Raymond H. Farmen

High-performance liquid chromatographic method for the determination of nefazodone and its metabolites in human plasma using laboratory robotics

A quantitative analytical method, using high-performance liquid chromatography and ultraviolet detection, has been established for the determination of nefazodone (NEF) and its metabolites, m-chlorophenylpiperazine (mCPP),p-hydroxynefazodone (PHN), and hydroxynefazodone (HO-NEF), in human plasma. The fully automated, robotic procedure consisted of addition of internal standard (aprindine), extraction with butyl chloride, followed by phase separation, organic phase evaporation, reconstitution of the residue, and injection onto the chromatographic system. The limits of detection for NEF, mCPP, PHN, and HO-NEF were 5, 1, 10, and 5 ng/ml, respectively, at a signal-to-noise ratio of 4. The method had a linear range of 10-1000 ng/ml for NEF and HO-NEF, 20-2000 ng/ml for PHN, and 2.5-250 ng/ml for mCPP. Correlation coefficients of 0.996 or greater were obtained during validation and study sample analysis.

The disposition of carboplatin in ovarian cancer patients

SummaryCarboplatin was given as a 30-min infusion to 11 ovarian cancer patients at doses of 170–500 mg/m2. The ages, weights, and creatinine clearances (Clcr) ranged from 44 to 75 years, from 44 to 74 kg, and from 32 to 101 ml/min, respectively. Plasma, plasma ultrafiltrate (PU), and urine samples were obtained at appropriate times for 96 h and were analyzed for platinum. The PU and urine were also analyzed for the parent compound by HPLC. In patients with a Clcr of about 60 ml/min or greater, carboplatin decayed biexponentially with a mean t1/2α of 1.6 h and a t1/2β of 3.0 h. The mean (±SD) residence time, total body clearance, and apparent volume of distribution were 3.5±0.4 h, 4.4±0.85 l/h, and 16±31l, respectively. Cmax and AUCinf values increased linearly with dose, and the latter values correlated better with the dose in mg than in mg/m2. No significant quantities of free, ultrafilterable, platinum-containing species other than the parent compound were found in plasma, but platinum from carboplatin became protein-bound and was slowly eliminated with a minimal t1/2 of 5 days. The major route of elimination was excretion via the kidneys. Patients with a Clcr of 60 ml/min or greater excreted 70% of the dose as the parent compound in the urine, with most of this occurring within 12–16 h. All of the platinum in 24-h urine was carboplatin, and only 2%–3% of the dosed platinum was excreted from 48 to 96 h. Patients with a Clcr of less than about 60 ml/min exhibited dose-disproportional increases in AUCinf and MRT values. The latter were inversely related to Clcr (r=-0.98). Over a dose range of 300–500 mg/m2, carboplatin exhibited linear, dose-independent pharmaco-kinetics in patients with a Clcr of about 60 ml/min or greater, but dose reductions are necessary for patients with mild renal failure.

Management of Pharmacokinetic Data Using HP-3357/Mainframe Ibm Interfacing

This article represents the first description of a complete pharmacokinetic data management system. This system uses an HP-3357 computer for data acquisition and an IBM mainframe for sample processing. This system is unique in that it provides sample management capabilities, automatic data collection, GLP documentation, and estimates of pharmacokinetic parameters. This computer system has greatly reduced the time necessary to analyze the data from a pharmacokinetic study. Furthermore, the reliability of the data is increased by eliminating data transposition errors and by forcing uniformity in sample processing.

The disposition of carboplatin in the beagle dog

SummaryCarboplatin was administered i.v. to four groups of three male beagle dogs at doses of 3, 6, 12, and 24 mg/kg (60–580 mg/m2). Plasma samples were obtained at appropriate times and protein-free plasma ultrafiltrates (PU) were generated with Amicon Centrifree micropartition systems. Urine was collected at 24-h intervals for 96 h. PU and urine samples were analyzed for carboplatin by HPLC and for total platinum by atomic absorption spectrophotometry. Carboplatin accounted for about 90% of the free platinum in plasma. The Cmax and AUCinf values for carboplatin and for free platinum increased linearly with dose. The terminal elimination half-life and mean residence times for carboplatin and free platinum were each about 1 h. Total-body clearances for carboplatin (5.6 l/h per m2) and free platinum (5.1 l/h per m2) were constant over the dose range studied, as were the respective volumes of distribution (5.7 and 5.0 l/m2). A mean of 46% of the dose was excreted as carboplatin in 24-h urine; and by 72 h, 70% of the platinum administered was excreted in the urine. Free platinum was cleared by both renal and nonrenal processes. These results show that a dose of carboplatin is rapidly excreted in the urine and that carboplatin and plasma-free platinum exhibit linear pharmacokinetics in the beagle dog.

Simultaneous quantitation of buspirone and 1-(2-pyrimidinyl)piperazine in human plasma and urine by capillary gas chromatography—mass spectrometry

Buspirone and a buspirone metabolite, 1-(2-pyrimidinyl)piperazine (1-PP), are extracted from matrix using C18 extraction columns. The metabolite and its internal standard (d4-1-PP) are derivatized with pentafluorobenzoyl chloride to the corresponding amides. The 1-PP derivatives, buspirone and the buspirone internal standard (5-fluorobuspirone) are co-chromatographed. Chromatography and detection are performed using capillary gas chromatography with a fused-silica column and selected-ion monitoring-mass spectrometry. Linear range of the standard curves in plasma is 0.1-14 ng/ml for buspirone and 0.2-25 ng/ml for 1-PP with lower limits of quantitation of 0.1 and 0.2 ng/ml, respectively. In urine the linear range of the standard curves is 0.2-14 ng/ml for buspirone and 8-500 ng/ml for 1-PP with lower limits of quantitation of 0.2 and 8.0 ng/ml, respectively. Intra-assay accuracies were within 14% for buspirone and 1-PP in plasma and urine. Intra-assay precision was within 12% for both compounds in both matrices.

Effect of Food on the Bioavailability of Gepirone in Humans

A randomized two‐period crossover study was conducted in 20 healthy male volunteers to assess the effect of food on the pharmacokinetics of gepirone (BMY‐13805) and its metabolite, 1‐(2‐pyrimidinyl)‐piperazine (1‐PP) after a single 20‐mg dose of gepirone either after fasting or after consumption of a standard high‐Fat breakfast. There was a 1‐week washout period between treatments. Plasma samples were obtained predose and at specified time points after dosing and analyzed for gepirone and 1‐PP content by a specific gas chromatographic‐mass spectrometric method. Food did not significantly affect gepirone maximum peak plasma concentration (Cmax) and half‐life (R 1/2). The mean gepirone Cmax was 16.98 ± 8.12 ng/mL (fed) and 18.73 ± 10.30 ng/mL (fasted), with mean t 1/2 of 3.32 ± 1.84 hours (fed) and 2.94 ± 0.90 hours (fasted). Food significantly increased the mean area under the curveinf (AUCinf) from 55.26 ± 35.74 ng.hour/mL (fasted) to 75.69 ± 42.79 ng.hour/mL (fed), and the mean residence timeinf (MRTinf) from 4.31 ± 0.78 hours (fasted) to 5.37 ± 1.21 hours (fed). The median time to maximum plasma concentration (tmax)for gepirone was also significantly increased in the presence of food, 2.0 hours, versus 0.75 hours in the absence of food. For 1‐PP, food had no affect on Cmax, t 1/2, or AUCinf. Mean t 1/2 for 1‐PP in the presence and absence of food was 6.06 ± 1.75 and 5.76 ± 1.75 hours, respectively. MRTinf, however, was increased significantly from 9.32 ± 2.68 hours (fasted) to 10.53 ± 2.89 hours (fed). Median tmax for 1‐PP was also significantly increased from 1.25 hours in the absence of food to 3.0 hours with food. The results of this study indicated that the onset and rate of absorption of gepirone were altered in the presence of food. The amount of gepirone reaching the systemic circulation was also increased in the presence of food. Food did not markedly affect peak blood levels of both parent and metabolite, however, or their elimination kinetics.

High-performance liquid chromatographic method for the determination of etoposide in plasma using electrochemical detection

A quantitative analytical method has been established for the determination of a semi-synthetic epipodophyllotoxin, etoposide, in plasma. The method employs reversed-phase high-performance liquid chromatography and electrochemical detection. Sample preparation consisted of extraction with 1,2-dichloroethane followed by phase separation, evaporation of the organic phase, and reconstitution of the residue. Observed recoveries were 76.8 and 87.5% for 50 and 500 ng/ml, respectively. The method had a linear range of 10-1000 ng/ml. Correlation coefficients of 0.997 or greater were obtained during validation experiments and study sample analysis.

High-performance liquid chromatographic method for the quantitative determination of butorphanol, hydroxybutorphanol, and norbutorphanol in human urine using fluorescence detection

A sensitive, quantitative reversed-phase high-performance liquid chromatographic method has been established for the simultaneous determination of butorphanol, a synthetic opioid, and its metabolites, hydroxybutorphanol and norbutorphanol, in human urine samples. The method involved extraction of butorphanol, hydroxybutorphanol, and norbutorphanol from urine (1.0 ml), buffered with 0.1 ml of 1.0 M ammonium acetate (pH 6.0), onto 1-ml Cyano Bond Elut columns. The eluent was evaporated under nitrogen and low heat, and reconstituted with the HPLC mobile phase, acetonitrile-methanol-water (20:10:70, v/v/v), containing 10 mM ammonium acetate and 10 mM TMAH (pH 5.0). The samples were chromatographed on a reversed-phase octyl 5-microns column. The analysis was accomplished by detection of the fluorescence of the three analytes, at excitation and emission wavelengths of 200 nm and 325 nm, respectively. The retention times for hydroxybutorphanol, norbutorphanol, the internal standard, and butorphanol were 5.5, 9.0, 13.0, and 23.4 min respectively. The validated quantitation range of the method was 1-100 ng/ml for butorphanol and hydroxybutorphanol, and 2-200 ng/ml for norbutorphanol in urine. The observed recoveries for butorphanol, hydroxybutorphanol, and norbutorphanol were 93%, 72%, and 50%, respectively. Standard curve correlation coefficients of 0.995 or greater were obtained during validation experiments and analysis of study samples. The method was applied on study samples from a clinical study of butorphanol, providing a pharmacokinetic profiling of butorphanol.

Database Design and Management in a Pharmacokinetic Department

A system automating the flow of information from setting up a pharmacokinetic study through sample processing to pharmacokinetic data interpretation is described. The system was developed to manage the tremendous volume of information and data generated by a department of about 45 people. Over 300,000 samples in 1,000 studies have been processed over the last six years. Utilization of this system has resulted in a dramatic increase in sample throughput and decrease in the report preparation time. The system uses two major user-generated files for this process, a database file created for each pharmacokinetic study and an output file created for each analytical run. Software to run this system has been written inhouse and interfaces with commercial software on the data collection system (HP 335X LAS) and SAS software on an IBM mainframe.