Plasma Pharmacokinetic Studies Research Articles

Review article: 5‐aminosalicylate formulations for the treatment of ulcerative colitis – methods of comparing release rates and delivery of 5‐aminosalicylate to the colonic mucosa

Many oral 5-aminosalicylic acid (5-ASA) formulations are designed to maximize 5-ASA release in the colon where it acts topically on the colonic mucosa. Delayed-release formulations and azo-prodrugs minimize 5-ASA absorption in the upper gastrointestinal (GI) tract. To review methods for assessing 5-ASA release and colonic distribution from oral formulations, and the potential use of this information for guiding clinical decisions. PubMed and recent conference abstracts were searched for articles describing techniques used to assess 5-ASA release from ulcerative colitis (UC) therapies. In-vitro GI models, although unable to simulate more complex aspects of GI physiology, can provide useful data on 5-ASA release kinetics and bioaccessibility. Gamma-scintigraphy is useful for investigating GI disintegration of different formulations, but may not accurately reflect 5-ASA distribution. Plasma pharmacokinetic studies provide data on systemic exposure, but not on colonic distribution or mucosal uptake. Mucosal biopsies provide direct evidence of colonic distribution and may predict clinical efficacy, but must be interpreted cautiously because of considerable inter-subject variability and other confounding factors. While assessment of 5-ASA release is important, limitations of individual measurement techniques mean that randomized clinical studies in UC patients remain the best guide for dosing and treatment regimen decisions.

Pharmacokinetics and brain uptake of diazepam after intravenous and intranasal administration in rats and rabbits

The purpose of this study was to investigate the plasma pharmacokinetics and brain uptake of a lipophilic benzodiazepine anticonvulsant, diazepam in New Zealand white rabbits and Sprague–Dawley rats to evaluate the possible absorption pathways after intravenous and intranasal administration. The intranasal formulation was prepared by dissolving DZ and 1% sodium glycocholate into microemulsion system composed of 15% ethyl laurate, 25% Labrasol ®, 37.5% Transcutol ®P, 12.5% ethanol, and 10% water. Diazepam was administered intravenously (1 mg/kg) or intranasally (2 mg/kg) to rats and rabbits. Drug concentrations in the plasma and six different regions of the brain tissues, i.e., olfactory bulb, olfactory tract, anterior, middle, and posterior segments of cerebrum and cerebellum were analyzed by LC/MS method after solid phase extraction. After IN administration, DZ was rapidly absorbed into the systemic circulation, and readily and homogenously distributed into the different regions of brain tissues with a t max of 5 and 10 min in rats and rabbits, respectively. The bioavailability of DZ in rat plasma (68.4%) and brain (67.7%) were 32–47% higher than those observed in rabbit plasma (51.6%) and brain (45.9%). The AUC brain/AUC plasma ratios in rabbits after IN administration (3.77 ± 0.17) were slightly lower than from IV administration (4.23 ± 0.08). However, in rats the AUC brain/AUC plasma ratios after IV (3.03 ± 0.07) and IN (3.00 ± 0.32) administration were nearly identical. The plasma pharmacokinetic and distribution studies in the two animal models clearly showed that lipophilic DZ molecules reached the brain predominantly from the blood by crossing the blood–brain barrier after IN administration with no significant direct nose-to-brain transport via olfactory epithelium.

In vivo and in vitro metabolism of aromatic amines in transgenic mice with liver‐selective expression of human arylamine N‐acetyltransferase NAT2

To aid studies into the role of liver‐selective expression of human arylamine N‐acetyltransferase NAT2 in tissue patterns of aromatic amine toxicity, we developed a transgenic mouse line that expresses human NAT2 selectively in liver by linking the human NAT2 protein‐coding exon to the mouse albumin promoter, injecting the transgene into mouse oocytes, and testing offspring for transgene incorporation by Southern blotting. We obtained one transgenic founder that possesses a single copy of the human NAT2 coding region. Transgenic animals and offspring of matings with Nat1/Nat2 null mice were assayed for human NAT2 expression using the human NAT2‐selective substrate sulfamethazine (SMZ) and the NAT1‐selective substrate p‐aminosalicylate (PAS) in in vitro enzyme assays and in vivo plasma pharmacokinetic studies. SMZ‐NAT activity was present in liver cytosols from transgenic animals at levels comparable to those observed in livers from human NAT2 rapid acetylators, while activity was absent in Nat1/Nat2 null controls. Activity in colon was low and that in other tissues was undetectable. SMZ was more efficiently cleared in vivo by human NAT2 transgenic mice than non‐transgenics, while the clearance of PAS was similar between the strains. These mice will be a valuable tool to investigate the importance of liver NAT2 expression in the metabolism and toxicity of aromatic amines in humans.

Tumor, tissue, and plasma pharmacokinetic studies and antitumor response studies of docetaxel in combination with 9-nitrocamptothecin in mice bearing SKOV-3 human ovarian xenografts

We evaluated the antitumor activity of two different schedules of docetaxel and 9-nitrocamptothecin (9NC) in mice bearing human SKOV-3 ovarian carcinoma xenografts and evaluated the plasma, tissue, and tumor disposition of each agent alone and in combination. The following treatment groups were evaluated: (1) docetaxel 10 mg/kg IV on days 0 and 7; (2) 9NC 0.67 mg/kg PO qdx5dx2wk; (3) 9NC 0.67 mg/kg PO qdx5dx2wk in combination with docetaxel 10 mg/kg IV on days 0 and 7; and (4) 9NC 0.67 mg/kg PO qdx5dx2wk in combination with docetaxel 10 mg/kg IV on days 4 and 11; (5) vehicle controls for each agent; and (6) no treatment controls. All treatment regimens produced significant antitumor activity as compared with control groups (P < 0.05). Docetaxel administered on days 0 and 7 or on days 4 and 11 in combination with 9NC resulted in similar antitumor activity (P > 0.05). High docetaxel concentrations in tumor were maintained at late time points as compared with plasma and tissues with the retention of docetaxel at 24 h being 132-fold and 15-fold higher in tumor than in plasma and liver, respectively. After administration of 9NC alone, the ratio of the 9-aminocamptothecin (9AC) area under the concentration versus time curve (AUC) to 9NC AUC in plasma and tumor was 0.15 and 1.34, respectively. The combination of docetaxel and 9NC was effective against SKOV-3 xenografts. The lack of a difference in sequence-dependent antitumor activity may reflect the sensitivity of the SKOV-3 xenograft to 9NC. The factors associated with tumor-specific retention of docetaxel and the ratio of 9NC to 9AC in tumors is unknown.

Convenient and rapid determination of cimetidine in human plasma using perchloric acid‐mediated plasma protein precipitation and high‐performance liquid chromatography

This study demonstrates the analysis of cimetidine in human plasma with HPLC using a simplified sample preparation by protein precipitation with perchloric acid. Plasma cimetidine concentration was determined by plotting peak height ratio of cimetidine to ranitidine (internal standard, IS) against cimetidine concentrations in plasma. The cimetidine and ranitidine peaks were completely separated and no interference from plasma was observed. The lower limit of quantification (LLOQ) of the method was established at 0.1 microg/mL with a precision of 4.3% and a relative error of 1.9%. The average analytical recovery was >90% over the range of cimetidine concentrations (0.1-15.0 microg/mL). The linearity of calibration curve was excellent (r(2) > 0.999). The within- and between-day precision and accuracy, expressed as the coefficients of variation and relative error, were found to be less than 5%. Compared with previously reported methods, the analytical technique for cimetidine determination in human plasma presented here demonstrates comparable accuracy and precision, an acceptable analysis time, shorter and simpler sample preparation, and a reduced need for complicated equipment. The method presented here is simple and rapid, and the precision and sensitivity are appropriate for the determination of cimetidine in plasma in pharmacokinetic studies.

Validated HPLC–MS–MS method for simultaneous determination of atorvastatin and 2-hydroxyatorvastatin in human plasma—pharmacokinetic study

Cholesterol-reducing statin drugs are the most frequently prescribed agents for reducing morbidity and mortality related to coronary heart disease. In this publication a validated, highly sensitive, and selective isocratic HPLC method is reported for quantitative determination of the major statin drug atorvastatin (ATV) and its metabolite 2-hydroxyatorvastatin (HATV). Detection was performed with an electrospray ionization triple-quadrupole mass spectrometer equipped with an ESI interface operating in positive-ionization mode. Multiple reaction monitoring (MRM) was used for MS-MS detection. The calibration plot was linear in the concentration range 0.10-40.00 ng mL(-1) for both ATV and HATV. Inter-day and intra-day precision and accuracy of the proposed method were characterized by measurement of relative standard deviation (RSD) and percentage deviation, respectively; both were less than 8% for both analytes. The limit of quantitation was 0.02 ng mL(-1) for ATV and 0.07 ng mL(-1) for HATV. The method was used for pharmacokinetic study of ATV and HATV. Pharmacokinetic data for all analytes are also reported.

Multiple‐Dose Plasma Pharmacokinetic and Safety Study of LY450108 and LY451395 (AMPA Receptor Potentiators) and Their Concentration in Cerebrospinal Fluid in Healthy Human Subjects

The objective of this study was to measure the steady-state cerebrospinal fluid (CSF) concentration of LY450108 and LY451395 (positive modulators of AMPA receptors) in healthy subjects after the administration of 1 mg and 5 mg. Secondary objectives included the evaluation of safety, pharmacokinetics, and steady-state ratio of plasma:CSF concentrations of LY450108 and LY451395 after multiple dosing. This study was an open-label, multiple oral dose study evaluating 1 mg and 5 mg LY450108 and 1 mg and 5 mg LY451395 in 12 (3 subjects per dosing group) healthy subjects, aged 18 to 49 years. Twelve healthy male subjects completed the study. LY450108 and LY451395 were quantifiable in CSF after 1-mg and 5-mg multiple-dose administrations with plasma:CSF ratio of 82:1 and 44:1, respectively. LY450108 and LY451395 1 mg and 5 mg were measured in the CSF. Single and multiple oral doses of LY450108 and LY451395 were determined to be safe and well tolerated in healthy subjects.

Peptide quantification by matrix-assisted laser desorption ionisation time-of-flight mass spectrometry: Investigations of the cyclotide kalata B1 in biological fluids

A rapid method has been developed for the quantification of the prototypic cyclotide kalata B1 in water and plasma utilizing matrix-assisted laser desorption ionisation time-of-flight (MALDI-TOF) mass spectrometry. The unusual structure of the cyclotides means that they do not ionise as readily as linear peptides and as a result of their low ionisation efficiency, traditional LC/MS analyses were not able to reach the levels of detection required for the quantification of cyclotides in plasma for pharmacokinetic studies. MALDI-TOF-MS analysis showed linearity ( R 2 > 0.99) in the concentration range 0.05–10 μg/mL with a limit of detection of 0.05 μg/mL (9 fmol) in plasma. This paper highlights the applicability of MALDI-TOF mass spectrometry for the rapid and sensitive quantification of peptides in biological samples without the need for extensive extraction procedures.

Development of high‐performance liquid chromatographic determination of salicylaldehyde isonicotinoyl hydrazone in rabbit plasma and application of this method to an in vivo study

An analytical methodology appropriate for the determination of the novel drug candidate salicylaldehyde isonicotinoyl hydrazone (SIH) in rabbit plasma has been developed and validated. Desirable chromatographic separation was achieved on a C18 column employing a mixture of phosphate buffer (0.01 M NaH2PO4 x 2 H2O with 2 mM EDTA, pH 6.0) and methanol (53:47; v/v) as the mobile phase. In order to develop a suitable sample preparation procedure, different methods have been tested (solid-phase extraction, liquid-liquid extraction, and protein precipitation). Protein precipitation using 0.1 M HClO4 and acetonitrile allowed the highest recoveries of the analyte to be reproducibly attained. The analytical methodology developed in this study was validated with respect to linearity (0.26-30.0 microg/mL), accuracy, precision, selectivity, recovery, and stability. A concentration of 0.26 microg/mL was determined as the LLOQ. The chromatographic method was applied to a preliminary plasma pharmacokinetic study. This study has provided the first information about the concentrations of SIH in plasma of a living subject. These results could have a significant impact on further progress in the development of this promising compound.

Assessment of an LC-MS Method for Plasma Quantification of the New Immunosuppressant FK778 Through Comparison With HPLC-UV

FK778 is a new immunosuppressive agent, derived from the leflunomide-active metabolite A77 1726. It inhibits de novo pyrimidine nucleotide synthesis showing efficacy in the prevention and treatment of rejection in experimental transplant models. The aim of this work was to develop an HPLC-MS method to measure FK778 in plasma for pharmacokinetic studies. The equipment used for mass evaluation was an HLPC coupled to an ion trap analyzer through an electrospray source. After precipitation of plasma proteins with acetonitrile, the supernatant was injected onto an analytical RP-C18 column. Chromatographic separation was performed under isocratic conditions, using a mobile phase consisting of ammonium acetate buffer and acetonitrile (55:45. vol/vol). MS detection was performed in the negative ionization mode by monitoring the molecular ion of FK778 (m/z 307) and IS (m/z 269), using selected ion monitoring for both. However, we observed peaks corresponding to dimers, trimers, and tetramers of FK778 (m/z 637, m/z 945, m/z 1274). The HPLC-MS method was applied to pharmacokinetics in animal models showing comparable results to those obtained by an HPLC-UV assay at 290 nm. Good agreement was observed in the plasma FK778 concentration versus time curves. The rapid preparation of samples and the short run-time make this method attractive for use in clinical practice.

Simultaneously quantifying parent drugs and screening for metabolites in plasma pharmacokinetic samples using selected reaction monitoring information‐dependent acquisition on a QTrap instrument

Bioanalytical support of plasma pharmacokinetic (PK) studies for drug discovery programs primarily involves the quantitative analysis of dosed compounds using liquid chromatography/atmospheric pressure ionization tandem mass spectrometry (LC/MS/MS) operated in selected reaction monitoring (SRM) mode. However, there is a growing need for information on the metabolism of new chemical entities (NCEs), in addition to the time-concentration profiles from these studies. In this paper, we present a novel approach to not only quantify parent drugs with SRM, but also simultaneously screen for metabolites using a hybrid triple quadrupole/linear ion trap (QqQ(LIT)) instrument. This was achieved by incorporating both the conventional SRM-only acquisition of parent compounds and the SRM-triggered information-dependent acquisition (IDA) of potential metabolites within the same scan cycle during the same LC/MS/MS run. Two test compounds were used to demonstrate the applicability of this approach. Plasma samples from PK studies were processed by simple protein precipitation and the supernatant was diluted with water before injection. The fast scanning capability of the linear ion trap allowed for the information-dependent acquisition of metabolite MS/MS spectra (<1 s/scan), in addition to the collection of adequate data points for SRM-only channels. The MS/MS spectra obtained from potential metabolites in post-dose samples correlated well with the spectra of the parent compounds studied, therefore providing additional confirmatory structure information without the need for repetitive analyses. Relative quantitative time-concentration profiles of identified metabolites were also obtained. Furthermore, this articulated SRM+SRM-IDA approach generated equivalent quantitative results for parent compounds to those obtained by conventional SRM-only analysis. This approach has been successfully used to support discovery PK screening programs.

Simultaneous determination of the lactone and carboxylate forms of irinotecan (CPT-11) and its active metabolite SN-38 by high-performance liquid chromatography: Application to plasma pharmacokinetic studies in the rat

Irinotecan (CPT-11) and its main metabolite SN-38 are potent anticancer derivatives of camptothecin (CPT), with active lactone and inactive carboxylate forms coexisting. A simple and sensitive HPLC method using the ion-pairing reagent tetrabutylammonium hydrogen sulfate (TBAHS) was developed to simultaneously determine all four analytes in rat plasma samples. Camptothecin (CPT) was used as internal standard. The mobile phase was 0.1 M potassium dihydrogen phosphate containing 0.01 M TBAHS (pH 6.4)–acetonitrile (75:25, v/v). Separation of the compounds was carried out on a Hypersil C 18 column, monitored at 540 nm (excitation wavelength at 380 nm). All four compounds gave linear response as a function of concentration over 0.01–10 μM. The limit of quantitation in rat plasma was 0.01, 0.008, 0.005 and 0.005 μM for CPT-11 lactone, CPT-11 carboxylate, SN-38 lactone and SN-38 carboxylate, respectively. The method was successfully used in the study on the effect of coadministered thalidomide on the plasma pharmacokinetics of CPT-11 and SN-38 in rats. Coadministered thalidomide (100 mg/kg body weight by intraperitoneal injection) significantly increased the AUC 0–10h values of CPT-11 lactone and CPT-11 carboxylate by 32.6% and 30.3 %, respectively, ( P < 0.01), but decreased the values by 19.2% and 32.4% for SN-38 lactone and carboxylate, respectively, ( P < 0.05). Accordingly, the value of total body clearance (CL) of CPT-11 lactone was significantly lower in combination group compared to the control (1.329 versus 1.837 L/h/kg, P = 0.0002). Plasma t 1/2β values for SN-38 lactone and carboxylate were significantly ( P < 0.01) smaller in rats with coadministered thalidomide, as compared to rats receiving CPT-11 alone. Further studies are needed to explore the underlying mechanisms for the observed kinetic interaction between CPT-11 and thalidomide.

Phase I/II trial of intravenous Doxil® and whole abdomen hyperthermia in patients with refractory ovarian cancer

Objective: A phase I/II study of Doxil® combined with whole abdomen hyperthermia was conducted in patients with refractory ovarian cancer. Liposomal doxorubicin combined with hyperthermia has been shown to increase both liposomal delivery and drug extravasation into tumour xenografts resulting in enhanced cytotoxic effects.Patients and methods: Thirty patients with either recurrent or persistent epithelial ovarian cancer were enrolled. All patients had either measurable or assessable disease. Patients received intravenous (IV) Doxil® at a dose of 40 mg m−2 as a 1-h infusion followed by whole abdomen hyperthermia. The phase I portion of the study was performed to determine the maximal tolerated dose (MTD) of hyperthermia. Quality of life (QoL) was performed at baseline, prior to each cycle and every 3 months. Plasma pharmacokinetic studies were performed with the first cycle.Results: Ten patients participated in the phase I portion of the study which demonstrated that the MTD of hyperthermia was 60 min after either average vaginal and rectal temperatures of 40°C had been achieved or after 30 min of power application, whichever was shorter. All 30 patients were either paclitaxel and/or platinum resistant initially or developed resistant disease. The median number of prior chemotherapeutic regimens was three (range 2–8) and six patients had been previously treated with Doxil®. There were three partial responses for a response rate of 10% (95% CI: [2%, 27%]) and eight patients (27%; 95% CI: [12%, 46%]) had disease stabilization. The median time to progression or death was 3.4 months (95% CI: [2.6, 5.2]) and the median survival was 10.8 months (95% CI: [8.8, 17.4]). Twelve patients (40%) experienced palmar-plantar erythrodysesthesia (PPE), but only four (13%) experienced grade 3–4 PPE toxicity. Doxil® systemic exposure was higher in those with grade 3–4 PPE compared to those with no PPE. None of the patients had grade 3–4 thermal toxicity due to hyperthermia. QoL was not decreased in patients responding to therapy.Conclusions: Therapy with intravenous Doxil® and whole abdomen hyperthermia for patients with platinum/paclitaxel resistant ovarian cancer is feasible and does not negatively impact quality of life.

Intermittent vs Continuous Levodopa Administration in Patients With Advanced Parkinson Disease

Levodopa-related motor complications can be an important source of disability for patients with advanced Parkinson disease. Current evidence suggests that these motor complications are related to the relatively short half-life of levodopa and its potential to induce pulsatile stimulation of striatal dopamine receptors. Motor complications can be diminished with a continuous infusion of levodopa. To investigate the specific pharmacokinetic changes associated with the benefits of levodopa infusion. We performed an open-label study in 6 patients with Parkinson disease who experienced severe motor complications while receiving standard oral formulations of levodopa/carbidopa. Patients were subsequently treated for 6 months with continuous daytime intraintestinal infusions of levodopa methyl ester. Levodopa pharmacokinetic studies were performed at baseline and 6 months in 3 of these patients. Compared with treatment with intermittent doses of a standard oral formulation of levodopa, continuous infusion provided significant improvement in both "off periods" and dyskinesia. Results of plasma pharmacokinetic studies demonstrated that compared with oral administration, continuous levodopa infusion was associated with a significant increase in the levodopa area under the curve and avoided the low plasma trough levels seen with oral drug administration. This study confirms that a continuous levodopa infusion is associated with reduced motor complications compared with the standard oral formulation of the drug in patients with advanced PD. Pharmacokinetic studies demonstrate that reduced motor complications are associated with avoiding low plasma levodopa trough levels and are not adversely affected by relatively high plasma levodopa concentrations. We propose that if levodopa/carbidopa could be administered orally in a manner that mirrors the pharmacokinetic pattern of the infusion, it might lead to a similar reduction in motor complications.

Determination of thalidomide by high performance liquid chromatography: Plasma pharmacokinetic studies in the rat

A sensitive and simple high performance liquid chromatography (HPLC) method was developed and validated for the determination of thalidomide in rat plasma. Chromatography was accomplished with a reversed-phase Hypersil C18 column. Mobile phase consisted of acetonitrile-10 mM ammonium acetate buffer (pH 5.50) (28:72, v/v), at a flow rate of 0.8 ml/min. Thalidomide was monitored by ultraviolet detector at 220 nm and it gave a linear response as a function of concentration over 0.02–50 μM. The limit of quantitation in rat plasma was 0.50 ng (0.02 μM plasma concentration) with an aliquot of 20 μl. Results from a 3-day validation study indicated that this method allows for simple and rapid quantitation of thalidomide with excellent accuracy and reliability. Using this validated assay, the effect of coadministered irinotecan (CPT-11) on the plasma pharmacokinetics of thalidomide in rats was determined. Coadministration of CPT-11 (intravenously, 60 mg/kg) increased the maximum plasma concentration ( C max) and area under the plasma concentration–time curve (AUC 0–10 h ) of thalidomide by 32.29 and 11.66%, respectively, as compared to the control, but none of the effect of CPT-11 was of statistical significance ( P > 0.05). Concomitant CPT-11 also caused a 10.04% decrease in plasma clearance (CL) and 14.51% decrease in volume of distribution ( V d) ( P > 0.05). These results suggest that coadministered CPT-11 did not significantly alter the plasma pharmacokinetics of thalidomide in rats. Further studies are warranted to explore the pharmacokinetic and pharmacodynamic interactions between CPT-11 and thalidomide.

New model for intravenous drug administration and blood sampling in the awake rat, designed to increase quality and throughput for in vivo pharmacokinetic analysis

Introduction: There is a continuing need for increased throughput in the examination of new chemical entities (NCEs) in terms of the pharmacokinetic (PK) parameters. The aim was to validate a new study method designed to improve throughput and reduce inter-animal variability and animal number requirement in routine bioavailability and plasma PK studies of NCEs in awake rats. Methods: The design uses a new method for intravenous (iv) administration via the saphenous vein in combination with serial blood sampling via the tail vein. The multiple sampling method was compared with single sampling (decapitation) and the effect on haematocrit (Hct) levels was studied. Direct injection in the saphenous vein was compared to iv administration using an indwelling jugular catheter. Results: Using structurally different NCEs, it was shown that a combination of direct injection via the saphenous vein and multiple sampling from the tail vein produces comparable plasma concentrations and subsequent PK results to the comparator methods. Furthermore, Hct levels remained within recommended levels using a total blood sampling volume of up to 2.1 ml/day for rats with a body weight of around 250 g. Discussion: The new model increases throughput by avoiding the time required for preparative surgery, increases quality by allowing inter-animal comparison of major PK parameters as concentration time curves can be obtained from each animal, and reduces the number of animals required.

Imatinib mesylate (STI571) for treatment of children with Philadelphia chromosome-positive leukemia: results from a Children's Oncology Group phase 1 study

AbstractThe purpose of this study was to determine dose-limiting toxicities and pharmacokinetics of imatinib in children with refractory or recurrent Philadelphia chromosome-positive (Ph+) leukemias. Oral imatinib was administered daily at dose levels ranging from 260 to 570 mg/m2. Plasma pharmacokinetic studies were performed on days 1 and 8 of course 1. There were 31 children who received 479 courses of imatinib. The most common toxicities encountered, which occurred in less than 5% of courses, were grade 1 or 2 nausea, vomiting, fatigue, diarrhea, and reversible increases in serum transaminases. One patient at the 440-mg/m2 dose level had dose-limiting weight gain. There were no other first-course dose-limiting toxicities. A maximum tolerated dosage was not defined. Among 12 chronic myeloid leukemia (CML) patients evaluable for cytogenetic response, 10 had a complete response and 1 had a partial response. Among 10 acute lymphoblastic leukemia (ALL) patients evaluable for morphologic response, 7 achieved an M1 and 1 achieved an M2 bone marrow. We observed marked interpatient variability in the pharmacokinetic parameters. In conclusion, we found that daily oral imatinib is well tolerated in children at doses ranging from 260 to 570 mg/m2. Doses of 260 and 340 mg/m2 provide systemic exposures similar to those of adults who are treated with daily doses of 400 and 600 mg, respectively. (Blood. 2004;104:2655-2660)

Plasma and cerebrospinal fluid pharmacokinetic study of BNP1350 in nonhuman primates.

BNP1350 (7-[(2-trimethylsilyl)ethyl]-20(S)-camptothecin, karenitecin), a highly lipophilic camptothecin, a high percentage of which is maintained in the active lactone form under physiologic conditions, has recently entered clinical trials in adults and children. BNP1350 has shown significant preclinical antitumor activity against a wide variety of adult and pediatric tumor cell lines. This study was undertaken to define the pharmacokinetics of BNP1350 in both plasma and cerebrospinal fluid (CSF) in a nonhuman primate model. Four nonhuman primates with indwelling Ommaya reservoirs received BNP1350, 0.1 mg/kg i.v, administered as a 60-min infusion. Frequent plasma and CSF samples were obtained for quantitation of BNP1350 concentrations using reverse-phase high-pressure liquid chromatography (HPLC). Disappearance of the lactone form from the plasma was biexponential with a mean distribution half-life of 57.5 min (CV +/-33%) and an elimination half-life of 457 min (CV +/-24%). The volume of distribution for the central compartment was 1.36 l/kg (CV +/-27%) and clearance from the central compartment was 10.6 ml/kg per minute (CV +/-28%). The peripheral compartment volume of distribution was 1.96 l/kg (CV +/-8.4%). Peak CSF lactone concentration, which occurred at 12 to 25 min after the end of the infusion, was 0.33 n M (CV +/-71%). The ratio of the CSF AUC to the plasma AUC was less than 5% (range 0.4% to 3.0%), similar to other highly protein-bound topoisomerase inhibitors such as 9-aminocamptothecin and SN-38 (the active metabolite of irinotecan).

High-performance liquid chromatographic determination of tianeptine in plasma applied to pharmacokinetic studies

An improved analytical method for the quantitative measurement of tianeptine and its main metabolite MC 5 in human plasma was designed. Extraction involved ion-paired liquid–liquid extraction of the compounds from 1.0 ml of human plasma adjusted to pH 7.0. HPLC separation was performed using a Nucleosil C 18, 5 μm column (150×4.6 mm I.D.) and a mixture of acetonitrile and pH 3, 2.7 g l −1 solution of sodium heptanesulfonate in distilled water (40:60, v/v) as mobile phase. UV detection was performed using a diode array detector in the 200–400 nm passband, and quantification of the analytes was made at 220 nm. For both tianeptine and MC 5 metabolite, the limit of quantitation was 5 μg l −1 and the calibration curves were linear from 5 to 500 μg l −1. Intra- and inter-assay precision and accuracy fulfilled the international requirements. The recovery of tianeptine and its metabolite from plasma was, respectively, 71.5 and 74.3% at 20 μg l −1, 71.2 and 70.8% at 400 μg l −1. The selectivity of the method was checked by verifying the absence of chromatographic interference from pure solutions of the most commonly associated therapeutic drugs. This method, validated according to the criteria established by the Journal of Chromatography B, was applied to the determination of tianeptine and MC 5-metabolite in human plasma in pharmacokinetic studies.

Complete hematologic and cytogenetic response to 2-amino-9-?-D-arabinosyl-6-methoxy-9H-guanine in a patient with chronic myelogeneous leukemia in T-cell blastic phase

T-cell lymphoid blastic phase (BP) transformation is rare in chronic myelogenous leukemia (CML). 2-amino-9-beta-D-arabinosyl-6-methoxy-9H-guanine (GW506U78), a prodrug of arabinosylguanine (ara-G), is effective in T-cell leukemias. The authors present a case of a 48-year-old male with Philadelphia chromosome (Ph) positive CML and T-cell lymphoid BP after 17 months in the chronic phase. Plasma pharmacokinetic studies after an infusion of GW506U78 at a dose of 40 mg/kg showed GW506U78 concentrations of 60 microM, and a peak ara-G concentration of 260 microM in the plasma. Cellular ara-G triphosphate (ara-GTP) concentration in the peripheral blood T-lymphoblasts was 80 microM at the end of GW506U78 infusion and reached a maximum of 150 microM. The patient achieved a complete response that lasted 13 months. Severe neurotoxicity related to GW506U78 was observed. GW506U78 showed antileukemic activity against Ph positive T-cell BP CML. Neurotoxicity was dose-limiting in this patient. Treatment with GW506U78 and modulation of ara-GTP concentrations are therapeutic strategies that require further exploration in T-cell malignancies. Investigation of other dosing schedules may limit neurotoxicity.