Simultaneous plasma level analysis of clomipramine, N-desmethylclomipramine, and fluvoxamine by reversed-phase liquid chromatography

Therapeutic Drug Monitoring of Antidepressants and Cytochrome P450 Genotyping in General Practice

In the psychiatric setting, therapeutic drug monitoring and genotyping for cytochrome P450 (CYP) polymorphisms help to ensure and maintain therapeutic drug levels. In this study, the authors extended the therapeutic drug monitoring and genotyping protocol routinely used in their psychiatric clinic to primary care patients treated with antidepressants. They examined the variation in serum concentrations and assessed the role of CYP polymorphisms, wrong dosing, and noncompliance in deviating serum concentrations. Of 227 serum concentrations obtained, 127 (56%) were more than 20% outside therapeutic ranges. Of these 127 cases, 64 (50%) were congruous with aberrant CYP2D6 or CYP2C19 genotypes, incorrect dosing, or a pharmacy record suggesting noncompliance. Prevalence of aberrant CYP2D6 and CYP2C19 genotypes did not differ significantly between the investigated primary care patients and 751 secondary care users of antidepressants. The therapeutic drug monitoring and the genotyping findings resulted in recommendations to physicians to alter the medication strategy of 146 (64%) patients. These results strongly suggest that the rationale for therapeutic drug monitoring and CYP genotyping when prescribing antidepressants in secondary care also applies to the primary care setting.

Plasma fluvoxamine levels and OCD symptoms/response in adult patients

OBJECTIVE

In this study, we explored the possible relationships between plasma fluvoxamine levels and clinical features and/or response in adult obsessive-compulsive disorder (OCD) patients treated with this drug for 6 months.

METHODS

Twenty OCD outpatients of both sexes who were already taking fluvoxamine (mean dose ± SD: 216.7 ± 86.2) for at least 4 weeks were included in the study. The severity of OCD was assessed by means of the Yale-Brown obsessive-compulsive scale (Y-BOCS). The fluvoxamine plasma levels were measured by high-performance liquid chromatography analysis. All evaluations were performed after 4 weeks (t1) and 6 months (t2) of fluvoxamine intake.

RESULTS

The plasma levels of fluvoxamine remained stable at the two assessment times, with no sex-related differences. Sixteen (80%) patients responded to treatment as shown by the significant (>35%) decrease of the Y-BOCS total score. Men's compulsions improved more than those of women. Significant and positive correlations were detected between fluvoxamine plasma levels at t1 and t2 and the difference (delta) of the Y-BOCS total and compulsion subscale scores between t1 and t2. Another significant, albeit negative, correlation was measured between the difference of the compulsion subscale score and the difference of fluvoxamine levels at t1 and t2.

CONCLUSIONS

These findings underline the potential importance of evaluating fluvoxamine plasma levels in OCD and their relationships with the clinical response that may be gender-related on specific symptoms.

HPLC method for the determination of fluvoxamine in human plasma and urine for application to pharmacokinetic studies

A simple, specific and sensitive high-performance liquid chromatographic (HPLC) method has been developed for the assay of fluvoxamine in human plasma and urine. The method was based on reaction of fluvoxamine with 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS) forming orange colored product. The fluvoxamine-NQ derivative was separated by isocratic reversed-phase HPLC and detected at 450 nm. The chromatographic conditions were as follows: Phenomenex C(18) (250 mm x 4.6 mm i.d., 5 microm) column, mobile phase consisting of acetonitrile/water (80:20 v/v) at a flow rate of 1 ml/min. Tryptamine was selected as an internal standard. The assay was linear over the concentration range of 5-145 and 2-100 ng/ml for plasma and urine, respectively. The limits of detection (LOD) were 1.4 and 1 ng/ml for plasma and urine estimation at a signal-to-noise (S/N) ratio of 3. The limits of quantification (LOQ) were 5 and 2 ng/ml for plasma and urine, respectively. The extraction recoveries were found to be 96.66+/-0.69 and 96.73+/-2.17% for plasma and urine, respectively. The intra-day and inter-day standard deviations (S.D.) were less than 1. The method indicated good performance in terms of specificity, linearity, detection and quantification limits, precision and accuracy. This assay was demonstrated to be applicable for clinical pharmacokinetic studies.

Pharmacokinetics of clomipramine and desmethylclomipramine after single-dose intravenous and oral administrations in cats

A cross-over study was performed in six adult spayed cats to determine the pharmacokinetics of clomipramine and its metabolite, desmethylclomipramine (DCMP) after intravenous (0.25 mg/kg) and oral (0.5 mg/kg) single-dose administrations. Plasma clomipramine and DCMP were measured by high-performance liquid chromatography at regular intervals for up to 30 h. Intravenous clomipramine best fit a two-compartmental model yielding an elimination rate constant of 0.037-0.09 h(-1) from which a mean half-life of 12.3 h was calculated. Mean clomipramine AUC(0--infinity) (ngxh/mL), clearance (L/hxkg), V(ss) (L/kg) and MRT (h) values were 652.5, 0.393, 5.0, and 13.5, respectively. Compartmental modeling for clomipramine, after oral administration, and DCMP after both administrations, produced wide parameter estimates and plots of residuals indicated poor goodness of fit. Noncompartmental analysis yielded mean AUC(0--30 h) (ngxh/mL), C(max) (ng/mL) and T(max) (h) of 948.3, 87.5 and 6.2 for clomipramine, and 613.8, 34.8, and 12.8 for DCMP respectively after oral administration. Clomipramine bioavailability was 90%. The present study showed marked pharmacokinetic variability for clomipramine and DCMP through biphasic absorption and potential genetic variability in clomipramine metabolism. It was concluded that population pharmacokinetics would allow better characterization of clomipramine variability that may explain the variability in clinical response noted in cats.

Electroanalytical study of fluvoxamine

Fluvoxamine (FVX) can be reduced at a mercury-drop electrode, with a maximum peak current intensity being obtained at a potential of -0.7 V vs. Ag/AgCl, in an aqueous electrolyte solution of pH 2. The compound was determined in a pharmaceutical product and in spiked human serum by square-wave adsorptive-stripping voltammetry (SWAdSV) after accumulation at the electrode surface, under batch conditions. Because the presence of dissolved oxygen did not interfere significantly with the analysis, it was also possible to determine FVX in the pharmaceutical product by use of a flow-injection analysis (FIA) system with SWAdSV detection. The methods developed were validated and successfully applied to the quantification of FVX in a pharmaceutical product. Recoveries between 76 and 89% were obtained in serum analysis. The FIA-SWAdSV method enabled analysis of up to 120 samples per hour at reduced cost, implying the possibility of competing with the chromatographic methods usually used for this analysis.

Determination of fluvoxamine and its metabolite fluvoxamino acid by liquid–liquid extraction and column-switching high-performance liquid chromatography

This study describes a new simultaneous determination of fluvoxamine and fluvoxamino acid by automated column-switching high-performance liquid chromatography. The test compounds were extracted from 1.5 ml of plasma using chloroform-toluene (15:85, v/v), and the extract was injected into a hydrophilic metaacrylate polymer column for clean-up and a C18 analytical column for separation. The mobile phase for separation consisted of phosphate buffer (0.02 M, pH 4.6), acetonitrile and perchloric acid (60%) (62.4:37.5:0.1, v/v/v) and was delivered at a flow rate of 0.6 ml/min. The peak was detected using a UV detector set at 254 nm. The method was validated for the concentration range 0.8-153.6 ng/ml for fluvoxamine and 0.6-115.2 ng/ml for fluvoxamino acid, and their good linearity (r > 0.998) were confirmed. Intra-day coefficient variations (CVs) for fluvoxamine and fluvoxamino acid were less than 6.6 and 6.0%, respectively. Inter-day CVs for corresponding compounds were 6.3 and 6.5%, respectively. Relative errors ranged from -18 to 9% and mean recoveries were 96-100%. The limit of quantification was 1.2 and 0.9 ng/ml for fluvoxamine and fluvoxamino acid, respectively. This method shows successful application for pharmacokinetic studies and therapeutic drug monitoring.

Therapeutic drug monitoring of 13 antidepressant and five neuroleptic drugs in serum with liquid chromatography-electrospray ionization mass spectrometry

Therapeutic drug monitoring of antipsychotic drugs has become more and more important in recent years, and a well-organized therapeutic drug monitoring service with fast turn-around times is very important. Therefore, an analytical method coupling high-performance liquid chromatography to mass spectrometry with electrospray ionization in the positive mode was established in our laboratory. Amitriptyline, citalopram, clomipramine (including norclomipramine), desipramine, dibenzepin, doxepin (including nordoxepin), escitalopram, flupentixol, fluphenazine, fluvoxamine, imipramine, nortriptyline, opipramol, pipamperone, reboxetine, thioridazine, trimipramine and zuclopenthixol were separated on a reversed-phase C18 column. The mobile phase consisted of acetonitrile and ammonium acetate buffer pH 4. Because of different organic solvents used for the liquid-liquid extraction and the different volumes of mobile phases in which the residues were dissolved, four analytical systems had to be applied. Within the run-time of maximal 10 minutes the 13 antidepressant and five neuroleptic drugs were baseline separated on the corresponding mass-to-charge track. The calibration range of each drug was linear, all between-day coefficients of variation were below 7% and the recovery rates were between 60 and 103%. Using 1 ml of serum, the lower limits of quantification were between 1.2 and 54 nmol/l for the different drugs and below the therapeutic range for each of the different drugs.

Simultaneous analysis of clozapine, clomipramine and their metabolites by reversed-phase liquid chromatography

1. The authors present here a sensitive and rapid reversed-phase liquid chromatographic method which enables the simultaneous analysis in plasma of two different drugs and their metabolites: the atypical neuroleptic clozapine and the tricyclic antidepressant clomipramine. 2. Samples and the internal standard (dibenzepine) were extracted through automated solid-phase procedure, evaporated dryness and injected into the chromatograph. Mobile phase was a mixture of water and acetonitrile (63:37, v:v) containing TEMED and triethylamine. The total chromatographic time was of 14 min and analyte peaks were detected by means of an ultraviolet spectrophotometer preset at 254 nm. 3. Results revealed an assay sensitivity of 5 microg/L for clozapine or norclozapine and of 10 microg/L for clomipramine and desmethylclomipramine. Recoveries for these drugs and their metabolites were more than 60% and their coefficient of variation (within day and day-to-day) ranged from 1.3 % to 2.5 %. In spiked plasma, within day and day-to-day coefficients of variability (CV) were less than 5%. The simultaneous evaluation of these two drugs with adequate sensitivity and precision makes it particularly useful for therapeutic drug monitoring during mono- or polypharmacotherapy.