Retention mechanisms of amitriptyline and its impurities on amide, amino, diol, and silica columns in hydrophilic interaction liquid chromatography.

Hydrophilic interaction liquid chromatography (HILIC) has been widely applied to challenging analysis in biomedical and pharmaceutical fields, bridging the gap between normal-phase high-performance liquid chromatography and reversed-phase high-performance liquid chromatography (RP-HPLC). This paper comprehensively explores the retention mechanisms of amitriptyline and its impurities A, B, C, D, F, and G on amide, amino, diol, and silica columns. Dual HILIC/RP-HPLC retention mechanisms were developed, and transitional points between HILIC and RP-HPLC mechanisms were calculated on amide, diol, and silica columns. Adsorption and partition contributions to overall retention mechanisms were evaluated using Python software in HILIC and RP-HPLC regions. The cation exchange mechanism dominates overall retention for ionized analytes in the silica column (R2 > 0.995), whereas the retention of ionized analytes increases with pH. Impacts of acetonitrile content, buffer ionic strength, and pH, along with their interactions on the retention of ionized analytes in the silica column, were determined using the chemometric approach. Acetonitrile content showed the most significant impact on the retention mechanisms. These findings highlight that a detailed investigation into retention mechanisms provides notable insights into factors influencing analyte retention and separation, promising valuable guidance for future analysis.

Structure- and Cation-Dependent Mechanism of Interaction of Tricyclic Antidepressants with NMDA Receptor According to Molecular Modeling Data.

Some tricyclic antidepressants (TCAs), including amitriptyline (ATL), clomipramine (CLO), and desipramine (DES), are known to be effective for management of neuropathic pain. It was previously determined that ATL, CLO, and DES are capable of voltage-dependent blocking of NMDA receptors of glutamate (NMDAR), which play a key role in pathogenesis of neuropathic pain. Despite the similar structure of ATL, CLO, and DES, efficacy of their interaction with NMDAR varies significantly. In the study presented here, we applied molecular modeling methods to investigate the mechanism of binding of ATL, CLO, and DES to NMDAR and to identify structural features of the drugs that determine their inhibitory activity against NMDAR. Molecular docking of the studied TCAs into the NMDAR channel was performed. Conformational behavior of the obtained complexes in the lipid bilayer was simulated by the method of molecular dynamics (MD). A single binding site (upper) for the tertiary amines ATL and CLO and two binding sites (upper and lower) for the secondary amine DES were identified inside the NMDAR channel. The upper and lower binding sites are located along the channel axis at different distances from the extracellular side of the plasma membrane. MD simulation revealed that the position of DES in the lower site is stabilized only in the presence of sodium cation inside the NMDAR channel. DES binds more strongly to NMDAR compared to ATL and CLO due to simultaneous interaction of two hydrogen atoms of its cationic group with the asparagine residues of the ion pore of the receptor. This feature may be responsible for the stronger side effects of DES. It has been hypothesized that ATL binds to NMDAR less efficiently compared to DES and CLO due to its lower conformational mobility. The identified features of the structure- and cation-dependent mechanism of interaction between TCAs and NMDAR will help in the further development of effective and safe analgesic therapy.

Numerical study of drop dynamics for inkjet based 3D printing of pharmaceutical tablets.

Interest in 3D printing has been growing rapidly especially in pharmaceutical industry due to its multiple advantages such as manufacturing versatility, personalization of medicine, scalability, and cost effectiveness. Inkjet based 3D printing gained special attention after FDA's approval of Spritam® manufactured by Aprecia pharmaceuticals in 2015. The precision and printing efficiency of 3D printing is strongly influenced by the dynamics of ink/binder jetting, which further depends on the ink's fluid properties. In this study, Computational Fluid Dynamics (CFD) has been utilized to study the drop formation process during inkjet-based 3D printing for piezoelectric and thermal printhead geometries using Volume of Fluid (VOF) method. To develop the CFD model commercial software ANSYS-Fluent was used. The developed CFD model was experimentally validated using drop watcher setup to record drop progression and drop velocity. During the study, water, Fujifilm model fluid, and Amitriptyline drug solutions were evaluated as the ink solutions. The drop properties such as drop volume, drop diameter, and drop velocity were examined in detail in response to change ink solution properties such as surface tension, viscosity, and density. A good agreement was observed between the experimental and simulation data for drop properties such as drop volume and drop velocity.

Improvements in the predictive accuracy of the hydrophobic subtraction model of reversed-phase selectivity.

The hydrophobic subtraction model (HSM) for characterizing the selectivity of reversed-phase liquid chromatography (LC) columns has been used extensively by the LC community since it was first developed in 2002. Continuing interest in the model is due in part to the large, publicly available set of column descriptors that has been assembled over the past 18 years. In the work described in this report, we sought to refine the HSM with the goal of improving the predictive accuracy of the model without compromising its physico-chemical interpretability. The approach taken here has the following facets. A set of retention measurements for 635 columns and the 16 probe solutes used to characterize new columns using the HSM was assembled. Principal components analysis (PCA) was used as a guide for the development of a refined version of the HSM. Several outlying columns (84) were eliminated from the analysis because they were either inconsistent with the PCA model or were outliers from the original HSM model. With the retention dataset for the 16 probe solutes on the remaining 551 columns, we determined that a six-component model is the most sophisticated form of the model that can be used without overfitting the data. In our refined version of the HSM, the S*σ term has been removed. Two new terms have been added, which more accurately account for the molecular volume of the solute (Vv), and the solute dipolarity (Dd), and the remaining terms have been adjusted to accommodate these changes. The refined model described here provides improved prediction of retention factors, with the model standard error being reduced from 1.0 for the original HSM to 0.35 for the refined model (16 solutes, 551 columns). Furthermore, the number of retention factors with errors greater than 10% are reduced from 231 to 25. A revised metric for column similarity, F, is also proposed as a part of this work.

Investigation of micellar and interfacial phenomenon of amitriptyline hydrochloride with cationic ester-bonded gemini surfactant mixture in different solvent media.

Herein, the interaction among the antidepressant drug amitriptyline hydrochloride (AMT) and a green gemini surfactant, ethane-1, 2-diyl bis(N,N-dimethyl-N-tetradecylammoniumacetoxy) dichloride (14-E2-14), via numerous techniques such as tensiometry, fluorimetry, FT-IR and UV-visible spectroscopy in three different media (aqueous 0.050 mol·kg-1 NaCl, 0.50 and 1.0 mol·kg-1 urea) were investigated. AMT is used to treat mental illness or mood problems, such as depression. The aggregation of biologically active ingredients can enhance the bioavailability of hydrophobic drugs. A significant interaction between AMT and 14-E2-14 was detected by tensiometric study as the critical micelle concentration (cmc) of AMT+14-E2-14 is reduced upon an increase of mole fraction (α1) of 14-E2-14. The decrease in cmc indicates the nonideality of studied mixtures of different compositions. Although, employed drug AMT is freely soluble in the aqueous and non-aqueous system but is not hydrophobic enough to act as its carrier. Instead, gemini surfactant formed spherical micelles in an aqueous system and their high solubilization capability, as well as their relatively lower cmc value, makes them highly stable in vivo. The cmc values of AMT+14-E-14 mixtures in all cases were further decreased and increased in NaCl and urea solutions respectively as compared with the aqueous system. Numerous micellar, interfacial, and thermodynamic parameters have been measured by applying various theoretical models. The obtained changes in the physicochemical assets of AMT upon adding of 14-E2-14 are likely to enhance the industrial and pharmaceutical applications of gemini surfactants. The negative interaction parameters (ßm and ßσ), indicate synergistic attraction is occurring in the mixed systems. The aggregation number (Nagg), Stern-Volmer constant (Ksv), etc. are attained through the fluorescence method, also supporting the attractive interaction behavior of AMT+14-E2-14 mixtures in all solvents. The Nagg was found to increase in the salt solution and decrease in the urea system compared with the aqueous solution. FT-IR and UV-visible analysis also depict the interaction between the constituent alike tensiometry and fluorimetry methods. The results suggested that gemini surfactants may serve as a capable drug delivery agent for antidepressants, improving their bioavailability.

ß-Cyclodextrin Polymerized in Cross-Flowing Channels of Biomass Sawdust for Rapid and Highly Efficient Pharmaceutical Pollutants Removal from Water.

Water pollution arising from pharmaceuticals has raised great concerns about the potential risks for biosphere and human health. However, rapid and efficient removal of pharmaceutical contaminants from water remains challenging. Wood sawdust, a byproduct of the wood-processing industry, is an abundant, cost-effective, and sustainable material with a unique hierarchically porous microstructure. These features make wood sawdust quite interesting as a filtration material. Here, we report a novel cross-flow filtration composite based on ß-cyclodextrin-polymer-functionalized wood sawdust (ß-CD/WS) in which the pharmaceutical contaminant water flows through the sawn-off vessel channels and the micropores on the surface of the cell walls, generating the turbulence. Such water flow characteristics ensure full contact between pharmaceutical pollutants and ß-CD grafted on the cellulose backbone of wood sawdust, thereby enhancing the water treatment efficiency. Consequently, the ß-CD/WS filter device shows a high removal efficiency of over 97.5% within 90 s for various pharmaceutical contaminants including propranolol, amitriptyline, chlortetracycline, diclofenac, and levofloxacin, and a high saturation uptake capacity of 170, 156, 257, 159, and 185 mg g-1, respectively. The high-performance wood-sawdust-based cross-flow filtration opens new avenues for solving the global water pollution issues, especially those caused by pharmaceutical contaminants.

Formulation design for inkjet-based 3D printed tablets.

The drug loading efficiency was evaluated using a binder-jet 3D printing process by incorporating an active pharmaceutical ingredient (API) in ink, and quantifying the printability property of ink solutions. A dimensionless parameter Ohnesorge was calculated to understand the printability property of the ink solutions. A pre-formulation study was also carried out for the raw materials and printed tablets using thermal analysis and compendial tests. The compendial characterization of the printed tablets was evaluated with respect to weight variation, hardness, disintegration, and size; Amitriptyline Hydrochloride was considered as the model API in this study. Four concentrations of the API ink solutions (5, 10, 20, 40 mg/mL) were used to print four printed tablet batches using the same tablet design file. The excipient mixture used in the study was kept the same and consists of Lactose monohydrate, Polyvinyl pyrrolidone K30, and Di-Calcium phosphate Anhydrate. The minimum drug loading achieved was 30 µg with a minimal variation (RSD) of <0.26%. The distribution of the API on the tablet surface and throughout the printed tablets were observed using SEM-EDS. In contrast, the micro-CT images of the printed tablets indicated the porous surface structure of the tablets. The immediate release properties of the printed tablets were determined using a dissolution study in a modified USP apparatus II.

Study of interactions between organic contaminants and a new phosphated biopolymer derived from cellulose.

The extensive use of organic molecules (Rhodamine B and Amitriptyline) also has contributed to environmental pollution; adsorption is a relevant method for removal of these contaminants in aqueous media. In this context, the objective of this study was to modify the surface of cellulose (Cel) with phosphoric acid and sodium tripolyphosphate to obtain a biopolymer with incorporated phosphate groups (PCel). The modification was confirmed by X-ray dispersive energy spectroscopy, solid state nuclear magnetic resonance, X-ray diffraction, and thermal analysis. The obtained material (PCel) was used as a Rhodamine B (RhB) or Amitriptyline (AmTP) adsorbent, and the highest adsorption capacity of this material was obtained at pH 3.0 (RhB) and 7.0 (AmTP) and the equilibrium time was achieved at 65 (RhB) and 150 min (AmTP). Moreover, the pseudo-first-order model best describes the kinetics of this adsorption. The experimental adsorption isotherms were adjusted to the Langmuir model, indicating that monolayer adsorption occurred and the highest experimental adsorption capacity obtained was 47.58 (RhB) and 45.52 mg g-1 (AmTP) in PCel. The thermodynamic parameters showed that the adsorption process is exothermic and non-spontaneous, with increase of non-spontaneity with enhance of the temperature. However, PCel was efficient in removing the contaminant (RhB or AmTP) in an aqueous solution.

ß-Cyclodextrin encapsulation of nortriptyline HCl and amitriptyline HCl: Molecular insights from single-crystal X-ray diffraction and DFT calculation.

The ß-CD encapsulation of two tricyclic antidepressants (TCAs), nortriptyline (NRT) HCl and amitriptyline (AMT) HCl (most widely used TCA), has been thoroughly investigated by single-crystal X-ray diffraction and DFT calculation for insights into the inclusion complexation. X-ray analysis reveals that both drugs insert the A-ring moiety vertically from the ß-CD O2H/O3H-side and are kept in position by C5H⋯π interactions, yielding thermodynamically favorable complexes. In the ß-CD cavity, NRT and AMT are less open as their butterfly angles are ~10° smaller than those in free HCl salt forms and in complex with proteins. The effect of HCl salt on both complexes is evaluated by DFT full-geometry optimization. When Cl- is directly linked with the NRT NH2Me+ group, the inclusion complex formed gains stability by 3.65 kcal mol-1 through N5'H⋯Cl⋯HO26 H-bond chain, compared to the complex of NRT base. The addition of HCl to N5' of the side chain marginally affects the structures of ß-CD-TCA complexes. This study provides a rigorous crystallographic evidence for the ß-CD-TCA complexation and a theoretical view on the improved stability of TCA in the CD cavity, supporting the pharmacological benefit of CD encapsulation in reducing the TCA side effects.

Preparation and characterization of nano amitriptyline hydrochloride particles by spray freeze drying.

Aim: To investigate the enhancement of bioavailability by the usage of drug nanoparticles for increasing the efficacy of antidepressant therapeutic value. Materials & methods: Nano-amitriptyline HCI (AMT·HCl) particles were successfully prepared via a simple spray freeze drying (SFD) method. Results: The as-prepared nanoparticles are amorphous instead of crystalline. The mean size of AMT·HCl nanoparticles is 90 nm. In in vitro evaluation, AMT·HCl nanoparticles have greatly improved the dissolution compared with pure bulk materials, which have potential for enhancing human bioavailability and diminishing toxic effect. A nanoparticle formation mechanism was also proposed. Conclusion: These findings promote the development of antidepressant therapeutic evaluation based on the usage of AMT·HCl nanoparticles by SFD method and indicate that SFD is an alternative for a range of nanoparticle preparation in industrial pharmacy.

Quality by Design oriented development of hydrophilic interaction liquid chromatography method for the analysis of amitriptyline and its impurities.

This paper presents integration of Quality by Design concept in the development of hydrophilic interactions liquid chromatographic methods for analysis of amitriptyline and its impurities (A, B, C, and F). This is the first time that HILIC method for amitriptyline and its impurities is developed. Using QbD concept, it is possible to design a robust method and incorporate quality directly into its development. QbD concept in combination of Design of Experiments methodology (DoE) enables creation of well-defined design space. In this study, for method optimization a Box-Behnken design was used to test the effect of acetonitrile content, buffer concentration and pH of water phase on critical system responses such as retention factor of impurity A, resolution between impurity B and impurity C, amitriptyline peak asymmetry factor and retention time of last eluted impurity F. The defined mathematical models and Monte Carlo simulations were used to identify the design space. For robustness testing, fractional factorial design was applied. Optimal chromatographic conditions were the analytical column ZORBAX NH2 (250 mm x 4.6 mm, 5 µm particle size); mobile phase consisted of acetonitrile-water phase (60 mM ammonium acetate, pH adjusted to 4.5 with glacial acetic acid) (92.5:7.5 v/v); column temperature 30 °C, mobile phase flow rate 1 mL min-1, wavelength of detection 254 nm. Finally, method was fully validated and applicability of the method in tablet analysis was confirmed.

Aggregation and interfacial phenomenon of amphiphilic drug under the influence of pharmaceutical excipients (green/biocompatible gemini surfactant).

In the current study, we have examined the interaction amongst an antidepressant drug amitriptyline hydrochloride (AMH) and ethane-1, 2-diyl bis(N,N-dimethyl-N-cetylammoniumacetoxy) dichloride (16-E2-16, a green gemini surfactant) through tensiometric and fluorimetric techniques in aqueous/electrolyte/urea solutions. Significant variations are observed in the various evaluated parameters in the present study. Gemini 16-E2-16 has outstanding surface properties along with a much lower cmc value, demonstrating very little toxicity as well as considerable antimicrobial activity. The cmc values of mixtures decrease through increase in mole fraction (α1) of 16-E2-16, which specifies the nonideality of the solution mixtures, along with demonstrating the occurrence of mixed micellization too. Negative ßRub values signify on the whole attractive force of interaction between constituents of mixed micelles. Owing to the incidence of electrolyte NaCl (50 mmol.kg-1), lowering of the micelles' surface charge happens, resulting in aggregation taking place at lower concentration while the presence of urea (NH2CONH2) halts micellization taking place, which means the cmc value increases in the attendance of urea. The [Formula: see text] values for all systems were negative along with the presence of electrolyte/urea. The excess free energy (Gex) of studied mixed systems was also estimated and found to be negative for all the systems. Using the fluorescence quenching method, the micelle aggregation number (Nagg) was evaluated and it was found that the contribution of gemini surfactant was always more than that of the AMH and their value enhances in the existence of electrolyte while decreasing in the attendance of NH2CONH2 in the system. In addition, other fluorescence parameters such as micropolarity (I1/I3), dielectric constant (Dexp) as well as Stern-Volmer binding constants (Ksv) of mixed systems were evaluated and the results showed the synergistic performance of the AMH + 16-E2-16 mixtures. Along with tensiometric and fluorimetric techniques, FT-IR spectroscopy was also engaged to reveal the interaction among constituents.

Multi-Spectroscopic Characterization of Human Serum Albumin Binding with Cyclobenzaprine Hydrochloride: Insights from Biophysical and In Silico Approaches.

Cyclobenzaprine hydrochloride (CBH) is a well-known muscle relaxant that is widely used to relieve muscle spasms and other pain associated with acute musculoskeletal conditions. In this study, we elucidated the binding characteristics of this muscle relaxant to human serum albumin (HSA). From a pharmaceutical and biochemical viewpoint, insight into the structure, functions, dynamics, and features of HSA-CBH complex holds great importance. The binding of CBH with this major circulatory transport protein was studied using a combination of biophysical approaches such as UV-VIS absorption, fluorescence quenching, and circular dichroism (CD) spectroscopy. Various in silico techniques, molecular docking and molecular dynamics, were also used to gain deeper insight into the binding. A reduction in the fluorescence intensities of HSA-CBH complex with a constant increase in temperature, revealed the static mode of protein fluorescence quenching upon CBH addition, which confirmed the formation of the HSA-CBH ground state complex. The alteration in the UV-VIS and far-UV CD spectrum indicated changes in both secondary and tertiary structures of HSA upon binding of CBH, further proving CBH binding to HSA. The analysis of thermodynamic parameters ∆H° and ∆S° showed that binding of CBH to HSA was dominated by intermolecular hydrophobic forces. The results of the molecular docking and molecular dynamics simulation studies also confirmed the stability of the complex and supported the experimental results.

Stability Assessment of Topical Amitriptyline Extemporaneously Compounded with Lipoderm Base, PLO Gel Mediflo 30, and Emollient Cream.

Extemporaneous topical compounds for neuropathic pain offers an alternative or adjunct approach to existing therapies for patients. Assigning evidence-based beyond-use dating prior to dispensing topical medications is a legal requirement by pharmacy governing bodies. The purpose of this study was to utilize a validated stability-indicating high-performance liquid chromatography assay to determine beyond-use dating of topical amitriptyline in three different bases (Lipoderm Base, PLO Gel Mediflo 30, Emollient Cream) at three different temperatures [room temperature (25°C), refrigeration (4°C), and high temperature (40°C)]. Amitriptyline was stable after 90 days at room temperature in both Lipoderm Base and PLO Gel Mediflo 30. However, it was not stable at 40°C in Emollient Cream, irrespective of storage conditions.

A rapid and simple extraction of anti-depressant drugs by effervescent salt-assisted dispersive magnetic micro solid-phase extraction method using new adsorbent Fe3O4@SiO2@N3.

In this work, a rapid and simple method is applied using a newly synthesized nanoadsorbent for the extraction and preconcentration of the drugs Amitriptyline (AMT) and Nortriptyline (NRT), which are then determined using high performance liquid chromatography. We focus on the facile synthesis of Fe3O4@SiO2@N3, as a new and effective adsorbent, and the effervescent salt-assisted dispersive magnetic micro solid-phase extraction method. The applied method and modification of the surface of Fe3O4@SiO2 with the nitrogen-rich group lead to an increase in the interaction between the nanoadsorbent used and the analytes, and increase the extraction recovery. The accuracy of the synthesized nanoadsorbent is confirmed by the FT-IR, FE-SEM, XRD, and VSM analytical techniques. In order to obtain the best experimental conditions, optimization of the main variables involved is carried out using the central composite design method. Under the optimum experimental conditions, the limits of detection (LODs), linear dynamic ranges (LDRs), and relative standard deviations (RSDs for n = 5) for NRT and AMT were found to be as follow: LODs, 0.03 and 0.05 ng/mL; RSDs, 2.04 and 1.1 for NRT and AMT, respectively; and LDRs, 0.07-2000 ng/mL. Furthermore, the results obtained show that the nanoadsorbent can be used for five times with an extraction recovery more than 80% and 70% for AMT and NRT, respectively.

Magnetic extraction of toxin binding liposomes; a method to ameliorate drug toxicity? Preliminary in vitro/ in vivo study.

AIM: Removal of a toxin from the body once absorbed is usually not possible. We describe the use of magnetite containing pH gradient 'MagnepH' liposomes to overcome limitations preventing removal. METHODS: MagnepH liposomes were added to albumin solution containing amitriptyline and dosed intravenously in rats prior to amitriptyline injection. Albumin solution or drawn blood was exposed to a magnet and sampled. RESULTS: One third of amitriptyline was extracted in vitro. In vivo amitriptyline concentrations were 1830 nmol/l (controls) and 10870 nmol/l (MagnepH; n = 2). Amitriptyline extraction increased from 0.6% (control) to 10.4% (MagnepH; 95% CI for difference 2.0-17.6%). CONCLUSION: MagnepH liposomes sequestered amitriptyline and could then be extracted. This method has potential to ameliorate limitations to extracorporeal removal of toxins in poisoning.

Five modified classical least squares based models for stability indicating analysis of cyclobenzaprine HCl with its major degradation products: A comparative study.

Five modified multivariate calibration models based on classical least squares (CLS) in addition to traditional CLS model are developed and validated for assaying cyclobenzaprine HCl (CZ) with its major degradants; dibenzocycloheptatrienone (DZ) and anthraquinone (AQ), whether in its pure form or in pharmaceutical dosage form. The five models are net analyte processing CLS (NAP-CLS), orthogonal signal correction CLS (OSC-CLS), direct orthogonal signal correction CLS (DOSC-CLS) and hybrid linear analysis following the strategy of Xu and Schechter (HLA-XS) or Goicoechea et al. (HLA-GO). The five modified CLS models in addition to traditional CLS were subjected to a comparative study through manipulation of ultra-violet absorption data in the region of 220-350 nm. Three factor four level experimental design was adopted which results in 16 mixtures calibration set covering various concentrations of CZ, DZ and AQ. An extra validation set, composed of nine mixtures, was prepared for validation of the prediction power of the presented models. Experimental results showed high capability of the proposed modified CLS models for assaying CZ successfully without any interference from the co-existing degradation products (DZ and AQ). A statistical comparison between the results of CZ analysis in its dosage form by the six CLS based models and the reported HPLC method was carried out presenting no significant difference in regards to precision and accuracy. Significance of CLS based models is a consequent of their high quantitative and qualitative power for assaying multi-components mixtures.

Photodegradation of amitriptyline in Fe(III)-citrate-oxalate binary system: Synergistic effect and mechanism.

Fe(III) and carboxylic acids are ubiquitous in surface water and atmospheric water droplets. Numerous documents have reported the photochemistry of Fe(III)-carboxylate complexes, typically including Fe(III)-oxalate and Fe(III)-citrate. Our previous study preliminarily showed that oxalate enhances the photoreactivity of Fe(III)-citrate system. Here, we further investigate the synergistic effect of Fe(III)-citrate-oxalate binary system at different conditions with pharmaceutical amitriptyline (AMT) as the model pollutant. In the Fe(III)-oxalate system, the photodegradation of AMT decreased with increasing pH from 3.0 to 8.0. In the Fe(III)-citrate system, the optimal pH for AMT degradation is around 5.0 in the same pH range. For the Fe(III)-citrate-oxalate system, the photodegradation of AMT decreased with increasing pH, indicating the combined effect of both oxalate and citrate on the photoreactivity. The addition of oxalate to the Fe(III)-citrate system markedly accelerated the photodegradation of AMT. The Fe(III)-carboxylate binary system exhibited excellent photoreactivity and up to 90% AMT was removed after 30 min at pH 6.0 with Fe(III)/citrate/oxalate ratio of 10:150:500 (µM). Synergistic effect was observed in Fe(III)-citrate-oxalate binary system in the pH range of 5.0-8.0. The presence of oxalate promoted the depletion of citrate in the Fe(III)-citrate system. The higher concentration ratios of oxalate to citrate facilitated the synergistic effect in the Fe(III)-citrate-oxalate system. By LC-MS analyses, a possible pathway of AMT degradation was proposed based on hydroxyl radicals (OH) mechanism. This finding could be helpful for the better understanding of synergistic mechanism of Fe(III)-citrate-oxalate binary complexes, which will be of great potential application in environmental photocatalysis at near neutral pH.

Molecular determinants of Kv7.1/KCNE1 channel inhibition by amitriptyline.

Amitriptyline (AMIT) is a compound widely prescribed for psychiatric and non-psychiatric conditions including depression, migraine, chronic pain, and anorexia. However, AMIT has been associated with risks of cardiac arrhythmia and sudden death since it can induce prolongation of the QT interval on the surface electrocardiogram and torsade de pointes ventricular arrhythmia. These complications have been attributed to the inhibition of the rapid delayed rectifier potassium current (IKr). The slow delayed rectifier potassium current (IKs) is the main repolarizing cardiac current when IKr is compromised and it has an important role in cardiac repolarization at fast heart rates induced by an elevated sympathetic tone. Therefore, we sought to characterize the effects of AMIT on Kv7.1/KCNE1 and homomeric Kv7.1 channels expressed in HEK-293H cells. Homomeric Kv7.1 and Kv7.1/KCNE1 channels were inhibited by AMIT in a concentration-dependent manner with IC50 values of 8.8 ±â€¯2.1 µM and 2.5 ±â€¯0.8 µM, respectively. This effect was voltage-independent for both homomeric Kv7.1 and Kv7.1/KCNE1 channels. Moreover, mutation of residues located on the P-loop and S6 domain along with molecular docking, suggest that T312, I337 and F340 are the most important molecular determinants for AMIT-Kv7.1 channel interaction. Our experimental findings and modeling suggest that AMIT preferentially blocks the open state of Kv7.1/KCNE1 channels by interacting with specific residues that were previously reported to be important for binding of other compounds, such as chromanol 293B and the benzodiazepine L7.

Suitability of 1-hexyl-3-methylimidazolium ionic liquids for the analysis of pharmaceutical formulations containing tricyclic antidepressants.

The reversed-phase chromatographic behaviour of six tricyclic antidepressants (amitryptiline, clomipramine, doxepin, imipramine, nortryptiline and maprotiline) was examined in this work with acetonitrile-water mobile phases, in the absence and presence of the ionic liquids 1-hexyl-3-methylimidazolium chloride and 1-hexyl-3-methylimidazolium tetrafluoroborate, which have interesting features for the separation of basic compounds, in terms of peak shape combined with reduced retention. Tricyclic antidepressants are low polarity drugs that strongly associate to the alkyl chains of conventional stationary phases. They are also positively charged in the usual working pH range (2-8) in reversed-phase liquid chromatography, due to their strong basic character. In consequence, they may interact with the residual ionised silanols present in conventional silica-based stationary phases, which is translated in stronger retention, and tailed and broad peaks. A simple chromatographic procedure for the control of tricyclic antidepressants in pharmaceutical formulations was developed using a C8 column and a mobile phase containing 30% acetonitrile/10 mM 1-hexyl-3-methylimidazolium chloride at pH 3, with UV detection. Intra- and inter-day precisions were usually below +1.0%, and intra- and inter-day bias (trueness) ranged between ‒2.1% and +2.4%, and between ‒3.0% and +2.3%, respectively. Sample preparation was simple and only required solubilisation and filtration previous to injection.