Potential targets of severe acute respiratory syndrome coronavirus 2 of clinical drug fluvoxamine: Docking and molecular dynamics studies to elucidate viral action.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has continued evolving for survival and adaptation by mutating itself into different variants of concern, including omicron. Several studies and clinical trials found fluvoxamine, an Food and Drug Administration-approved antidepressant drug, to be effective at preventing mild coronavirus disease 2019 (COVID-19) from progressing to severe diseases. However, the mechanism of fluvoxamine's direct antiviral action against COVID-19 is still unknown. Fluvoxamine was docked with 11 SARS-CoV-2 targets and subjected to stability, conformational changes, and binding free energy analyses to explore its mode of action. Of the targets, nonstructural protein 14 (NSP14), main protease (Mpro), and papain-like protease (PLpro) had the best docking scores with fluvoxamine. Consistent with the docking results, it was confirmed by molecular dynamics simulations that the NSP14 N7-MTase ((N7-guanine)-methyltransferase)-fluvoxamine, Mpro-fluvoxamine, and PLpro-fluvoxamine complexes are stable, with the lowest binding free energies of -105.1, -82.7, and - 38.5 kJ/mol, respectively. A number of hotspot residues involved in the interaction were also identified. These include Glu166, Asp187, His41, and Cys145 in Mpro, Gly163 and Arg166 in PLpro, and Glu302, Gly333, and Phe426 in NSP14, which could aid in the development of better antivirals against SARS-CoV-2.

Tuning the activity of known drugs via the introduction of halogen atoms, a case study of SERT ligands - Fluoxetine and fluvoxamine.

The selective serotonin reuptake inhibitors (SSRIs), acting at the serotonin transporter (SERT), are one of the most widely prescribed antidepressant medications. All five approved SSRIs possess either fluorine or chlorine atoms, and there is a limited number of reports describing their analogs with heavier halogens, i.e., bromine and iodine. To elucidate the role of halogen atoms in the binding of SSRIs to SERT, we designed a series of 22 fluoxetine and fluvoxamine analogs substituted with fluorine, chlorine, bromine, and iodine atoms, differently arranged on the phenyl ring. The obtained biological activity data, supported by a thorough in silico binding mode analysis, allowed the identification of two partners for halogen bond interactions: the backbone carbonyl oxygen atoms of E493 and T497. Additionally, compounds with heavier halogen atoms were found to bind with the SERT via a distinctly different binding mode, a result not presented elsewhere. The subsequent analysis of the prepared XSAR sets showed that E493 and T497 participated in the largest number of formed halogen bonds. The XSAR library analysis led to the synthesis of two of the most active compounds (3,4-diCl-fluoxetine 42, SERT Ki = 5 nM and 3,4-diCl-fluvoxamine 46, SERT Ki = 9 nM, fluoxetine SERT Ki = 31 nM, fluvoxamine SERT Ki = 458 nM). We present an example of the successful use of a rational methodology to analyze binding and design more active compounds by halogen atom introduction. 'XSAR library analysis', a new tool in medicinal chemistry, was instrumental in identifying optimal halogen atom substitution.

Physiologically-Based Pharmacokinetic Models for CYP1A2 Drug-Drug Interaction Prediction: A Modeling Network of Fluvoxamine, Theophylline, Caffeine, Rifampicin, and Midazolam.

This study provides whole-body physiologically-based pharmacokinetic models of the strong index cytochrome P450 (CYP)1A2 inhibitor and moderate CYP3A4 inhibitor fluvoxamine and of the sensitive CYP1A2 substrate theophylline. Both models were built and thoroughly evaluated for their application in drug-drug interaction (DDI) prediction in a network of perpetrator and victim drugs, combining them with previously developed models of caffeine (sensitive index CYP1A2 substrate), rifampicin (moderate CYP1A2 inducer), and midazolam (sensitive index CYP3A4 substrate). Simulation of all reported clinical DDI studies for combinations of these five drugs shows that the presented models reliably predict the observed drug concentrations, resulting in seven of eight of the predicted DDI area under the plasma curve (AUC) ratios (AUC during DDI/AUC control) and seven of seven of the predicted DDI peak plasma concentration (Cmax ) ratios (Cmax during DDI/Cmax control) within twofold of the observed values. Therefore, the models are considered qualified for DDI prediction. All models are comprehensively documented and publicly available, as tools to support the drug development and clinical research community.

Structural basis for recognition of diverse antidepressants by the human serotonin transporter.

Selective serotonin reuptake inhibitors are clinically prescribed antidepressants that act by increasing the local concentrations of neurotransmitters at synapses and in extracellular spaces via blockade of the serotonin transporter. Here we report X-ray structures of engineered thermostable variants of the human serotonin transporter bound to the antidepressants sertraline, fluvoxamine, and paroxetine. The drugs prevent serotonin binding by occupying the central substrate-binding site and stabilizing the transporter in an outward-open conformation. These structures explain how residues within the central site orchestrate binding of chemically diverse inhibitors and mediate transporter drug selectivity.

Influence of photolabile pharmaceuticals on the photodegradation and toxicity of fluoxetine and fluvoxamine.

Pharmaceuticals in the aquatic environment may be decomposed by abiotic and biotic factors. Photodegradation is the most investigated abiotic process, as it occurs in the natural environment and may be applied in wastewater treatment technology. Although pharmaceuticals are detected in effluents and surface water in a mixture, the photodegradation process is mainly evaluated with single compounds. The photodegradation of fluoxetine (FLU) and fluvoxamine (FLX) in the presence of diclofenac (DCF) and triclosan (TCS) was investigated with HPLC and bioassay. FLU did not degrade under UV-Vis irradiation in SunTest CPS+ either with or without the tested additives, although small amounts of desmethyl fluoxetine and 4-(trifluoromethyl)phenol were formed. In contrast, during irradiation, FLX isomerized to cis-FLX. This process was enhanced by DCF and TCS, but to a lesser degree than by humic acids. Thus, the presence and composition of the matrix should be considered in the environmental risk assessment of pharmaceuticals. As the toxicity of the tested solutions depended only on the concentration of the tested drugs, it was suggested that the biological activity of the photodegradation products was lower than that of the parent compounds.

Parallel artificial liquid membrane extraction as an efficient tool for removal of phospholipids from human plasma.

Generic Parallel Artificial Liquid Membrane Extraction (PALME) methods for non-polar basic and non-polar acidic drugs from human plasma were investigated with respect to phospholipid removal. In both cases, extractions in 96-well format were performed from plasma (125µL), through 4µL organic solvent used as supported liquid membranes (SLMs), and into 50µL aqueous acceptor solutions. The acceptor solutions were subsequently analysed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using in-source fragmentation and monitoring the m/z 184→184 transition for investigation of phosphatidylcholines (PC), sphingomyelins (SM), and lysophosphatidylcholines (Lyso-PC). In both generic methods, no phospholipids were detected in the acceptor solutions. Thus, PALME appeared to be highly efficient for phospholipid removal. To further support this, qualitative (post-column infusion) and quantitative matrix effects were investigated with fluoxetine, fluvoxamine, and quetiapine as model analytes. No signs of matrix effects were observed. Finally, PALME was evaluated for the aforementioned drug substances, and data were in accordance with European Medicines Agency (EMA) guidelines.

Quantitative assessment of photostability and photostabilisation of Fluvoxamine and its design for actinometry.

Despite the numerous concerns that have been raised in relation to considering 0(th), 1(st) and 2(nd)-order kinetic treatments for photodegradation characterisation and assessment of drugs, they still are employed, as they are the only tools available for these types of studies. The recently developed Φ-order kinetic models have opened new perspectives in the treatment of photoreaction kinetics and stand as the best known alternative to the classical approach. The Φ-order kinetics have been applied here to Fluvoxamine (Fluvo) with the aim of setting out a detailed and comprehensive procedure capable of rationalising photodegradation/photostability of drugs and proposing a platform for photosafety studies. Our results prove that quantum yields of drugs (0.0016 < Φ(λirr)(Fluvo) < 0.43) should a priori be considered wavelength-dependent; their photostabilisation (up to 75% for Fluvo) by means of absorption competitors can explicitly be related to a decrease of the photokinetic factor, and photoreversible drugs can be developed into efficient actinometers (as Fluvoxamine in the 260-290 nm range). A pseudo-rate-constant factor was proposed as a descriptive parameter, circumventing the limitations of overall rate-constants and allowing a comparison between kinetic data of drugs obtained under different conditions.

[Addition of fluvoxamine to clozapine: theory and practice]. / Additie van fluvoxamine aan clozapine: theorie en praktijk.

BACKGROUND: The addition of fluvoxamine to clozapine induces a rise of plasma concentrations of clozapine. This enables the prescription of a lower number of clozapine tablets, yet it attains sufficient clozapine plasma concentrations, and facilitates treatment adherence. AIM: Providing practical advice for the practical implementation of the addition of fluvoxamine to clozapine. METHOD: A review of the literature with Ovid Medline and the presentation of a case series (N=7). RESULTS: Addition of 25 or 50 mg fluvoxamine induces a mean rise of plasma concentrations of clozapine with a factor 2-3, probably even higher with the addition of 100 mg. However, the range of this factor varies considerably between individuals. The use of clozapine and fluvoxamine at the same time possibly has a favourable impact on the metabolic side-effects of clozapine. CONCLUSION: Addition of fluvoxamine to clozapine can lead to a dangerous rise of clozapine plasma concentrations. However, it can also be used to prescribe a lower number of clozapine tablets and to facilitate treatment adherence. A sufficient safety margin should be taken and regular control of clozapine plasma concentrations is mandatory.

Photoassisted defluorination of fluorinated substrates and pharmaceuticals by a wide bandgap metal oxide in aqueous media.

Persistent fluorinated substances, such as the fluorine-bearing pharmaceutical drugs Fluoxetine (FLX; Prozac) and Fluvoxamine maleate (FOM) together with several other substrates (fluorobenzoic acid and fluoroaliphatic model compounds), were photochemically defluorinated and degraded under UVC illumination in relatively good yields in the presence of a wide band gap metal oxide (ß-Ga2O3) in heterogeneous aqueous media. The formation of fluoride ions increased with increasing illumination time under an inert nitrogen atmosphere, the transformation of the aromatic moiety was slower under these conditions, but nonetheless it did occur. The optimal amount of ß-Ga2O3 loading for defluorination was 50 mg in aqueous media (0.10 mM, 100 mL); the optimal pH to defluorinate FLX was pH 6. Platinization (1 wt%) of the gallium oxide particles enhanced defluorination under an inert nitrogen atmosphere, but was decreased under an oxygen atmosphere; however, in the latter case the degradation of the substrates was facilitated as witnessed by loss of the aromatic moiety. The Ames test on the intermediate products from the photodegradation of FLX and 4-(trifluoromethyl)benzoic acid after long illumination times revealed that none were mutagenic.

In silico and intuitive predictions of CYP46A1 inhibition by marketed drugs with subsequent enzyme crystallization in complex with fluvoxamine.

Cytochrome P450 46A1 (cholesterol 24-hydroxylase) is an important brain enzyme that may be inhibited by structurally distinct pharmaceutical agents both in vitro and in vivo. To identify additional inhibitors of CYP46A1 among U.S. Food and Drug Administration-approved therapeutic agents, we used in silico and intuitive predictions and evaluated some of the predicted binders in the enzyme and spectral binding assays. We tested a total of 298 marketed drugs for the inhibition of CYP46A1-mediated cholesterol hydroxylation in vitro and found that 13 of them reduce CYP46A1 activity by >50%. Of these 13 inhibitors, 7 elicited a spectral response in CYP46A1 with apparent spectral K(d) values in a low micromolar range. One of the identified tight binders, the widely used antidepressant fluvoxamine, was cocrystallized with CYP46A1. The structure of this complex was determined at a 2.5 Å resolution and revealed the details of drug binding to the CYP46A1 active site. The NH(2)-containing arm of the Y-shaped fluvoxamine coordinates the CYP46A1 heme iron, whereas the methoxy-containing arm points away from the heme group and has multiple hydrophobic interactions with aliphatic amino acid residues. The CF(3)-phenyl ring faces the entrance to the substrate access channel and has contacts with the aromatic side chains. The crystal structure suggests that only certain drug conformers can enter the P450 substrate access channel and reach the active site. Once inside the active site, the conformer probably further adjusts its configuration and elicits the movement of the protein side chains.

Impact of sample hemolysis on drug stability in regulated bioanalysis.

Being regulated by agencies' guidances, the importance of a robust validated bioanalytical method is crucial as it may impact the validity of the pharmacokinetic data generated. During blood collection and processing, the presence of hemolyzed plasma samples may occur and as a result its impact must be investigated to ensure method robustness. Indeed, hemolyzed samples may affect the analyte recovery efficiency, as well as the chromatography. Furthermore, the stability of an analyte in hemolyzed plasma can be an issue as analyte degradation may occur. In this article we report two case studies where the analyte instability was a result of sample hemolysis. A description of the appropriate actions undertaken for the resolution of the issue will be discussed.

Spectrophotometric study for the reaction between fluvoxamine and 1,2-naphthoquinone-4-sulphonate: Kinetic, mechanism and use for determination of fluvoxamine in its dosage forms.

Spectrophotometric study was carried out, for the first time, to investigate the reaction between the antidepressant fluvoxamine (FXM) and 1,2-naphthoquinone-4-sulphonate (NQS) reagent. In alkaline medium (pH 9), an orange-colored product exhibiting maximum absorption peak (lambda(max)) at 470nm was produced. The kinetics of the reaction was investigated and its activation energy was found to be 2.65kcalmol(-1). Because of this low activation energy, the reaction proceeded easily. The stoichiometry of the reaction was determined and the reaction mechanism was postulated. This color-developing reaction was successfully employed in the development of simple and rapid spectrophotometric method for determination of FXM in its pharmaceutical dosage forms. Under the optimized reaction conditions, Beer's law correlating the absorbance (A) with FXM concentration (C) was obeyed in the range of 0.6-8microgml(-1). The regression equation for the calibration data was A=0.0086+0.1348C, with good correlation coefficient (0.9996). The molar absorptivity (epsilon) was 5.9x10(4)lmol(-1)cm(-1). The limits of detection and quantification were 0.2 and 0.6microgml(-1), respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 2%. The proposed method was successfully applied to the determination of FXM in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 100.47+/-0.96%. The results obtained by the proposed method were comparable with those obtained by the official method. The proposed method is superior to all the previously reported spectrophotometric methods for determination of FXM in terms of its simplicity and sensitivity. The method is practical and valuable for its routine application in quality control laboratories for analysis of FXM.

Spectrofluorimetric determination of fluvoxamine in dosage forms and plasma via derivatization with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole.

A highly sensitive and simple spectrofluorimetric method has been developed and validated for the determination of the antidepressant fluvoxamine (FXM) in its dosage forms and plasma. The method was based on nucleophilic substitution reaction of FXM with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole in an alkaline medium (pH 8) to form a highly fluorescent derivative that was measured at 535 nm after excitation at 470 nm. The factors affecting the reaction was carefully studied and optimized. The kinetics of the reaction was investigated, and the reaction mechanism was presented. Under the optimized conditions, linear relationship with good correlation coefficient (0.9995) was found between the fluorescence intensity and FXM concentration in the range of 65-800 ng ml(-1). The limits of detection and quantitation for the method were 21 and 64 ng ml(-1), respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 2.17%. The proposed method was successfully applied to the determination of FXM in its pharmaceutical tablets with good accuracy; the recovery values were 97.8-101.4 +/- 1.08-2.75%. The results obtained by the proposed method were comparable with those obtained by the official method. The high sensitivity of the method allowed its successful application to the analysis of FXM in spiked human plasma. The proposed method is superior to the previously reported spectrofluorimetric method for determination of FXM in terms of its simplicity. The proposed method is practical and valuable for its routine application in quality control and clinical laboratories for analysis of FXM.

Characterization of drug-protein binding process by employing equilibrium sampling through hollow-fiber supported liquid membrane and Bjerrum and Scatchard plots.

The technique equilibrium sampling through membrane (ESTM) was extended to measuring the free drug concentration in solutions of drug and protein. Bjerrum and Scatchard plots were employed for characterizing individual drug binding to pure human blood proteins. Four drugs were investigated as a model system: fluvoxamine and ropivacaine which dominantly bind to alpha-acid glycoprotein (AGP), and R,S-ibuprofen and S-ketoprofen which highly bind to human serum albumin (HSA). The level of drug binding to AGP and HSA relied on drug and protein concentrations. Bjerrum and Scatchard plots revealed high affinity constants (Ka) at low protein concentration. Both Bjerrum and Scatchard plots of fluvoxamine and ropivacaine binding to AGP showed one specific binding site (n1=1) with ropivacaine Ka value close to 5 times higher than the Ka of fluvoxamine at 22.9 microM AGP concentration. Bjerrum plots of ketoprofen and ibuprofen gave total number of binding sites or bound molecules of 6-7, which did not depend on the drug or protein concentration. Scatchard plots of ketoprofen and ibuprofen exhibited two binding sites (n1 and n2) at 0.15 microM and 0.75 microM HSA concentrations. On one hand, at 0.15 microM HSA, ketoprofen and ibuprofen were bound to site I at n1=1.2 and n1=1.0, respectively. However, at 0.75 microM HSA, ketoprofen and ibuprofen were bound to site I at n1=1.2 and n1=1.9, respectively. On the other hand, site II, at 0.15 microM HSA, interacted with ketoprofen and ibuprofen at n2=5.6 and 6.7, respectively. However, at 0.75 microM HSA, site II interacted with ketoprofen at n2=7.4 and ibuprofen at n2=6.2. It would be concluded that, upon mixing ketoprofen and ibuprofen in a HSA solution, a ketoprofen-ibuprofen interaction would most likely occur at site II in HSA.

Quality assessment of fluoxetine and fluvoxamine pharmaceutical formulations purchased in different countries or via the Internet by 19F and 2D DOSY 1H NMR.

A simple and selective (19)F NMR method has been validated for the quantitation of fluoxetine (FLX) and fluvoxamine (FLV) in methanol solutions and in human plasma and urine. The regression equations for FLX and FLV showed a good linearity in the range of 1.4-620 microg mL(-1) (3.3 x 10(-6)-1.8 x 10(-3) mol L(-1)) with a limit of detection of approximately 0.5 microg mL(-1) (1.3 x 10(-6) mol L(-1)) and a limit of quantification of approximately 2 microg mL(-1) (4.6 x 10(-6) mol L(-1)). The precision of the assay depends on the concentrations and is comprised between 1.5 and 9.5% for a range of concentrations between 1.2 x 10(-3) and 3.2 x 10(-6) mol L(-1). The accuracy evaluated through recovery studies ranged from approximately 96 to 103% in methanol solutions and in urine, and from approximately 93 to 104% in plasma, with standard deviations <7.5%. The low sensitivity of the method precludes its use for the assay of these antidepressants in biofluids at least at therapeutic doses as the ranges of FLX and FLV plasma levels are 0.15-0.5 microg mL(-1) and 0.15-0.25 microg mL(-1), respectively. The method was applied successfully to the determination of FLX and FLV contents in pharmaceutical samples (brand-named and generic) purchased in several countries or via the Internet. All the commercial formulations contain the active ingredient in the range 94-103% of stated concentration. A "signature" of the formulations (solid and liquid) was obtained with 2D Diffusion-Ordered SpectroscopY (DOSY) (1)H NMR which allowed the characterisation of the active ingredient and excipients present in the formulations studied. Finally, the DOSY separation of FLX and FLV whose molecular weights are very close was obtained by using beta-cyclodextrin as host-guest complexing agent.

Saturable uptake of lipophilic amine drugs into isolated hepatocytes: mechanisms and consequences for quantitative clearance prediction.

The hepatic uptake of quinine, fluvoxamine, and fluoxetine (0.1-10 microM) was investigated with freshly isolated rat hepatocytes. The cell-to-medium concentration ratios (K(p)) were concentration-dependent: the mean maximum K(p) values (at 0.1 microM) were 150 (quinine), 500 (fluvoxamine), and 2000 (fluoxetine). There was also a large capacity site that was not saturable over the concentration range used (possibly partition into the phospholipid component of membranes); representing this site, the mean minimum K(p) values (at 10 microM) were 30 (quinine), 200 (fluvoxamine), and 500 (fluoxetine). To eliminate concomitant metabolism, cells were pretreated with the irreversible P450 inhibitor, aminobenzotriazole. The saturable uptake was substantially eliminated after exposure to carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (ATP inhibitor). The difference between the maximum and minimum K(p) for these three amine drugs, as well as for dextromethorphan, propranolol, and imipramine, was within a limited range of 3-fold, indicating a common magnitude of saturable uptake. Basic, permeable drugs are expected to be sequestered into lysosomes, which actively maintain their low internal pH (approximately 5) using ATP, and this process is predictable from the combined effects of pH-driven ion accumulation and unsaturable binding representing partition into membranes. The resultant predicted maximum K(p) correlated strongly with the observed maximum K(p). Thus, at low substrate concentrations, the fraction of drug unbound in the hepatocyte incubation (critical for assessing drug clearance and drug-drug interaction potential) may be dependent upon saturable as well as unsaturable binding, and for lipophilic, basic drugs, this can be readily estimated assuming a common degree of uptake into lysosomes.

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.

The spermicidal and antitrichomonas activities of SSRI antidepressants.

The study investigated spermicidal and antitrichomonas activities of selective serotonin reuptake inhibitor (SSRI) antidepressants with a view to generate new lead for development of dual-function spermicidal microbicides, which is an urgent global need. Fluoxetine, Sertraline, and Fluvoxamine exhibited both spermicidal and anti-STI (antitrichomonas) activities in vitro, whereas Paroxetine and Citalopram showed only the spermicidal activity. Fluoxetine exhibited better activity profile than the other antidepressant drugs with its spermicidal and antitrichomonas activities being comparable to that of the OTC contraceptive Nonoxynol-9. The non-detergent nature of Fluoxetine and a much lower spermicidal ED50 value (than N-9) may add considerably to its merit as a candidate for microbicidal contraceptive. Thus, the antidepressants exhibiting both spermicidal and antitrichomonas activities might provide useful lead for the development of novel, dual-function spermicidal contraceptives.

Fluvoxamine: a selective serotonin re-uptake inhibitor for the treatment of obsessive-compulsive disorder.

Fluvoxamine is the selective serotonin re-uptake inhibitor with the largest database in the treatment of obsessive-compulsive disorder, a severe, and often chronic, anxiety disorder associated with substantial impairment in functioning. The selective serotonin re-uptake inhibitors represent a first-line treatment in patients with obsessive-compulsive disorder. These agents work primarily by blocking the re-uptake of serotonin into the presynaptic nerve terminal, which is believed to be mediated by their effects on the serotonin transport system. In the last two decades, the anti-obsessional effect of fluvoxamine has been tested in several double-blind, placebo-controlled and active-comparison studies, demonstrating its superior efficacy over obsessions and compulsions compared with non-serotonergic antidepressants (i.e., desipramine) and equal efficacy to clomipramine (a tricyclic antidepressant with potent serotonin re-uptake inhibition) and other selective serotonin re-uptake inhibitors (paroxetine and citalopram). However, compared with clomipramine, the selective serotonin re-uptake inhibitor fluvoxamine showed fewer side effects and better tolerability. This reflects the poor affinity of this compound for adrenergic, muscarinic, cholinergic or histaminergic receptors.

A sensitive HPLC method for the determination of fluoxetine and norfluoxetine in human plasma with fluorescence detection.

A selective, sensitive, and precise HPLC method for the simultaneous determination of fluoxetine (FL) and its N-demethylated metabolite norfluoxetine (NFL) in human plasma has been developed. Following extraction with n-hexane, FL, NFL, and fluvoxamine (internal standard) were derivatized with 7-chloro-4-nitrobenzofurazan (NBD-Cl) under weakly alkaline conditions. NBD derivatives were extracted with chloroform after acidification and chromatographed on a reversed-phase column with gradient elution using acetonitrile and 0.1 mol/L nitric acid (pH 3) solution. Calibration curves were linear over the range of 1.0-100.0 ng/mL and 0.1-50.0 ng/mL for FL and NFL, respectively, with inter- and intraassay precision given by a relative standard deviation (RSD%) of less than 9.2%. The lower limits of quantification were 1.0 ng/mL for FL and 0.1 ng/mL for NFL. Recoveries of FL and NFL from plasma at three different concentrations were assessed. Average recovery was about 100% for both substances. The assay was applied to pharmacokinetic study in 2 healthy volunteers after a single oral administration of 40 mg of FL.