Application of Parallel Reaction Monitoring to the Development and Validation of a Quantitative Assay for ST-246 in Human Plasma.

In this work, we developed and validated a robust and sensitive method of liquid chromatography with high-resolution mass spectrometry in parallel reaction monitoring (PRM) mode for ST-246 (tecovirimat) quantification in human blood plasma. The method was compared with the multiple reaction monitoring (MRM) technique and showed better selectivity and similar sensitivity in a wider concentration range (10-5000 ng/mL). Within this range, intra- and interday variability of precision and accuracy were within acceptable ranges in accordance with the European Medicines Agency guidelines, and recovery was 87.9-100.6%. Samples were stable at 4 °C within 48 h and at -20 °C up to 3 months. The recovery and matrix effects in the proposed HRMS method were about 5% higher than those reported for the MRM method, but the PRM method showed better accuracy with comparable precision. It was found that the ST-246 concentration shown by the PRM method is approximately 24% higher than the output of the MRM one. Nonetheless, the high selectivity with similar sensitivity, as compared with traditional MRM methods, makes the proposed approach attractive for research and clinical use.

Estimating Efflux Transporter-Mediated Disposition of Molecules beyond the Rule of Five (bRo5) Using Transporter Gene Knockout Rats.

Transporter gene knockout models are a practical and widely used tool for pharmacokinetic studies in drug discovery. P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) are major efflux transporters that control absorption and bioavailability, and are important when determining oral drug disposition. To the best of our knowledge, beyond the rule of five (bRo5) molecules launched on the market to date tend to be substrates for efflux transporters. The purpose of this study is to evaluate in vivo the impact of efflux transporters on the oral absorption process and systemic clearance using rats which lack P-gp and/or Bcrp expression. We administered five bRo5 substrates (asunaprevir, cyclosporine, danoprevir, ledipasvir, and simeprevir) intravenously or orally to wild-type and Mdr1a, Bcrp, and Mdr1a/Bcrp knockout rats, calculated the clearance, oral bioavailability, and absorption rate profile of each substrate, and compared the results. Systemic clearance of the substrates in knockout rats changed within approximately ±40% compared to wild-types, suggesting the efflux transporters do not have a significant influence on clearance in rats. On the other hand, the oral absorption of substrates in the knockout rats, especially those lacking Mdr1a, increased greatly-between 2- and 5-fold more than in wild-types. This suggests that rat efflux transporters, especially P-gp, greatly reduce the oral exposure of these substrates. Moreover, results on the absorption rate-time profile suggest that efflux transporters are constantly active during the absorption period in rats. Transporter knockout rats are a useful in vivo tool for estimating the transporter-mediated disposition of bRo5 molecules in drug discovery.

Simultaneous determination of tandospirone and its active metabolite, 1-[2-pyrimidyl]-piperazine in rat plasma by LC-MS/MS and its application to a pharmacokinetic study.

A rapid, sensitive and selective liquid chromatography-tandem mass spectrometry method for the detection of tandospirone (TDS) and its active metabolite 1-[2-pyrimidyl]-piperazine (1-PP) in Sprague-Dawley rat plasma is described. It was employed in a pharmacokinetic study. These analytes and the internal standards were extracted from plasma using protein precipitation with acetonitrile, then separated on a CAPCELL PAK ADME C18 column using a mobile phase of acetonitrile and 5 mm ammonium formate acidified with formic acid (0.1%, v/v) at a total flow rate of 0.4 mL/min. The detection was performed with a tandem mass spectrometer equipped with an electrospray ionization source. The method was validated to quantify the concentration ranges of 1.000-500.0 ng/mL for TDS and 10.00-500.0 ng/mL for 1-PP. Total time for each chromatograph was 3.0 min. The intra-day precision was between 1.42 and 6.69% and the accuracy ranged from 95.74 to 110.18% for all analytes. Inter-day precision and accuracy ranged from 2.47 to 6.02% and from 98.37 to 105.62%, respectively. The lower limits of quantification were 1.000 ng/mL for TDS and 10.00 ng/mL for 1-PP. This method provided a fast, sensitive and selective analytical tool for quantification of tandospirone and its metabolite 1-PP in plasma necessary for the pharmacokinetic investigation.

Pharmacokinetic and pharmacodynamic modeling of oral mitiglinide on glucose lowering in healthy Chinese volunteers.

BACKGROUND: Mitiglinide is a widely used agent for diabetic treatment. We established a pharmacokinetic-pharmacodynamic (PK-PD) model to illustrate the relationship between mitiglinide plasma concentration and its glucose lowering effects in healthy volunteers. METHODS: The volunteers participated in the test after the administration of a single dose of 10 mg mitiglinide. The drug concentration in Plasma and the values of glucose levels were determined by LC-MS/MS assay and hexokinase method. A PK-PD model was established with a series of equations to describe the relationship between plasma medicine and glucose, and the equations were solved numerically and fitted to the data with the Phoenix NLME software. RESULTS: The results of the two-compartment model analysis were based on the maximum likelihood criterion and visual inspection of the fittings. The terminal elimination half-life (t 1/2) was 1.69 ± 0.16 h and the CL/F was 7.80 ± 1.84 L/h. The plasma glucose levels began to decline by 0.2 h, and hit its bottom decreasing values of 2.6 mg/L at 0.5 h after administration. The calculated parameter and fitting curve indicated that the model established in our experiment fitted well. CONCLUSIONS: A PK/PD model illustrates that the relationship between mitiglinide concentration in plasma and glucose lowering effect in healthy volunteers was established. The results of our experiment suggested that the model can be used reasonably to predict the relationship between PK and PD in mitiglinide, which could be used in diabetes mellitus dosage control in clinical trials and other fields.

Rapid and highly sensitive analysis of benzodiazepines and tandospirone in human plasma by automated on-line column-switching UFLC-MS/MS.

A high-throughput method was developed for the detection of 31 benzodiazepine drugs and tandospirone in human plasma by on-line column-switching ultra-fast liquid chromatography-tandem mass spectrometry. Plasma samples (100µl) spiked with the 32 drugs and oxazepam-d5 (internal standard) were diluted with 300µl of 13.3mM ammonium acetate/acetonitrile (33:67, v/v). After centrifugation and filtration, the clear supernatant was injected directly onto the extraction column (Oasis HLB cartridge column). The following procedure was fully automated. The analytes retained on the extraction column were eluted by backflushing of the extraction column and introduced into an analytical column (SUMIPAX ODS D-Swifter column, 30mm×3.0mm i.d.; particle size 2µm) by column switching. Quantification was performed by multiple reaction monitoring with positive-ion electrospray ionization. Distinct peaks appeared for each drug and the internal standard on each channel within 7min, including the extraction time. All drugs spiked into plasma showed recoveries of 83-95%. The regression equations for the 32 drugs showed excellent linearities in the range of 50-2000pg/ml of plasma and the limits of detection ranged from 20 to 50pg/ml. The lower and upper limits of quantitation were 50-100ng/ml and 2000pg/ml, respectively. Intra- and interday coefficients of variation for none of the drugs were greater than 13.6%. The accuracies of quantitation were 87-112%. The multiple reaction monitoring information-dependent acquisition of enhanced product ions method enabled the quantification and confirmation of diazepam, triazolam, and lorazepam obtained from actual plasma.

Prediction of CNS occupancy of dopamine D2 receptor based on systemic exposure and in vitro experiments.

The effect of drugs in the central nervous system (CNS) is closely related to occupancy of their target receptor. In this study, we integrated plasma concentrations, in vitro/in vivo data for receptor or protein binding, and in silico data, using a physiologically based pharmacokinetic model, to examine the predictability of receptor occupancy in humans. The occupancy of the dopamine D2 receptor and the plasma concentrations of the antipsychotic drugs quetiapine and perospirone in humans were collected from the literature or produced experimentally. Association and dissociation rate constants and unbound fractions in the serum and brain were determined in vitro/in vivo using human D2 receptor-expressing membrane fractions, human serum and mouse brain. The permeability of drugs across the blood-brain barrier was estimated based on their physicochemical properties. The effect of a metabolite of perospirone, ID-15036, was also considered. The time profiles of D2 receptor occupancy following oral dose of quetiapine and perospirone predicted were similar to the observed values. This approach could assist in the design of clinical studies for drug development and the prediction of the impact of drug-drug interactions on CNS function in clinical settings.

Lead optimization of the VU0486321 series of mGlu1 PAMs. Part 3. Engineering plasma stability by discovery and optimization of isoindolinone analogs.

This Letter describes the further lead optimization of the VU0486321 series of mGlu1 positive allosteric modulators (PAMs), focused on addressing the recurrent issue of plasma instability of the phthalimide moiety. Here, we evaluated a number of phthalimide bioisosteres, and ultimately identified isoindolinones as the ideal replacement that effectively address plasma instability, while maintaining acceptable mGlu1 PAM potency, DMPK profile, CNS penetration and mGluR selectivity.

Discovery of 3-n-butyl-2,3-dihydro-1H-isoindol-1-one as a potential anti-ischemic stroke agent.

To develop novel anti-ischemic stroke agents with better therapeutic efficacy and bioavailability, we designed and synthesized a series of 3-alkyl-2,3-dihydro-1H-isoindol-1-ones compounds (3a-i) derivatives, one of which (3d) exhibited the strongest inhibitory activity for the adenosine diphosphate-induced and arachidonic acid-induced platelet aggregation. This activity is superior to that of 3-n-butylphthalide and comparable with aspirin and edaravone. Meanwhile, 3d not only exhibited a potent activity in scavenging free radicals and improving the survival of HT22 cells against the reactive oxygen species-mediated cytotoxicity in vitro but also significantly attenuated the ischemia/reperfusion-induced oxidative stress in ischemic rat brains. Results from transient middle cerebral artery occlusion and permanent middle cerebral artery occlusion model, indicated that 3d could significantly reduce infarct size, improve neurobehavioral deficits, and prominently decrease attenuation of cerebral damage. Most importantly, 3d possessed a very high absolute bioavailability and was rapidly distributed in brain tissue to keep high plasma drug concentration for the treatment of ischemic strokes. In conclusion, our findings suggest that 3-alkyl-2,3-dihydro-1H-isoindol-1-ones, a novel series of compounds, might be candidate drugs for the treatment of acute ischemic strokes, and 3d may be a promising therapeutic agent for the primary and secondary prevention of ischemic stroke.

Perturbation of mitiglinide metabolism by chronic unpredicted mild stress in rats.

Many diabetic patients complicated with wild to severe depression. It is unclear in diabetic medication whether depression perturbs the drug metabolic process of the hypoglycemic agents or not. The present study was designed to investigate the impact of chronic unpredicted mild stress (CUMS) -induced depression on mitiglinide (MGN) pharmacokinetics in rats. Adult female Sprague-Dawley rats in CUMS group were subjected to different types of stressors and the stress procedures lasted for 8 weeks. Control group without receiving stress had free access to food and water. Open-field test and 5-HT levels were assayed to evaluate the depression. After CUMS all rats were given 2.5 mg/kg of mitiglinide per os. The blood samples were collected at different time and mitiglinide plasma concentration was measured by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Non-compartmental statistical moment analysis was processed with DAS software. In CMUS-induced depression group, peak concentration (Cmax), peak time (Tmax), area under curve (AUC0 → ∞), mean residence time (MRT0 → ∞), and half-life (T1/2z) were reduced while total plasma clearance (CLz/F) was increased compared to control group. These preliminary results indicated that CUMS-induced depression alter the drug metabolic process of mitiglinide in rats. This finding will be significant in clinic.

Effect of food on the pharmacokinetics of lurasidone: results of two randomized, open-label, crossover studies.

OBJECTIVE: This study aimed to investigate the effect of prandial status and caloric and fat composition of meals on the pharmacokinetics of lurasidone. METHODS: Two randomized, open-label, crossover studies were conducted in clinically stable adults with schizophrenia or schizoaffective disorder. Study 1 (n = 16) evaluated the effect of fasting and three meal types (100 kcal/medium fat, 200 kcal/medium fat, and 800-1000 kcal/high fat), and Study 2 (n = 26) evaluated the effect of fasting and five meal types (350 kcal/high fat, 500 kcal/low fat, 500 kcal/high fat, 800-1000 kcal/low fat, and 800-1000 kcal/high fat) on the bioavailability of lurasidone. Subjects received lurasidone 120 mg once daily. Maximum serum concentration (Cmax ) and area under the serum concentration-time curve over the dosing interval (AUC0-tau ) were determined on Day 5 for each meal type. RESULTS: In Study 1, the geometric mean Cmax in the fasted state was 56.7 ng/mL compared with 123.0 ng/mL for the 800- to 1000-kcal meal; mean AUC0-tau was 360.0 versus 752.4 ng·h/mL (both p < 0.001). Lurasidone exposure following meals containing 100 and 200 kcal was substantially lower than with meals containing 800-1000 kcal. In Study 2, the geometric mean Cmax was 52.9 ng/mL in the fasted state, 161 ng/mL for the 350-kcal/high-fat meal, 135 ng/mL for the 500-kcal/high-fat meal, and 131 ng/mL for the 800- to 1000-kcal/high-fat meal; mean AUC0-tau was 390, 743, 727, and 769 ng·h/mL, respectively. For all comparisons, the 90% confidence interval of the fed to fasted ratios indicated nonequivalence. Lurasidone exposure was similar following meals containing 350-1000 kcal and was independent of fat content. CONCLUSION: Lurasidone should be administered with food-at least 350 kcal-to ensure maximum exposure.

Pharmacokinetics and interspecies allometric scaling of ST-246, an oral antiviral therapeutic for treatment of orthopoxvirus infection.

Plasma pharmacokinetics of ST-246, smallpox therapeutic, was evaluated in mice, rabbits, monkeys and dogs following repeat oral administrations by gavage. The dog showed the lowest Tmax of 0.83 h and the monkey, the highest value of 3.25 h. A 2- to 4-fold greater dose-normalized Cmax was observed for the dog compared to the other species. The mouse showed the highest dose-normalized AUC, which was 2-fold greater than that for the rabbit and monkey both of which by approximation, recorded the lowest value. The Cl/F increased across species from 0.05 L/h for mouse to 42.52 L/h for dog. The mouse showed the lowest VD/F of 0.41 L and the monkey, the highest VD/F of 392.95 L. The calculated extraction ratios were 0.104, 0.363, 0.231 and 0.591 for mouse, rabbit, monkey and dog, respectively. The dog showed the lowest terminal half-life of 3.10 h and the monkey, the highest value of 9.94 h. The simple allometric human VD/F and MLP-corrected Cl/F were 2311.51 L and 51.35 L/h, respectively, with calculated human extraction ratio of 0.153 and terminal half-life of 31.20 h. Overall, a species-specific difference was observed for Cl/F with this parameter increasing across species from mouse to dog. The human MLP-corrected Cl/F, terminal half-life, extraction ratios were in close proximity to the observed estimates. In addition, the first-in-humans (FIH) dose of 485 mg, determined from the MLP-corrected allometry Cl/F, was well within the dose range of 400 mg and 600 mg administered in healthy adult human volunteers.

Safety and pharmacokinetics of the anti-orthopoxvirus compound ST-246 following a single daily oral dose for 14 days in human volunteers.

ST-246 is being evaluated as a treatment for pathogenic orthopoxvirus infections in humans. To this end, a phase 2, double-blind, randomized, placebo-controlled, multicenter trial was conducted to assess the safety, tolerability, and pharmacokinetics (PK) of ST-246 when administered as a single daily oral dose (400 mg or 600 mg) for 14 days in fed adult volunteers. ST-246 was safe and well tolerated, with no deaths or serious adverse events reported during the study. There was a low incidence of treatment-emergent adverse events (TEAEs), the most common of which were mild nausea and headache. There were no clinically significant results from laboratory assessments, vital sign measurements, physical examinations, or electrocardiograms. The PK and dose proportionality of ST-246 were determined. The PK analysis showed that steady state was achieved by day 5 for the ST-246 400-mg treatment group and by day 6 for the 600-mg group. The dose proportionality analysis showed that the 400- and 600-mg ratio of dose-normalized peak drug concentration in plasma (C(max)) and relative exposure for each dosing interval (AUC(τ)) ranged from 80% to 85%. However, the 90% confidence intervals did not include 1.0, so dose proportionality could not be concluded. Overall, ST-246 was shown to be safe, and the PK was predictable. These results support further testing of ST-246 in a multicenter pivotal clinical safety study for licensure application.

Lurasidone for the acute treatment of adults with schizophrenia: what is the number needed to treat, number needed to harm, and likelihood to be helped or harmed?

OBJECTIVE: To describe the efficacy, safety and tolerability of lurasidone for the acute treatment of schizophrenia using the metrics number needed to treat (NNT) and number needed to harm (NNH). METHODS: Study data were pooled from six Phase II and III, 6-week, randomized, placebo-controlled trials that were conducted to test the efficacy and safety of lurasidone for the acute treatment of schizophrenia. Included were the following interventions: fixed doses of lurasidone 20, 40, 80, 120 and 160 mg/d; haloperidol 10 mg/d; olanzapine 15 mg/d; quetiapine extended-release 600 mg/d; placebo. The following outcomes were assessed: responder rates as defined by a reduction of ≥20, 30, 40 or 50% from baseline on the Positive and Negative Syndrome Scale (PANSS) total score; study completion; discontinuation due to an adverse event (AE); weight gain ≥7% from baseline; incidence of spontaneously reported AEs; incidence of total cholesterol ≥240 mg/dL, low-density lipoprotein cholesterol ≥160 mg/dL, fasting triglycerides ≥200 mg/dL and glucose ≥126 mg/dL at endpoint. NNT for the efficacy outcomes were calculated after excluding one failed study. NNH for the safety/tolerability outcomes were calculated using all six studies. Likelihood of being helped or harmed (LHH) was also calculated to illustrate trade-offs between outcomes of improvement ≥30% on the PANSS vs. incidence of akathisia, nausea, sedation, somnolence and parkinsonism. RESULTS: NNT vs. placebo for PANSS reductions ≥30% were 6, 6, 7 and 4 for lurasidone doses of 40, 80, 120 and 160 mg/d, respectively, and 4 and 3 for olanzapine 15 mg/d and quetiapine extended-release 600 mg/d, respectively. Lurasidone was not associated with any statistically significant disadvantages over placebo for weight gain or metabolic abnormalities; NNH vs. placebo for weight gain ≥7% from baseline was 4 for olanzapine and 9 for quetiapine extended-release in contrast to a NNH for this outcome ranging from 43 to 150 for lurasidone 40-160 mg/d. The 5 most consistently encountered adverse events attributable to lurasidone were akathisia, nausea, sedation, somnolence and parkinsonism, with NNH vs. placebo for lurasidone 40-120 mg/d ranging from 6 (akathisia with 120 mg/d) to 30 (parkinsonism with 80 mg/d). Lurasidone 160 mg/d appeared better tolerated than doses of 40, 80 or 120 mg/d for akathisia, nausea, sedation or somnolence, with no NNH values for these adverse events for 160 mg/d vs. placebo being statistically significant. LHH was favorable for lurasidone when contrasting PANSS reductions vs. adverse events. CONCLUSIONS: NNT and NNH can help quantify efficacy, safety and tolerability outcomes and place lurasidone into clinical perspective. Advantages for lurasidone include a low propensity for weight gain and metabolic abnormalities. More commonly encountered adverse events include akathisia, nausea, sedation, somnolence and parkinsonism, but NNH values are generally in the double digits, reflecting an overall tolerable profile. Individual patient characteristics, values and preferences will need to be considered when selecting lurasidone over other antipsychotics.

Hollow fiber liquid-phase microextraction combined with high performance liquid chromatography for the determination of trace mitiglinide in biological fluids.

A hollow fiber liquid phase microextraction (HF-LPME) in conjunction with reversed phase HPLC-UV method was developed for the extraction and determination of trace amounts of the antidiabetic drug, mitiglinide (MIT) in biological fluids. The drug was extracted from 10 mL aqueous sample (donor phase (DP)) into an organic phase impregnated in the pores of hollow fiber, followed by the back extraction into a second aqueous solution (acceptor phase (AP)) located in the lumen of the hollow fiber. Parameters influencing the extraction efficiency including the kind of organic solvent, composition of DP and AP, extraction time, stirring rate and salt addition were investigated and optimized. Under the optimized extraction conditions, high enrichment factors (210-fold), good linearity (5-1000 ng mL(-1)) and detection limit lower than 1.38 ng mL(-1) were achieved. Recoveries of spiked samples were in the range (88.3-96.3%) and (92.0-99.3%) for urine and plasma samples, respectively. The percent relative standard deviation (n=9) for the extraction and determination of three concentration levels (100, 400 and 800 ng mL(-1)) of MIT were less than 10.6% and 13.6% for urine and plasma samples, respectively. The developed method is simple, sensitive and has been successfully applied to the analysis of MIT in biological fluids.

Pharmacokinetics of lurasidone, a novel atypical anti-psychotic drug, in rats.

This study aimed to characterise the pharmacokinetics of lurasidone, a new atypical anti-psychotic drug, in rats after intravenous and oral administration at dose range 0.5-2.5 and 2.5-10 mg/kg, respectively. Moreover, tissue distribution, liver microsomal stability and plasma protein binding were estimated. After intravenous injection, systemic clearance, steady-state volumes of distribution and half-life remained unaltered as a function of dose with values in the range 22.1-27.0 mL/min/kg, 2,380-2,850 mL/kg and 229-267 min, respectively. Following oral administration, absolute oral bioavailability was not dose dependent with approximately 23%. The recoveries of lurasidone in urine and bile were 0.286% and 0.0606%, respectively. Lurasidone was primarily distributed to nine tissues (brain, liver, kidneys, heart, spleen, lungs, gut, muscle and adipose) and tissue-to-plasma ratios of lurasidone were ranged from 1.06 (brain) to 9.16 (adipose). Further, lurasidone was unstable in rat liver microsome and the plasma protein binding of lurasidone was concentration independent with approximately 99.6%. In conclusion, lurasidone showed dose-independent pharmacokinetics at an intravenous dose of 0.5-2.5 mg/kg and an oral dose of 2.5-10 mg/kg. Lurasidone was primarily distributed to nine tissues and appeared to be primarily eliminated by its metabolism.

Determination of tandospirone in human plasma by a liquid chromatography-tandem mass spectrometry method.

A rapid, sensitive, and selective liquid chromatography-tandem mass spectrometry method for the detection of tandospirone in human plasma is described. It was employed in a pharmacokinetic study. The analyte and internal standard diphenhydramine were extracted from plasma using liquid-liquid extraction, then separated on a Zorbax XDB C(18) column using a mobile phase of methanol-water-formic acid (80:20:0.5, v/v/v). The detection was performed with a tandem mass spectrometer equipped with an electrospray ionization source. Linearity was established in the concentration range of 10.0-5,000 pg/ml. The lower limit of quantification was 10.0 pg/ml. The intraday and interday relative standard deviation across three validation runs over the entire concentration range was less than 13%. Accuracy determined at three concentrations (25.0, 200, and 4,000 pg/ml for tandospirone) ranged from 94.4 to 102.1%. Each plasma sample was chromatographed within 3.4 min. The method proved to be highly selective and suitable for bioequivalence evaluation of different formulations containing tandospirone and clinical pharmacokinetic investigation of tandospirone.

Quantification of lurasidone, an atypical antipsychotic drug, in rat plasma with high-performance liquid chromatography with tandem mass spectrometry.

A liquid chromatography-tandem mass spectrometric (LC/MS/MS) method was developed for the determination of an atypical antipsychotic drug, lurasidone, in rat plasma. The method involves the addition of acetonitrile and ziprasidone (internal standard) solution to plasma samples, followed by centrifugation. An aliquot of the supernatant was diluted with water and directly injected into the LC/MS/MS system. The separations were performed on a column packed with octadecylsilica (5 µm, 2.0 × 50 mm) with 0.1% formic acid and 0.1% formic acid in acetonitrile as mobile phase and the detection was performed using tandem mass spectrometry by multiple-reaction monitoring via an electrospray ionization source. The standard curve was linear (r = 0.9982) over the concentration range 0.002-1 µg/mL. The intra- and inter-assay precisions were 1.7 and 8.6%, respectively. The accuracy range was from 90.3 to 101.8%. The lower limit of quantification was 2.0 ng/mL using 50 µL of rat plasma sample. The developed analytical method was successfully applied to the pharmacokinetic study of lurasidone in rats.

[First death case of serotonin syndrome in Japan induced by fluvoxamine and tandospirone].

We experienced the first death case of the serotonin syndrome in Japan caused by fluvoxamine and tandospirone. A 15-year-old man was transported to our hospital for shock, muscle hypertonia and hyperthermia after cardiopulmonary arrest. His serum concentrations of fluvoxamine and tandospirone were 3,554 ng/mL and 698 ng/mL respectively after 24 hours from oral intake. He was dead in spite of intensive treatments. The progress of the serotonin syndrome is usually rapid. So, it should be monitored appropriately a patient with serotonin syndrome. If he has hyperthermia, immediate paralysis should be induced. We should aware of the serotonin syndrome a case of overdose on a serotonergic agent.

[Determination of plasma concentration of N-methylcantharidimide by HPLC and its pharmacokinetics after intravenous administration in dogs].

OBJECTIVES: To establish a HPLC method for determination of N-methylcantharidimide in dogs' plasma and to study the pharmacokinetics of N-methylcantharidimide in dogs'. METHOD: The plasma samples were extracted by methanol. The acetonitrile and the purified water composed mobile phase. The flow rate was 0. 7 mL x min(-1), ultraviolet detection wavelength was at 212 nm. RESULT: The calibration curve was linear over the range from 0.01-10.0 mg x L(-1) with a correlation coefficiency of 0.996 3. The lower limit of quantitation was 0.01 mg x L(-1). The mean recovery was 92.3%. the relative standard deviation (RSD) of intra-day and inter-day were all less than 10%. After intravenous administration of N-methylcantharidimide with 3 dosages of 10, 15, 20 mg x kg(-1) to dogs, the corresponding distribution half-livers (t1/2alpha) were 1.8, 2.1, 1.7 min, and the elimination half-lives (t1/2beta) were 144,139, 146 min, respectively. CONCLUSION: This method is convenient, accurate and reliable. It can be used for determination of N-methylcantharidimide in dogs' plasma and pharmacokinetic studies.

The wide variability of perospirone metabolism and the effect of perospirone on prolactin in psychiatric patients.

BACKGROUND: Perospirone was developed in Japan and is used for the treatment of schizophrenia and related illnesses. The authors investigated the relationship between the dosage of perospirone and the plasma levels of perospirone and its active metabolite, ID15036, and also evaluated the impact of the plasma concentrations of perospirone and ID15036 on the plasma prolactin level to examine whether perospirone or ID15036 affected the dopamine D(2) blockade, in psychiatric patients treated with perospirone. METHODS: The subjects consisted of 21 adults treated with perospirone (4-60 mg/day). The plasma perospirone and ID15036 levels were measured in 21 patients and serum prolactin levels were investigated in 10 male patients with schizophrenia. RESULTS: The plasma ID15036 level was higher than the plasma perospirone, and a positive correlation was observed between the dosage of perospirone and the ID15036 levels (p=0.032). The 10 male patients showed a positive correlation between the plasma perospirone levels and plasma prolactin levels (r=0.688, p=0.028) and between the plasma ID15036 levels and prolactin levels (r=0.775, p=0.009). CONCLUSION: The plasma levels of ID15036 may have a greater impact on the dopamine D(2) blockade than perospirone in patients treated with perospirone.