Single-Dose Pharmacokinetics and Safety of Solriamfetol in Participants With Normal or Impaired Renal Function and With End-Stage Renal Disease Requiring Hemodialysis.

Solriamfetol (JZP-110), a selective dopamine and norepinephrine reuptake inhibitor with wake-promoting effects, is renally excreted ∼90% unchanged within 48 hours. Effects of renal impairment and hemodialysis on the pharmacokinetics and safety of 75-mg single-dose solriamfetol were evaluated in adults with normal renal function (n = 6); mild (n = 6), moderate (n = 6), or severe (n = 6) renal impairment; and end-stage renal disease (ESRD) with and without hemodialysis (n = 7). Relative to normal renal function, geometric mean area under the plasma concentration-time curve from time zero to infinity increased 53%, 129%, and 339%, and mean half-life was 1.2-, 1.9-, and 3.9-fold higher with mild, moderate, and severe renal impairment, respectively. Renal excretion of unchanged solriamfetol over 48 hours was 85.8%, 80.0%, 66.4%, and 57.1% in normal, mild, moderate, and severe renal impairment groups, respectively; mean maximum concentration and time to maximum concentration did not vary substantially. Decreases in solriamfetol clearance were proportional to decreases in estimated glomerular filtration rate. Geometric mean area under the plasma concentration-time curve from time zero to time of last quantifiable concentration increased 357% and 518% vs normal in ESRD with and without hemodialysis, respectively, with half-life >100 hours in both groups. Over the 4-hour hemodialysis period, ∼21% of solriamfetol dose was removed. Adverse events included headache (n = 1) and nausea (n = 1). Six days after dosing, 1 participant had increased alanine and aspartate aminotransferase, leading to study discontinuation. While these adverse events were deemed study-drug related, they were mild and resolved. Results from this study combined with population pharmacokinetic modeling/simulation suggest that solriamfetol dosage adjustments are necessary in patients with moderate or severe but not with mild renal impairment. Due to significant exposure increase/prolonged half-life, dosing is not recommended in patients with ESRD.

A randomised trial of the effect of the glycine reuptake inhibitor Org 25935 on cognitive performance in healthy male volunteers.

OBJECTIVE: Cognitive impairment is integral to many neurological illnesses. Specific enhancement of glutamatergic transmission may improve memory and learning. Org 25935 increases the synaptic availability of glycine, an obligate co-agonist with glutamate at N-methyl-D-aspartate receptors. We hypothesised that Org 25935 would acutely improve the learning and memory of healthy volunteers. METHODS: A randomised, double-blind, parallel-group, single-dose study of Org 25935 and placebo was carried out. Thirty-two healthy male volunteers took either 12-mg Org 25935 or matching placebo and were later assessed with the manikin task, digit span and verbal memory tests. Systematic assessments of cardiovascular and adverse events were also taken. RESULTS: There was no effect of Org 25935 on reaction time, number of correct responses or learning (greater or slower improvement over successive tasks) compared with placebo. Org 25935 caused significantly more dizziness and drowsiness compared with placebo; these side effects were mainly mild. CONCLUSIONS: A single dose of Org 25935 does not improve learning or memory in healthy male individuals. However, the drug was well tolerated, and it remains to be seen whether it would have a positive effect on cognition in patient groups with pre-existing cognitive deficits.

AS1069562, the (+)-isomer of indeloxazine, but not duloxetine has a curative-like analgesic effect in a rat model of streptozotocin-induced diabetic neuropathy.

AS1069562 is the (+)-isomer of indeloxazine, which had been clinically used as a cerebral activator for the treatment of cerebrovascular diseases with serotonin and norepinephrine reuptake inhibition (SNRI) and neuroprotection. Here, we compared the analgesic effects of repeated treatment with AS1069562 and duloxetine, a selective SNRI, on pain-related behavior in a rat model of streptozotocin (STZ)-induced diabetic neuropathy. Further, we also evaluated the effects on the expression of neurotrophic factors and nerve conduction velocity. AS1069562 and duloxetine by single daily administration for 4 weeks significantly improved mechanical allodynia in STZ-induced diabetic rats and did not affect plasma glucose level or body weight. Interestingly, the analgesic effect of AS1069562 continued after a consecutive 1-week treatment discontinuation, although the plasma concentration of AS1069562 was reduced to undetectable levels. In contrast, the efficacy of duloxetine disappeared after treatment discontinuation. Expression analysis demonstrated that AS1069562 significantly restored decreased insulin-like growth factor 1 and fibroblast growth factor 2 mRNA levels in dorsal root ganglion and spinal cord, respectively, whereas duloxetine did not affect the expression levels of neurotrophic factors. In addition, AS1069562 reversed the slowing of nerve conduction velocity. The results of this study indicate that the analgesic effect of repeated dosing of AS1069562 but not duloxetine is persistent even after a 1-week drug discontinuation in STZ-induced diabetic rats. Restoration of neurotrophic factors may be involved in the curative-like pharmacological effect of this agent. Thus, AS1069562 may potentially offer a better treatment option for patients with painful diabetic neuropathy than duloxetine via different mechanisms.

A case series of patients with lamotrigine toxicity at one center from 2003 to 2012.

INTRODUCTION: Lamotrigine is a phenyltriazine compound that inhibits voltage-gated sodium channels, decreasing release of glutamate and aspartate, and inhibits serotonin, norepinephrine and dopamine reuptake. Reports of toxicity in the literature are limited to case reports and primarily involve coingestants. This case series is intended to report the clinical manifestations of lamotrigine toxicity. METHODS: This retrospective case series from 2003 to 2012 studies the effects of lamotrigine toxicity when not confounded by coingestants. Admission records at an inpatient toxicology center were reviewed for lamotrigine-only exposure based on history with supporting laboratory data when available. After identification, these charts were reviewed again to characterize vital signs, neurological examination findings, specific laboratory and electrocardiography parameters, and complications. RESULTS: Fifty-seven patients were identified with possible lamotrigine toxicity. Nine patients, including three toddlers, had lamotrigine-only ingestions. Three of these patients had seizures, four were hypertensive, five were tachycardic, and four experienced tachypnea. Mental status was altered in all nine (depressed (n = 4), agitated (n = 5) or both (n = 3)). Five patients were hyperreflexic and experienced intermittent myoclonus, and two had inducible clonus. On electrocardiogram, two patients experienced QRS prolongation (114-116 ms), and four had QTc prolongation (463-586 ms). No patient had life-threatening symptoms or signs. Serum levels of lamotrigine were available in seven patients, and averaged 35.4 mg/L (17-90 mg/L). The therapeutic range for sLTG is 3-14 mg/L. CONCLUSIONS: Lamotrigine toxicity manifested with minor-moderate neurologic and/or electrocardiographic effects. Toxicity reflects the known pharmacologic actions of lamotrigine: serotonin, norepinephrine and dopamine reuptake inhibition, and sodium channel blockade.

Biopharmaceutical characterization, metabolism, and brain penetration of the triple reuptake inhibitor amitifadine.

Amitifadine (EB-1010, formerly DOV 21,947) is a serotonin-preferring triple reuptake inhibitor that is a drug candidate for major depressive disorder. We investigated several relevant biopharmaceutic and drug-like characteristics of amitifadine using in vitro methodology and additionally determined the in vivo brain to plasma ratio of the drug in rats. Amitifadine was highly plasma protein bound with over 99% of drug bound to human plasma proteins. Using Caco-2 cell lines, amitifadine was bidirectionally highly permeable and showed no evidence of active secretion. Amitifadine was metabolized slowly by human hepatocytes and the major metabolite was the lactam EB-10101. In vitro studies using human liver microsomes demonstrated that EB-10101 was formed by monoamine oxidase A (MAO-A) and a NADPHdependent enzyme, possibly a cytochrome P450 (CYP) isoform. Amitifadine was a moderate inhibitor of the human isoforms of the major drug metabolizing enzymes CYP2D6, CYP3A4, CYP2C9, and CYP2C19 (IC50 = 9 - 100 µM), but was a potent inhibitor of human CYP2B6 (IC50 = 1.8 µM). The brain to plasma ratio for amitifadine varied from 3.7 - 6.5 at various time points, indicating preferential partitioning into rat brain versus plasma. The low affinity for the major drug metabolizing CYP enzymes and metabolism by multiple pathways may reduce pharmacokinetic drug-drug interactions and effects of enzyme polymorphisms. Overall, these studies suggest that amitifadine has drug-like characteristics favorable for drug development.

Dispersive liquid-liquid microextraction based on solidification of floating organic droplets followed by high performance liquid chromatography for the determination of duloxetine in human plasma.

A novel dispersive liquid-liquid microextraction method based on solidification of floating organic droplets (DLLME-SFO) technique was developed for the determination of duloxetine in human plasma samples by high performance liquid chromatography with fluorescence detection (HPLC-FLD). During the extraction procedure, plasma protein was precipitated by using a mixture of zinc sulfate solution and acetonitrile. After the protein precipitation step, duloxetine in an alkaline sample solution was quickly extracted by DLLME-SFO with 50 µL of 1-undecanol (extractant). Disperser was unnecessary because the small amount of remaining acetonitrile, which acts as a protein precipitating reagent, was also employed as a disperser; therefore, organic solvent consumption was reduced as much as possible. The emulsion was centrifuged and then fine droplets were floated to the top of the sample solution. The floated droplets were solidified in an ice bath and easily transferred. Various DLLME-SFO parameters such as extractant type, extractant amount, ionic strength, pH and extraction time were optimized. The chromatographic separation of duloxetine was carried out using ethanol as mobile phase. Validation of the method was performed with respect to linearity, intra- and inter-day accuracy and precision, limit of quantification (LOQ), and recovery. Calibration curves for duloxetine showed good linearity with correlation coefficients (r²) higher than 0.99. The method showed good precision and accuracy, with intra- and inter-assay coefficients of variation less than 15% (LOQ: less than 20%) at all concentrations. The recovery was carried out following the standard addition procedure with yields ranging from 59.6 to 65.5%. A newly developed environmentally friendly method was successfully applied to the pharmacokinetic study of duloxetine in human plasma and was shown to be an alternative green approach compared with the conventional solid-phase microextraction (SPME) and dispersive liquid-liquid microextraction (DLLME) techniques.

Postmortem distribution of tapentadol and N-desmethyltapentadol.

Postmortem distribution concentrations of the pain medication tapentadol and its metabolite N-desmethyltapentadol are reported. Tapentadol (Nucynta®) is a synthetic mu-opioid receptor agonist that also has norepinephrine reuptake inhibitor action. The laboratory received two cases. Case 1: a 19-year-old, morbidly obese male with sudden unexpected death. Toxicology results revealed tapentadol (femoral blood: 0.77 mg/L, liver: 1.65 mg/kg), N-desmethyltapentadol (femoral blood: 0.07 mg/L, liver: 0.19 mg/kg), diazepam (femoral blood: 0.04 mg/L), nordiazepam (femoral blood: 0.06 mg/L) and amiodarone (femoral blood: 5.30 mg/L). Case 2: a 60-year-old female who died from complications following hip replacement. Only tapentadol (femoral blood: 0.26 mg/L, liver: 0.52 mg/kg) was found in the toxicology results. Quantitative results of tapentadol/N-desmethyltapentadol were achieved using liquid chromatography-tandem mass spectrometry in multiple reactions monitoring mode. This is the first known distribution study of tapentadol and N-desmethyltapentadol values in postmortem cases.

Venlafaxine in human breast milk and nursing infant plasma: determination of exposure.

OBJECTIVE: Venlafaxine use during pregnancy has increased over the past decade in concert with accumulating reproductive safety data; however, systematic data on venlafaxine during lactation remain sparse. The current study characterizes the level and determinants of venlafaxine and desvenlafaxine concentrations in breast milk and in nursing infant plasma. METHOD: Women participating in a prospective investigation of perinatal pharmacokinetics from January 2001 through July 2006 who were treated with venlafaxine and who chose to continue venlafaxine during lactation were included in the analysis. Breast milk samples were collected via breast pump from foremilk to hindmilk from a single breast to determine the excretion gradient, and serial samples were collected over 24 hours to determine the time course of excretion. Paired maternal/infant plasma samples were also collected. Venlafaxine and desvenlafaxine concentrations were determined using high-performance liquid chromatography with ultraviolet detection. Statistical analyses of breast milk and infant plasma concentrations and their determinants were conducted. RESULTS: Thirteen women and their nursing infants participated, providing 106 breast milk samples. The mean milk/plasma ratio was 275.3% (95% CI = 144.8% to 405.7%). There were statistically significant time courses of excretion for venlafaxine (R = 0.36, F = 6.82, P < .02), desvenlafaxine (R = 0.48, F = 4.41, P < .009), and combined venlafaxine/desvenlafaxine (R = 0.51, F = 5.16, P < .004), with the highest venlafaxine and desvenlafaxine concentrations in the breast milk occurring 8 hours after maternal ingestion. Infant plasma concentrations for combined venlafaxine/desvenlafaxine were 37.1% of maternal plasma concentrations. The theoretical infant venlafaxine/desvenlafaxine dose was 0.208 mg/kg/d, and the relative infant venlafaxine/desvenlafaxine dose was 8.1%. The theoretical and relative infant doses for desvenlafaxine were 197% and 224% higher, respectively, than those for venlafaxine. No adverse events were observed or reported in the nursing infants. CONCLUSIONS: Consistent with previous investigations of medications in breast milk, the venlafaxine and desvenlafaxine milk/plasma ratios were highly variable. The rate of venlafaxine/desvenlafaxine excretion into human breast milk is relatively higher than that observed for other antidepressants, largely due to higher desvenlafaxine excretion. These data expand the extant literature on venlafaxine and desvenlafaxine in lactation.

Serum concentrations of antidepressant drugs in a naturalistic setting: compilation based on a large therapeutic drug monitoring database.

A compilation of therapeutic drug monitoring data for 15 antidepressant drugs in a naturalistic routine clinical setting is presented. A substantial number of serum concentrations, at different daily doses, are outlined, and the intraindividual and overall serum concentration coefficient of variation for a respective substance is presented. Also, concentration comparisons between women and men, and patients older or younger than 65 years are made. The drugs included are amitriptyline (n = 394), citalopram (n = 5457), clomipramine (n = 400), escitalopram (n = 3066), fluoxetine (n = 793), fluvoxamine (n = 165), mianserin (n = 1063), mirtazapine (n = 1427), moclobemide (n = 200), nortriptyline (n = 206), paroxetine (n = 1677), reboxetine (n = 85), sertraline (n = 2998), trimipramine (n = 158), and venlafaxine (n = 1781). Of the 9 drugs exhibiting linear (first order) kinetics, all but reboxetine gave a significant negative dose-to-dose-normalized correlation with concentrations, that is an increased clearance with higher dose. When dose was correlated to the metabolite:parent substance ratio for drugs exhibiting linear kinetics, citalopram and mianserin gave a positive slope, contrary to a negative slope shown for sertraline and venlafaxine. The intraindividual variations of the serum concentrations were lower than the overall variations, and the intraindividual variation of the metabolite:parent substance ratio was lower than the intraindividual variation of respective parent substance (except clomipramine and mianserin). Women had significantly higher serum concentrations than men (significant for citalopram, escitalopram, mianserin, mirtazapine, and venlafaxine), and patients older than 65 years had higher serum concentrations than the younger ones for all drugs except amitriptyline, moclobemide, and trimipramine. By presenting a comprehensive compilation of therapeutic drug monitoring data for each drug, a reference tool is created, in addition to improved pharmacokinetic knowledge of antidepressant drugs.

Tesofensine (NS 2330), a monoamine reuptake inhibitor, in patients with advanced Parkinson disease and motor fluctuations: the ADVANS Study.

OBJECTIVE: To assess the safety and efficacy of tesofensine, a triple monoamine reuptake inhibitor, in patients with advanced Parkinson disease (PD). DESIGN: A pilot phase 2, randomized, double-blind, placebo-controlled, parallel-group trial. The study occurred in hospital-based outpatient clinics and in clinical trial units. Patients with advanced PD and levodopa-related motor fluctuations were enrolled. Tesofensine (0.125, 0.25, 0.5, or 1 mg) or placebo tablets were administered once daily for 14 weeks. MAIN OUTCOME MEASURES: Coprimary end points were the changes from baseline in Unified Parkinson Disease Rating Scale (UPDRS) subscale II (activities of daily living) plus subscale III (motor function) total score and in percentage of waking hours spent in "off" time noted in self-scoring diaries. Secondary end points were safety, pharmacokinetics, responder analysis (> or =20% reduction in UPDRS score and in off time), and changes in percentage of waking hours spent in "on" time with and without troublesome dyskinesia. RESULTS: The adjusted mean differences (relative to placebo) were -4.7 points in UPDRS subscale II plus subscale III total score (P =.005) with tesofensine, 0.5 mg, and -7.1% in off time (-68 minutes, P =.02) with tesofensine, 0.25 mg. Other dosages did not induce statistically significant effects. The plasma concentration increased with the dosage, but no clear dose-response relationship was observed. Gastrointestinal tract and neuropsychiatric adverse events were more frequent with tesofensine than with placebo, especially at the higher dosages. CONCLUSIONS: Patients with PD in advanced stages showed modest improvements in UPDRS subscale II plus subscale III total score and in off time when treated with tesofensine, but a dose-response relationship could not be established for efficacy, while adverse drug reactions tended to be more frequent at higher dosages. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00148512.

Distribution of antidepressants between plasma and red blood cells.

OBJECTIVE: The distribution of different antidepressants between plasma and red blood cells (RBCs) or between water and erythrocyte membranes (ghosts) has not been sufficiently compared so far. MATERIALS AND METHODS: Distribution of seven antidepressants (amitriptyline, nortriptyline, imipramine, desipramine, didesmethylimipramine, dothiepin, and citalopram) was measured in vitro in small volumes of blood or erythrocyte membrane suspension using radiolabeled drugs. Blood samples were taken from healthy subjects. RESULTS: The distribution of antidepressants between plasma and RBCs is strongly affected by temperature; however, it does not depend on the antidepressant concentration in the range of their therapeutic concentrations. The data analysis proved that the ratio of RBCs to plasma volume concentrations is the suitable parameter characterizing antidepressant distribution in whole blood. Significantly higher ratios of RBCs to plasma concentrations were found for demethylated metabolites of tricyclic antidepressants and in the case of citalopram. Citalopram showed the highest accumulation in intact RBCs and at the same time the lowest binding to isolated membranes. The binding of drugs to isolated erythrocyte membranes was much higher than in whole blood. CONCLUSION: The concentration ratio of antidepressant in RBCs and in plasma is sensitive not only to the binding properties of plasma proteins and cell membranes, but also to changes in drug molecule, both in aminopropyl chain and in aromatic rings. This ratio is to a large extent characteristic of a particular antidepressant.

DOV 216,303, a "triple" reuptake inhibitor: safety, tolerability, and pharmacokinetic profile.

This report describes the first evaluation in humans of DOV 216,303, a putative antidepressive that inhibits the reuptake of norepinephrine, serotonin, and dopamine. Subjects received single oral doses of 5 to 150 mg of DOV 216,303 or placebo. At 150 mg, 4 of 7 subjects reported gastrointestinal disturbances. In the multiple-dose phase of the evaluation, subjects received total daily doses of 50, 75, or 100 mg of DOV 216,303 or placebo for 10 days. At a total daily dose of 100 mg, gastrointestinal disturbances were reported in 4 of 6 volunteers. In both the single- and multiple-dose evaluations, no significant changes were noted in vital signs, electrocardiogram, hematology, or clinical chemistry. DOV 216,303 was rapidly absorbed (plasma t(max) of 0.7-1.2 hours and t(1/2) of 3.3-4.4 hours), with dose-proportional C(max) and AUC values. Furthermore, no remarkable difference was apparent in either the C(max) or AUC(tau) of DOV 216,303 following 1 and 10 days of dosing. The present results demonstrate that DOV 216,303 is safe and well tolerated both at single doses of up to 100 mg and multiple doses of up to 100 mg/day for 10 days. Plasma concentrations of DOV 216,303 after doses > 10 mg exceed its reported IC(50) values for inhibition of biogenic amine reuptake.

Stereoselective central nervous system effects of the R- and S-isomers of the GABA uptake blocker N-(4, 4-di-(3-methylthien-2-yl)but-3-enyl) nipecotic acid in the rat.

1. The 'effect compartment' model was applied to characterize the pharmacodynamics of the R- and S-isomers of tiagabine in conscious rats in vivo using increase in the beta activity of the EEG as a pharmacodynamic endpoint. 2. No pharmacokinetic differences in plasma were observed between R- and S-tiagabine. The values for clearance and volume of distribution at steady-state were 103+/-10 versus 90+/-6 ml min(-1) kg(-1) and 1.8+/-0.2 versus 1.6+/-0.2 l kg(-1) for the R- and S-isomer, respectively. In contrast, plasma protein binding showed a statistically significant difference with values of the free fraction of 5.7+/-0.5 and 11.4+/-0.6%. In addition the rate constant for transport to the effect compartment was also different with values of 0.027 versus 0.067 min(-1). 3. For both isomers the relationship between concentration and EEG effect was non-linear and successfully characterized on basis of the Hill equation. A statistically significant difference in the value of EC(50) of 328+/-11 versus 604+/-18 ng ml(-1) was observed for R- and S-tiagabine respectively. The values of the other pharmacodynamic parameters were identical. 4. It is concluded that the differences in in vivo pharmacodynamics of R- and S-tiagabine can be explained by stereoselective differences in both the affinity to the GABA-uptake transporter and the degree of non-specific protein binding in plasma and at the effect site.

Hemodynamic and cerebral blood flow effects of cocaine, cocaethylene and benzoylecgonine in conscious and anesthetized fetal lambs.

We studied hemodynamic responses to cocaine and two metabolites, cocaethylene (CE) and benzoylecgonine (BE), in five conscious ewes and fetuses, which were chronically instrumented to measure maternal and fetal aortic pressures, uterine artery blood flow (Qutr) and fetal common carotid artery blood flow (Qcar) to estimate cerebral blood flow. Conscious ewes of 121 to 128 days' (mean, 124 days) gestation received 1.0 mg/kg i.v. of cocaine (n = 12 doses), CE (n = 14) or BE (n = 12) and responses were compared to seven additional ewes and fetuses at 115 to 127 days' (mean, 122 days) gestation each given one 1.0 mg/kg i.v. of cocaine dose while anesthetized with halothane. In conscious ewes, cocaine, CE and BE all caused maternal and fetal hypertension. Qutr decreased 31% after cocaine, increased 37% after CE and was unaffected by BE. Cocaine induced fetal hypoxemia; fetal arterial blood gas tensions were unaffected by CE or BE. Fetal Qcar was reduced 51% at peak effect by cocaine (57 +/- 8 to 28 +/- 6 ml/min) and 46% by CE (65 +/- 7 to 33 +/- 6 ml/min), and was unaffected by BE because of variable subject response, although all three drugs increased calculated fetal cerebral vascular resistance. The cocaine-induced changes were attenuated or abolished in anesthetized sheep. Fetal/maternal peak serum concentrations were 100% for CE and only 2% for BE; amniotic fluid concentrations of CE were 10-fold higher than both fetal and maternal serum concentrations. Cocaine and cocaine metabolites have important effects on maternal and fetal hemodynamics and fetal cerebral blood flow which, for CE and BE, are not dependent on decreased uterine blood flow or fetal hypoxemia.

Analysis of cocaine and metabolites in brain using solid phase extraction and full-scanning gas chromatography/ion trap mass spectrometry.

A method is described for the determination of cocaine, benzoylecgonine and cocaethylene in the human brain using Clean Screen solid phase extraction cartridges and gas chromatography/ion trap mass spectrometry with electron impact and full scan analysis. The procedure uses deuterated internal standards. Run-to-run and within-run coefficients of variation are < 7% and the sensitivity proved to be 50 ng/g from 1 g of sample. The procedure has been applied to a number of forensic cases involving cocaine intoxication. Cocaine was relatively unstable in brain tissue stored at 4 degrees C when compared to storage at -80 degrees C.

Serial plasma concentrations of cocaethylene, cocaine, and ethanol in trauma victims.

Cocaethylene (EC), cocaine (COC), and ethanol (ETOH) concentrations were measured in 46 serial plasma samples from 15 male trauma victims. In all but two patients EC was detected on admission to the hospital. In the remaining two, EC was not detected throughout hospitalization. However, these two patients had the lowest ETOH concentrations in the series (200 and 300 mg/L). Plasma concentrations ranged up to 128 micrograms/L for EC, up to 421 micrograms/L for COC, and up to 5,100 mg/L for ETOH. Ratios of EC to COC concentration (EC/COC) were as high as 4.1. Concentrations of EC showed statistically significant correlation with those of COC (p < 0.01). The plasma half-life (T1/2) of EC was found to be longer than that reported for COC (1 h) and was estimated to be 3.5, 4.5, and 5.5 h in three patients.

Determination of cocaethylene, cocaine and their metabolites in rat serum microsamples by high-performance liquid chromatography, and its application to pharmacokinetic studies in rodents.

A single-solvent extraction step high-performance liquid chromatographic method is described for quantitating cocaethylene in rat serum microsamples (50 microliters), a substance formed in vivo when cocaine and ethanol are present concurrently. The separation used a 2 mm I.D. reversed-phase Nova-Pak C18 column with a mobile phase of acetonitrile-phosphate buffer containing an ion-pairing reagent. With an ultraviolet detector operated at 230 nm, a linear response was observed from 0.05 to 2.0 micrograms/ml with a detection limit of 5 ng/ml for cocaethylene, cocaine and norcocaine. The method showed a longer half-life for cocaethylene than for cocaine in rat.

Column liquid chromatographic assay of the dopamine reuptake inhibitor vanoxerine (GBR 12909) in human serum.

A method for the assay of the dopamine reuptake inhibitor vanoxerine (GBR 12909, I) in human serum is described. Serum was diluted in urea (8 M) and extracted using C18 extraction columns. Compound I was eluted from the columns using methanol containing 1% (v/v) ammonia. The extracts were analysed by high-performance liquid chromatography with fluorescence detection. The limit of quantitation was 2 nM, corresponding to 1.04 ng/ml. Validation of the method showed acceptable recovery, accuracy, precision and specificity. The method has been used for drug assay in several clinical studies of the pharmacokinetics and therapeutic efficacy of compound I.