0000000000018645
AUTHOR
Harald Weigmann
Micellar electrokinetic capillary chromatography for therapeutic drug monitoring of carbamazepine and its main metabolites.
In carbamazepine (CBZ) therapy the concomitant monitoring of concentrations of CBZ and its metabolites is strictly recommended, primarily to avoid toxic side effects. Currently, clinical routine monitoring of CBZ is accomplished by high-performance liquid chromatography or immunological methods. In this study a micellar electrokinetic capillary chromatographic (MECC) method was developed for routine drug monitoring of CBZ and its main metabolites, carbamazepine 10,11-diol and carbamazepine 10,11-epoxide, in human serum or plasma samples. The MECC method enabled baseline separation of all analytes within 2.5 min. The assay revealed sufficient precision and sensitivity and the results of eith…
Automated determination of reboxetine by high-performance liquid chromatography with column-switching and ultraviolet detection.
A fully automated method including column-switching and isocratic high-performance liquid chromatography (HPLC) was developed for quantitative analysis of the new antidepressant reboxetine, a noradrenaline reuptake inhibitor. After serum injection into the HPLC system and on-line sample clean-up on a silica C8 (10x4.0 mm I.D.) clean-up column with an eluent consisting of 2.5% acetonitrile in deionized water, the chromatographic separation was performed on an analytical column (Lichrospher CN; 250x4.6 mm I.D.) with an eluent of acetonitrile-aqueous potassium phosphate buffer (0.008 M, pH 6.4) (50:50). The UV detector was set at 273 or 226 nm. The limit of quantification was about 15 ng/ml at…
Fishing for a drug: solid-phase microextraction for the assay of clozapine in human plasma
Solid-phase microextraction (SPME) was investigated as a sample preparation method for assaying the neuroleptic drug clozapine in human plasma. A mixture of human plasma, water, loxapine (as internal standard) and aqueous NaOH was extracted with a 100-micron polydimethylsiloxane (PDMS) fiber (Supelco). Desorption of the fiber was performed in the injection port of a gas chromatograph at 260 degrees C (HP 5890; 30 m x 0.53 mm I.D., 1 micron film capillary; nitrogen-phosphorous selective detection). Fibers were used repeatedly in up to about 75 analyses. The recovery was found to be 3% for clozapine from plasma after 30 min of extraction. However, in spite of the low recovery, the analyte was…
Differential Effects of Fluvoxamine and Other Antidepressants on the Biotransformation of Melatonin
Melatonin, the predominant product of the pineal gland, is involved in the maintenance of diurnal rhythms. Nocturnal blood concentrations of melatonin have been shown to be enhanced by fluvoxamine, but not by other serotonin reuptake inhibitors. Because fluvoxamine is an inhibitor of several cytochrome P450 (CYP) enzymes, the authors studied the biotransformation of melatonin and the effects of fluvoxamine on the metabolism of melatonin in vitro using human liver microsomes and recombinant human CYP isoenzymes. Melatonin was found to be almost exclusively metabolized by CYP1A2 to 6-hydroxymelatonin and N-acetylserotonin with a minimal contribution of CYP2C19. Both reactions were potently in…
Combination treatment with clozapine and paroxetine in schizophrenia: safety and tolerability data from a prospective open clinical trial.
Clozapine is a drug with many side effects, some of them with potentially hazardous outcome (e.g. seizures, agranulocytosis), if not carefully monitored. It has been shown that the metabolism of clozapine may be affected by concomitant treatment with selective serotonin reuptake inhibitors (SSRIs), while there have been reports of improved efficacy on negative symptomatology of clozapine in combination with SSRIs. Therefore, this prospective open clinical trial was performed to investigate the safety and tolerability of the coadministration of clozapine and paroxetine under control of serum concentrations of clozapine and its metabolites and the effect of this combination treatment on psych…
Automated determination of clozapine and major metabolites in serum and urine.
Clozapine is an atypical neuroleptic that is increasingly used for the treatment of schizophrenia. An automated method was developed for the routine quantification of clozapine and its major metabolites, N-desmethylclozapine and clozapine N-oxide, in human serum and urine by column switching and online high-performance liquid chromatography with ultraviolet detection. The method included adsorption of clozapine and its metabolites on a cyanopropyl-coated clean-up column (10 microns; 10 mm x 4.0 mm ID), washing interfering serum constituents to waste by deionized water, and, after column switching, separation on C18 ODS Hypersil reversed-phase material (5 microns; 250 mm x 4.6 mm ID). The co…
Fluvoxamine augmentation of olanzapine in chronic schizophrenia: pharmacokinetic interactions and clinical effects.
Olanzapine is a substrate of the cytochrome P450 enzyme (CYP) 1A2. In this study, pharmacokinetic interactions and clinical effects of adding the CYP1A2 inhibitor fluvoxamine to steady-state olanzapine was examined in patients suffering from schizophrenia. Eight patients had been treated for at least 3 months with 10 to 20 mg/day olanzapine. Fluvoxamine (100 mg/day) was added (week 0) to the olanzapine treatment and continued for 8 weeks. Concentrations of olanzapine and its metabolite N-desmethylolanzapine and of fluvoxamine were analyzed at weeks 0, 1, 4, and 8. Addition of fluvoxamine resulted in a 12% to 112% (0.01) increase of olanzapine from 31 +/- SD 15 ng/mL (week 0) to 56 +/- 31 ng…
Pharmacokinetic Interactions of Clozapine With Selective Serotonin Reuptake Inhibitors
Pharmacokinetic interactions of clozapine and its metabolites N-desmethylclozapine and clozapine N-oxide with the selective serotonin reuptake inhibitors (SSRIs) fluvoxamine and paroxetine were investigated in a prospective study in schizophrenic patients under steady-state conditions. Thirty patients were treated with clozapine at a target dose of 2.5 to 3.0 mg/kg of body weight. After gradual dose escalation, serum concentrations of clozapine and two metabolites were determined twice at 7-day intervals after steady-state conditions had been reached. Then, fluvoxamine (50 mg/day) or paroxetine (20 mg/day) was added in 16 and 14 patients, respectively. Serum concentrations of clozapine and …
Therapeutic drug monitoring of tricyclic antidepressants: how does it work under clinical conditions?
Therapeutic drug monitoring (TDM) of tricyclic antidepressants (TCA) is established in the treatment of depression to optimize outcome and safety. However, there are few reports on TDM under naturalistic clinical conditions. In the present study, we investigated a TDM group (TDM) and a randomly assigned parallel group without TDM (no-TDM) while on TCA treatment. Serum levels were analyzed in both cohorts, but feedback and dose recommendation were only provided for the TDM group. Serum levels of TCA were assessed by high-performance liquid chromatography (HPLC). The outcome was measured weekly using the Hamilton Depression Rating Scale (HAMD), the Clinical Global Impressions Scale (CGI), and…
Distribution of clozapine and desmethylclozapine between blood and brain in rats.
Desmethylclozapine is the major metabolite of clozapine in serum. Although the metabolite is pharmacologically active in vitro, the occurrence of desmethylclozapine in brain under steady-state conditions and its role for clinical actions of clozapine are unclear. In this study 20 male Sprague-Dawley rats received five oral doses of clozapine 20 mg/kg at 1.5-h intervals. At 0.5, 1, 2 and 5 h after the last administration, at a time four animals were killed for analysis of clozapine and desmethylclozapine concentrations in serum and brain. The treatment yielded steady-state serum concentrations of clozapine that are considered as therapeutically effective in man. Desmethylclozapine concentrat…
Automated determination of amisulpride by liquid chromatography with column switching and spectrophotometric detection.
A fully automated chromatographic method including on-line blood serum or plasma clean-up, isocratic high-performance liquid chromatography (HPLC) and spectrophotometric detection was developed for quantitative analysis of the new antipsychotic drug amisulpride. After injection of serum or plasma onto the HPLC system and clean-up on a pre-column (10x4.0 mm I.D.) filled with Silica CN 20 micrometer (pore size 10 nm) by an eluent consisting of 8% acetonitrile in deionized water, the chromatographic separation was performed on Lichrospher CN (5 micrometer; 250x4.6 mm I.D.) by an eluent consisting of 50% acetonitrile and 50% aqueous potassium phosphate buffer (0.008 M, pH 6.4). The UV detector …
Chronic oral haloperidol and clozapine in rats: A behavioral evaluation.
The present study evaluated chronic oral treatment of rats with haloperidol or clozapine. Drugs were given in the drinking water for a 23-day period . Rat behavior was analyzed once a week in an open field. Rats ingested either 1.7 mg/kg haloperidol or 40 mg/kg clozapine daily. Blood serum analysis revealed concentrations of 6 ng/ml for haloperidol and 22 ng/ml for clozapine at the end of the treatment. Haloperidol decreased overall activity from the onset of treatment. Clozapine showed similar effects only on the last test day. Control animals showed a slight habituation in exploration-related parameters. In conclusion, these results indicate that oral drug administration through the drink…
Randomized, placebo-controlled, double-blind and open-label studies in the treatment and prevention of acute diarrhea with Enterococcus faecium SF68
Enterococcus faecium SF68® (SF68) is a licensed pharmaceutical for treatment and prevention of diarrhea in Austria, Italy and Switzerland. However, as for other probiotics, evidence for its efficacy is based on small to medium-sized studies. Four unpublished studies on the treatment of acute diarrhea and the prevention of antibiotic-associated diarrhea were analyzed: one randomized, double blind, placebo-controlled trial (RCT) for treatment (n = 1,143), one open-label study for treatment (n = 5,093), one RCT for prevention (n = 1,397) and one open-label study for prevention (n = 4,340). Patients in the treatment-arm and the open-label studies received SF68 (b.i.d. for the prevention studies…
Fluvoxamine but not sertraline inhibits the metabolism of olanzapine: evidence from a therapeutic drug monitoring service.
Therapeutic drug monitoring data of the new atypical neuroleptic drug olanzapine were used to study interactions with the selective serotonin reuptake inhibitors fluvoxamine and sertraline. The distribution of the ratio of concentration/daily dose (C/D; ng/mL per mg/d) of olanzapine was compared in three groups: patients treated with olanzapine (n = 134), patients treated with olanzapine plus fluvoxamine (n = 10) concomitantly, and patients treated with olanzapine plus sertraline (n = 21) concomitantly. No significant difference was seen between the olanzapine and the olanzapine plus sertraline groups. Patients receiving fluvoxamine in addition to olanzapine had C/D ratios that were in the …
Addition of Low-Dose Fluvoxamine to Low-Dose Clozapine Monotherapy in Schizophrenia: Drug Monitoring and Tolerability Data from a Prospective Clinical Trial
Combining fluvoxamine and clozapine may be a strategy to improve therapeutic effects on negative symptoms in schizophrenic patients. Fluvoxamine, however, markedly inhibits the metabolism of clozapine, and hazardous side effects may result. This study prospectively investigated the safety and tolerability of an add-on therapy with fluvoxamine to a clozapine monotherapy in schizophrenic patients. Sixteen schizophrenic patients received 50 mg fluvoxamine as a comedication after having reached steady-state conditions under clozapine monotherapy. Patients were monitored for subjective adverse events, laboratory parameters, EEG and ECG recordings, orthostatic hypotension and their psychopatholog…
Simultaneous determination of olanzapine, clozapine and demethylated metabolites in serum by on-line column-switching high-performance liquid chromatography.
An automated method for simultaneous routine quantification of the antipsychotic drugs clozapine, olanzapine and their demethylated metabolites is described. The method included adsorption on a cyanopropyl (CPS) coated clean-up column (10 microm; 10 x 2.0 mm I.D.), washing off interfering serum constituents to waste, and separation on C18 ODS Hypersil reversed phase material (5 microm; 250 x 4.6 mm I.D.) using acetonitrile-water-tetramethylethylenediamine (37:62.6:0.4, v/v/v) adjusted to pH 6.5 with concentrated acetic acid. UV-detection was performed at 254 nm. The limit of quantification was 10-20 ng/ml. Relative day to day standard variations ranged between 4.5 and 13.5%. The method is s…
Chronical haloperidol and clozapine treatment in rats: Differential RNA display analysis, behavioral studies and serum level determination
1. Adult, female rats were treated orally for 23 days with 1.6 mg/kg haloperidol or 36 mg/kg clozapine per day, to study chronic effects of the two neuroleptics. 2. At five time points during the neuroleptic treatment, animal behavior was recorded in an open field and locomotive activity was analysed. At the end of the experiment, rats were decapitated, blood samples were collected and serum concentrations of haloperidol and clozapine were determined by a radioreceptor or HPLC assay, respectively. RNA was isolated from each brain, without cerebellum, and subjected to differential RNA display. 3. Mean serum concentrations were 8 ng/ml for haloperidol and 21 ng/ml for clozapine. Analysis of o…
Automated determination of clomipramine and its major metabolites in human and rat serum by high-performance liquid chromatography with on-line column-switching
A fully automated method including column-switching and isocratic high-performance liquid chromatography (HPLC) was developed for simultaneous determination of the tricyclic antidepressant clomipramine and its metabolites demethylclomipramine, 2-, 8-, and 10-hydroxyclomipramine, 2-, and 8-hydroxydemethylclomipramine and didemethylclomipramine in serum. After serum injection into the HPLC system and on-line sample clean-up on a clean-up column (Hypersil CN; 10 x 4.6 mm) by an eluent consisting of 35% acetonitrile and 65% deionized water, the chromatographic separation was performed on an analytical column (LiChrospher CN; 250 x 4.6 mm I.D.) by an eluent consisting of 38% acetonitrile and 62%…
Increased bioavailability of oral melatonin after fluvoxamine coadministration*1
Background Fluvoxamine, a selective serotonin reuptake inhibitor, is known to elevate melatonin serum concentrations. It has not been clear whether these effects might be attributed to an increased melatonin production or to an decreased elimination of melatonin. The latter hypothesis was tested by this study. Methods Five healthy male volunteers (one CYP2D6 poor metabolizer) received 5 mg melatonin either with or without coadministration of 50 mg fluvoxamine. Serum concentrations of melatonin and fluvoxamine were assessed from 0 to 28 hours after melatonin intake. Results Coadministration of fluvoxamine, on average, led to an 17-fold higher (P <.05) area under concentration–time curve (AUC…
Steady state concentrations of clomipramine and its major metabolite desmethylclomipramine in rat brain and serum after oral administration of clomipramine.
Twenty male Sprague-Dawley rats received five oral doses of clomipramine 20 mg/kg at 4-h intervals. The animals were decapitated 1, 2, 3, 5 and 12 h after the last dose for determination of clomipramine and desmethylclomipramine in serum and frontal cerebral cortex. Time dependent concentrations of clomipramine and desmethylclomipramine paralleled in serum and brain. Half-lives were similar in serum and brain with 7.8 versus 6.2 h and 5.5 versus 5.0 h for clomipramine and desmethylclomipramine, respectively. Absolute concentrations, however, were markedly higher in brain than in serum - 12.5 fold for clomipramine and 7.4 fold for desmethylclomipramine. The data indicate that serum and brain…