly .while Mean CK, SGOT, SGPT in non-malnourished individuals is 15.7±11.3 IU/L,32.4±8.8 IU/L, 28.7±7.8 IU/L respectively. No correlation was observed between elevated serum drug concentrations, clinical response and side effects. Conclusion. We observed that clinical response and side effects are serum concentration independent hence our research make unnecessary to monitor serum drug concentration for every individual and drug monitoring should be restricted to subjects with severe ADR’s. Our data also suggest Valproate unveiled mitochondrial myopathy is limited to subgroup of population.

Monitoring Protein-Unbound Valproic Acid Serum Concentrations in Clinical Practice.

Valproic acid (VPA) is an effective antiepileptic drug and mood stabilizer. A key characteristic of VPA is its high and saturable protein binding at higher concentrations. Although the unbound concentration of VPA is responsible for its pharmacological activity, total drug concentrations are monitored in routine clinical practice. Therapeutic drug monitoring (TDM) of unbound VPA is recommended for specific clinical situations. The goal of this study was to evaluate TDM requests for unbound VPA in clinical practice. All TDM requests at our laboratory for unbound VPA in 2014 and 2015 were evaluated retrospectively. In patients with potentially toxic unbound VPA concentrations (ie, >12 mg/L), we evaluated whether toxicity was noted and whether the dose adjustment advice was followed. Total and unbound VPA concentrations were measured by means of a validated immunoassay. A total of 273 unbound VPA serum concentrations in 132 different patients were analyzed. The main reasons for unbound VPA TDM were decreased renal function (34%) and a low serum albumin (27%). The median (range) unbound VPA concentration was 9.8 (2.5-47.6) mg/L. In 49 patients (37%), the initial unbound VPA concentration was above the threshold of 12 mg/L, potentially resulting in toxicity. Only 6 of these 49 patients had elevated total VPA concentrations. Clinical toxicity was noted in 38 of the 49 patients (77.6%) with elevated unbound VPA concentrations. Toxicities included drowsiness (n = 26), decreased consciousness (n = 4), rigidity (n = 2), and confusion (n = 2). In 36 of the 38 patients with elevated unbound VPA concentrations and clinical toxicity, a dose reduction was applied. In 27 of 36 patients who had their dose reduced, dose reduction was associated with improvement or resolution of VPA toxicity. TDM of unbound VPA is an important tool to manage VPA therapy in selected, vulnerable patients.

Pharmacokinetic-driven phase I study of DCC-2618 a pan-KIT and PDGFR inhibitor in patients (pts) with gastrointestinal stromal tumor (GIST) and other solid tumors.

2515 Background: DCC-2618 is a potent switch control inhibitor of KIT and PDGFR kinases active in a broad range of mutations. GIST is an important disease to achieve a proof-of-concept due to the heterogeneity of KIT resistance mutations, which emerge on treatment with approved KIT inhibitors. Methods: This was a PK-guided dose escalation study of oral DCC-2618 (QD or BID q28 days) in advanced solid tumors. FDG-PET scans were used to assess changes in FDG uptake in GIST pts after 3 wks of therapy. Next generation sequencing (NGS) of plasma cell-free (cf) DNA was performed throughout the study to assess and quantify KIT and other molecular alterations in drug targets and potential mechanisms of resistance. Results: 38 pts were enrolled (30 GIST; 4 glioma; 1 mastocytosis, 3 other carcinoma) to 8 dose levels: BID doses: 20 (4 pts), 30 (4), 50 (5), 100 (6), 150 (6) and 200 mg (3); QD doses: 100 (5) and 150 mg (4). Safety of evaluable pts is as follows: G3 or G4 adverse effects (regardless of attribution and occurring in > 1 pt) included anemia (5), lipase increase (4), hypertension (2). Two of the G3/4 lipase increase at 100 mg BID and 200 mg BID were DLTs. All G3/4 lipase increase were asymptomatic. G1/2 AEs (considered at least possibly related to DCC-2618) and occurring in ≥15% (n > 5) of pts include fatigue (12), alopecia & lipase increase (7), weight decrease (6). Starting with 50 mg BID dose level, trough concentrations of total drug exceeded the IC90 of the least sentivitive KIT mutations. Plasma concentrations > 5μM were achieved starting at 100 mg BID and the selection of the expansion phase dose is being finalized. Of 18 pts with KIT mutant GIST assessed by FDG PET, 14 (78%) had partial metabolic response per EORTC criteria. RANO/RECIST partial responses (PRs) were reported in 3 patients (1 GBM with PDGFRA/KIT amplifications and 2 GIST with Ex 11 & 17 / Ex 11 & 18 mutations, respectively). NGS of plasma cfDNA revealed 44 KIT mutations in baseline samples from 19 of 21 pts with GIST. Conclusions: DCC-2618 is well tolerated with encouraging preliminary activity in GIST pts with a broad spectrum of mutations and prior therapies. PR was also seen in a pt with GBM with PDGFRA/KIT amplifications. Clinical trial information: NCT02571036.

Effects of the summer holiday season on UV filter and illicit drug concentrations in the Korean wastewater system and aquatic environment

Seasonal variations in the concentrations of eight ultraviolet (UV) filters and 22 illicit drugs including their metabolites in the Korean aquatic environment were investigated. Seawater samples from three beaches, water samples from two rivers, and influents and effluents from three wastewater treatment plants were analyzed. The UV filter concentrations in the seawater, river water, and effluent samples were 39.4–296, 35.4–117, and 6.84–51.1 ng L-1, respectively. The total UV filter concentrations in the seawater samples were 1.9–4.4 times higher at the peak of the holiday season than outside the peak holiday season. An environmental risk assessment showed that ethylhexyl methoxy cinnamate (EHMC) could cause adverse effects on aquatic organisms in the seawater at the three beaches during the holiday period. Seven of the 22 target illicit drugs including their metabolites were detected in the wastewater influent samples, and the total illicit drug concentrations in the influent samples were 0.08–65.4 ng L-1. The estimated daily consumption rates for cis-tramadol (Cis-TRM), methamphetamine (MTP), meperidine (MEP), and codeine (COD) were 25.7–118.4, 13.8–36.1, 1.36–12.6, and 1.75–8.64 mg d-1 (1000 people)−1, respectively. In popular vacation area, the illicit drug consumption rates (Cis-TRM, MTP and MEP) were 1.6–2.6 times higher at the peak of the summer holiday season than at the beginning of the summer.

Combined PET and microdialysis for in vivo estimation of drug blood-brain barrier transport and brain unbound concentrations

Methods to investigate blood-brain barrier transport and pharmacologically active drug concentrations in the human brain are limited and data translation between species is challenging. Hence, there is a need to further develop the read-out of techniques like positron emission tomography (PET) for studying neuropharmacokinetics. PET has a high translational applicability from rodents to man and measures total drug concentrations in vivo. The aim of the present study was to investigate the possibility of translating total drug concentrations, acquired through PET, to unbound concentrations, resembling those measured in the interstitial fluid by microdialysis sampling.Simultaneous PET scanning and brain microdialysis sampling were performed in rats throughout a 60min infusion of [N-methyl-11C]oxycodone in combination with a therapeutic dose of oxycodone and during a 60min follow up period after the end of infusion. The oxycodone concentrations acquired with PET were converted into unbound concentrations by compensating for brain tissue binding and brain intracellular distribution, using the unbound volume of distribution in brain (Vu,brain), and were compared to microdialysis measurements of unbound concentrations.A good congruence between the methods was observed throughout the infusion. However, an accumulating divergence in the acquired PET and microdialysis data was apparent and became more pronounced during the elimination phase, most likely due to the passage of radioactive metabolites into the brain. In conclusion, the study showed that PET can be used to translate non-invasively measured total drug concentrations into unbound concentrations as long as the contribution of radiolabelled metabolites is minor or can be compensated for.

Antibody Drug-Target Engagement Measurement in Tissue Using Quantitative Affinity Extraction Liquid Chromatography-Mass Spectrometry: Method Development and Qualification.

We demonstrate a novel strategy using affinity extraction (AE) LC-MS to directly measure drug exposure and target engagement, two critical pharmacological questions, with a single assay. The assay measures total drug and target concentration at the site of therapeutic action, as well as the amount of target bound to drug. The case study presented applies the strategy to measure drug engagement of a membrane bound receptor (CD40) that is critical to immune regulation in colon biopsies collected from monkey dosed with an anti-CD40 antibody. Unlike other techniques that measure receptor occupancy, such as flow cytometry, this technique does not rely on viable cells allowing measurement of frozen samples in a remote setting from the clinic.

Which Metabolic Panel for Psychiatric Practice: Basic or Comprehensive?

Which Metabolic Panel for Psychiatric Practice: Basic or Comprehensive?