Plasma levels and tricyclic antidepressant therapy: Part I. A review of assay methods

Response surface methodology in the development of a stacking-sensitive capillary electrophoresis method for the analysis of tricyclic antidepressants in human serum

Stacking methods are very important in overcoming the poor detection limits in capillary electrophoresis (CE). In this paper, the separation and determination of several tricyclic antidepressants by a stacking method is described. The inclusion of acetonitrile (ACN) in the sample causes stacking (transient pseudoisotachophoresis) especially in presence of sodium chloride. An experimental design (central composite design) together with the response surface methodology has been used to find the optimum composition of the separation buffer and the optimal stacking conditions in few experiments. The response functions used are the product of the total resolution by the number of peaks, for the optimization of the separation buffer, and the product of the total resolution by the mean of the peak heights, for the optimization of the stacking conditions. About 28% of the capillary volume is loaded with sample. The calibration curves are linear over the working range (50-300 ng/mL). With a bubble capillary, the limits of detection (LODs) are in the order of 5 ng/mL. For the analysis of serum samples, enrichment with sodium chloride and the protein precipitation with ACN are enough to avoid interferences and to get stacking. Recoveries between 91.6 and 104% and RSD between 0.6 and 12% are obtained in the analysis of samples of lyophilized human serum and non-lyophilized human serum, spiked with the drugs.

Structural and concentration effects on the deposition of tricyclic antidepressants in human hair

In order to elucidate the possibility of a long-term compliance analysis the hair samples of 56 patients, who were under a permanent treatment with tricyclic antidepressants, were analyzed for amitriptyline, clomipramine, doxepine, imipramine and maprotiline as well as their nor-metabolites. The hair concentrations varied between 0.4 and 40 ng/mg with no strong difference between the five drugs. In comparison to the therapeutic plasma levels described in literature the nor-metabolites always accumulate less in hair than drugs. No correlation was found between the hair concentration and the daily dose. The investigation of the full hair length in 3-cm sections for several examples of all five drugs shows that they can be detected in normally kept hair at least 1 year after intake.

Dual ultraviolet wavelength high-performance liquid chromatographic method for the forensic or clinical analysis of seventeen antidepressants and some selected metabolites

A sensitive method suitable for the determination of tricyclic and other antidepressants in postmortem and clinical specimens is presented. The procedure, which utilizes reversed-phase HPLC combined with dual ultraviolet wavelength detection, enables the separation of 17 commonly prescribed antidepressants and some selected metabolites in a single extraction. Peak purity was confirmed using absorbance ratios at 220 nm and 254 nm wavelengths and revealed little interference from other eluting analytes. The blood detection limit for most antidepressants was 50 ng/ml. The most commonly observed antidepressants in 281 forensic cases analysed over a two-year period with the described method were dothiepin, amitriptyline, nortriptyline and doxepin.

Drug level monitoring: antidepressants

The determination of antidepressant drugs which act by blocking neuronal uptake of biogenic amines, because of their widespread use and high toxicity, remains one of the most commonly requested drug assays in clinical laboratories. Easy to use immunoassay reagents for the estimation of these drugs are commercially available. However, immunoassays have not been universally accepted because of high probability of these reagents producing false negative and false positive results. At present, column liquid chromatography with absorbance detection and coupled with solid-phase extraction is the most viable technique for a general procedure for the identification and determination of these drugs. The technique of liquid chromatography is economical, environmental friendly since water-miscible and biodegradable solvents can be used for extraction of drugs and their chromatographic separation, and amenable to full automation. New techniques of separation, such as supercritical fluid chromatography and capillary zone electrophoresis, have not yet been applied for the determination of therapeutic concentrations of antidepressants.

Determination of the tricyclic compound adosupine and its three metabolites in plasma and brain of rat using high-performance liquid chromatography

An analytical method for the detection in biological samples of the novel tricyclic compound adosupine (10-acetoamido-5-methyl-5,6-dihydro-11H-dibenzo[b,e]azepin-6 ,11-dione), which is capable of influencing various forms of urinary bladder hyperreflexia has been developed using high-performance liquid chromatography with UV detection. Liquid-liquid extraction was used to isolate the parent compound, three metabolites and an analogue (added as internal standard) from plasma and brain of rat. Adosupine was well separated from its three metabolites with 0.01 M disodium hydrogenphosphate-acetonitrile-methanol-nonylamine (59.986:38:2:0.014) at pH 4.5 as mobile phase using a C18 reversed-phase column. The standard curves were linear in the range 50-5000 ng/ml (or ng/g) for adosupine and metabolites in both plasma and brain. The between- and within-assay variations for high and low concentrations of the parent compound and the three metabolites were 8.2-14%. In the range 50-5000 ng/ml (or ng/g) the accuracy of the method was satisfactory, with the relative error always lower than 10%. Analytical recoveries of added adosupine and the three metabolites were higher than 82%. The method has been applied successfully, to investigate the pharmacokinetics of the drug and its distribution in the central nervous system of rats.

Antidepressants in serum determined by isolation with two on-line sorbent cartridges and liquid chromatography

A selective method for measuring tricyclic antidepressants in serum is reported. A single assay can be done within ca. 30 min and eight samples can be assayed in less than 150 min. A 1-ml serum sample was diluted and the drugs were extracted from it by passage through a graphitized carbon black (Carbopack B) cartridge. After one washing, this cartridge was connected on line to another one containing a silica-based strong acid exchanger. The tricyclics were removed from the Carbopack surface and selectively readsorbed onto the cation-exchange surface by passing 4 ml of methylene chloride-methanol (60:40, v/v) through the two cartridges. After another wash, the drugs were desorbed from the cation-exchange surface with 0.8 ml of acetonitrile-methanol-water (72:18:10, v/v) saturated with potassium chloride. An aliquot of this solution was chromatographed on a cyano column, and the absorbance of the effluent was measured at 215 nm. The mean analytical recoveries of tricyclic antidepressants added to serum within the range 10-200 micrograms/l exceeded 90%, except for 8-hydroxyamoxapine (mean recovery 85.3%) and amoxapine (mean recovery 83.8%) at the lowest serum concentration considered.

Gas chromatographic-mass spectrometric assessment of the pharmacokinetics of amineptine and its main metabolite in volunteers with liver impairment

A pharmacokinetic study of amineptine (Survector) and its C5 metabolite, resulting from a beta-oxidation of the heptanoic acid side-chain, was undertaken with ten human volunteers, who received a single 100-mg tablet of amineptine orally. They were affected with liver impairment in order to determine if this situation would alter greatly the pharmacokinetic parameters. The internal standard was the octanoic acid homologue. Analyses were carried out by gas chromatography (GC) and GC-mass spectrometry using TMS ester derivatives. Plasma samples were extracted using a C18 reversed-phase cartridge at pH 4.0. Mass fragmentographic measurements on the plasma samples were performed on the m/z ions (M + H)+ and (base peak)+ using ammonia chemical ionization. The global evaluation of precision was good and the coherence between the two modes of measurements, (base peak)+ and (M + H)+ ions, gave a regression factor r close to unity. For amineptine the total body clearance and mean residence time were accurate and precise with eight volunteers, but only four volunteers showed such coherent data for the slope of the elimination curve, beta, and half-life. However, the beta value, half-life and mean residence time of the C5 metabolite were accurate and precise with seven, eight and ten volunteers, respectively. It is concluded that the drug was still detoxified at normal levels.

Determination of metapramine, imipramine, trimipramine and their major metabolites in plasma by reversed-phase column liquid chromatography

The determination of metapramine, imipramine, trimipramine and their desmethyl metabolites after alkaline diethyl ether extraction from plasma is achieved by column liquid chromatography using two internal standards and mu Bondapak C18 column. Elution is carried out isocratically at 1 or 0.6 ml min-1 with two mixtures of acetonitrile-potassium dihydrogen phosphate-distilled water (45:55:10 for metapramine and its metabolites; 45:50:5 for imipramine, trimipramine and their metabolites). Detection is monitored by absorption at 254 nm. The detection limit is less than 5 ng ml-1 for each compound. The coefficients of variation (within-day and day-to-day) for the eight compounds are less than 11.3%. Interference from several possible co-medications is discussed. The technique can be used for routine therapeutic monitoring of the antidepressants as well as analytical toxicology. However, the three antidepressants cannot be analysed simultaneously by this method because metapramine requires a different elution system and imipramine interferes with monodesmethyltrimipramine (retention times 8.90 and 8.60 min, respectively).

Useful sample handlings for reversed phase high performance liquid chromatography in emergency toxicology

Some physicochemical treatments of biological samples, before being injected into a liquid chromatograph, are discussed. The advantages of dilution, liquid and solid extraction are compared referring mainly to unpublished results. Assays of antiepileptic drugs, caffeine, theophylline, tricyclic antidepressants, valproic acid, and meprobamate are used to demonstrate the importance of sample handlings in toxicological analyses in which reversed phase high performance liquid chromatographies are applied.

Determination of tricyclic antidepressant drugs by gas chromatography with the use of a capillary column

A universal gas chromatographic procedure for the determination of the commonly prescribed tricyclic antidepressant drugs in 1 mL of plasma is described. After the addition of internal standards the samples are washed with pentane at acidic pH and extracted with pentane at alkaline pH. The pentane extract is evaporated after the addition of acetic anhydride. Aliquots of a methanolic solution of the residue of evaporated extract are analyzed isothermally on a Durabond 30 m fused silica column. This column is well suited for use with a nitrogen selective detector. The liquid phase is not extracted by repeated injections of methanolic solutions of plasma extracts. When compared to a packed column, this column allows shorter analysis time.

Sensitive assay for the tricyclic antidepressant Ro 11-2465 in biological fluids by high-performance liquid chromatography and fluorescence detection

A high-performance liquid chromatographic assay, suitable for pharmacokinetic studies, has been developed for the new tricyclic antidepressant Ro 11-2465, at present under clinical investigation. For concentrations above 0.5 ng/ml, the method involves a simple extraction at basic pH with an organic solvent followed by direct chromatography of this extract on a silica gel column using fluorescence detection. For concentrations below 0.5 ng/ml, an extensive clean-up procedure is required. In both procedures, however, evaporation of the extract and reconstitution of the residue is avoided. The detection limit, using 1 ml of plasma, is about 0.1 ng/ml. This sensitivity is sufficient for following single-dose kinetics of Ro 11-2465 in man.

Metabolic oxidation of desmethylchlorimipramine in vitro by 9000 g rabbit-liver preparations

1. The metabolism of desmethylchlorimipramine (I) has been investigated in vitro using fortified 9000 g liver homogenates of male rabbits. 2. Four metabolic products: N-hydroxydesmethylchlorimipramine (II), 3-(3-chloro-10, 11-dihydro-5H-dibenz[b,f]azepin-5-yl)propanoic acid (III), 10/11-hydroxydesmethylchlorimipramine (IV) and 2/8-hydroxydesmethylchlorimipramine (V) were isolated and identified by electron-impact mass spectrometry and n.m.r. spectroscopy. 3. Desmethylchlorimipramine (I) undergoes both N- and alpha-carbon oxidation in addition to aromatic and alicyclic carbon oxidation.