Simultaneous determination of duloxetine and 4-hydroxy duloxetine glucuronide in human plasma and back-conversion study.

Aim: To develop an LC-MS/MS method for simultaneous determination of duloxetine and its metabolite, 4-hydroxy duloxetine glucuronide (4HDG) in human plasma and to investigate the potential back-conversion of 4HDG to duloxetine using stability study. Materials & methods: The LC-MS/MS method was validated according to the EMA and USFDA Bioanalytical Method Validation Guidelines and applied to pilot bioequivalence study. Results & conclusion: The method validation results were within the acceptance limits. The stability study and incurred sample reanalysis results ruled out the occurrence of back-conversion. The study highlighted the conduct of back-conversion test and the advantages of LC-MS/MS method in terms of sensitivity, specificity and low consumption of organic solvents.

A rapid LC-MS/MS method for simultaneous determination of quetiapine and duloxetine in rat plasma and its application to pharmacokinetic interaction study.

Combinations of new antidepressants like duloxetine and second-generation antipsychotics like quetiapine are used in clinical treatment of major depressive disorder, as well as in forensic toxicology scenarios. The drug-drug interaction (DDI) between quetiapine and duloxetine is worthy of attention to avoid unnecessary adverse effects. However, no pharmacokinetic DDI studies of quetiapine and duloxetine have been reported. In the present study, a rapid and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for simultaneous determination of quetiapine and duloxetine in rat plasma. A one-step protein precipitation with acetonitrile was applied for sample preparation. The analytes were eluted on an Eclipse XDB-C18 column using the mixture of acetonitrile and 2 mM ammonium formate containing 0.1% formic acid at a gradient elution within 6.0 min. Quantification was performed in multiple-reaction-monitoring mode with the ion transitions m/z 384.4 â†’ 253.2 for quetiapine, m/z 298.1 â†’ 154.1 for duloxetine and m/z 376.2 â†’ 165.2 for IS (haloperidol), respectively. Good linearity was obtained in the range of 0.50-100 ng/mL for quetiapine (r2 = 0.9972) and 1.00-200 ng/mL for duloxetine (r2 = 0.9982) using 50 µL of rat plasma, respectively. The method was fully validated with accuracy, precision, matrix effects, recovery and stability. The validated data have met the acceptance criteria in FDA guideline. The method was applied to a pharmacokinetic interaction study and the results indicated that quetiapine had significant effect on the enhanced plasma exposure of duloxetine in rats under combination use. This study could be readily applied in therapeutic drug monitoring of major depressive disorder patients receiving such drug combinations.

Duloxetine plasma level and antidepressant response.

BACKGROUND: Major Depressive Disorder (MDD) is associated with a high rate of inadequate treatment response, which is mainly due to the large inter-individual genetic variability in pharmacokinetic and pharmacodynamic targets of antidepressant drugs. Little is still known about the exact association between plasma level of first-line antidepressants and clinical response. This is particularly true for duloxetine, a dual serotonin and norepinephrine reuptake inhibitor recommended as first-line treatment for MDD. The aim of this study was to investigate the association between serum concentration of duloxetine (SCD) and antidepressant response (AR). METHODS: 66 MDD patients treated with duloxetine 60 mg/day monotherapy were recruited in an outpatient setting and followed for three months. Hamilton Depression Rating Scale - 21 (HAMD-21) was administrated at baseline, at month 1, and at month 3 to assess AR. SCD was measured at steady state. Linear regression analysis and nonlinear least-squares regression were used to estimate association between SCD and AR. RESULTS: SCD showed a high inter-individual variability in our sample, despite the duloxetine fixed oral dosage. We found a strong association between SCD and AR following a bell-shaped function at month 1 and at month 3. Nonetheless, within the recommended SCD range of 30-120 ng/mL a more linear correlation between SCD and AR was observed. DISCUSSION: Our results suggest that for duloxetine the association between SCD and AR likely follows a bell-shaped quadratic function with poor AR at subtherapeutic SCD and progressive decrease of AR at higher SCD. The maximum antidepressant efficacy seems to require SCD values next to the highest recommended SCD (30-120 ng/mL), probably because of the optimal saturation of both serotonin and norepinephrine transporters. Thus, taking into account the observed high interindividual variability of SCD, our findings suggest that for MDD patients treated with duloxetine, SCD could be a useful tool to guide the treatment by optimizing the oral dosage in order to increase the AR rate.

Effects of Magnesium Oxide on the Serum Duloxetine Concentration and Antidepressant-Like Effects of Duloxetine in Rats.

Duloxetine is a serotonin/noradrenaline reuptake inhibitor that is used as an antidepressant. However, it is known to cause constipation as a side effect. Magnesium compounds, such as magnesium oxide and magnesium hydroxide aqueous solution, are often combined with duloxetine to ameliorate the constipation caused by duloxetine. However, there is concern that these magnesium compounds might alter the effects of duloxetine via physicochemical interactions. In this study, we attempted to clarify the interactions that take place between duloxetine and magnesium oxide using in vivo and in vitro experiments. We evaluated the influence of magnesium oxide on in vitro duloxetine concentrations using HPLC. In addition, we examined the in vivo antidepressant-like effects and serum concentrations of duloxetine in rats. In the in vitro experiment, the duloxetine concentration was significantly decreased by co-treatment with magnesium oxide. In the in vivo experiment, the antidepressant-like effects of duloxetine were not affected by the combined oral administration of magnesium oxide and a duloxetine formulation although the serum duloxetine level was significantly decreased. However, the antidepressant-like effects of a duloxetine reagent were significantly attenuated by the co-administration of magnesium oxide. These results suggest that duloxetine and magnesium oxide directly interact and that such interactions affect the absorption and antidepressant-like effects of duloxetine.

Differences in Duloxetine Dosing Strategies in Smoking and Nonsmoking Patients: Therapeutic Drug Monitoring Uncovers the Impact on Drug Metabolism.

BACKGROUND: For certain psychotropic drugs, such as clozapine or olanzapine, the influence of smoking on drug metabolism is well studied. Tobacco smoke increases the metabolism of drugs that are substrates for cytochrome P450 (CYP) 1A2 due to CYP induction. The antidepressant duloxetine, acting as a serotonin-norepinephrine reuptake inhibitor, is mainly metabolized via CYP1A2. To date, little is known about the influence of smoking on serum duloxetine concentrations. METHODS: A therapeutic drug monitoring database consisting of plasma concentrations of duloxetine collected from January 2013 to June 2017 was analyzed. A group of nonsmoking patients undergoing treatment with duloxetine (n = 89) was compared to a group of active smokers also receiving duloxetine (n = 36). Serum concentrations of duloxetine and dose-adjusted serum concentrations were compared using non-parametric tests. RESULTS: Groups did not differ concerning sex (P = .063), but the group of active smokers was younger (P < .001) and received higher daily doses of duloxetine (P = .001). Smokers showed significantly lower median serum duloxetine concentrations (38.4% lower, P = .002) and 53.6% lower dose-adjusted serum concentrations (0.325 [ng/mL]/[mg/d] in smokers vs 0.7 [ng/mL]/[mg/d] in nonsmokers, P < .001). CONCLUSIONS: Despite higher daily doses, smokers had considerably lower serum duloxetine concentrations. The induction of CYP1A2 by tobacco smoke is a clinically relevant factor for drugs that are substrates for CYP1A2. Clinicians should actively assess smoking status, inform patients about the effect of smoking on duloxetine metabolism, and anticipate higher serum concentrations in the case of smoking cessation. Therapeutic drug monitoring ensures treatment efficacy by enabling the personalizing of treatment, as smokers need higher duloxetine doses to target serum concentrations within the therapeutic reference range.

Reference Brain/Blood Concentrations of Citalopram, Duloxetine, Mirtazapine and Sertraline.

Postmortem blood samples may not accurately reflect antemortem drug concentrations, as the levels of some drugs increase due to postmortem redistribution (PMR). The brain has been suggested as an alternative sampling site. The anatomically secluded site of the brain limits redistribution and prolongs the detection window, thereby enabling sampling from deceased individuals where blood is no longer suitable for analysis. We report concentrations in brain tissue and blood from 91 cases for the four antidepressants citalopram, duloxetine, mirtazapine and sertraline. The cases were classified according to their role in the cause of death, as follows: (A) concentrations where the drug was the sole cause of fatal intoxication; (B) concentrations where the drug contributed to a fatal outcome; and (C) concentrations where the drug was not related to the cause of death. The analytical method was successfully validated in brain tissue in terms of linearity, process efficiency, precision and accuracy. Quantification of analytes was performed by ultra-performance liquid chromatography with tandem mass spectrometry. Correlations between blood and brain concentrations were achieved with R2-values between 0.67 and 0.91. The following median brain-blood ratios were obtained: 3.71 for citalopram (range: 1.4-5.9), 11.0 for duloxetine (range: 5.0-21.6), 1.53 for mirtazapine (range: 1.02-4.71) and 7.38 for sertraline (range: 3.2-14.2). The S/R ratio of racemic citalopram was the same in brain (0.80) and blood (0.85), whereas the median citalopram/N-desmethylcitalopram ratio was higher in brain (9.1) than blood (4.1). The results of this study may serve as reference concentrations in brain for forensic cases.

Occupancy of Norepinephrine Transporter by Duloxetine in Human Brains Measured by Positron Emission Tomography with (S,S)-[18F]FMeNER-D2.

Background: The norepinephrine transporter in the brain has been targeted in the treatment of psychiatric disorders. Duloxetine is a serotonin and norepinephrine reuptake inhibitor that has been widely used for the treatment of depression. However, the relationship between dose and plasma concentration of duloxetine and norepinephrine transporter occupancy in the human brain has not been determined. In this study, we examined norepinephrine transporter occupancy by different doses of duloxetine. Methods: We calculated norepinephrine transporter occupancies from 2 positron emission tomography scans using (S,S)-[18F]FMeNER-D2 before and after a single oral dose of duloxetine (20 mg, n = 3; 40 mg, n = 3; 60 mg, n =2). Positron emission tomography scans were performed from 120 to 180 minutes after an i.v. bolus injection of (S,S)-[18F]FMeNER-D2. Venous blood samples were taken to measure the plasma concentration of duloxetine just before and after the second positron emission tomography scan. Results: Norepinephrine transporter occupancy by duloxetine was 29.7% at 20 mg, 30.5% at 40 mg, and 40.0% at 60 mg. The estimated dose of duloxetine inducing 50% norepinephrine transporter occupancy was 76.8 mg, and the estimated plasma drug concentration inducing 50% norepinephrine transporter occupancy was 58.0 ng/mL. Conclusions: Norepinephrine transporter occupancy by clinical doses of duloxetine was approximately 30% to 40% in human brain as estimated using positron emission tomography with (S,S)-[18F]FMeNER-D2.

Duloxetine Plasma Concentrations and Its Effectiveness in the Treatment of Nonorganic Chronic Pain in the Orofacial Region.

OBJECTIVE: The purpose of this study was to examine the relationship between the pain-relieving effects of duloxetine and its plasma concentrations in patients with burning mouth syndrome and atypical odontalgia characterized by chronic nonorganic pain in the orofacial region. METHODS: We administered duloxetine to 77 patients diagnosed as having burning mouth syndrome or atypical odontalgia for 12 weeks. The initial dose of duloxetine was established as 20 mg/d and was increased to 40 mg/d after week 2. We evaluated pain using the visual analog scale and depressive symptoms using the Structured Interview Guide for the Hamilton Depression Rating Scale at weeks 0, 2, 4, 6, 8, 10, and 12 and measured plasma concentrations of duloxetine 12 weeks after the start of its administration. RESULTS: Visual analog scale scores were significantly lower 12 weeks after than at the start of the administration of duloxetine (paired t test, t = 6.65, P < 0.0001). We examined the relationship between the rate of decreases in visual analog scale scores and plasma concentrations of duloxetine. There was no significant linear regression or quadratic regression. CONCLUSIONS: Duloxetine significantly relieved pain in patients with chronic nonorganic pain in the orofacial region. However, no relationship was observed between its pain-relieving effects and plasma concentrations.

Bioanalytical Method Validation for Dronedarone and Duloxetine in Blood Serum.

The present work relates to the development and validation of reversed-phase HPLC-UV-photodiode array methods for the estimation of two drugs in blood serum: dronedarone hydrochloride (DDN), a class III antiarrhythmic drug, and duloxetine hydrochloride (DLX), an antidepressant. Chromatographic analysis of DLX was carried out on a Nucleodur C18 column (250 × 4.6 mm, 5 µm) using ammonium acetate buffer (32 mM, pH 5.5) and acetonitrile (40 + 60, v/v; flow rate of 1.0 mL/min; detection wavelength of 290 nm) as the mobile phase. A Waters XTerra C18 column (250 × 4.6 mm, 5 µm) was used for the chromatographic analysis of DDN using an acetonitrile-ammonium formate buffer (20 mM, pH 3.0, with formic acid; 45 + 55, v/v; flow rate 1.0 mL/min) as the mobile phase. Pentazocine and bupropion HCl were used as the internal reference standards for DLX and DDN, respectively. Excellent linearity was observed for DLX (r2 = 0.9996; concentration range 0.2-10.0 µg/mL) and DDN (r2 = 0.9997; concn. range 2.0-50.0 µg/mL). The LODs for DLX and DDN were 0.022 and 0.78 µg/mL, respectively, and the LOQs 0.066 and 2.4 µg/mL, respectively.

Duloxetine enters the brain - But why is it not found in the cerebrospinal fluid.

BACKGROUND: Antidepressants enter the brain to reach their site of action in a different extent. However, there has been no study to date about duloxetine's ability to enter the brain and cerebrospinal fluid. Aim of this study was to measure blood and cerebrospinal fluid concentrations of duloxetine and to account for the distribution between the two compartments. METHODS: Concentrations of duloxetine were measured in blood serum and cerebrospinal fluid of 19 patients treated with daily doses of 30-120mg. Daily doses were correlated with serum and cerebrospinal fluid concentrations and serum concentrations were correlated with concentrations in cerebrospinal fluid. RESULTS: Serum concentrations of duloxetine showed a moderate but significant correlation with the applied daily dose, r=+0.473, p=0.04. Duloxetine concentrations in the cerebrospinal fluid above the designated limit of quantification of 2.0ng/mL were only found in three of the 19 patients. CONCLUSIONS AND LIMITATIONS: Contrasting to own preceding studies on venlafaxine, mirtazapine and citalopram with comparably high concentrations in cerebrospinal fluid, the here presented findings indicate that duloxetine shows a very different distribution pattern. Very low concentrations in the cerebrospinal fluid may be due to the fact that the drug crosses the blood-cerebrospinal fluid barrier much worse than other antidepressants do, suggesting a low ability of duloxetine to enter the brain. Alternatively, low drug concentrations may be interpreted in a sense of a missing residence time in cerebrospinal fluid due to active transport mechanisms out of this environment either back into the bloodstream or into the brain.

Pharmacodynamics of norepinephrine reuptake inhibition: Modeling the peripheral and central effects of atomoxetine, duloxetine, and edivoxetine on the biomarker 3,4-dihydroxyphenylglycol in humans.

Norepinephrine, a neurotransmitter in the autonomic sympathetic nervous system, is deaminated by monoamine oxidase to 3,4-dihydroxyphenylglycol (DHPG). Inhibition of the NE transporter (NET) using DHPG as a biomarker was evaluated using atomoxetine, duloxetine, and edivoxetine as probe NET inhibitors. Pharmacokinetic and pharmacodynamic data were obtained from healthy subjects (n = 160) from 5 clinical trials. An indirect response model was used to describe the relationship between drug plasma concentration and DHPG concentration in plasma and cerebrospinal fluid (CSF). The baseline plasma DHPG concentration (1130-1240 ng/mL) and Imax (33%-37%) were similar for the 3 drugs. The unbound plasma drug IC50 (IC50U ) based on plasma DHPG was 0.973 nM for duloxetine, 0.136 nM for atomoxetine, and 0.041 nM for edivoxetine. The baseline CSF DHPG concentration (1850-2260 ng/mL) was similar for the 3 drugs, but unlike plasma DHPG, the Imax for DHPG was 38% for duloxetine, 53% for atomoxetine, and75% for edivoxetine. The IC50U based on CSF DHPG was 2.72 nM for atomoxetine, 1.22 nM for duloxetine, and 0.794 nM for edivoxetine. These modeling results provide insights into the pharmacology of NET inhibitors and the use of DHPG as a biomarker.

Development of sensitive spectrofluorimetric and spectrophotometric methods for the determination of duloxetine in capsule and spiked human plasma.

A new, sensitive and selective spectrofluorimetric method has been developed for the determination of duloxetine (DLX) in capsule and spiked human plasma. DLX, as a secondary amine compound, reacts with 7-chloro-4-nitrobenzofurazon (NBD-Cl), a highly sensitive fluorogenic and chromogenic reagent used in many investigations. The method is based on the reaction between the drug and NBD-Cl in borate buffer at pH 8.5 to yield a highly fluorescent derivative that is measured at 523 nm after excitation at 478 nm. The fluorescence intensity was directly proportional to the concentration over the range 50-250 ng/mL. The reaction product was also measured spectrophotometrically. The relation between the absorbance at 478 nm and the concentration is rectilinear over the range 1.0-12.0 µg/mL. The methods were successfully applied for the determination of this drug in pharmaceutical dosage form. The spectrofluorimetric method was also successfully applied to the determination of duloxetine in spiked human plasma. The suggested procedures could be used for the determination of DLX in pure form, capsules and human plasma being sensitive, simple and selective.