Determination of mianserin and metabolites in plasma by liquid chromatography with electrochemical detection

The CYP2D6 genotype and plasma concentrations of mianserin enantiomers in relation to therapeutic response to mianserin in depressed Japanese patients

The relationship between therapeutic response to racemic mianserin and steady-state plasma concentrations of S(+)- and R(-)-mianserin was studied in 26 Japanese patients with major depression. The daily dose of mianserin was 30 mg, and the duration of treatment was 3 weeks. Regarding S-mianserin, the proportion of responders (final Montgomery-Asberg Depression Rating Scale score of 10 or less) was significantly higher in the plasma concentration range of 10 to 23 ng/mL than outside (10 of 11 vs. 3 of 15, p = 0.0005). Such a plasma concentration difference between responders and nonresponders was not found for R-mianserin. In 15 patients, the relationships between the CYP2D6 genotype, determined by allele-specific polymerase chain reaction analysis and Escherichia coli RI restriction fragment length polymorphism, plasma concentrations of the enantiomers, and the therapeutic response were studied. Five patients were homozygous for the wild type (wt) allele (wt/wt), nine were heterozygous for the CYP2D6Ch (Ch) allele causing decreased CYP2D6 activity (Ch/wt), and one patient was heterozygous for the Ch allele and the defect allele CYP2D6D (D) (Ch/D). The Ch/wt group showed significantly higher plasma concentrations of S-mianserin (mean +/- SD: 15 +/- 6 vs. 8 +/- 1 ng/mL, p = 0.007) and proportion of responders (8 of 9 vs. 1 of 5, p = 0.023) than the wt/wt group. The patient with the Ch/D genotype had the highest plasma concentration of S-mianserin (37 ng/mL) and a poor response. No significant relationship was found between the CYP2D6 genotype and plasma concentration of R-mianserin. The study presented here thus suggests that the CYP2D6 genotype plays a major role in controlling plasma concentration of the S-enantiomer of mianserin, which contributes to a major extent to the antidepressant effect during mianserin treatment.

Determination of the enantiomers of mianserin, desmethylmianserin, and 8-hydroxymianserin in the plasma and urine of mianserin-treated patients

An HPLC method is presented which allows the measurement in the same run of the enantiomers of mianserin, desmethylmianserin, and 8-hydroxymianserin in plasma and urine of mianserin-treated patients. Limits of quantitation for the (S)- and (R)-enantiomers of mianserin and desmethylmianserin were 4 and 2.5 ng/ml, respectively, in plasma, and for the (S)- and (R)-enantiomers of mianserin, desmethylmianserin, and 8-hydroxymianserin 5, 2.5, and 5 ng/ml, respectively, in urine. The measured ratios of (S)-mianserin/(R)-mianserin and (S)-desmethylmianserin/(R)-desmethylmianserin in the plasmas of 10 mianserin-treated patients, all extensive metabolizers of debrisoquine as determined by CYP2D6 genotyping, varied, respectively, from 1.0 to 4.06 and from 0.19 to 0.64. As the enantiomers of mianserin differ in their pharmacological profile, these results could partially explain why, until now, no consistent relationship has been established between the therapeutic response and total [(S) + (R)] plasma levels of this antidepressant.

Automated high-performance liquid chromatographic method for the determination of mianserin in plasma using electrochemical detection

An automated high-performance liquid chromatographic method for the determination of mianserin in plasma is described. Extraction and injection of the samples were automatically done by the Gilson ASPEC system using C8, 100-mg Supelclean solid-phase extraction columns. The extracts were chromatographed on a reversed-phase C18 column (150 mm x 3.9 mm I.D.) with a phosphate buffer-acetonitrile-methanol mobile phase and the analytes detected electrochemically. Calibration curves were linear to at least 53.7 ng/ml at which the between-day relative standard deviation was 5% and the recovery 101%. The limit of quantification was 1.67 ng/ml at which the between-day relative standard deviation was 9% and the recovery 92% using a sample volume of 0.5 ml. The method was applied to the determination of mianserin in the plasma of normal human volunteers participating in a comparative bioavailability study.

A sensitive method for assay of a novel tricyclic compound using coulometric electrochemical detection

A reversed-phase high-performance liquid chromatographic method using coulometric electrochemical detection in the oxidative mode has been developed for the analysis of 3-(9-chloro-5,6-dihydro-11-H-pyrrolo[2,1-b][3]benzazepine-11-ylidene- N,N-dimethyl-1-propanamine(E)-Z-butenedioate hydrogen maleate (1) in plasma of patients dosed with 2-8 mg/kg/d of the drug. Concentrations as little as 0.1 ng/mL of 1 in plasma can be estimated with a mean coefficient of variation of 7.4 +/- 1.08%. The utility of the procedure was demonstrated by the analysis of 500 patient samples from a rising multiple-dose study.

Plasma melatonin levels in depressed patients before and after treatment with antidepressant medication

Daytime melatonin was measured by radioimmunoassay in 113 depressed outpatients before and after treatment with imipramine, mianserin, phenelzine, and placebo. At baseline, elevation of daytime melatonin values above expected levels suggests nonspecificity of the assay. After 6 weeks of treatment, melatonin levels were somewhat lower in patients on imipramine, mianserin, and placebo and slightly increased in patients treated with phenelzine. Changes in melatonin levels during treatment were significantly different for phenelzine compared with the other treatments. These findings are consistent with alterations in beta-adrenergic functioning or changes in serotonin levels.

Implications of chirality and geometric isomerism in some psychoactive drugs and their metabolites

Many drugs contain a chiral centre, or such a centre is introduced during metabolism of the drug in man and in animals. If a single chiral centre is present, the drug will normally exist as a mixture of two enantiomers, of which one may have quite different pharmacologic and/or toxic effects than the other. Chiral drugs that are used in psychiatry, and some other pharmacologically related drugs are identified, and the implications of the presence of one or two chiral centres in these drugs are discussed. Differences in pharmacologic properties of drug and metabolite enantiomers are identified and discussed. Also reviewed are the properties of some drugs used in psychiatry that both are chiral and display geometric isomerism.

Determination of clomipramine and its hydroxylated and demethylated metabolites in plasma and urine by liquid chromatography with electrochemical detection

A procedure for the determination of clomipramine and its 8-hydroxy, demethyl, 8-hydroxydemethyl and didemethyl metabolites in plasma and urine by high-performance liquid chromatography with electrochemical detection is described. A 1-ml plasma or urine sample is made alkaline with a carbonate buffer (pH 9.8) and extracted with 20% ethyl acetate in n-heptane. After back-extraction into an acid phosphate buffer (pH 2.4), an aliquot is injected into a 5-microns ion-paired reversed-phase column and eluted with a mobile phase containing a phosphate buffer with tetramethylammonium chloride-acetonitrile (57:43). The detection is coulometric with a first cell at +0.40 V, a second at +0.73 V and a guard cell set at 0.75 V for oxidation of the mobile phase. The method provides recoveries in the general range of 80-110% and a day-to-day precision of 3.7-8.8%, depending on the compound. The minimum quantifiable level for all compounds was 0.2 ng/ml with a 20-microliters injection. Steady-state plasma concentration data and urinary levels are reported for 24 depressed patients receiving daily either 75-150 mg orally or 50-75 mg by infusion.

HPLC of trazodone in serum after microscale protein precipitation

Trazodone, an anti-depressant medication, is found in serum in the 500-1000 ng/mL range in patients taking therapeutic doses. Because of this relatively high concentration, it has been possible to devise an HPLC assay system using the rapid, convenient microscale procedure described previously by Lam et al. (Clin. Chem. 26, 963 1980) to prepare the sample for chromatography. To 0.1 mL serum were added 0.1 mL acetonitrile and 10 microL of 10% zinc sulfate in water. The mixture was centrifuged and 50 microL of the clear supernatant was injected into a reversed-phase column which was eluted with 65% 0.05 M potassium phosphate-35% acetonitrile, with detection by ultraviolet absorbance at 210 nm. The trazodone elutes in 6 min, clearly resolved from endogenous interferences. The recovery of trazodone added to serum was better than 90%. Peak height was proportional to concentrations in the serum sample from 125 ng/mL to 3000 ng/mL.

Drug level monitoring: chromatography of some minor groups of drugs

Some important facts about the chromatographic separation of a number of selected categories of drugs are summarized. The data refer to the chromatographic method of choice, stationary phase, mobile phase (carrier gas), detection procedure and (where available) method sensitivity. Also, fundamental instrumental parameters, namely injector, column and detector temperature, carrier gas and mobile phase flow-rate and gradient set-up are reported here. In all cases also the source material used for analysis is specified. The data are presented in table form, each table dealing with a particular category of drugs. The following categories of drugs are being dealt with: anthelmintics, antiarteriosclerotics, antibacterials, anticholinergics and cholinergics, anticoagulants, antidiabetics, antiemetics, antimycotics, antihistamines, antimalarials, antiparasitics, antiparkinsonics, antitussives, antiulcer drugs, antiviral compounds, appetite depressants and immunosuppressives.

Analysis of tricyclic antidepressant drugs in plasma and serum by chromatographic techniques

A review of methods for the determination of tricyclic antidepressants in plasma or serum, based on the application of chromatographic techniques, is presented. A general discussion of the techniques in terms of their precision, accuracy, sensitivity and selectivity, with respect to parent drug and metabolites, is used to facilitate a comparison of methods. No one technique can be claimed as the method of choice for these drugs, although gas-liquid chromatography with nitrogen selective detection has some strong claims, viz. generally good sensitivity and reproducibility of assays and ready availability of equipment in most laboratories. The ultimate choice of a method for determining tricyclics will be determined more by the clinical application (routine monitoring versus pharmacokinetics) than by other factors.

Adrenoreceptor interactions of the enantiomers and metabolites of mianserin: are they responsible for the antidepressant effect?

Mianserin is a tetracyclic antidepressant whose postulated mechanism of action involves release of noradrenaline mediated via cortical alpha 2-adrenergic autoreceptor blockade. This property resides stereoselectively in the S(+)-enantiomer of mianserin, which is also more potent in behavioural tests indicative of antidepressant activity, and in the reversal of clonidine-induced effects. Cortical receptor binding studies have indicated that although a similar stereoselectivity prevails for the inhibition of both alpha 2-binding (clonidine) and alpha 1-binding (prazosin), mianserin and its enantiomers are more potent antagonists at alpha 2- than at alpha 1-binding sites. However, no stereoselectivity is apparent for the antagonism of cortical alpha 2-heteroreceptors controlling serotonin release. Following chronic administration, (+/-)- and S(+)-mianserin, but not the R(-)-enantiomer, produce functional supersensitivity at alpha 2-autoreceptors which is unaccompanied by changes in clonidine binding. Neither mianserin nor its enantiomers alter the sensitivity of alpha 2-heteroreceptors following chronic administration. Like mianserin and its S(+)-enantiomer, but unlike R(-)-mianserin and the 8-hydroxy metabolite, the desmethyl metabolite inhibits noradrenaline uptake in vitro. 8-hydroxymianserin and, to a lesser extent, desmethylmianserin release noradrenaline from cortical slices via alpha 2-autoreceptor antagonism, but only the 8-hydroxy metabolite blocks alpha 2-autoreceptors and alpha 2-heteroreceptors in synaptosomal preparations. It is likely that S(+)-mianserin, desmethylmianserin, and 8-hydroxymianserin contribute substantially to the overall facilitating effect of mianserin on noradrenergic transmission in vivo. As yet it is unclear whether this effect is exclusively responsible for the antidepressant activity of mianserin or whether the stereoselectivity also shown by the mianserin enantiomers towards serotonin receptors plays a complementary role.

Determination of chlorprothixene and its sulfoxide metabolite in plasma by high-performance liquid chromatography with ultraviolet and amperometric detection

This communication describes a rapid, sensitive and selective method for the assay of chlorprothixene and its sulfoxide metabolite in human plasma, using reversed-phase high-performance liquid chromatography. Alkalinized plasma was extracted with heptane--isoamyl alcohol (99:1), after addition of thioridazine as the internal standard. The residue obtained after evaporation of this extract was chromatographed on a cyano column, using acetonitrile--0.02 M potassium dihydrogen phosphate pH 4.5 (60:40) as the mobile phase with ultraviolet (229 nm) detection. Quantitation was based on peak height ratios over the concentration range of 5.0-50.0 ng/ml for both compounds with 85% and 90% recovery for chlorprothixene and its sulfoxide metabolite, respectively, using a 1.0-ml plasma sample. The assay chromatographically resolves chlorprothixene and the sulfoxide metabolite from the N-desmethyl metabolite, which can only be semi-quantitated owing to low and variable recoveries. The method was used to obtain plasma concentration versus time profiles in two subjects after oral administration of 100 mg of chlorprothixene suspension and in two additional subjects following overdosages of chlorprothixene estimated to exceed several hundred milligrams. These analyses demonstrated that the sulfoxide metabolite is the predominant plasma component following therapeutic administration and overdosages. High-performance liquid chromatography with oxidative amperometric detection with the glassy carbon electrode was also evaluated. Although this procedure demonstrated comparable sensitivity and precision to ultraviolet detection for the analysis of chlorprothixene and N-desmethyl chlorprothixene, the sulfoxide metabolite could not be measured with high sensitivity (less than 100 ng/ml) owing to endogenous interferences. Hence the utility of this alternative assay technique is limited.

Determination of trimipramine and metabolites in plasma by liquid chromatography with electrochemical detection

A procedure for the determination of trimipramine, the demethyl, 2-hydroxy, and 2-hydroxy demethyl metabolites in plasma by liquid chromatography with electrochemical detection is described. A 1-mL plasma sample is made alkaline with a carbonate buffer (pH 9.8) and extracted with 20% ethyl acetate in n-heptane. After back-extraction into an acid phosphate buffer, an aliquot is injected onto a reverse-phase trimethylsilyl-packed column and eluted with a phosphate buffer-acetonitrile mobile phase (65:35) containing n-butylamine. The peaks were detected at +1.1 V versus the silver-silver chloride reference electrode. The method provides absolute recoveries of 60-91% and a day-to-day precision of less than 9% for all compounds. The minimum quantifiable level for all compounds was 3 ng/mL. Steady-state plasma concentration data for 29 depressed patients receiving either 75 mg or 150 mg/d is reported.