Accuracy of Valproic Acid Concentration Correction Based on Serum Albumin.

BACKGROUND: Patient-specific factors can alter the pharmacokinetic disposition of valproic acid. Specifically, the free fraction of valproic acid can increase substantially in patients with hypoalbuminemia or as serum drug concentrations rise due to saturable protein binding. Direct measurement of free serum drug concentrations allows for accurate assessment of drug levels, but the assay may not be readily available in all institutions. The effect of hypoalbuminemia on free fraction has been quantified and serves as the basis of an equation used to "correct" measured total valproic acid concentrations. The aim of this study was to evaluate the accuracy of the equation. METHODS: This retrospective study included adult patients with measurable free and total valproic acid concentrations between July 2014 and June 2017. The primary aim was to assess the relationship between measured and predicted free valproic acid concentrations. Free levels were categorized as subtherapeutic, therapeutic, or supratherapeutic based on the reference range of 7-23 mg/L. Concordance was defined as measured and predicted concentrations falling within the same category. RESULTS: The analysis included 174 patients with a median age of 58 years and a median albumin of 3 g/dL. The majority of patients were hospitalized (88.5%). Concordance occurred in 56.9% of samples. A Spearman's correlation coefficient of 0.60 (p < 0.001) was found between the measured and predicted free valproic acid concentrations. Concordance of concentrations was 42% for ICU patients, 63% for floor patients, and 65% for outpatients. Of those with discordant concentrations, 97% of the predicted concentrations underestimated the measured concentrations. CONCLUSIONS: There is discordance between predicted and measured free serum valproic acid concentrations when using the proposed equation. Because of the potential impact of underestimation and variability of free valproic acid concentrations, a measured free level is the ideal option for therapeutic drug monitoring of valproic acid.

Simulation of PET scan timings for receptor occupancy studies of CNS drugs: a simple fixed-time design performed as well as scattered time point designs.

PURPOSE: This study aimed to determine the effect of PET scan timings on the reliability of occupancy parameter estimates and to identify the scan timing design that gives the most reliable occupancy parameter estimates. METHODS: We compared the performance of designs with various sets of sampling time points using the stochastic simulation and estimation method in Perl-speaks-NONMEM. Biases, relative standard errors, relative estimation errors, and root mean square errors were used to compare the performance of designs. RESULTS: Unlike the results of a previous report, we found that rather complicated designs where each subject or group of subjects are allocated to different scan timings were not superior to the simple, conventional fixed-time designs regardless of whether effect compartment or receptor binding models were used. CONCLUSIONS: We conclude that the conventional fixed-time designs that have been used so far may give robust PD parameter estimates for occupancy data obtained from human PET studies of CNS drugs.

Circadian rhythms of hemostatic factors in tetraplegia: a double-blind, randomized, placebo-controlled cross-over study of melatonin.

STUDY DESIGN: This is a double-blind, randomized, placebo-controlled cross-over study of melatonin in complete tetraplegia. OBJECTIVES: Tetraplegic patients have an increased risk of venous thrombosis despite prophylaxis, blunted variations in melatonin and altered circadian variation of several hemostatic markers. To examine whether melatonin could modify the regulation of hemostasis, we measured plasma melatonin and several markers of hemostasis in tetraplegic subjects with or without melatonin supplement. SETTING: The study was conducted in the Section for Spinal Cord Injury, Sunnaas Hospital, Nesoddtangen, Norway. METHODS: Six subjects with long-standing complete tetraplegia were included in this cross-over study with 2 mg of melatonin or placebo given 4 days before sampling. We also included six able-bodied men without any intervention. Plasma samples were then collected frequently during a 24-h awake/sleep cycle. The plasma concentrations of melatonin and the various markers were analyzed using linear mixed models. RESULTS: The 24-h profiles of prothrombin fragment 1+2 and von Willebrand factor, but not D-dimer, activated FVII, tissue factor pathway inhibitor and plasminogen activator inhibitor type 1, differed (P<0.05) between tetraplegic patients and able-bodied subjects. The absolute plasma concentration of activated FVII was higher (P<0.05) among the able-bodied compared with the tetraplegic groups. Supplementation of melatonin had no impact on these findings. CONCLUSIONS: We found differences in circadian variation of several hemostatic markers between able-bodied and tetraplegics. These differences were apparently unrelated to fluctuations in the melatonin concentrations, suggesting little or no role of melatonin in the regulation of hemostasis in tetraplegia. SPONSORSHIP: Financial support was provided from the Throne Holst Foundation.

Confounding parameters in preclinical assessment of blood-brain barrier permeation: an overview with emphasis on species differences and effect of disease states.

Drug delivery across the brain-blood interfaces is a complex process involving physicochemical drug properties, transporters, enzymes, and barrier dysfunction in diseased conditions. Intact blood-brain barrier (BBB) limits the entry of potentially harmful compounds into the brain but may also reduce the CNS permeability of therapeutic agents. BBB permeability is typically assessed by measuring brain-to-plasma ratio in rodents (referred to as B/P ratio, BB, or Kp, often calculated as logBB), an approach that suffers significant limitations as discussed in the present review. Kp is not a permeability measurement but a partition coefficient mainly driven by the relative binding to plasma and brain tissue components including lipids, phospholipids, and proteins. Compounds with high Kp are often lipophilic with low free fraction available to mediate CNS activities. Efforts should be more concentrated on measuring pharmacologically relevant free drug concentrations at the target site. Using healthy rodents to predict brain penetration in patients might be biased due to species differences in BBB-related parameters such as transporter expression and functional activities. In addition, pathophysiological conditions such as aging, multiple sclerosis, and Alzheimer's and Parkinson's diseases have been described to affect BBB permeability, with barrier leakage and altered transporter activity. The impact of these species differences and disease states on drug delivery to the brain is largely overlooked. More data are needed to better understand their clinical implication in order to design more appropriate screening strategies and ultimately better mitigate the risk for failure in late stage development.

In vitro, in vivo and in silico models of drug distribution into the brain.

Achieving sufficient brain penetration to elicit efficacy in humans is one of the most challenging tasks for scientists in CNS Drug Discovery. Substantial progress has been made in the past decade in understanding the factors influencing the rate and extent of brain distribution via a variety of in vivo, in vitro and in silico methodologies, and hence, predict their likelihood of success in man. This purpose of this review is to summarize the current approaches with a special focus on parameters related to free drug concentrations in brain which are the most pharmacologically relevant for the majority of CNS disease targets. Due to the dynamic and complex nature of this targeted organ, it is inevitable that these approaches have not been able to provide a fully comprehensive assessment of brain distribution and are expected to evolve further in the years to come.

Modeling of PET data in CNS drug discovery and development.

Positron emission tomography (PET) is increasingly used in drug discovery and development for evaluation of CNS drug disposition and for studies of disease biomarkers to monitor drug effects on brain pathology. The quantitative analysis of PET data is based on kinetic modeling of radioactivity concentrations in plasma and brain tissue compartments. A number of quantitative methods of analysis have been developed that allow the determination of parameters describing drug pharmacokinetics and interaction with target binding sites in the brain. The optimal method of quantification depends on the properties of the radiolabeled drug or radioligand and the binding site studied. We here review the most frequently used methods for quantification of PET data in relation to CNS drug discovery and development. The utility of PET kinetic modeling in the development of novel CNS drugs is illustrated by examples from studies of the brain kinetic properties of radiolabeled drug molecules.

Cerebral microdialysis in clinical studies of drugs: pharmacokinetic applications.

The ability to deliver drug molecules effectively across the blood-brain barrier into the brain is important in the development of central nervous system (CNS) therapies. Cerebral microdialysis is the only existing technique for sampling molecules from the brain extracellular fluid (ECF; also termed interstitial fluid), the compartment to which the astrocytes and neurones are directly exposed. Plasma levels of drugs are often poor predictors of CNS activity. While cerebrospinal fluid (CSF) levels of drugs are often used as evidence of delivery of drug to brain, the CSF is a different compartment to the ECF. The continuous nature of microdialysis sampling of the ECF is ideal for pharmacokinetic (PK) studies, and can give valuable PK information of variations with time in drug concentrations of brain ECF versus plasma. The microdialysis technique needs careful calibration for relative recovery (extraction efficiency) of the drug if absolute quantification is required. Besides the drug, other molecules can be analysed in the microdialysates for information on downstream targets and/or energy metabolism in the brain. Cerebral microdialysis is an invasive technique, so is only useable in patients requiring neurocritical care, neurosurgery or brain biopsy. Application of results to wider patient populations, and to those with different pathologies or degrees of pathology, obviously demands caution. Nevertheless, microdialysis data can provide valuable guidelines for designing CNS therapies, and play an important role in small phase II clinical trials. In this review, we focus on the role of cerebral microdialysis in recent clinical studies of antimicrobial agents, drugs for tumour therapy, neuroprotective agents and anticonvulsants.

Computational prediction of CNS drug exposure based on a novel in vivo dataset.

PURPOSE: To develop a computational model for predicting CNS drug exposure using a novel in vivo dataset. METHODS: The brain-to-plasma (B:P) ratio of 43 diverse compounds was assessed following intravenous administration to Swiss Outbred mice. B:P ratios were subjected to PLS modeling using calculated molecular descriptors. The obtained results were transferred to a qualitative setting in which compounds predicted to have a B:P ratio > 0.3 were sorted as high CNS exposure compounds and those below this value were sorted as low CNS exposure compounds. The model was challenged with an external test set consisting of 251 compounds for which semi-quantitative values of CNS exposure were available in the literature. RESULTS: The dataset ranged more than 1700-fold in B:P ratio, with 16 and 27 compounds being sorted as low and high CNS exposure drugs, respectively. The model was a one principal component model based on five descriptors reflecting molecular shape, electronegativity, polarisability and charge transfer, and allowed 74% of the compounds in the training set and 76% of the test set to be predicted correctly. CONCLUSION: A qualitative computational model has been developed which accurately classifies compounds as being high or low CNS exposure drugs based on rapidly calculated molecular descriptors.

Pharmacokinetics of beta-asarone in rabbit blood, hippocampus, cortex, brain stem, thalamus and cerebellum.

beta-Asarone has significant pharmacological effects on the central nervous system. As a potential therapeutic agent to manage brain diseases, analysis of the pharmacokinetics of beta-asarone in brain is necessary. We used cardio-perfusion method to exclude the beta-asarone in the brain blood. The brain was divided into five regions: hippocampus, cortex, brain stem, thalamus and cerebellum, and pharmacokinetic differences were investigated. We found that concentration-time profile of beta-asarone in blood, hippocampus, cortex, brain stem and cerebellum could be adequately described by a first-order equation, consistent with a linear two-compartmental model, but a first-order equation with a linear one-compartmental model in thalamus. The half lives of beta-asarone in blood, hippocampus, cortex, brain stem, thalamus and cerebellum were 1.3801, 1.300, 1.937, 7.142, 2.832 and 8.149 h, respectively. Gender differences do not significantly influence plasma pharmacokinetics of beta-asarone.

Risk factors for valproic acid induced hyperammonemia and its association with cognitive functions.

OBJECTIVE: Valproic acid (VPA)-induced hyperammonemia (VIH), is an increase in blood ammonia levels without any alteration of hepatic enzymes, which can occur during VPA treatment. We aimed to determine the prevalence rate and the risk factors for VIH and its association with cognitive functions. METHOD: A prospective, cross-sectional study was conducted. Patients aged between 18 and 64 who were on VPA treatment and who diagnosed with mood disorders or epilepsy were enrolled in this study (n = 107). For cognitive assessment, Serial 7's and Subjective Memory Complaints Questionnaire (SMCQ) were used. Blood samples were collected for blood VPA and ammonia levels along with other laboratory tests. RESULTS: 55,3% of the sample were considered as VIH. Blood ammonia level significantly correlates with VPA blood levels, total daily dose of VPA and total number of medications concurrently used, but no significant correlation was found between blood ammonia level and cognitive test scores. Gender, body weight, blood VPA levels and the total number of medications concurrently used significantly predicted blood ammonia levels (F(4,81) = 2670, p = 0,038, R2 = 0,116). CONCLUSION: VIH is relatively high in our sample. There is a dose-dependent association between VPA and blood ammonia level. No association was found between cognitive functions and hyperammonemia however with some limitations. Future, prospective cohort studies are needed.

The apolipoprotein E epsilon4 allele and memory performance in HIV-1 seropositive subjects: differences at baseline but not after acute oral lorazepam challenge.

RATIONALE: The APOE epsilon4 allele, an established genetic risk factor for late-onset Alzheimer's disease, has been linked to an increased risk for dementia especially in older individuals with HIV-1 infection. This allele has also been associated with increased memory impairment following oral lorazepam challenge in healthy elderly. Lorazepam and other benzodiazepines are widely prescribed in individuals with HIV-1 infection who are at increased risk for cognitive impairment. OBJECTIVE: The aim of this study was to examine if the epsilon4 allele influences lorazepam-induced memory deficits in this population. MATERIALS AND METHODS: Forty-one non-demented, HIV-1 seropositive adults (15 epsilon4 carriers, mean age = 43.47 +/- 8.25; 26 epsilon4 non-carriers, mean age = 46.77 +/- 8.56) participated in a double-blind, placebo-controlled crossover design, receiving single acute oral doses of lorazepam 0.5, 1.0 mg, or placebo over three sessions, each 1 week apart. Standardized neuropsychological assessments, including measures of immediate and delayed verbal recall, were conducted at baseline and at 1, 2.5, and 5 h post-drug administration in each condition. RESULTS: Acute lorazepam administration produced dose- and time-dependent impairments in measures of verbal recall. However, the e4 allele did not modulate these adverse effects. An APOE epsilon4 group by time interaction was also found such that the APOE-epsilon4-positive subjects had significantly better immediate and delayed verbal recall than the negative subjects at baseline assessment, but the groups did not significantly differ at any subsequent time point. CONCLUSION: Future studies should clarify the role of epsilon4 in the modulation of drug-induced cognitive toxicity and baseline performance and their relationship to progressive decline, especially in older individuals with HIV-1 infection, a group at increased risk for dementia.

Prediction of brain:blood unbound concentration ratios in CNS drug discovery employing in silico and in vitro model systems.

Recent years have seen a paradigm shift away from optimizing the brain:blood concentration ratio toward the more relevant brain:blood unbound concentration ratio (Kp,uu,br) in CNS drug discovery. Here, we review the recent developments in the in silico and in vitro model systems to predict the Kp,uu,br of discovery compounds with special emphasis on the in-vitro-in-vivo correlation. We also discuss clinical 'translation' of rodent Kp,uu,br and highlight the future directions for improvement in brain penetration prediction. Important in this regard are in silico Kp,uu,br models built on larger datasets of high quality, calibration and deeper understanding of experimental in vitro transporter systems, and better understanding of blood-brain barrier transporters and their in vivo relevance aside from P-gp and BCRP.

High brain distribution of a new central nervous system drug candidate despite its P-glycoprotein-mediated efflux at the mouse blood-brain barrier.

Efficacy of drugs aimed at treating central nervous system (CNS) disorders rely partly on their ability to cross the cerebral endothelium, also called the blood-brain barrier (BBB), which constitutes the main interface modulating exchanges of compounds between the brain and blood. In this work, we used both, conventional pharmacokinetics (PK) approach and in situ brain perfusion technique to study the blood and brain PK of PKRinh, an inhibitor of the double-stranded RNA-dependent protein kinase (PKR) activation, in mice. PKRinh showed a supra dose-proportional blood exposure that was not observed in the brain, and a brain to blood AUC ratio of unbound drug smaller than 1 at all tested doses. These data suggested the implication of an active efflux at the BBB. Using in situ brain perfusion technique, we showed that PKRinh has a very high brain uptake clearance which saturates with increasing concentrations. Fitting the data to a Michaelis-Menten equation revealed that PKRinh transport through the BBB is composed of a passive unsaturable flux and an active saturable protein-mediated efflux with a km of ≅ 3 µM. We were able to show that the ATP-binding cassette (ABC) transporter P-gp (Abcb1), but not Bcrp (Abcg2), was involved in the brain to blood efflux of PKRinh. At the circulating PKRinh concentrations of this study, the P-gp was not saturated, in accordance with the linear brain PKRinh PK. Finally, PKRinh had high brain uptake clearance (14 µl/g/s) despite it is a good P-gp substrate (P-gp Efflux ratio ≅ 3.6), and reached similar values than the cerebral blood flow reference, diazepam, in P-gp saturation conditions. With its very unique brain transport properties, PKRinh improves our knowledge about P-gp-mediated efflux across the BBB for the development of new CNS directed drugs.

Therapeutic regimen of L-arginine for MELAS: 9-year, prospective, multicenter, clinical research.

OBJECTIVE: To examine the efficacy and safety of the therapeutic regimen using oral and intravenous L-arginine for pediatric and adult patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). METHODS: In the presence and absence of an ictus of stroke-like episodes within 6 h prior to efficacy assessment, we correspondingly conducted the systematic administration of oral and intravenous L-arginine to 15 and 10 patients with MELAS in two, 2-year, prospective, multicenter clinical trials at 10 medical institutions in Japan. Subsequently, patients were followed up for 7 years. The primary endpoint in the clinical trial of oral L-arginine was the MELAS scale, while that for intravenous L-arginine was the improvement rates of headache and nausea/vomiting at 2 h after completion of the initial intravenous administration. The relationships between the ictuses of stroke-like episodes and plasma arginine concentrations were examined. RESULTS: Oral L-arginine extended the interictal phase (p = 0.0625) and decreased the incidence and severity of ictuses. Intravenous L-arginine improved the rates of four major symptoms-headache, nausea/vomiting, impaired consciousness, and visual disturbance. The maximal plasma arginine concentration was 167 µmol/L when an ictus developed. Neither death nor bedriddenness occurred during the 2-year clinical trials, and the latter did not develop during the 7-year follow-up despite the progressively neurodegenerative and eventually life-threatening nature of MELAS. No treatment-related adverse events occurred, and the formulations of L-arginine were well tolerated. CONCLUSIONS: The systematic administration of oral and intravenous L-arginine may be therapeutically beneficial and clinically useful for patients with MELAS.

Reduced clearance of venlafaxine in a combined treatment with quetiapine.

Venlafaxine and the atypical antipsychotic quetiapine are often administered concomitantly. Both drugs share several metabolic hepatic pathways. However, pharmacokinetic interactions between venlafaxine and quetiapine have not been studied yet. A therapeutic drug monitoring database containing serum concentrations of venlafaxine (VEN) and its active metabolite O-desmethylvenlafaxine (ODVEN) was analyzed. Two groups of patients were compared: venlafaxine monotherapy V0 (n = 153) and co-medication with quetiapine, VQUE (n = 71). Serum concentrations of VEN, ODVEN, and active moiety, AM (VEN + ODVEN), metabolite to parent compound ratio (ODVEN/VEN) and dose adjusted serum concentrations were compared using non-parametrical tests without information on CYP2D6 genotype. The two groups did not differ in terms of the daily dosage of venlafaxine, age, or sex. Median serum concentrations in the quetiapine group showed significantly, 15.8% and 29.3% higher values for AM and ODVEN (p = 0.002, Cohen's d = 0,41; p = 0.003, d = 0,44), respectively. Dose adjusted serum concentrations of active moiety and ODVEN revealed comparable differences (p = 0.038, d = 0,32; p = 0.015, d = 0,28) with significantly higher values in the co-medicated group. Significantly higher values for ODVEN and AM suggest a reduced clearance of ODVEN and active moiety when quetiapine is co-administered. This may be a consequence of a reduced metabolism of venlafaxine to the inactive metabolite N-desmethylvenlafaxine via CYP3A4, the main metabolizing enzyme for quetiapine, and a shift towards a higher proportion of the active metabolite ODVEN. Therapeutic drug monitoring is recommended in the case of co-medication to ensure clinical efficacy and patient safety. Although the increase of AM is moderate, we consider it relevant for clinicians given the prevalence of concomitant medication of quetiapine and venlafaxine.

Fingerprints of CNS drug effects: a plasma neuroendocrine reflection of D2 receptor activation using multi-biomarker pharmacokinetic/pharmacodynamic modelling.

BACKGROUND AND PURPOSE: Because biological systems behave as networks, multi-biomarker approaches increasingly replace single biomarker approaches in drug development. To improve the mechanistic insights into CNS drug effects, a plasma neuroendocrine fingerprint was identified using multi-biomarker pharmacokinetic/pharmacodynamic (PK/PD) modelling. Short- and long-term D2 receptor activation was evaluated using quinpirole as a paradigm compound. EXPERIMENTAL APPROACH: Rats received 0, 0.17 or 0.86 mg·kg-1 of the D2 agonist quinpirole i.v. Quinpirole concentrations in plasma and brain extracellular fluid (brainECF ), as well as plasma concentrations of 13 hormones and neuropeptides, were measured. Experiments were performed at day 1 and repeated after 7-day s.c. drug administration. PK/PD modelling was applied to identify the in vivo concentration-effect relations and neuroendocrine dynamics. KEY RESULTS: The quinpirole pharmacokinetics were adequately described by a two-compartment model with an unbound brainECF -to-plasma concentration ratio of 5. The release of adenocorticotropic hormone (ACTH), growth hormone, prolactin and thyroid-stimulating hormone (TSH) from the pituitary was influenced. Except for ACTH, D2 receptor expression levels on the pituitary hormone-releasing cells predicted the concentration-effect relationship differences. Baseline levels (ACTH, prolactin, TSH), hormone release (ACTH) and potency (TSH) changed with treatment duration. CONCLUSIONS AND IMPLICATIONS: The integrated multi-biomarker PK/PD approach revealed a fingerprint reflecting D2 receptor activation. This forms the conceptual basis for in vivo evaluation of on- and off-target CNS drug effects. The effect of treatment duration is highly relevant given the long-term use of D2 agonists in clinical practice. Further development towards quantitative systems pharmacology models will eventually facilitate mechanistic drug development.

Distribution of Eight QT-Prolonging Drugs and Their Main Metabolites Between Postmortem Cardiac Tissue and Blood Reveals Potential Pitfalls in Toxicological Interpretation.

Femoral blood concentrations are usually used in postmortem toxicology to assess possible toxic effects of drugs. This includes QT-prolongation and other cardiac dysrhythmia, which could have been the cause of death. However, blood concentration is only a surrogate for the active site concentration, and therefore cardiac tissue concentration may provide a more accurate toxicological interpretation. Thus, cardiac tissue and femoral and cardiac blood concentrations were examined for eight frequently used QT-prolonging drugs (QTD) and their metabolites in a mentally ill population. In total, 180 cases were included from the Danish autopsy-based forensic study SURVIVE. The concentrations were analyzed using ultra-performance liquid chromatography coupled with tandem mass spectrometry utilizing stable isotopically labeled internal standards. The results showed that the cardiac tissue concentrations were significantly higher compared to femoral and cardiac blood concentrations, with two exceptions. The median cardiac tissue-to-femoral blood concentration ratio (Kb) ranged from 2.2 (venlafaxine) to 15 (nortriptyline). The inter-individual fold difference between the minimum and maximum Kb ranged from 2.6-fold (Z-hydroxynortriptyline) to 61 (venlafaxine). For 12 compounds, postmortem redistribution appeared to be minimal, whereas four compounds displayed some degree of postmortem redistribution. Citalopram and quetiapine were selected for in-depth analysis of the relation between the toxicological interpretation and femoral blood/cardiac tissue concentrations. Within this dataset, citalopram displayed a wide overlap in cardiac tissue concentrations (~50%) between non-toxic and toxic citalopram cases, as estimated from femoral blood concentrations. In contrast, quetiapine displayed no overlap in cardiac tissue concentrations between non-toxic and toxic quetiapine cases based on femoral blood concentrations. The implication of the citalopram finding is that possible intoxications can be overlooked when only considering femoral blood concentrations. Based on the present findings, non-toxic cardiac tissue 10th-90th percentile concentration ranges were estimated for citalopram (0.93-4.4 mg/kg) and quetiapine (0.0073-0.60 mg/kg).

Pharmacokinetics of Gastrodin in rat plasma and CSF after i.n. and i.v.

The pharmacokinetic behavior of Gastrodin in rat plasma and cerebrospinal fluid (CSF) after intranasal and intravenous administration (50mg kg(-1)) was investigated. Intranasal administration of Gastrodin provided a comparable AUC in CSF compared with the intravenous administration. But Gastrodin level in plasma was very low. The ratios of AUC values of intranasal to intravenous administration were 8.85% and 105.5% in plasma and CSF, respectively. The drug targeting index (DTI) was 12.34. In conclusion, intranasal administration of Gastrodin is a promising alternative to traditional administration. Olfactory mucosa did present another pathway for transport Gastrodin to the brain.

Simultaneously determination of five ginsenosides in rabbit plasma using solid-phase extraction and HPLC/MS technique after intravenous administration of 'SHENMAI' injection.

In this study, a sensitive and reliable analytical method for the simultaneous determination of five ginsenosides (R(g1), R(f), R(e), R(d) and R(b1)) in rabbit plasma was developed by high performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS). Chromatographic separation was carried out on a Zorbax SB-C18 Column (150 mm x 2.1 mm i.d., 5.0 microm particle size) with a simple linear gradient elution. The detection was conducted on a single quadrupole mass spectrometer by selected ion monitoring mode via electrospray ionization source. Good linearity over the investigated concentration ranges was observed with the values of R(2) higher than 0.991 for all the analytes. Limits of detection of the analytes varied from 0.25 ng/ml to 1.45 ng/ml, and the average recoveries, examined at three concentration levels, ranged from 90.6% to 106.9%. The validated method was successfully applied to the determination of the ginsenosides in the rabbit plasma after intravenous administration of 'SHENMAI' injection.

Recommendations for toxicological investigation of drug impaired driving.

Investigation of a suspected alcohol or drug impaired driving (DUID) case ideally contains several key elements, including a trained officer documenting observations of driving and subject behavior, and collection of a biological specimen for comprehensive toxicology testing. There is currently no common standard of practice among forensic toxicology laboratories in the United States as to which drugs should be tested for, and at what analytical cutoff. Having some uniformity of practice among laboratories would ensure that drugs most frequently associated with driving impairment were consistently evaluated, that appropriate methods were used to screen and confirm the presence of drugs, and that more accurate data were collected on the extent of drug use among drivers. A survey of United States laboratories actively involved in providing analytical support to the Drug Evaluation and Classification Program identified marijuana, benzodiazepines, cocaine, prescription and illicit opiates, muscle relaxants, amphetamines, CNS depressants, and sleep aids used as hypnotics, as being the most frequently encountered drugs in these cases. This manuscript presents recommendations as to what specific members of these drug classes should at a minimum be tested for in the investigation of suspected DUID cases. Additionally we include recommendations for analytical cutoffs for screening and confirmation of drugs in blood and urine. Adopting these guidelines would ensure that the most common drugs would be detected, that laboratories could compare epidemiological findings between jurisdictions, and that aggregate national statistics on alcohol and drug use in drivers involved in fatal injury collisions were representative of the true rates of drug use in the driving population.