Toxic Plasma Concentrations Research Articles

A novel approach for pharmacological substantiation of safety signals using plasma concentrations of medication and administrative/healthcare databases: A case study using Danish registries for an FDA warning on lamotrigine

PHARMACOM-EPI is a novel framework to predict plasma concentrations of drugs at the time of occurrence of clinical outcomes. In early 2021, the U.S. Food and Drug Administration (FDA) issued a warning on the antiseizure drug lamotrigine claiming that it has the potential to increase the risk of arrhythmias and related sudden cardiac death due to a pharmacological sodium channel-blocking effect. We hypothesized that the risk of arrhythmias and related death is due to toxicity. We used the PHARMACOM-EPI framework to investigate the relationship between lamotrigine’s plasma concentrations and the risk of death in older patients using real-world data. Danish nationwide administrative and healthcare registers were used as data sources and individuals aged 65 years or older during the period 1996 – 2018 were included in the study. According to the PHARMACOM-EPI framework, plasma concentrations of lamotrigine were predicted at the time of death and patients were categorized into non-toxic and toxic groups based on the therapeutic range of lamotrigine (3–15 mg/L). Over 1 year of treatment, the incidence rate ratio (IRR) of all-cause mortality was calculated between the propensities score matched toxic and non-toxic groups. In total, 7286 individuals were diagnosed with epilepsy and were exposed to lamotrigine, 432 of which had at least one plasma concentration measurement The pharmacometric model by Chavez et al. was used to predict lamotrigine’s plasma concentrations considering the lowest absolute percentage error among identified models (14.25 %, 95 % CI: 11.68–16.23). The majority of lamotrigine associated deaths were cardiovascular-related and occurred among individuals with plasma concentrations in the toxic range. The IRR of mortality between the toxic group and non-toxic group was 3.37 [95 % CI: 1.44–8.32] and the cumulative incidence of all-cause mortality exponentially increased in the toxic range. Application of our novel framework PHARMACOM-EPI provided strong evidence to support our hypothesis that the increased risk of all-cause and cardiovascular death was associated with a toxic plasma concentration level of lamotrigine among older lamotrigine users.

Virtual Clinical Trials Guided Design of an Age-Appropriate Formulation and Dosing Strategy of Nifedipine for Paediatric Use

The rapid onset of action of nifedipine causes a precipitous reduction in blood pressure leading to adverse effects associated with reflex sympathetic nervous system (SNS) activation, including tachycardia and worsening myocardial and cerebrovascular ischemia. As a result, short acting nifedipine preparations are not recommended. However, importantly, there are no modified release preparations of nifedipine authorised for paediatric use, and hence a paucity of clinical studies reporting pharmacokinetics data in paediatrics. Pharmacokinetic parameters may differ significantly between children and adults due to anatomical and physiological differences, often resulting in sub therapeutic and/or toxic plasma concentrations of medication. However, in the field of paediatric pharmacokinetics, the use of pharmacokinetic modelling, particularly physiological-based pharmacokinetics (PBPK), has revolutionised the ability to extrapolate drug pharmacokinetics across age groups, allowing for pragmatic determination of paediatric plasma concentrations to support drug licensing and clinical dosing. In order to pragmatically assess the translation of resultant dissolution profiles to the paediatric populations, virtual clinical trials simulations were conducted. In the context of formulation development, the use of PBPK modelling allowed the determination of optimised formulations that achieved plasma concentrations within the target therapeutic window throughout the dosing strategy. A 5 mg sustained release mini-tablet was successfully developed with the duration of release extending over 24 h and an informed optimised dosing strategy of 450 µg/kg twice daily. The resulting formulation provides flexible dosing opportunities, improves patient adherence by reducing frequent administration burden and enhances patient safety profiles by maintaining efficacious levels of consistent drug plasma levels over a sustained period of time.

Lidocaine Intraoperative Infusion Pharmacokinetics during Partial Hepatectomy for Living Liver Donation.

Postoperative pain associated with open partial hepatectomy can be intense and persistent. The multimodal approach used to lessen this problem includes an intraoperative intravenous infusion of lidocaine hydrochloride. Decreased hepatic metabolism after resection raises concerns about safe lidocaine dosing in this patient population. The hypothesis was that the elimination clearance of lidocaine and its metabolites, monoethylglycinexylidide and glycinexylidide, is reduced after a partial hepatectomy, as reflected by observed plasma concentrations that are higher and have a longer half-life than expected based on pharmacokinetic modeling (estimated for normal liver function). Secondarily, this study postulated that plasma concentrations of lidocaine, monoethylglycinexylidide, and glycinexylidide do not reach toxic concentrations with institutional protocol up to 24 h after surgery. Blood samples were collected from 15 patients undergoing a partial hepatectomy for living liver donation, at the following specific time points: before and immediately after induction of anesthesia, during hepatectomy, 30 min after hepatectomy completion, at case end, and 24 h after the end of surgery. Plasma concentrations of lidocaine and metabolites were measured by liquid chromatography-mass spectrometry. The population lidocaine pharmacokinetics were estimated, and total body weight and the fraction of remaining liver mass as potential model covariates were evaluated. The detection of any lidocaine, monoethylglycinexylidide, or glycinexylidide toxic plasma concentrations at any time point during and after hepatectomy were also evaluated. The typical value for lidocaine elimination clearance was 0.55 ± 0.12 l/min (± standard error of the estimate) which, on average, was reduced to about one third of the baseline clearance, 0.17 ± 0.02 l/min, once the donor graft was surgically isolated, and remained so for 24 h according to the current data and model. The fraction of remaining liver was a significant covariate for the posthepatectomy lidocaine clearance' such that if 50% of the liver is removed the clearance is reduced by approximately 60%. Plasma concentrations of lidocaine and its metabolites remained below their theoretical combined toxic threshold concentrations throughout the surgical and postoperative course in all patients, with one exception obtained near induction of anesthesia. Plasma lidocaine concentrations decreased at case end and postoperatively, while metabolite concentrations continued to rise at the end of surgery with reduction postoperatively. Pharmacokinetic modeling revealed that the only significant covariate in the model was the fraction of liver remaining after isolation of the donor graft. Intravenous lidocaine infusions are an acceptable option for multimodal pain management in patients undergoing a hepatectomy for living donation if the lidocaine infusion is stopped when the liver resection is complete. Clearance of lidocaine is decreased proportionally to the remaining liver mass, which should guide lidocaine infusion administration or dosing adjustments for patients undergoing liver resection surgery.

Exome sequencing allows detection of relevant pharmacogenetic variants in epileptic patients.

Beyond the identification of causal genetic variants in the diagnosis of Mendelian disorders, exome sequencing can detect numerous variants with potential relevance for clinical care. Clinical interventions can thus be conducted to improve future health outcomes for patients and their at-risk relatives, such as predicting late-onset genetic disorders accessible to prevention, treatment or identifying differential drug efficacy and safety. To evaluate the interest of such pharmacogenetic information, we designed an "in house" pipeline to determine the status of 122 PharmGKB (Pharmacogenomics Knowledgebase) variant-drug combinations in 31 genes. This pipeline was applied to a cohort of 90 epileptic patients who had previously an exome sequencing (ES) analysis, to determine the frequency of pharmacogenetic variants. We performed a retrospective analysis of drug plasma concentrations and treatment efficacy in patients bearing at least one relevant PharmGKB variant. For PharmGKB level 1A variants, CYP2C9 status for phenytoin prescription was the only relevant information. Nineteen patients were treated with phenytoin, among phenytoin-treated patients, none were poor metabolizers and four were intermediate metabolizers. While being treated with a standard protocol (10-23 mg/kg/30 min loading dose followed by 5 mg/kg/8 h maintenance dose), all identified intermediate metabolizers had toxic plasma concentrations (20 mg/L). In epileptic patients, pangenomic sequencing can provide information about common pharmacogenetic variants likely to be useful to guide therapeutic drug monitoring, and in the case of phenytoin, to prevent clinical toxicity caused by high plasma levels.

Half-dose glucarpidase as efficient rescue for toxic methotrexate levels in patients with acute kidney injury

PurposeHigh-dose methotrexate (HDMTX)-associated acute kidney injury with delayed MTX clearance has been linked to an excess in MTX-induced toxicities. Glucarpidase is a recombinant enzyme that rapidly hydrolyzes MTX into non-toxic metabolites. The recommended dose of glucarpidase is 50 U/kg, which has never been formally established in a dose finding study in humans. Few case reports, mostly in children, suggest that lower doses of glucarpidase might be equally effective in lowering MTX levels.MethodsSeven patients with toxic MTX plasma concentrations following HDMTX therapy were treated with half-dose glucarpidase (mean 25 U/kg, range 17–32 U/kg). MTX levels were measured immunologically as well as by liquid chromatography–mass spectrometry (LC–MS). Toxicities were assessed according to National Cancer Institute—Common Terminology Criteria for Adverse Events (CTCAE) v5.0.ResultsAll patients experienced HDMTX-associated kidney injury (median increase in creatinine levels within 48 h after HDMTX initiation compared to baseline of 251%, range 80–455%) and showed toxic MTX plasma concentrations (range 3.1–182.4 µmol/L) before glucarpidase injection. The drug was administered 42–70 h after HDMTX initiation. Within one day after glucarpidase injection, MTX plasma concentrations decreased by ≥ 97.7% translating into levels of 0.02–2.03 µmol/L. MTX rebound was detected in plasma 42–73 h after glucarpidase initiation, but concentrations remained consistent at < 10 µmol/L.ConclusionHalf-dose glucarpidase seems to be effective in lowering MTX levels to concentrations manageable with continued intensified folinic acid rescue.

Evaluation of Imatinib Concentrations in Samples Submitted for BCR-ABL1 or Imatinib Testing-Evidence to Support Therapeutic Drug Monitoring for Dose Optimization?

Imatinib is one of the first-line therapies for chronic myeloid leukemia. Achieving a major molecular response early in treatment, as indicated by a BCR-ABL1 major international scale result of ≤0.1% within 6 months, is associated with better patient outcomes and is statistically associated with a trough imatinib concentration of approximately 1000 ng/mL. Adherence to therapy, drug resistance, drug-drug interactions, and pharmacokinetic/pharmacodynamic factors may hinder attaining this target. Therapeutic drug monitoring of imatinib is not currently standard-of-care, but may help to evaluate adherence and optimize treatment of patients with chronic myeloid leukemia. This study aimed to evaluate imatinib concentrations in real-world patient plasma samples to identify the proportion of imatinib-treated patients who achieved the therapeutic target of 1000 ng/mL. This was a retrospective, observational study that measured imatinib in residual plasma samples used for BCR-ABL1 tests (n = 1022) and analyzed clinician-ordered imatinib tests for therapeutic drug monitoring (n = 116). Imatinib was measured by competitive immunoassay. The frequency of imatinib concentrations achieving the therapeutic target was determined and correlated with BCR-ABL1 major international scale, age, and sex. Seventy-two percent of patients tested for BCR-ABL1 may not have been prescribed or were not adherent to imatinib therapy. In the 29% of patients who did not achieve major molecular response, but had quantifiable imatinib concentrations, the therapeutic concentration was not met. For clinician-ordered imatinib tests, 45% of samples did not exceed the therapeutic target and 4% had potentially toxic plasma concentrations (>3000 ng/mL). Therapeutic drug monitoring for imatinib may assist clinicians in the identification of patients who may not be adherent to therapy, display variable pharmacokinetics or pharmacodynamics, or may be experiencing toxicity or treatment failure.

Palbociclib in combination with simvastatin induce severe rhabdomyolysis: a case report

BackgroundPalbociclib is a selective well-tolerated antineoplastic drug used in the treatment of advanced HER2-negative, estrogen-receptor positive breast cancer that has shown significant improvement in progression-free survival. We present a patient that developed severe rhabdomyolysis with tetra-affection and loss of gait after initiating the first cycle of Palbociclib concomitantly with Simvastatin 40 mg treatment.Case presentationA 71-year-old woman with metastatic breast cancer developed tetraparesis and near fatal rhabdomyolysis after initiation of first cycle Palbociclib. For 10 years prior to this treatment, the patient had been treated with Simvastatin without myalgia or other neuromuscular complaints prior to the first cycle of Palbociclib. The patient was admitted at the neurology department, where Palbociclib and Simvastatin were discontinued. The patient was aggressively hydrated and treated with intravenous immunoglobulin therapy with slowly remission and finally regaining independent gait function. Evaluation showed a negative myositis antibody work-up. Muscle magnetic resonance imaging showed edema in multiple foci, but skeletal muscle biopsy did not show necrosis. Post discharge genetic analysis showed single heterozygosity for nucleotide polymorphism rs4149056.ConclusionWe present a patient who developed severe rhabdomyolysis induced by a combination of Palbociclib and Simvastatin treatment. Rhabdomyolysis was most likely induced by toxic plasma concentrations of Simvastatin due to Palbociclibs inhibition of the CYP3A4 enzyme in combination with a decreased hepatic uptake of Simvastatin due to single nucleotide polymorphism rs4149056. The study underscores that combining Simvastatin and Palbociclib should be done cautiously and genetic testing of the rs4149056 SNP is warranted. If present, Simvastatin should be discontinued or replaced with a lesser myopathic statin in regard to patients risk of cardiovascular events.

Risk factors associated with insufficient and potentially toxic voriconazole plasma concentrations: an observational study

The aim of this study was to identify potential factors associated with insufficient/toxic voriconazole trough concentrations (VTCs) in patients in order to screen the high-risk population. A total of 119 VTCs were obtained from 67 patients. Multivariate regression analysis suggested that insufficient VTCs (<1.0 mg/L) were significantly associated with younger age and underlying hematological malignancy, and toxic VTCs (>5.5 mg/L) were significantly associated with lower serum albumin (ALB) level. Receiver operating characteristic curve analysis indicated that patients whose age < 47 years were the high-risk population of insufficient VTCs, and patients whose ALB <27 g/L were the high-risk population of toxic VTCs. Younger age and underlying hematological malignancy were significant predictors of insufficient VTCs, and lower ALB level was found to be a significant predictor of toxic VTCs. Therefore, we recommend to increase the monitoring on these high-risk population to avoid treatment failure and to prevent toxic adverse events.

Pathological Concentration of C-reactive Protein is Correlated to Increased Concentrations of Quetiapine, But Not of Risperidone, Olanzapine and Aripiprazole in a Naturalistic Setting.

Infections can alter drug clearance, but the impact of inflammation-induced changes is still not well known. The aim of the investigation was to examine the effect of pathological C-reactive protein (CRP) values (≥0.5 mg/dL) and leukocyte count on the metabolism of 4 different atypical antipsychotics. Steady-state serum concentrations of individual patients under therapy with risperidone (n=45), aripiprazole (n=30), olanzapine (n=24), and quetiapine (n=166) were retrospectively analyzed during a period of inflammation by Spearman's Rho correlation analysis. Mann-Whitney U test was applied for comparison of patients with serum concentrations above and below the upper limit of the therapeutic reference range of each target drug with regard to CRP concentration and leukocyte count. Linear regression analysis was applied to correct for confounding parameters age and sex. Pathological concentrations of CRP were significantly associated with elevated values of C/D of quetiapine (n=166, Spearman's Rho: r=0.269, p<0.001; linear regression: p<0.001). Among patients with quetiapine serum concentrations below 500 ng/mL, CRP concentrations were significantly (p=0.006) lower compared to patients with quetiapine concentrations above 500 ng/mL. A trend for a positive correlation between CRP and serum concentration was found for olanzapine (n=24, Spearman's Rho: r=0.385, p=0.063; linear regression: p=0.086). During a period of inflammation in patients taking quetiapine, according to our results, attention in dosing strategies is required to prevent toxic plasma concentrations.

Approaches of validation of a 2-week combined repeated oral dose toxicity study with plasma micro sampling toxicokinetics (PMS-TK) in common marmosets.

We investigated the viability of a combined repeated dose toxicity study, including toxicokinetics (TK), in common marmosets according to the ICH-S4, ICH-S3A and ICH-S7A Guidelines using valsartan as test article whose non-clinical repeated dose toxicity studies had been conducted using this species for regulatory purpose. Valsartan was administered orally to 3 animals/sex at 200 mg/kg/day for 2 weeks. In addition to the routine parameters in repeated dose toxicity studies, safety pharmacology parameters (examinations of the central nervous, respiratory and cardiovascular systems) were also evaluated. The Plasma Micro Sampling Toxicokinetics (PMS-TK) method required ultrasensitive quantitation, was employed to evaluate the relationship between toxic changes and plasma concentrations as well as the effects of frequent blood sampling in individual animals. In valsartan, toxic findings (a deteriorated physical condition; moribundity of one male and one female on Day 14; sporadic vomitus; decreases in body weights and food consumption; decreases in erythrocytic parameters; and renal changes such as an increase in urea nitrogen, dilation of the tubules and hypertrophy of the tubular epithelium) were similar and plasma concentrations comparable to the results in the approval information. Furthermore, no side effects caused by frequent blood sampling were confirmed in the negative control group. Consequently, a combined repeated dose toxicity study including TK analysis using the PMS-TK method is viable in common marmosets and contributes to animal welfare.

Repeated Piperacillin-Tazobactam Plasma Concentration Measurements in Severely Obese Versus Nonobese Critically Ill Septic Patients and the Risk of Under– and Overdosing*

Obesity and critical illness modify pharmacokinetics of antibiotics, but piperacillin-tazobactam continuous IV infusion pharmacokinetics has been poorly studied in obese critically ill patients. We aimed to compare pharmacokinetics of piperacillin in severely obese and nonobese patients with severe sepsis or septic shock. We hypothesized that plasma concentration variability would expose the critically ill to both piperacillin under and overdosing. Prospective comparative study. Consecutive critically ill severely obese (body mass index, > 35 kg/m) and nonobese patients (body mass index, < 30 kg/m) were treated with 16 g/2 g/24 hr continuous piperacillin-tazobactam infusion. Piperacillin plasma concentration was measured every 12 hours over a 7-day period by high-pressure liquid chromatography. Unbound piperacillin plasma concentration and fractional time of plasma concentration spent over 64 mg/L (4-fold the minimal inhibitory concentration for Pseudomonas aeruginosa) were compared between the two groups. We performed 5,000 Monte Carlo simulations for various dosing regimens and minimal inhibitory concentration and calculated the probability to spend 100% of the time over 64 mg/L. We enrolled 11 severely obese and 12 nonobese patients and obtained 294 blood samples. We did not observe a statistically significant difference in piperacillin plasma concentrations over time between groups. The fractional time over 64 mg/L was 64% (43-82%) and 93% (85-100%) in obese and nonobese patients, respectively, p = 0.027 with intra- and intergroup variability. Five nonobese and two obese patients experienced potentially toxic piperacillin plasma concentrations. When 64 mg/L was targeted, Monte Carlo simulations showed that 12 g/1.5 g/24 hr was inadequate in both groups and 16 g/2 g/24 hr was adequate only in nonobese patients. Using a conventional dosing of 16 g/2 g/24 hr continuous infusion, obese patients were more likely than nonobese patients to experience piperacillin underdosing when facing high minimal inhibitory concentration pathogens. The present study suggests that piperacillin drug monitoring might be necessary in the sickest patients who are at the highest risk of unpredictable plasma concentration exposing them to overdose, toxicity, underdosing, and treatment failure.

Formulation of Monodisperse Alginate (Micro) Spheres Containing Tenofovir for Extended Release Dosage Form

Tenofovir (TF) belongs to a class of antiretroviral drugs known as nucleotide analogue reverse transcriptase inhibitors (NRTIs) used in the treatment of human immunodeficiency virus 1 (HIV-1) and hepatitis B. Despite its safety and effectiveness, TF oral administration limited by several factors : low bioavailability (25%), adverse effects like decrease in bone mineral density and severe renal adverse events, including fanconis syndrome due to frequent dosing, and high circulating plasma levels. By developing particulate drug carriers it is possible to achieve effective plasma concentration without significant fluctuation, to avoid sub-therapeutic or toxic plasma concentrations, to achieve an effective therapy with a low dosage and to reduce the dosage frequency. TF loaded floating particulate drug carriers for control release medication were designed and constructed to prolong the retention in the stomach and to facilitate drug absorption over a prolonged period of time using Extrusion ionic gelation technique employing sodium alginate alone and in combination with MC, HPMC K100M, HPMC K15M. The drug release for the optimized formulation, F10, followed first order kinetics and Higuchi plot of F10 formulation showed an R2 value of 0.9582. The data were fitted to the Korsmeyer-Peppas equation and the values of diffusion exponent ‘n’ for the batch F10 was 0.623 which indicated the drug release by Non-Fickian diffusion, suggesting that the diffusion along with erosion/swelling plays an important role in extending the drug release. Surface morphology of microspheres was found to be Smooth. These results suggested that the TF microbeads are promising and should be investigated further in the near future as an effective oral delivery system.

A prospective study to assess the association between genotype, phenotype and Prakriti in individuals on phenytoin monotherapy

BackgroundGenetic polymorphisms in drug metabolizing enzymes (DMEs) impart distinct drug metabolizing capacity and a unique phenotype to an individual. Phenytoin has large inter-individual variability in metabolism due to polymorphisms in CYP2C9 and CYP2C19. As per Ayurveda, Prakriti imparts a unique phenotype to an individual. ObjectiveTo assess whether Prakriti can substitute phenotyping [therapeutic drug monitoring (TDM)] and genotyping in individualizing therapy with phenytoin in epilepsy patients. Methods and materialsThis was a cross-sectional study conducted over a period of three years. Prakriti was assessed using standardized and validated software. Polymorphisms in CYP2C9 and CYP2C19 were assessed using Polymerase Chain Reaction (PCR)-Restriction fragment length polymorphism (PCR-RFLP). Plasma concentrations of phenytoin (phenotype) were determined using reverse phase-high performance liquid chromatography (RF-HPLC). ResultsTotal 351 patients were enrolled for the study. Kapha vata (KV) (39%) was the predominantly observed Prakriti followed by vata kapha (VK) (20.8%) and vata pitta (VP) (8.83%) among the patients. The CYP2C9 and CYP2C19 genotype distributions were in accordance with Hardy–Weinberg equilibrium. There was no association between Prakriti and genotypes and Prakriti and phenotype (p > 0.05 each). Patients with CYP2C9 *1/*3 genotype were thrice more likely to have toxic plasma concentrations of phenytoin as compared to those with wild-type genotype (*1/*1) (Adjusted odds ratio – 3.36; 95% C.I. 1.61, 7.01). However, no such association was observed between polymorphisms of CYP2C19 and phenotype. ConclusionsWe did not find any association between Prakriti and either phenotype or genotypes suggesting that Prakriti assessment would be of limited utility in individualizing phenytoin therapy in epilepsy patients.

Development and validation of a fast ionic liquid-based dispersive liquid–liquid microextraction procedure combined with LC–MS/MS analysis for the quantification of benzodiazepines and benzodiazepine-like hypnotics in whole blood

To date, thorough clean-up of complex biological samples remains an essential part of the analytical process. The solid phase extraction (SPE) technique is the well-known standard, however, its main weaknesses are the labor-intensive and time-consuming protocols. In this respect, dispersive liquid–liquid microextractions (DLLME) seem to offer less complex and more efficient extraction procedures. Furthermore, ionic liquids (ILs) – liquid salts – are emerging as new promising extraction solvents, thanks to their non-flammable nature, negligible vapor pressure and easily adaptable physiochemical properties. In this study, we investigated whether ILs can be used as an extraction solvent in a DLLME procedure for the extraction of a broad range of benzodiazepines and benzodiazepine-like hypnotics in whole blood samples. 1.0mL whole blood was extracted using an optimized 30-min IL-based DLLME procedure, followed by LC-ESI(+)-MS/MS analysis in scheduled MRM scan mode. The optimized analytical method was successfully validated for 7-aminoflunitrazepam, alprazolam, bromazepam, clobazam, clonazepam, clotiazepam, diazepam, estazolam, ethyl loflazepate, etizolam, flurazepam, lormetazepam, midazolam, oxazepam, prazepam, temazepam, triazolam, zolpidem and zopiclone. The method showed good selectivity for endogenous interferences based on 12 sources of blank whole blood. No benzodiazepine interferences were observed, except for clorazepate and nordiazepam, which were excluded from the quantitative method. Matrix-matched calibration curves were constructed covering the whole therapeutic range, including low toxic plasma concentrations. Accuracy and precision results met the proposed acceptance criteria for the vast majority of compounds, except for brotizolam, chlordiazepoxide, cloxazolam, flunitrazepam, loprazolam, lorazepam and nitrazepam, which can only be determined in a semi-quantitative way. Recoveries were within the range of 24.7%–127.2% and matrix effects were within 20.0%–92.6%. Both parameters were tested using 5 sources of whole blood and coefficients of variance were below 20%. Overall, the applicability of ILs as promising solvents for the extraction of benzodiazepines in whole blood samples has been proven. Moreover, a fast and easy IL-based DLLME procedure was developed for the quantification of 19 benzodiazepines and benzodiazepine-like hypnotics.

Efavirenz biotransformation as an up-stream event of mood changes in HIV-infected patients

Efavirenz is a drug of choice for adults and children infected with the human immunodeficiency virus. Notably, up to 35% of patients on efavirenz suffer from mood changes.This work aimed to investigate efavirenz biotransformation into 8-hydroxy-efavirenz as an up-stream event of mood changes and to evaluate the suitability of 8-hydroxy-efavirenz biomonitoring for the minimization of these manifestations. A case-control study with two age-matched groups of HIV-infected male patients was performed in a group without adverse central nervous system complaints (28 patients) and a group presenting mood changes (14 patients). The plasma concentration of non-conjugated 8‐hydroxy‐efavirenz was higher in patients with mood changes (p=0.020). An association between efavirenz and 8-hydroxy-efavirenz-glucuronide was found (Spearman r=0.414, p<0.010), only within therapeutic efavirenz concentrations. This correlation was not observed in patients with toxic (>4mg/L) plasma concentrations of the parent drug. We conclude that metabolism to 8-hydroxy-efavirenz is associated with efavirenz-related mood changes, which suggests that the concentration of this metabolite is a suitable parameter for therapeutic drug monitoring aimed at controlling these manifestations. Moreover, our data suggest that 8-hydroxy-efavirenz is able to cross the blood-brain barrier and that the peripheral detoxification of 8-hydroxy-efavirenz by glucuronidation may be inhibited by toxic efavirenz concentrations.

Proliposomal Ropivacaine Oil: Pharmacokinetic and Pharmacodynamic Data After Subcutaneous Administration in Volunteers.

Slow-release liposomal formulations of local anesthetics prolong plasma redistribution and reduce peak plasma drug concentration, allowing safer administration of larger doses and further prolonging sensory effects. However, their clinical applicability is limited by expensive manufacture and liposomal leakage. Previously, we described the simple preparation of a novel proliposomal ropivacaine oil that produces multilamellar liposomal vesicles on exposure to aqueous media and that has a shelf-life of >2 years at room temperature. In this study, we present both pharmacodynamic and pharmacokinetic data in healthy volunteers after subcutaneous injection of this novel proliposomal preparation of ropivacaine. In the pharmacodynamic phase of this study, 15 volunteers received 3 separate subcutaneous injections of 2.5 mL containing 1 of the following drugs: proliposomal 4% ropivacaine, plain 0.5% ropivacaine, and the ropivacaine-free proliposomal vehicle. Drugs were administered into the lower back, and their location was randomized and blinded; a separate area was used as an uninjected, open control. Experimental sensory assessment was made at repeated intervals over 72 hours using both pinprick sensation and experimental heat pain tolerance (assessed using quantitative sensory testing). In a separate pharmacokinetic phase of this study, 9 volunteers received subcutaneous injections of 2.5 mL of either proliposomal 4% ropivacaine (n = 6) or plain 0.5% ropivacaine (n = 3); these participants had plasma ropivacaine concentrations assessed at repeated intervals over 72 hours. The mean ± SE duration of pinprick anesthesia after proliposomal and plain ropivacaine administration lasted 28.8 ± 6.0 and 15.9 ± 3.5 hours, respectively (mean difference, 16.8 hours; 95% confidence interval, 10.0-23.7; P = 0.001). For experimental heat pain, the anesthesia duration was approximately 36 and 12 hours, respectively, with mean ± SE area under the curve of the normalized heat pain tolerance over time 55.0 ± 28.8 Δ°C·min for proliposomal ropivacaine and 9.6 ± 26.0 Δ°C·min for plain ropivacaine (mean difference, 64.6 Δ°C·min; 95% confidence interval, 10.2-119.0; P = 0.036). In the pharmacokinetic study, there was no significant difference in peak plasma concentration in the proliposomal ropivacaine group (164 ± 43 ng/mL compared with 100 ± 41 ng/mL in the plain ropivacaine group; P = 0.07) despite an 8-fold increase in ropivacaine dose in the proliposomal group. The 99% upper prediction limit for peak plasma concentrations (351 ng/mL proliposomal; 279 ng/mL plain) was well below the putative toxic plasma concentration for both groups. The mean ± SE terminal half-life and area under the curve for proliposomal ropivacaine versus plain ropivacaine were 13.8 ± 3.6 hours vs 5.9 ± 2.3 hours (P = 0.011) and 5090 ± 1476 h·ng/mL vs 593 ± 168 h·ng/mL (P = 0.0014), respectively. The prolonged pharmacodynamic effect of proliposomal ropivacaine, together with its delayed elimination and prolonged redistribution to plasma, is compatible to depot-related slow-release and similar to the performance of other liposomal local anesthetics. The advantage of the proliposomal oil is its ease of preparation and its extended shelf-stability at room temperature.

Synergistic anti-tumor activity through combinational intratumoral injection of an in-situ injectable drug depot

Here, we describe combinational chemotherapy via intratumoral injection of doxorubicin (Dox) and 5-fluorouracil (Fu) to enhance the efficacy and reduce the toxicity of systemically administered Fu and Dox in cancer patients. As the key concept in this work, mixture formulations of Dox-loaded microcapsules (Dox-M) and Fu-loaded Pluronic® hydrogels (Fu-HP) or Fu-loaded diblock copolymer hydrogels (Fu-HC) have been employed as drug depots. The in vitro and in vivo drug depot was designed as a formulation of Dox-M dispersed inside an outer shell of Fu-HP or Fu-HC after injection. The Dox-M/Fu-HP and Dox-M/Fu-HC formulations are free flowing at room temperature, indicating injectability, and formed a structural gelatinous depot in vitro and in vivo at body temperature. The Fu-HP, Fu-HC, Dox-M/Fu-HP, Dox-M/Fu-HC, and Dox-M formulations were easily injected into tumor centers in mice using a needle. Dox-M/Fu-HC produced more significant inhibitory effects against tumor growth than that by Dox-M/Fu-HP, while Fu-HP, Fu-HC and Dox-M had the weakest inhibitory effects of the tested treatments. The in vivo study of Dox and Fu biodistribution showed that high Dox and Fu concentrations were maintained in the target tumor only, while distribution to normal tissues was not observed, indicating that Dox and Fu concentrations below their toxic plasma concentrations should not cause significant systemic toxicity. The Dox-M/Fu-HP and Dox-M/Fu-HC drug depots described in this work showed excellent performance as chemotherapeutic delivery systems. The results reported here indicate that intratumoral injection using combination chemotherapy with Dox-M/Fu-HP or Dox-M/Fu-HC could be of translational research by enhancing the synergistic inhibitory effects of Dox and Fu on tumor growth, while reducing their systemic toxicity in cancer patients.

The Impact of Hypothermia on the Pharmacokinetics of Drugs Used in Neonates and Young Infants.

Therapeutic hypothermia (HT) is frequently used in neonates with hypoxic-ischemic encephalopathy and young infants during cardiopulmonary bypass (CPB). Hypothermia and CPB result in physiological changes contributing to pharmacokinetic (PK) and pharmacodynamic (PD) changes. Changes in the absorption, the volume of distribution (Vd) and the total body clearance (CL) of drugs used during hypothermia and CPB might lead to the interindividual PK variability resulting in either insufficient or toxic plasma concentrations and have an impact on the biodisposition and action of drugs. Both under- or overdosing of medicines in these critically ill patients may contribute to a worse overall outcome. Overall, hypothermia decreases CL but may decrease or increase Vd by changing intravascular blood volume, organ perfusion and enzymatic metabolic processes. In addition, maturational as well as organ specific changes may occur during hypothermia superimposed on the underlying disease and/or procedures such as extracorporeal membrane oxygenation (ECMO) or CPB. This paper will provide an overview of variables and potential covariates (e.g., asphyxia, sepsis, multiorgan dysfunction syndrome, cardiac arrest) determining the PK of frequently used drugs. In addition, the effects of hypothermia on individual drugs are described as well as alternative ways for future study designs such as the use of population PK-PD and opportunistic sampling. Ultimately, these investigations are warranted to obtain specific dosing nomograms of medicines for use in clinical practice and to improve the treatment results of this vulnerable group of pediatric patients.

Hepatocyte spheroid culture on fibrous scaffolds with grafted functional ligands as an in vitro model for predicting drug metabolism and hepatotoxicity

The identification of a biologic substrate for maintaining hepatocyte functions is essential to provide reliable and predictable models for in vitro drug screening. In the current study, a three-dimensional culture of hepatocytes was established on highly porous fibrous scaffolds with grafted galactose and RGD to afford extensive cell–cell and cell–scaffold interactions spatially. The pore size and ligand densities indicated significant effects on the formation of hepatocyte spheroids in balancing the cell retention, adhesion, and migration on fibrous scaffolds. Fibrous scaffolds with an average pore size of 60μm and surface grafting densities of galactose at 5.9nmol/cm2 and RGD at 6.9pmol/cm2 provided optimal microenvironments for hepatocyte infiltration and multicellular spheroid formation. Significant promotions were also demonstrated in the syntheses of albumin and urea and the activities of phase I (CYP 3A11 and CYP 2C9) and phase II enzymes. The in vitro metabolism tests on testosterone and acetaminophen by hepatocytes on the optimal scaffolds indicated the predicated clearance rates of 50.7 and 22.6ml/min/kg, respectively, which were comparable to the in vivo values of rats. The in vitro hepatotoxicity tests on amiodarone hydrochloride and acetaminophen predicted the half maximal effective concentrations (EC50) to reflect the in vivo toxic plasma concentrations in human. In addition, the enzyme activities, predicted clearance rates and hepatotoxicity values of hepatocytes on the optimal scaffolds experienced sensitive responsiveness to specific inducers or inhibitors of CYP 3A11 and phase II enzymes, exhibiting in vivo–in vitro correlations to a certain extent. These results demonstrate the feasibility of hepatocyte spheroid culture on fibrous scaffolds as an potential in vitro testing model to predict the in vivo drug metabolism, hepatotoxicity, and drug–drug interactions.

PO-123: Bupivacaine lozenge induces no risk of toxic plasma concentration in healthy subjects and head/neck cancer patients

PO-123: Bupivacaine lozenge induces no risk of toxic plasma concentration in healthy subjects and head/neck cancer patients