Identification of photodegradation product of amisulpride by ultra-high-pressure liquid chromatography–DAD/ESI-quadrupole time-of-flight-mass spectrometry

Photocatalytic Degradation of Pharmaceutical Amisulpride Using g-C3N4 Catalyst and UV-A Irradiation

In the present study, the photocatalytic degradation of amisulpride using g-C3N4 catalyst under UV-A irradiation was investigated. The photocatalytic process was evaluated in terms of its effectiveness to remove amisulpride from ultrapure and real municipal wastewater. High removal percentages were achieved in both aqueous matrices. However, a slower degradation rate was observed using wastewater as matrix that could be attributed to its complex chemical composition. The transformation products (TPs) were identified with liquid chromatography–mass spectrometry (LC–MS) in both ultrapure and real municipal wastewater. Based on the identified TPs, the photocatalytic degradation pathways of amisulpride are proposed which include mainly oxidation, dealkylation, and cleavage of the methoxy group. Moreover, the contribution of reactive species to the degradation mechanism was studied using well-documented scavengers, and the significant role of h+ and O2•− in the reaction mechanism was proved. The evolution of ecotoxicity was also estimated using microalgae Chlorococcum sp. and Dunaliella tertiolecta. Low toxicity was observed during the overall process without the formation of toxic TPs when ultrapure water was used as matrix. In the case of real municipal wastewater, an increased toxicity was observed at the beginning of the process which is attributed to the composition of the matrix. The application of heterogeneous photocatalysis reduced the toxicity, and almost complete detoxification was achieved at the end of the process. Our results are in accordance with literature data that reported that heterogeneous photocatalysis is effective for the removal of amisulpride from aqueous matrices.

Persistence of N-oxides transformation products of tertiary amine drugs at lab and field studies

This work aimed at studying the formation and persistence of N-oxides transformation products (TPs) of tertiary amine drugs by combining laboratory and field studies relevant for surface water. A monitoring study using passive samplers was first achieved for assessing attenuation of selected pharmaceuticals and their related N-oxides and N-, O-dealkylated TPs (i.e., venlafaxine, tramadol, amisulpride and sulpiride) along a 1.7 km river stretch between two sampling sites. This study revealed the stability of tramadol-N-oxide, amisulpride-N-oxide and the fast dissipation of O-desmethylvenlafaxine-N-oxide, as well as the significance of N-oxidized TPs in comparison to N-dealkylated TPs and parent compounds in river. Lab-scale experiments were then implemented for a better understanding of their mechanisms of formation and degradation under aerobic water/sediment testing and under simulated solar photochemistry. N-oxidation reactions were always a minor transformation pathway under both degradation conditions with respect to N-and O-dealkylation reactions. The amount of generated N-oxides were similar for venlafaxine, tramadol and sulpiride and peaked in the 8.4-12.8% and <4% of their initial concentration (100 μg/L), during photodegradation and biodegradation experiments, respectively. Other transformation pathways such as hydroxylation and α-C-hydroxylation followed by oxidation to amide or dehydration were also identified. Investigated N-oxides TPs (except O-desmethylvenlafaxine-N-oxide) were found stable under solar photolysis and aerobic biodegradation with a very slight reverse reaction to parent compound observed for tramadol-N-oxide and amisulpride-N-oxide. Lab-scale degradation experiments were not able to anticipate the high occurrence levels of N-oxide compounds in the environment. This was most likely due to faster degradation kinetics and/or higher sorption to sediment of parent compounds and dealkylated TPs over N-oxide TPs, resulting in higher relative accumulation of the latter.

The overall assessment of simultaneous photocatalytic degradation of Cimetidine and Amisulpride by using chemical and genotoxicological approaches

Pharmaceutical Active Compounds (PhACs) are of particular interest among the emerging contaminants detected in the aquatic environment. Commonly, PhACs exist as complex mixtures in aquatic systems, causing potential adverse effects to the environment and human health than those of individual compounds. Based on the increasing interest in the contamination of water resources by PhACs, the photocatalytic degradation of Cimetidine and Amisulpride as a mixture in combination with their toxic and genotoxic effects before and after the treatment were evaluated for the first time. The toxic, genotoxic and cytotoxic effects were investigated using the Trypan Blue Exclusion Test and the Cytokinesis Block MicroNucleus (CBMN) assay in cultured human lymphocytes. The photocatalytic degradation of the PhACs was studied in ultrapure water and environmentally relevant matrices using UV-A and visible (Vis) irradiation and C-TiO₂ (TiO₂ Kronos vlp 7000) as photocatalyst. High removal percentages were observed for both compounds under UV-A and Vis irradiation in ultrapure water. In lake and drinking water a slower degradation rate was shown that could be attributed to the complex composition of these matrices. Scavenging experiments highlighted the significant role of h⁺ and O₂^●- in the degradation mechanisms under both irradiation sources. Oxidation, dealkylation and deamination were the main degradation pathways. Regarding the individual compounds, Amisulpride was found to be more cytotoxic than Cimetidine. No significant differences of the genotoxic effects during the treatment were observed. However, a slight increase in cytotoxicity was observed at the first stages of the process. At the end of the process under both UV-A and Vis light, non-significant cytotoxic/toxic effects were observed. Based on the results, heterogeneous photocatalysis can be considered as an effective process for the treatment of complex mixtures without the formation of harmful transformation products.

A rapid FTIR spectroscopic assay for quantitative determination of Memantine hydrochloride and Amisulpride in human plasma and pharmaceutical formulations

A selective, new, rapid and nondestructive Fourier transform Infrared spectroscopic assay has been developed for simultaneous determination of Memantine hydrochloride and Amisulpride in human plasma and their pharmaceutical formulations without interference from common dugs excipients. A binary mixture of ME and nonselective β-blocker namely; carvidalol has been determined the solid-state by FTIR spectroscopy for the first time. The linear range had been extent from 1.0 to 8.0 and 1.0 to 10.0 μg/mg, for ME and AMS respectively. The detection limits were 0.29 and 0.23 μg/mg while quantitation limits were 0.90 and 0.71 μg/mg for ME and AMS respectively. The developed assay has been validated according to ICH & USP recommendations and successfully applied for quantitative determination of selected drugs in biological fluid.

Photodegradation assessment of amisulpride, doxepin, haloperidol, risperidone, venlafaxine, and zopiclone in bulk drug and in the presence of excipients

Abstract

Photostability of amisulpride, doxepin, haloperidol, risperidone, venlafaxine, and zopiclone in APIs and powdered tablets during exposure to UVA irradiation was studied. In order to evaluate the photodegradation process an ultrahigh performance liquid chromatography method coupled with tandem mass spectrometry (UHPLC-MS/MS) was developed and validated. It was found that the photodegradation of the studied compounds depends on the type of drug and co-existing excipients. Different percentage of photodegradation of the studied drugs was observed, and therefore amisulpride decomposed at 2.63% in bulk drug and at 5.74% in pharmaceutical preparation, doxepin: 29% and 72.38%, haloperidol: 3.71% and 26.20%, risperidone: 7.13% and 12.86%, venlafaxine: 38.59% and 4.22%, zopiclone: 18.62% and 31.42% respectively, after 114 days of UVA irradiation. In addition, kinetic evaluation of the photodegradation process was performed by determining the order of reaction, reaction rate constant k and time t0.1 and t0.5. The photodegradation products of studied drugs were identified, and their fragmentation pathways, derived from MS/MS data, were proposed. The photostability testing is an integral part of the drug stability assessment to ensure quality, efficacy and safety of the formulated products during manufacturing process, storage as well as normal use.

Graphic abstract

Photocatalytic Treatment of Pharmaceuticals in Real Hospital Wastewaters for Effluent Quality Amelioration

The presence of pharmaceutically active compounds (PhACs) in the wastewater effluents has confirmed that conventional wastewater treatment technologies are not sufficiently effective in the pharmaceuticals’ removal. The objective of the present study was to evaluate and compare the photocatalytic degradation of PhACs using TiO2-P25, graphitic carbon nitride (g-C3N4, CN) and a heterojunction of perovskite strodium titanate and graphitic carbon nitride SrTiO3/g-C3N4 (20% g-C3N4, 20CNSTO) photocatalytic materials, in hospital wastewater effluents, by simulated solar irradiation. The experiments were performed by using real wastewater samples collected from the university hospital wastewater treatment plant (WWTP) effluent of Ioannina city (Northwestern Greece) and inherent pharmaceutical concentration levels. The analysis of the samples was accomplished by solid phase extraction followed by liquid chromatography-Orbitrap high-resolution mass spectrometry. In the cases of TiO2 and CN, more than 70% of the initial concentration (e.g., venlafaxine) was degraded after 90 min, while 20CNSTO presented lower photocatalytic performance. Furthermore, some compounds were sporadically detected (e.g., fluoxetine) or their concentrations remained stable during the photocatalytic treatment time period (e.g., trimethoprim). In total 11 transformation products (TPs) were formed along the degradation processes and were identified by using liquid chromatography high resolution mass spectrometry.

Photolytic and photocatalytic degradation of tandospirone: Determination of kinetics, identification of transformation products and in silico estimation of toxicity

The photolytic and photocatalytic transformation of tandospirone with the use of TiO₂ and H₂O₂ was investigated. A micro-scale method for simultaneous irradiation with simulated full solar spectrum of multiple samples in photostability chamber was proposed. RP-UHPLC-DAD coupled with ESI-Q-TOF mass spectrometer was used for the quantitative and qualitative analysis of the processes. The developed method was fully validated and the kinetic parameters of tandospirone photodegradation were compared. The structures of eighteen photoproducts as well as phototransformation pathways were proposed. Based on the elucidated structures, computational toxicity assessment with the use of various software was performed and most of the photoproducts were found as less or similarly toxic to the parent compound. Nevertheless, several products, including one of the drug main metabolites, were significantly more toxic than the parent drug. The multivariate chemometric method (principal component analysis) was used to compare the toxicity of phototransformation products as well as the toxicity of the assessment methods.

Application of an Untargeted Chemometric Strategy in the Impurity Profiling of Pharmaceuticals: An Example of Amisulpride

The untargeted chemometric methodology for the impurity profiling of amisulpride pharmaceutical formulations was successfully applied and developed. For this purpose a fast, accurate and specific analytical method was elaborated with the use of ultra high pressure liquid chromatography coupled with high resolution hybrid electrospray ionization quadrupole time of flight mass spectrometer in a fast polarity switching mode. All the obtained chromatographic profiles were aligned and a multivariate chemometric analysis including principal component analysis and partial least square (PLS) was performed. The developed PLS-DA pattern recognition model allowed the identification of all the analyzed pharmaceutical formulations of amisulpride as well as their manufacturers. Additionally, six impurities of amisulpride were identified by the use of MS/MS fragmentation and one of them was found as the main impurity (Imp-1) and can be regarded as the primary impurity "marker" for the analyzed formulations. Furthermore, one new impurity of amisulpride was found and its chemical structure was proposed (4-amino-5-(ethylsulfinyl)-2-methoxy-N-[(1-ethylpyrrolidin-2-yl)methyl]benzamide).

Studies on photodegradation process of psychotropic drugs: a review

Consumption of psychotropic drugs is still increasing, especially in high-income countries. One of the most crucial consequences of this fact is significant release of them to the environment. Considerable amounts of atypical antipsychotics, benzodiazepines, antidepressants, and their metabolites were detected in river, lake, and sea water, as well as in tissues of aquatic organisms. Their ecotoxicity was proved by numerous studies. It should be noticed that interaction between psychotropic pharmaceuticals and radiation may lead to formation of potentially more toxic intermediates. On the other hand, photo-assisted wastewater treatment methods can be used as an efficient way to eliminate them from the environment. Many methods based on photolysis and photocatalysis were proposed and developed recently; nevertheless, the problem is still unsolved. However, according to recent studies, photocatalysis could be considered as the most promising and far more effective than regular photolysis. An overview on photolytic as well as homogenous and heterogeneous photocatalytic degradation methods with the use of various catalysts is presented. The photostability and phototoxicity of pharmaceuticals were also discussed. Various analytical methods were used for the photodegradation research, and this issue was also compared and summarized. Use of high-resolution multistage mass spectrometry (Q-TOF, ion trap, Orbitrap) was suggested. The combined techniques such as LC-MS, GC-MS, and LC-NMR, which enable qualitative and quantitative analyses in one run, proved to be the most valuable in this case. Assembling of MS/MS spectra libraries of drug molecules and their phototransformation products was identified as the future challenge.

Occurrence and fate of amisulpride, sulpiride, and lamotrigine in municipal wastewater treatment plants with biological treatment and ozonation

This study examines the transformation and removal of the atypical antipsychotics amisulpride and sulpiride and the anticonvulsant lamotrigine in municipal wastewater treatment plants (WWTPs). Amisulpride, sulpiride and lamotrigine were selected using a tailored non-target screening approach. In WWTPs, lamotrigine concentrations increased from 1.1 to 1.6μg/L while sulpiride and amisulpride exhibited similar concentrations, up to 1.1μg/L and 1.3μg/L, respectively. It was found that N2-glucuronide conjugates of lamotrigine were cleaved to form lamotrigine. Both lamotrigine and amisulpride were detected in groundwater with a concentration of 0.07μg/L. Sulpiride was identified but not quantified. This demonstrates that amisulpride, sulpiride and lamotrigine might be used as indicators for treated wastewater in raw waters used for drinking water production. Furthermore, it could be shown that all three pharmaceutical compounds are efficiently oxidized by ozonation, leading mainly to N-oxide oxidation products. No significant removal of the N-oxides of amisulpride, sulpiride and lamotrigine was observed in the bench-scale biodegradation experiments with activated sludge. This indicated their high biological persistence. Therefore, N-oxides might be appropriate as indicators for post-ozonation as a major technology for the advanced treatment of secondary effluent.

Photolysis of the antidepressants amisulpride and desipramine in wastewaters: Identification of transformation products formed and their fate

Attenuation of pharmaceuticals due to natural sunlight is expected to be an important removal pathway in wastewater treatment plants using treatment lagoon systems. In this work, the photolysis of two antidepressants, amisulpride and desipramine, has been investigated in both ultrapure water and wastewater under simulated solar irradiation. Results showed that for amisulpride short irradiation times (t1/2 approximately 3h in pure water and 4h in wastewater) were adequate to degrade the parent compound while a longer exposure period was required for desipramine (t1/2 of approximately 36 h in pure water), although its degradation is enhanced almost three times by indirect photolysis in wastewaters. A significant number of transformation products (TPs) were identified for both pharmaceuticals by high-resolution mass spectrometry. In general, TPs formed are not persistent although acute toxicity tests for desipramine and its TPs showed an increase of the mixture toxicity after solar irradiation, suggesting that some TPs may be more toxic than the parent compound. In wastewaters collected from treatment lagoons, only amisulpride and one of its major TPs, TP 357, were detected. This indicates that long solar exposure times may be necessary for an effective elimination of these substances in lagoon systems or that photolysis may not be the main removal pathway for these particular compounds.

Spectrofluorimetric determination of amisulpride and bumidazone in raw materials and tablets

A highly sensitive, simple and rapid spectrofluorimetric method was developed for the determination of amisulpride (AMS) and bumidazone (BUM) in tablet form. The proposed method is based on measuring the native fluorescence of the studied drugs in methanol at 360 and 344 nm after excitation at 276 and 232 nm for AMS and BUM, respectively. The fluorescence-concentration plots were rectilinear over the ranges of 5.0-60.0 ng/mL for AMS and 0.5-5.0 µg/mL for BUM. The lower detection limits were 0.70 ng/mL and 0.06 µg/mL, and the lower quantification limits were 2.0 ng/mL and 0.18 µg/mL for AMS and BUM, respectively. The method was successfully applied for the analysis of AMS and BUM in commercial tablets. Statistical evaluation and comparison of the data obtained using the proposed and comparison methods revealed good accuracy and precision for the proposed method.

Photodegradation of pharmaceuticals in the aquatic environment by sunlight and UV-A, -B and -C irradiation

In order to investigate the effect of sunlight on the persistence and ecotoxicity of pharmaceuticals contaminating the aquatic environment, we exposed nine pharmaceuticals (acetaminophen (AA), amiodarone (AM), dapsone (DP), dexamethasone (DX), indomethacin (IM), naproxen (NP), phenytoin (PH), raloxifene (RL), and sulindac (SL)) in aqueous media to sunlight and to ultraviolet (UV) irradiation at 254, 302 or 365 nm (UV-C, UV-B or UV-A, respectively). Degradation of the pharmaceuticals was monitored by means of high-performance liquid chromatography (HPLC). Sunlight completely degraded AM, DP and DX within 6 hr, and partly degraded the other pharmaceuticals, except AA and PH, which were not degraded. Similar results were obtained with UV-B, while UV-A was less effective (both UV-A and -B are components of sunlight). All the pharmaceuticals were photodegraded by UV-C, which is used for sterilization in sewage treatment plants. Thus, the photodegradation rates of pharmaceuticals are dependent on both chemical structure and the wavelength of UV exposure. Toxicity assay using the luminescent bacteria test (ISO11348) indicated that UV irradiation reduced the toxicity of some pharmaceuticals to aquatic organisms by decreasing their amount (photodegradation) and increased the toxicity of others by generating toxic photoproduct(s). These results indicate the importance of investigating not only parent compounds, but also photoproducts in the risk assessment of pharmaceuticals in aquatic environments.