Metabolite O-desmethylvenlafaxine Research Articles

Serum concentrations of venlafaxine and its metabolites O-desmethylvenlafaxine and N-desmethylvenlafaxine in heterozygous carriers of the CYP2D6*3, *4 or *5 allele

Increased systemic exposure of the antidepressant venlafaxine and increased risk of side effects has previously been observed in patients with defective CYP2D6 function [poor metabolisers (PMs)]. The aim of this study was to evaluate venlafaxine pharmacokinetics in carriers of one functional and one defective CYP2D6 allele [heterozygous extensive metabolisers (HEMs)]. Data was collected retrospectively from a therapeutic drug-monitoring database. All CYP-genotyped patients with steady-state serum concentration measurements of venlafaxine and metabolites were included in the study. Patients were divided in groups: *1/*1 [homozygous extensive metabolisers (EMs)], *1/*3, *4 or *5 (HEMs) and *4/*4 (PMs). Dose-adjusted serum concentrations of venlafaxine, O-desmethylvenlafaxine, N-desmethylvenlafaxine, and the metabolic ratio (O-desmethylvenlafaxine/venlafaxine) were compared between the different genotype groups. The sum of venlafaxine and O-desmethylvenlafaxine serum concentrations was not significantly different between genotype groups. Metabolic ratio was 50% lower in HEMs (n = 18) than in EMs (n = 20) (p < 0.05). Serum concentration of N-desmethylvenlafaxine was 5.5-fold higher in HEMs (p < 0.01) and 22-fold higher in PMs (p < 0.001) than in EMs. The study showed a shift in the metabolic pathway resulting in substantially higher levels of N-desmethylvenlafaxine in HEMs than in EMs. The metabolic pattern of venlafaxine in HEMs was similar to previous observations in PMs and possibly represents an increased risk of venlafaxine-related side effects in HEM patients.

Pharmacokinetic/Pharmacodynamic Modelling of Venlafaxine

Venlafaxine and its major active metabolite O-desmethylvenlafaxine selectively inhibit serotonin and norepinephrine reuptake from the synaptic gap. The inhibition of norepinephrine uptake is assumed to enhance antidepressant efficacy when venlafaxine is given at higher therapeutic doses. Thus investigation of the concentration-response relationship of noradrenergic effects is of clinical interest. We used pupillography as a test system for the pharmacodynamic response to venlafaxine, since it had been shown to be useful for assessment of noradrenergic effects on the autonomous nervous system. The aim of the study was to develop a pharmacokinetic/pharmacodynamic model by means of nonlinear mixed-effects modelling in order to describe the time course of the noradrenergic response to venlafaxine. Twelve healthy male subjects received venlafaxine 37.5 mg or placebo orally twice daily for 7 days and subsequently 75 mg or placebo twice daily for another 7 days. After a 14-day washout phase, the two groups were crossed over. After the last dose of venlafaxine or placebo on day 14, blood samples were drawn to determine venlafaxine and O-desmethylvenlafaxine concentrations and the amplitude and recovery time of the pupillary light reflex were measured. A pharmacokinetic/pharmacodynamic model was developed to describe the data using nonlinear mixed-effects modelling. The pharmacokinetic part of the model could be simultaneously fitted to both venlafaxine and O-desmethylvenlafaxine data, yielding precise parameter estimates that were similar to published data. The model detected high variability of the intrinsic clearance of venlafaxine (94.8%), most likely due to cytochrome P450 2D6 polymorphism. Rapid development of tolerance of the pupillary light reflex parameters was seen and could be successfully accounted for in the pharmacodynamic part of the model. The half-life of development and regression of tolerance was estimated to be 30 minutes for the amplitude and 40 minutes for the recovery time. The time course of the effect and the concentration-response relationship were successfully described by a pharmacokinetic/pharmacodynamic model that takes into account the rapid development of tolerance of pupillary light reflex parameters. This provides a basis for further investigations of the applicability of pupillography as a surrogate measurement of the effectivity of antidepressant drugs with norepinephrine reuptake-inhibiting properties.

Analysis of the second generation antidepressant venlafaxine and its main active metabolite O-desmethylvenlafaxine in human plasma by HPLC with spectrofluorimetric detection

A high-performance liquid chromatographic method has been developed for the determination of the recent serotonin and norepinephrine reuptake inhibitor (SNRI) venlafaxine and its main active metabolite, O-desmethylvenlafaxine, in human plasma. Separation was obtained by using a reversed-phase column (C8, 150 × 4.6 mm I.D., 5 μm) and a mobile phase composed of 75% aqueous phosphate buffer containing triethylamine at pH 6.8 and 25% acetonitrile. Fluorescence detection was used, exciting at λ = 238 nm and monitoring the emission at λ = 300 nm. Citalopram was used as the internal standard. A careful pre-treatment of plasma samples was developed, using solid-phase extraction with C1 cartridges (100 mg, 1 mL). The limit of quantification (LOQ) was 1.0 ng mL −1 and the limit of detection (LOD) was 0.3 ng mL −1 for both analytes. The method was applied with success to plasma samples taken from patients undergoing treatment with venlafaxine. Precision data, as well as accuracy results, were satisfactory and no interference from other drugs was found. Hence, the method is suitable for therapeutic drug monitoring of venlafaxine and its main metabolite in depressed patients’ plasma.

Employing atmospheric pressure photoionization in liquid chromatography/tandem mass spectrometry to minimize ion suppression and matrix effects for the quantification of venlafaxine and O‐desmethylvenlafaxine

During the development of a method for quantitative determination of venlafaxine and its major metabolite O-desmethylvenlafaxine, elevated concentrations of the analyte as well as co-eluting matrix compounds caused ion suppression. This ion suppression was inconsistent and therefore influenced the reproducibility of detection. The use of atmospheric pressure photoionization (APPI) in the positive mode was investigated as a tool to circumvent this problem. Employing APPI resulted in negligible ion suppression and increased linearity of the concentration range. A selective, sensitive and rapid liquid chromatography/tandem mass spectrometry method for the determination of venlafaxine and its major metabolite O-desmethylvenlafaxine in human plasma was developed. The analyte was extracted from plasma into tert-butyl methyl ether followed by back extraction into 2% formic acid. An Agilent 1100 high-performance liquid chromatography (HPLC) system, employing reversed-phase chromatography on a cyano column, coupled to an Applied Biosystems API 3000 triple quadrupole mass spectrometer set to multiple reaction monitoring (MRM) mode, was used for separation and detection of the analytes. The method was validated between 2.36-605 ng per mL with a mean recovery of approximately 88% for both parent compound and metabolite analytes. APPI technology was employed to improve the reproducibility of detection enabling rapid, selective and sensitive quantification of venlafaxine and O-desmethylvenlafaxine in human plasma samples.

High performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-MS/ESI) method for simultaneous determination of venlafaxine and its three metabolites in human plasma

A high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-MS/ESI) method for simultaneous determination of venlafaxine (VEN) and its three metabolites O-desmethylvenlafaxine (ODV), N-desmethylvenlafaxine (NDV) and N, O-didesmethylvenlafaxine (DDV) in human plasma has been developed and validated. Estazolam was used as the internal standard. The compounds and internal standard were extracted from plasma by a liquid–liquid extraction. The HPLC separation of the analytes was performed on a Thermo BDS HYPERSIL C 18 (250 mm × 4.6 mm, 5 μm, USA) column, using a gradient elution program with solvents constituted of water (ammonium acetate: 30 mmol/l, formic acid 2.6 mmol/l and trifluoroacetic acid 0.13 mmol/l) and acetonitrile (60:40, V/V) at a flow-rate of 1.0 ml/min. All of the analytes were eluted within 6 min. The compounds were ionized in the electrospray ionization (ESI) ion source of the mass spectrometer and were detected in the selected ion recording (SIR) mode. Calibration curves in spiked whole blood were linear from 4.0–700 ng/ml, 2.0–900 ng/ml, 3.0–800 ng/ml and 2.0–700 ng/ml for VEN, ODV, NDV and DDV, respectively, all of them with coefficients of determination above 0.9991. The average extraction recoveries for all the four analytes were above 77%. The methodology recoveries were higher than 91%. The limits of detection were 0.4, 0.2, 0.3, and 0.2 ng/ml for VEN, ODV, NDV and DDV, respectively. The intra- and inter-day variation coefficients were less than 11%. The method is accurate, sensitive and reliable for the pharmacokinetic study of venlafaxine as well as therapeutic drug monitoring (TDM).

Simultaneous stereoselective analysis of venlafaxine and O-desmethylvenlafaxine enantiomers in human plasma by HPLC-ESI/MS using a vancomycin chiral column

A high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI/MS) method for simultaneous stereoselective analysis of venlafaxine (VEN) and its major metabolite O-desmethylvenlafaxine (ODV) enantiomers in human plasma has been developed and validated. Chiral chromatography is performed on the CHRIOBIOTIC V ™ (5 μm, 250 mm × 4.6 mm) column with mobile phase constituted of 30 mmol/l ammonium acetate–methanol (15:85, pH 6.0) at a flow rate of 1.0 ml/min and a postcolumn splitting ratio of 3:1. The compounds were ionized in the electrospray ionization (ESI) ion source of the mass spectrometer and detected using the selected ion recording (SIR) mode. Calibration curves obtained from spiked plasma were linear in the range of 5.0–400 ng/ml for S-(+)-VEN and R-(−)-VEN, 4.0–280 ng/ml for S-(+)-ODV and R-(−)-ODV, respectively, with linear correlation coefficient all above 0.999. The average extraction recoveries for all the four analytes were above 76%. The methodology recoveries were higher than 92%. The limit of detection were 1.0 ng/ml for S-(+)-VEN and R-(−)-VEN, 1.5 ng/ml for S-(+)-ODV and R-(−)-ODV, respectively. The intra- and inter-day variation coefficients were less than 9%.

CYP2D6 genotype and venlafaxine‐XR concentrations in depressed elderly

The elderly are at increased risk for medication-related adverse events. Recent reports indicate that venlafaxine may put the elderly at increased risk of cardio- and cerebrovascular adverse events. We investigated the relationship between the CYP2D6 polymorphism and steady-state plasma concentration of venlafaxine (VEN) and its primary metabolite o-desmethylvenlafaxine (ODV) in elderly participants receiving venlafaxine-XR for major depression in order to explore the contribution of pharmacogenetics to medication tolerability. Forty-six elderly participants received venlafaxine-XR for the treatment of major depression. CYP2D6 genotype and steady-state plasma levels of VEN and ODV were determined. Sixty-five percent of participants were homozygous of the wild type (WT) allele, whereas 35% carried one or more variant alleles associated with intermediate and poor 2D6 metabolizer status. VEN concentration per unit dose was significantly higher and ODV concentration per unit dose was significantly lower in participants who carried one or more variant alleles compared to participants who were homozygous for the WT allele. The VEN and ODV concentrations per unit dose were also correlated with creatinine clearance. CYP2D6 genotype was not associated with medication associated side-effects. Plasma dose-corrected concentrations of VEN and ODV correlated with genetically determined CYP2D6 enzymatic activity in depressed elders treated with venlafaxine-XR. This relationship was not masked by the effects of age-related illness or polypharmacy. Future clinical application of pharmacogenetics to examine 2D6-dependent medications may help reduce the incidence of medication adverse events particularly in those elders at higher risk for medication adverse events due to impaired renal or cardiac function.

Interference By Venlafaxine Ingestion in the Detection of Tramadol By Liquid Chromatography Linked to Tandem Mass Spectrometry for the Screening of Illicit Drugs in Human Urine

Confirmation of the presence of illicit drugs in human fluids by liquid chromatography linked to atmospheric pressure ionisation tandem mass spectrometry (LC/MS/MS) is becoming increasingly popular. A rapid LC/MS/MS method is described using reversed phase gradient elution chromatography on a 50 × 3 mm base deactivated C8 column with identification of drugs based on their Multiple Reaction monitoring (MRM) transitions, retention time, and co-elution of stable isotopic analogues where available. The method is used for drug confirmation following initial screening by immunoassay, and identification of drugs such as tramadol, for which no immunoassay is available. False positive results for tramadol were observed in cases where subjects were being treated with the commonly prescribed antidepressant drug venlafaxine. This was a result of the presence of the metabolite O-desmethylvenlafaxine, which has a similar transition to tramadol. This study highlights the need to consider drug metabolites, as well as parent drugs in interferences in LC/MS/MS methods.

Liquid chromatography–tandem mass spectrometry (LC–MS–MS) method for simultaneous determination of venlafaxine and its active metabolite O-desmethyl venlafaxine in human plasma

A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS-MS) method has been developed and validated for simultaneous quantification of venlafaxine (VEN) and O-desmethyl venlafaxine (ODV) in human plasma. The analytes were extracted from human plasma by using solid-phase extraction (SPE) technique. Escitalopram (ESC) was used as the internal standard. A Betasil C18 column provided chromatographic separation of analytes followed by detection with mass spectrometry. The mass transition ion-pair has been followed as m/z 278.27-->121.11 for VEN, m/z 264.28-->107.10 for ODV and m/z 325.00-->262.00 for ESC. The method involves a solid phase extraction from plasma, simple isocratic chromatography conditions and mass spectrometric detection that enables detection at nanogram levels. The proposed method has been validated with linear range of 3-300 ng/ml for VEN and 6-600 ng/ml for ODV. The intrarun and interrun precision and accuracy values are within 10%. The overall recoveries for VEN and ODV were 95.9 and 81.7%, respectively. Total elution time as low as 3 min only.

Quantification of venlafaxine and O-desmethylvenlafaxine in human serum using HPLC analysis

We describe an isocratic reversed-phase liquid chromatographic method for the determination of venlafaxine (VLX) and its main active metabolite O-desmethylvenlafaxine (ODV) in serum, using haloperidol as internal standard and liquid/liquid extraction for sample preparation. VLX and ODV were separated on a C18 column with a mobile phase of acetonitrile/buffer (30/70, v:v) at 60 degrees C and a flow rate of 1.5 ml/min. The measurement of the native fluorescence signals of the eluted compounds were carried out at 227/300 nm (excitation/emission) without interference from endogenous components in serum. High linearities for VLX and ODV for concentrations between 20 and 500 microg/l were obtained (r = 0.9997). A large spectrum of routinely prescribed drugs did not interfere in the assay. The coefficients of variation for repeatability varied between 5.40% and 5.99% and for reproducibility between 9.43% and 21.63%. Absolute recoveries were more than 52% for both substances.

Efficacy and tolerability of venlafaxine in geriatric outpatients with major depression: a double‐blind, randomised 6‐month comparative trial with citalopram

The objectives of the study were to compare efficacy and tolerability of venlafaxine ER 75-150 mg/day with that of citalopram 10-20 mg/day in elderly patients with major depression according to DSM-IV criteria. A randomised, double-blind, parallel group 6-month study. Efficacy was assessed by MADRS, CGI Global Improvement, CGI Severity of Illness and GDS-20 scores and safety by physical examinations, vital signs, adverse events and UKU side effect rating. Plasma levels of venlafaxine, its major metabolite O-desmethylvenlafaxine and citalopram were followed. One hundred and fifty-one male and female patients (64-89 years) were enrolled and 118 patients completed the study. Comparable improvements in MADRS, CGI Severity of Illness, CGI Global Improvement and GDS-20 were observed during venlafaxine and citalopram treatment. The MADRS remission rate was 19% for venlafaxine and 23% for citalopram. Side effects were common during both treatments but differed in tremor being more common during citalopram and nausea/vomiting during venlafaxine treatment. There were no clinically significant changes in blood pressure or body weight. The observed benefits of venlafaxine treatment in elderly patients with major depression were similar to those observed in younger adults as were reported adverse events and side effects. Treatment with venlafaxine ER was well tolerated and induced beneficial effects of similar magnitude as those of citalopram.

Use of vancomycin silica stationary phase in packed capillary electrochromatography: II. Enantiomer separation of venlafaxine and O-desmethylvenlafaxine in human plasma

A capillary electrochromatography method, using vancomycin chiral stationary phase packed capillary, was optimized for the simultaneous chiral separation of the antidepressant drug venlafaxine and its main active metabolite O-desmethylvenlafaxine. Simultaneous baseline enantiomeric separation of the two compounds was obtained using a mobile phase composed of 100 mM ammonium acetate buffer pH 6/water/acetonitrile (5:5:90, v/v). The electrokinetic injection for sample introduction provided a limit of quantitation for both the compounds of 0.05 μg/ml racemate concentration suitable for the analysis of venlafaxine and metabolite in biological samples. The acetonitrile mobile phase concentration was found to modulate the analytes elution times, the enantiomeric resolution and the efficiency of the separation. The column was tested for repeatability and linearity showing RSD values (%) in the range of 0.13–0.24, 2.47–3.66 and 1.35–2.50 for migration time, sample/internal standard peak area ratio and enantiomeric resolution, respectively and correlation coefficients higher than 0.9990. The method was applied to the analysis of clinical samples of patients under depression therapy showing a stereoselective metabolism for venlafaxine.

Rapid determination of venlafaxine and O-desmethylvenlafaxine in human plasma by high-performance liquid chromatography with fluorimetric detection

A rapid and sensitive high-performance liquid chromatographic technique for simultaneous measurement of plasma venlafaxine (VEN) and its active metabolite O-desmethylvenlafaxine (ODV) is described. The process begins with the extraction of VEN and ODV, with maprotiline (MAP) as internal standard, from human plasma into an intermediate organic mixture of hexane–isoamyl alcohol and finally into an aqueous solution of 0.05% phosphoric acid. Isocratic separation of VEN, ODV and MAP is carried out by utilizing a reversed-phase butyl-bonded column (C 4/E) with mobile phase consisting of acetonitrile and 40 m M phosphate buffer, pH 6.8 (50:50, v/v). Detection of VEN, ODV and MAP is done by mean of fluorimetry with excitation and emission wavelengths set at 276 and 598 nm, respectively. As low as 1.0 ng/ml VEN is detectable; while the limit of detection for ODV is 5 ng/ml. C.V. (%) of intra-day samples for both VEN and ODV are less than 10% at three concentrations tested (10.0, 50.0, 100.0 ng/ml). Similarly, over the same nominal concentrations, the precision of inter-day (5 days) samples also results in C.V. (%) smaller than 10% for both compounds, except for ODV measured at 10 ng/ml (C.V.<15%). Approximately, 100% VEN can be extracted from plasma; whereas, for ODV the recovery rate is nearly 70%. This present method is rapid, sensitive, accurate and simple for routine clinical monitoring of plasma VEN and its major metabolite ODV.

Pharmacokinetics of once-daily venlafaxine extended release in healthy volunteers

Three pharmacokinetic studies were performed to assess the effects of food intake and morning versus evening administration of once-daily venlafaxine extended release (XR) on the pharmacokinetic disposition of venlafaxine and its active metabolite O-desmethylvenlafaxine (ODV). Forty-six healthy adults (43 men and 3 women), 18 to 45 years of age with body weight within 15% of normal for height and frame, were enrolled in these studies. In two studies, venlafaxine XR 75-mg or 150-mg capsules were administered to healthy subjects in fasting state or after a high-fat breakfast. In a third study, once-daily venlafaxine XR 75 mg was administered for 4 days (to steady state) either in the morning or in the evening. All three studies were conducted with a two-period crossover study design, and the plasma samples were assayed using high-performance liquid chromatography for the concentrations of venlafaxine and ODV. The steady-state pharmacokinetic profile of venlafaxine XR was not affected by the time of administration (morning or evening), and the single-dose pharmacokinetic profile was not affected by the presence or absence of food. Therefore, the venlafaxine XR formulation exhibits a controlled rate of release, and administration of venlafaxine XR with a high-fat meal does not produce a dose-dumping effect. Based on the results of these studies in healthy volunteers, once-daily venlafaxine XR 75 or 150 mg may be given without regard to meals and once-daily venlafaxine XR 75 mg may be taken either in the morning or evening without affecting the pharmacokinetic disposition of or systemic exposure to venlafaxine and ODV.

The effect of renal disease on the disposition of venlafaxine

The pharmacokinetics of venlafaxine and its active metabolite O-desmethylvenlafaxine were studied in subjects with various degrees of renal dysfunction, including subjects requiring maintenance hemodialysis. Venlafaxine was administered as a single 50 mg dose, with blood and urine samples obtained at intervals up to 48 hours after administration for the subjects receiving dialysis or 72 hours for the subjects not receiving dialysis. Six subjects receiving dialysis also completed an intradialysis evaluation to estimate dialysis clearance. Concentrations of venlafaxine and O-desmethylvenlafaxine in plasma, urine, and dialysate fluid were determined by high-performance liquid chromatography. Apparent total clearance of venlafaxine and O-desmethylvenlafaxine were both significantly decreased by approximately 55% in the subjects receiving dialysis, and terminal disposition half-life was significantly prolonged for both compounds. Venlafaxine and O-desmethylvenlafaxine are poorly dialyzable. In conclusion, the disposition of venlafaxine and O-desmethylvenlafaxine is markedly altered in renal disease; therefore dosage adjustment is warranted for patients with creatinine clearance values below 30 ml/min.