Quantification Of Drug Concentrations Research Articles

Drug content determination of low-dosed hot-melt extruded filaments using Raman spectroscopy

The aim of this study was to evaluate the suitability of a non-disruptive Raman spectroscopic method to quantify drug concentrations below 5 w% within a polymer matrix produced by hot-melt extrusion (HME). For calibration, praziquantel (PZQ)—polyvinylpyrrolidone-vinylacetat-copolymer (PVP-VA) mixtures were extruded. By focusing the laser light of the Raman probe to a diameter of 1 mm and implementing a self-constructed filament holder, the signal-to-noise (S/N) ratio could be reduced considerably. The obtained Raman spectra show quite high fluorescence, which is likely to be caused by dissolved pharmaceutical active ingredient (API) in the polymer matrix. For content determination, HPLC analysis was conducted as a reference method using the same filament segments. A partial least squares (PLS) model, regressing the PZQ concentrations from HPLC method analysis versus the off-line collected Raman spectra, was developed. The linear correlation for a suitable extrusion run for the production of low-dosed filaments (extrusion 1, two kneading zones) is acceptable (R 2 = 0.9915) while the correlation for a extrusion set-up with low miscibility (extrusion 2; without kneading zone) is unacceptable (R 2 = 0.5349). The predictive performance of the calibration model from extrusion 1 is rated by the root mean square error of estimation (RMSEE), which was 0.08%. This calibration can now be used to validate the content of low-dosed filaments during HME.

HPLC method for the determination of thymoquinone in growth cell medium.

Preclinical drug testing requires in vitro and in vivo assessments that are vital for studying drug pharmacokinetics and toxicity. Distinct factors that play an important role in drug screening, such as hydrophobicity, solubility of the substance and serum protein binding can be challenging by inducing result inconsistencies. Hence, establishing accurate methods to quantify drug concentrations in cell cultures becomes pivotal for reliable and reproducible results important for in vivo dosing predictions. This research focuses on developing an optimized analytical approach via high-pressure liquid chromatography (HPLC) to determine thymoquinone (TQ) levels in monolayer cell cultures. The method's validation adheres to the International Council for Harmonisation (ICH) guideline M10, ensuring its acceptance and applicability. Using an HPLC system with a Diode Array Detector (DAD), the study fine-tuned various parameters to achieve an efficient separation of TQ. Validation covered specificity, sensitivity, matrix effects, linearity, precision, and accuracy, alongside assessing TQ stability in RPMI-1640 medium. The HPLC method exhibited remarkable TQ specificity, free from interfering peaks at the analyte retention. Sensitivity analysis at the lower limit of quantification (LLOQ) revealed 5.68% %CV and 98.37% % mean accuracy. Matrix effect evaluation showcased accuracy within 85-115%. Linearity spanned in the concentration range of 2-10 μM with a correlation coefficient (r2) of 0.9993. Precision and accuracy were aligned with acceptance criteria. The proposed method was found to be greener in terms of usage of persistent, bioaccumulative, and toxic chemicals and solvents, corrosive samples, and waste production. The developed HPLC-DAD method emerges as specific, accurate, sensitive, and reliable for TQ determination in cell cultures. It ensures robust TQ quantification, enhancing precise in vitro assessments and dependable dosing predictions for in vivo studies. Further research is advocated to investigate TQ's stability across diverse environmental conditions.

Dermal microdialysis: A method to determine drug levels in the skin of patients with Post kala-azar dermal leishmaniasis (PKDL)

ObjectivesPost-kala-azar-dermal leishmaniasis (PKDL) is an infectious skin disease that occurs as sequela of visceral leishmaniasis (VL) and causes cutaneous lesions on the face and other exposed body parts. While the first-line drug miltefosine is typically used for 28 days to treat VL, 12 weeks of therapy is required for PKDL, highlighting the need to evaluate the extent of drug penetration at the dermal site of infection. In this proof-of-concept study, we demonstrate the use of a minimally invasive sampling technique called microdialysis to measure dermal drug exposure in a PKDL patient, providing a tool for the optimization of treatment regimens. Methods and materialsOne PKDL patient receiving treatment with miltefosine (50 mg twice daily for 12 weeks) was recruited to this proof-of-concept study and consented to undergo dermal microdialysis. Briefly, a μDialysis Linear Catheter 66 for skin and muscle, a probe with a semi-permeable membrane, was inserted in the dermis. A perfusate (a drug-free physiological solution) was pumped through the probe at a low flow rate, allowing miltefosine present in the dermis to cross the membrane and be collected in the dialysates over time. Protein-free (dialysates) and total (blood and skin biopsies) drug concentrations were analysed using LC-MS/MS. Resultsand conclusions: Using microdialysis, protein-free miltefosine drug concentrations could be detected in the infected dermis over time (Cmax ≈ 450 ng/ml). This clinical proof-of-concept study thus illustrates the potential of dermal microdialysis as a minimally invasive alternative to invasive skin biopsies to quantify drug concentrations directly at the pharmacological site of action in PKDL.

Maternal, fetal, neonatal and breastmilk flecainide concentration during maternal therapy and lactation: a case report

BackgroundMothers requiring the antiarrhythmic agent flecainide are often advised not to breastfeed, because of the lack of data concercing neonatal effects and flecainide plasma concentrations following maternal exposure as well as via lactation. This is the first report on combined maternal, fetal, neonatal and breastmilk flecainide concentrations in a breastfed infant of a mother requiring flecainide treatment.Case presentationA 35-year old Gravida 2 Para 1, known with ventricular arrhythmia, was referred to our tertiary center at 35 + 4 weeks of gestation. Because of an increase of ventricular ectopy, oral metoprolol 11.9 milligrams once daily was switched to oral flecainide 87.3 milligrams twice daily. Weekly collected maternal flecainide plasma trough concentrations fell within the therapeutic range of 0.2 to 1.0 mg/L and no further clinically significant arrhythmias occurred during the study period. A healthy son was born at 39 weeks of gestation and had a normal electrocardiogram. The fetal to maternal flecainide ratio was 0.72 and at three different timepoints, the flecainide concentration was higher in breastmilk than in maternal plasma. The relative infant dose received via breastmilk compared to maternal dose was 5.6%. Neonatal plasma concentrations were not detectable, despite the flecainide passage into breastmilk. All electrocardiograms to assess the neonatal antiarrhytmic effect were normal.ConclusionsOur results assume that flecainide can be prescribed safely to lactating mothers. Quantification of drug concentrations in neonatal blood in addition to measurements in maternal and fetal blood, and breastmilk, are helpful to evaluate the effects and safety of maternal medication use during pregnancy and lactation.

Can scene bloodstains be used to quantify drug concentration at the moment of injury?

Blood is the primary material for quantitative toxicological analysis and interpretation of the results. However, in some cases like hit-and-run, it may be collected after a long time since the incident, resulting in the complete elimination or a significant decrease in the concentrations of potentially present drugs. If the suspect was injured and bloodstains were revealed, they can become the best or sometimes, the only material to be used to prove driving under the influence of drugs. In this context, the aim of this work was to develop a simple procedure that would allow for the estimation of drug concentrations in forensic bloodstains of unknown volume. In this work endogenous amino acids: valine and leucine were used to determine the unknown volume of blood from which the stain was formed. In order to isolate the analytes from bloodstains on different surfaces (plastic and cotton) the elution mixture consisted of an acetonitrile: water (60:40) and sodium chloride (0.9%) was used. The developed protocol was tested on 32 authentic forensic samples (mostly cases of people driving under the influence of amphetamine). The results of bloodstains analyses were compared with the results of whole blood analyses. The accuracy was in the range from −87.7 to +471.0%. However, for most of the cases, more accurate results were obtained. The differences between amphetamine values estimated from bloodstains and determined from whole blood were analysed using the Bland-Altman difference plots that revealed significant agreement. The variables concentrations estimated from bloodstains and concentrations calculated from whole blood were found to be strongly correlated. The Pearson correlation coefficients were: for plastic r(29) = 0.85 and for cotton r(25) = 0.91. This is the first work in which quantitative analyses of drugs in bloodstains have been attempted. A special protocol was developed for this purpose. The conducted research indicates that estimation of the concentration of drugs in bloodstains from the blood of an unknown volume is possible. The developed protocol has been extensively tested on authentic forensic samples and the obtained results were successfully compared with drug concentrations determined in whole blood. Nevertheless, the proposed method of estimating drug concentrations in bloodstains is characterized by many disadvantages, and the determined values should be treated with great caution, at best as estimates.

Can scene bloodstains be used to quantify drug concentration at the moment of injury?

Develop a procedure that would allow the estimation of drug concentrations in forensic bloodstains of unknown volume. Blood is the primary material for quantitative toxicological analysis and interpretation of the results. However, in some cases it may be collected after a long time after the incident that is of interest to investigative bodies. This time interval may result in the elimination or a significant decrease in the concentrations of possibly present drugs, which may have a key influence on the interpretation. An example of such events may be hit-and-run cases that relate to causing a car accident and fleeing the scene. In such accidents, injuries are common and there is a chance that bloodstains will remain in the car or on the driver's clothes. Therefore bloodstains can become the best or sometimes the only material to be used to prove driving under the influence of drugs. Quantitative analysis of forensic bloodstains samples is impossible without determining the volume of blood from which the stain was formed. The ability to quantify the blood volume is therefore necessary. In this work, endogenous amino acids: valine and leucine were used to determine the volume of blood. In order to isolate the analytes from bloodstains on different surfaces (plastic and cotton) the elution mixture consisted of an acetonitrile:water (60:40) and sodium chloride (0.9%) was used. Analyses were carried out using LC-MS/MS technique. The developed protocol was tested on 32 authentic forensic samples (mostly cases of people driving under the influence of amphetamine). Different volume bloodstains were prepared for each forensic case. The results of bloodstains analyses were compared with the results of whole-blood analyses. The accuracy was in the range from −87.7 to +471.0%, however, for most of the cases more accurate results were obtained. The mean and median agreement between the concentration estimated from bloodstain and concentration determined in whole-blood were 48.8% and 13.4% for plastic, and 37.7% and 33.9% for cotton, respectively. The variables concentrations estimated from bloodstains and concentrations calculated from whole-blood were found to be strongly correlated. The Pearson correlation coefficients were: for plastic r(29) = 0.85 and for cotton r(25) = 0.91 (the P -value for both < 0.00001). The best correlation coefficients were observed for the smallest bloodstains. The slope of the line for all results was 1.0784 (R2 = 0.7588). The relative standard deviation between concentrations estimated using valine and leucine were in the range 0.5–28.3% ( n = 40). In the hit-and-run incident, the suspected person may be arrested after such a long time that toxicological analysis of possibly disclosed bloodstains may be the only option to prove driving under the influence of drugs. In the procedure presented here, the authors used endogenous blood components to determine its volume. Critical factor in the calculations is the estimation of the volume of the blood on the basis of amino acids, as the content of these compounds may differ due to individual variation. Taking into account this possible diversity, significant correlations between concentrations in authentic whole-blood and bloodstains were observed. This is the first work in which quantitative analysis of drugs in bloodstains have been attempted. A special protocol was developed for this purpose. The research indicates that estimation of the concentration of drugs in bloodstains from the blood of an unknown volume is possible. The best accuracy was obtained by analysing 3 stains of different sizes and calculating the average. The protocol has been extensively tested on real forensic samples and the obtained results were successfully compared with drug concentrations determined in whole-blood.

Carbamazepine Overdose after Psychiatric Conditions: A Case Study for Postmortem Analysis in Human Bone

Carbamazepine is the main option used as a preventive medication to treat bipolar disorder when there is no response to lithium. Carbamazepine toxicity is defined as serum levels greater than 12 μg/mL, with severe toxicity occurring over 40 μg/mL, reduced to 30 μg/mL when combined with pharmacological treatment, i.e., benzodiazepines or antidepressants. For these reasons, it is necessary to find a validated tool to determine carbamazepine levels in an autopsy to rule out suicide or to know if the death was a consequence of an adverse drug reaction (ADR), especially when only bones can be accessed. We have validated a tool to detect and quantify drug concentration in bone. Our results showed a peak for carbamazepine at minute 12 and a mass fragment of 193 m/z. This case study is the first time in the literature that carbamazepine has been detected and quantified in bone. These results demonstrate that carbamazepine can be detected in bone tissue from forensic cases, but almost more importantly, that the method proposed is valid, reliable, and trustworthy.

Predicting CNS penetration of precision medicine therapies in oncology: A comparison of the CNS TAP tool and the BOILED-Egg computational model.

2062 Background: The number of available targeted therapies has vastly expanded in recent years; however, only a selection of such therapies achieve adequate central nervous system (CNS) penetration. The CNS Targeted Agent Prediction (CNS TAP) Tool was developed to aid in the selection of precision medicine therapies based on preclinical data, clinical data, patient-specific genomic data, and importantly, optimal blood brain barrier penetration. Using a standardized murine pharmacokinetic (PK) model, we sought to determine the concordance of CNS penetration prediction by the CNS TAP Tool compared to the SwissADME BOILED-Egg computational model. Methods: Eleven drugs were chosen based on the most commonly altered and targeted pathways by our CNS tumor board. Mice were injected individually with the compounds of interest and sacrificed at four different time points to quantify drug concentration via LC-MS in brain tissue and blood samples for PK analyses (1,2,4,7 hours). The percent brain penetration (AUCbrain/plasma) was compared to published human phase I PK data and pathway IC-50 to determine if agents were adequately CNS penetrant. These results were compared against the CNS TAP Tool and BOILED-Egg prediction of CNS penetrance. Results: All 11 drugs chosen (Table) demonstrated adequate CNS penetration, suggesting likely CNS efficacy. The CNS TAP Tool correctly predicted 10/11 agents (91% concordance), the lone exception being panobinostat. In contrast, the BOILED-Egg model only successfully predicted 3/11 agents (27%). When restricting the analysis to drugs with &gt;50% CNS penetration (ponatinib, panobinostat, and ONC-201), the BOILED-Egg model successfully predicted CNS penetration of all agents. Conclusions: The clinician-curated CNS TAP Tool more accurately predicted CNS penetration of precision medicine therapies than the BOILED-Egg computational model, which performed best for drugs that achieve extremely high CNS penetration. The resulting PK and CNS penetration data for all agents was utilized to update and refine the CNS TAP tool for future patient use. [Table: see text]

Development and Validation of a Dried Blood Spot Assay Using UHPLC-MS/MS to Identify and Quantify 12 Antihypertensive Drugs and 4 Active Metabolites: Clinical Needs and Analytical Limitations.

As nonadherence to antihypertensive drugs (AHDs) can increase the risk of cardiovascular events, hospitalization, and higher costs, there is a need for a reliable, objective, and easy method to assess nonadherence in patients. The dried blood spot (DBS) sampling method used to measure drug concentrations meets these requirements. For detecting nonadherence, identification is more important than quantification. Owing to their use in clinical practice, it is important to measure multiple AHDs with a single method. Therefore, we developed and validated a single DBS method for 17 commonly used AHDs and 4 active metabolites using ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Analytical validation of the DBS assay was performed in accordance with the guidelines on bioanalytical method validation of the European Medicines Agency and US Food and Drug Administration as well as the International Association of Therapeutic Drug Monitoring and Clinical Toxicology guidelines. We validated 12 of the 17 AHDs according to the European Medicines Agency and Food and Drug Administration requirements for bioanalytical method validation. Eleven AHDs were validated for both identification and quantification of drug concentrations, whereas nifedipine was only validated for identification. However, 5 of the 17 AHDs were excluded due to suboptimal validation results. Lercanidipine was excluded due to nonlinearity, and all 4 AHDs measured in the negative mode of UHPLC-MS/MS were not in accordance with one or more of the acceptance criteria and were therefore excluded. The described method accurately measured AHDs in DBS and can be used to determine nonadherence in patients. However, method validation revealed a challenging balance between analytical limitations and clinical needs when analyzing multiple drugs using the same method.

Multi-Site Evaluation of Immunoassays for Antipsychotic Drug Measurement in Clinical Samples.

Atypical antipsychotic drugs are frequently used in the treatment of serious mental illness (SMI), specifically schizophrenia and bipolar disorder. Adherence to these prescribed drug regimens is a challenge to successful treatment with these drugs. For some of the more common drugs in this class, novel turbidimetric immunoassays have been developed for therapeutic drug monitoring (TDM) to aid in the management of patients prescribed these drugs. Immunoassays for aripiprazole, clozapine, olanzapine, paliperidone, quetiapine, and risperidone were set up at 2 centers: Johns Hopkins Hospital (JHH) on the Roche Cobas® c501, and the Hospital of the University of Pennsylvania (HUP) on the Beckman AU480. Assay imprecision, limit of quantification (LOQ), functional sensitivity, linearity, and recovery were assessed. Remnant clinical samples were obtained from a reference laboratory (ARUP), and immunoassay results were compared with those obtained by LC-MS/MS. Imprecision at both sites for all analytes and concentrations tested was <10%. The manufacturer's LOQ was confirmed for each assay, and the functional sensitivity for each assay was found to be lower than the LOQ. All assays were found to be linear over the measuring range, with recoveries ranging from 91% to 123%. For method comparison, Deming regression slopes were found to be between 0.84 to 1.28. The immunoassays evaluated here are suitable for quantifying drug concentrations to be used in TDM for all 6 drugs. Commercialization of these assays will enable increased access for TDM in psychiatric patient management.

Development and validation of a simple, selective, and sensitive LC-MS/MS assay for the quantification of remdesivir in human plasma

Remdesivir, formerly GS-5734, has recently become the first antiviral drug approved by the U.S. Food and Drug Administration (FDA) to treat COVID-19, the disease caused by SARS-CoV-2. Therapeutic dosing and pharmacokinetic studies require a simple, sensitive, and selective validated assay to quantify drug concentrations in clinical samples. Therefore, we developed a rapid and sensitive LC-MS/MS assay for the quantification of remdesivir in human plasma with its deuterium-labeled analog, remdesivir-2H5, as the internal standard. Chromatographic separation was achieved on a Phenomenex® Synergi™ HPLC Fusion-RP (100 × 2 mm, 4 μm) column by gradient elution. Excellent accuracy and precision (<5.2% within-run variations and.<9.8% between-run variations) were obtained over the range of 0.5–5000 ng/mL. The assay met the FDA Bioanalytical Guidelines for selectivity and specificity, and low inter-matrix lot variability (<2.7%) was observed for extraction efficiency (77%) and matrix effect (123%) studies. Further, stability tests showed that the analyte does not degrade under working conditions, nor during freezing and thawing processes.

Whole blood or plasma: what is the ideal matrix for pharmacokinetic-driven drug candidate selection?

In the present era of drug development, quantification of drug concentrations following pharmacokinetic studies has preferentially been performed using plasma as a matrix rather than whole blood. However, it is critical to realize the difference between measuring drug concentrations in blood versusplasmaand the consequences thereof. Pharmacokinetics using plasma data may be misleading if concentrations differ between plasma and red blood cells (RBCs) because of differential binding in blood. In this review, factors modulating the partitioning of drugs into RBCs are discussed andthe importance of determining RBC uptake of drugs for drug candidate selection is explored. In summary, the choice of matrix (plasma vs whole blood) is an important consideration to be factored induring drug discovery.

Visualizing topical drug uptake with conventional fluorescence microscopy and deep learning

Mapping the uptake of topical drugs and quantifying dermal pharmacokinetics (PK) presents numerous challenges. Though high resolution and high precision methods such as mass spectrometry offer the means to quantify drug concentration in tissue, these tools are complex and often expensive, limiting their use in routine experiments. For the many topical drugs that are naturally fluorescent, tracking fluorescence emission can be a means to gather critical PK parameters. However, skin autofluorescence can often overwhelm drug fluorescence signatures. Here we demonstrate the combination of standard epi-fluorescence imaging with deep learning for the visualization and quantification of fluorescent drugs in human skin. By training a U-Net convolutional neural network on a dataset of annotated images, drug uptake from both high "infinite" dose and daily clinical dose regimens can be measured and quantified. This approach has the potential to simplify routine topical product development in the laboratory.

Fabrication of Microfluidic Cell Culture Platform for Real-time Monitoring of Lidocaine Concentration

We describe a microfluidic cell culture platform for real-time measurement of drug concentrations during cell cultivation. This is the first attempt to quantify drug concentrations during cell cultivation in real-time combining ultraviolet–visible (UV–Vis) spectroscopy with a microfluidic cell culture system in a single microfluidic chip. The microfluidic chip has two specific micro-chambers, one for spectroscopic measurements and the other for cell culture. NIH/3T3 fibroblast cells were seeded and cultured in the microfluidic chip, and then the local anesthetic lidocaine was applied and its concentration was monitored in real time. The test results showed that lidocaine negatively affected the cell growth. The lidocaine concentration was decreased due to its intake by cells for the first 3 h, after which an equilibrium concentration was reached. This is a simple but innovative method that can observe and analyze the correlation between cells and drugs in real time. The microfluidic system presented here can be a useful tool in various fields such as in cytotoxicity and drug screening studies.

Utilising Magnetically Isolated Lysosomes for Direct Quantification of Intralysosomal Drug Concentrations by LC-MS/MS Analysis: An Investigatory Study With Imipramine

Lysosomes are acidic intracellular organelles that can extensively sequester basic lipophilic drugs due to pH and membrane partitioning, and therefore may significantly influence subcellular drug concentrations. Current in vitro methods for lysosomal drug sequestration evaluation typically lack the ability to accurately and sensitively quantify drug concentrations directly within the lysosome. In the current study, magnetic lysosomal isolation was used in the lysosome rich rat NR8383 cell line and combined with LC-MS/MS analysis to quantify intralysosomal concentrations and lysosomal partitioning (KpLysosome) values of imipramine. The purity of the isolated lysosomes was validated by enzymatic and electron microscopy analysis. Lysosomal imipramine accumulation was explored using 2 methods: addition of imipramine to cells followed by lysosomal isolation (Method 1), and direct addition of imipramine to isolated lysosomes (Method 2). This work highlighted that both experimental buffers and ATP influence intralysosomal drug concentrations, and non-specific drug binding and re-distribution limits the use of Method 1. Method 2 may benefit future lysosomal drug accumulation studies, as imipramine demonstrated high KpLysosome values (3500), comparable to in silico predictions. This study reports a novel method for the direct quantification of intralysosomal drug concentrations that has the ability to be adapted to other cell types.

In-line monitoring of low drug concentration of flowing powders in a new sampler device.

A novel sampler device for flowing powders was tested to quantify drug concentrations as low as 0.76% w/w in pharmaceutical powder blends. The sampler device was developed based on the powder flow behavior within a tablet press feed frame, following the principles laid down in the Theory of Sampling. Two Near-Infrared (NIR) spectroscopic calibration models were developed with powder blends that varied from 0.52 to 2.52% w/w and 1.51-4.52% w/w. The calibration models were able to determine caffeine concentration in test set blends with root mean square error of predictions and bias below 0.1% w/w. Samples were collected from the sampler device and analyzed by ultraviolet-visible (UV-Vis) to determine the caffeine concentration. A high agreement between the in-line NIR predictions and the sampled UV-Vis results was found. The paddle wheel speed in the sampler can be varied up to ±10% without affecting NIR predictions; however, the models did not respond adequately to a 25% increase in this speed. Variographic analysis showed that the sampler device may quantify low drug concentrations with nugget effects below 0.0050 (%w/w)2. This study demonstrate that the sampler device may handle throughputs up to 45kg/h, without significantly affecting the physical properties of powder blends.

ACTR-58. BASELINE REQUIREMENTS FOR NOVEL AGENTS BEING CONSIDERED FOR BRAIN CANCER EFFICACY TRIALS: REPORT OF AN ABTC WORKSHOP

Abstract Despite advances in the understanding of molecular pathways, the availability of NGS panels to identify potentially drugable mutations, the proliferation of targeted therapies, and the progress seen in other cancers, only one novel agent (temozolomide) has significantly improved the survival of patients with glioblastoma in the past three decades. A major factor distinguishing brain cancer from other malignancies is the presence of the blood-brain barrier that restricts entry into the central nervous system of over 95% of drugs currently approved by the FDA. Clinical investigators have historically justified glioblastoma efficacy trials with pharmacokinetic data documenting measurable brain concentrations in animals or in contrast enhancing brain tumor specimens from patients. However, the discovery of effective therapeutic agents (whose mechanism of action requires that the drug directly reaches the cancer) will likely require that therapeutic drug concentrations (rather than measurable levels or blood:brain ratios) be delivered to non-contrast enhancing regions of the brain. The importance of delivering therapeutic concentrations of drug to non-enhancing brain is highlighted by knowledge that a gross total resection of all enhancing portions of a glioblastoma provides no chance of cure and limited improvement in overall survival. Utilizing these more stringent emerging criteria to select novel agents for efficacy studies will encourage pre-clinical and phase I studies to define the CNS penetration of new drugs and determine a therapeutic concentration for each agent. This will aid in the rational prioritization of agents selected for phase II studies. A full report of the outcome of the ABTC workshop on this topic will be presented. This will include: 1) methods to determine “therapeutic” drug concentrations for glioblastoma, 2) methods to quantify drug concentrations in non-enhancing brain, 3) pharmacokinetic and pharmacodynamic considerations, and 4) potential shortcomings of this approach.

Confocal Raman spectroscopy: Evaluation of a non-invasive technique for the detection of topically applied ketorolac tromethamine in vitro and in vivo.

Current information about the pharmacokinetics of an ocular drug can only be achieved by invasive sampling. However, confocal Raman spectroscopy bears the potential to quantify drug concentrations non-invasively. In this project, we evaluated the detection and quantification of ocular ketorolac tromethamine levels with confocal Raman spectroscopy after topical administration. Confocal Raman spectroscopy and high-performance liquid chromatography (HPLC) were compared in terms of sensitivity of detection. Enucleated pig eyes were treated with different concentrations of ketorolac. Hereafter, ketorolac concentrations in the aqueous humor of pig eyes were analyzed by confocal Raman spectroscopy and HPLC. Subsequently, twelve rabbits were treated with Acular™ for four weeks. At several time points, ketorolac concentrations in aqueous humor of the rabbits were measured by confocal Raman spectroscopy followed by drawing an aqueous humor sample for HPLC analysis. In ketorolac treated pig eyes, both ex vivo Raman spectroscopy as well as HPLC were able to detect ketorolac in a broad concentration range. However, in vivo confocal Raman spectroscopy in rabbits was unable to detect ketorolac in contrast to HPLC. To conclude, confocal Raman spectroscopy has the capacity to detect ketorolac tromethamine in vitro, but currently lacks sensitivity for in vivo detection.

Pregnancy exposure to quetiapine – Therapeutic drug monitoring in maternal blood, amniotic fluid and cord blood and obstetrical outcomes

RationaleThis prospective study is the first to measure and correlate quetiapine concentrations in maternal blood, amniotic fluid and umbilical cord blood to account for the distribution of quetiapine. MethodsConcentrations of quetiapine are quantified in seven mother infant pairs at the time of delivery. Data are provided as median values, first (Q1) and third (Q3) quartiles and ranges. To account for the penetration ratio, the concentration of quetiapine in amniotic fluid and cord blood was divided by maternal concentrations. Correlations between daily dosage, maternal serum and umbilical cord blood concentrations were computed for seven patients while calculations for amniotic fluid were only available for six mother-infant pairs. ResultsThe median daily dosage of quetiapine was 300mg (Q1: 300mg, Q3: 600mg, range 200–800mg). There was a strong and significant correlation between maternal serum and cord blood concentrations (r=0.893, p=0.007). The median penetration ratio into fetal circulation was 0.18 (Q1: 0.16, Q3: 0.32; range 0.13–0.42), suggesting a low penetration. The median penetration ratio into amniotic fluid was 0.44 (Q1: 0.15, Q3: 0.96; range 0.09–1.70). ConclusionsQuetiapine concentrations in amniotic fluid and cord blood give evidence that quetiapine is constantly accessible to the fetus with a relatively low penetration ratio. A high correlation between maternal serum and umbilical cord blood concentrations highlights a predictive role of quantifying drug concentrations in maternal serum for assessing drug concentrations in fetal circulation. Findings support the important role of therapeutic drug monitoring in supporting the efficacy and safety of psychopharmacological treatment strategies in highly vulnerable populations.

Pregnancy exposure to citalopram – Therapeutic drug monitoring in maternal blood, amniotic fluid and cord blood

RationaleAim of the study was to measure and correlate citalopram concentrations in maternal blood, amniotic fluid and umbilical cord blood to account for the distribution of the drug between these three compartments. MethodsConcentrations of citalopram were measured in twelve mother infant pairs at the time of delivery. Data are provided as median values, first (Q1) and third (Q3) quartiles as well as ranges. To account for the penetration ratio into amniotic fluid and cord blood, the concentration of citalopram in was divided by the concentration in maternal serum. Correlations between daily dosage, maternal serum concentrations and umbilical cord blood concentrations were computed for twelve patients. As amniotic fluid was only available for nine mother infant pairs, appropriate calculations are provided for these mother-infant pairs. ResultsThe median daily dosage of citalopram was 20mg (Q1: 10mg, Q3: 20mg; range 10–40mg). The relation between the daily dosage of citalopram and its concentrations in maternal serum was highly significant (r=0.667, p=0.018). Maternal serum concentrations and cord blood concentrations were positively correlated (r=0.790, p=0.002) with a median penetration ratio into the fetal circulation of 0.78 (Q1: 0.52, Q3: 1.16, range 0.46–1.66). The median penetration ratio into amniotic fluid was 1.8 (Q1: 1.07, Q3: 2.64; range 0.52–6.97). ConclusionsCitalopram concentrations in amniotic fluid and cord blood give evidence that maternally administered citalopram is constantly accessible to the fetus via amniotic fluid. A high correlation between maternal serum concentrations of citalopram and umbilical cord blood concentrations highlights a predictive role of quantifying drug concentrations in maternal serum for assessing drug concentrations in the fetal circulation. Findings support the important role of therapeutic drug monitoring in maintaining the safety of pregnant women and exposed infants.