Moolchand Kurmi

Implementation of design of experiments for optimization of forced degradation conditions and development of a stability-indicating method for furosemide

The study involved optimization of forced degradation conditions and development of a stability-indicating method (SIM) for furosemide employing the design of experiment (DoE) concept. The optimization of forced degradation conditions, especially hydrolytic and oxidative, was done by application of 2(n) full factorial designs, which helped to obtain the targeted 20-30% drug degradation and also enriched levels of degradation products (DPs). For the selective separation of the drug and its DPs for the development of SIM, DoE was applied in three different stages, i.e., primary parameter selection, secondary parameter screening and method optimization. For these three, IV-optimal, Taguchi orthogonal array and face-centred central composite designs were employed, respectively. The organic modifier, buffer pH, gradient time and initial hold time were selected as primary parameters. Initial and final organic modifier percentage, and flow rate came out as critical parameters during secondary parameter screening, which were further evaluated during method optimization. Based on DoE results, an optimized method was obtained wherein a total of twelve DPs were separated successfully. The study also exposed the degradation behaviour of the drug in different forced degradation conditions.

Stability behaviour of antiretroviral drugs and their combinations. 4: Characterization of degradation products of tenofovir alafenamide fumarate and comparison of its degradation and stability behaviour with tenofovir disoproxil fumarate.

In this study, stress degradation behaviour of tenofovir alafenamide fumarate (TAF), a novel prodrug of tenofovir, was investigated and compared with currently used prodrug congener, tenofovir disoproxil fumarate (TDF), whose intrinsic stability was reported by us earlier [14]. Also, pH stability and gastrointestinal stability studies were conducted on both the drugs. High performance liquid chromatography (HPLC) analysis of stressed samples of TAF revealed formation of six degradation products (DPs) against twelve characterized earlier in the case of TDF (RSC Adv. 5(2015) 96117-96129). Like TDF, characterization of DPs of TAF was done by using sophisticated hyphenated liquid chromatography-high resolution mass spectrometry (LC-HRMS) and multistage mass spectrometry (MSn) tools. pH-stability studies between pH 1.2-10 revealed greater stability of TAF, except in acidic conditions, where TAF was degraded extensively. Investigation of gastrointestinal stability in simulated gastric fluid (SGF), simulated intestinal fluid (SIF) and fed state simulated gastric fluid (FeSSGF) suggested that TAF must be administered in fed state, as the drug was practically stable in FeSSGF as compared to extensive loss at acidic pH and in SGF.

Stability behaviour of antiretroviral drugs and their combinations. 2: Characterization of interaction products of lamivudine and tenofovir disoproxil fumarate by mass and NMR spectrometry.

This study focused on drug-drug interaction behaviour among lamivudine (3TC) and tenofovir disoproxil fumarate (TDF), the two anti-retroviral drugs. Apart from pre-known degradation products of individual drugs, a total of twelve interaction products were detected by high performance liquid chromatography (HPLC) using a C18 column as the stationary phase, and methanol and ammonium formate in gradient mode as the mobile phase. The same HPLC method was employed for liquid chromatography-high resolution mass spectrometry (LC-HRMS) and liquid chromatography-multi stage mass spectrometry (LC-MS(n)). For the characterization of interaction products, stability samples were subjected to LC-HRMS, LC-MS(n) and online hydrogen/deuterium exchange studies. Two isomeric interaction products were isolated and subjected to 1D and 2D nuclear magnetic resonance (NMR) studies. The collated information was utilized for the characterization of all twelve interaction products of the two drugs. Pathway of their formation was also outlined.

Stability behaviour of antiretroviral drugs and their combinations. 5: Characterization of novel degradation products of abacavir sulfate by mass and nuclear magnetic resonance spectrometry

HIGHLIGHTSSolution and solid state stress studies conducted on abacavir sulfate.A total of eleven degradation products detected by HPLC and characterized by mass tools.Seven degradation products isolated and structures confirmed by NMR studies.Fragmentation pattern of all degradation products along with the drug established.Pathway of formation of all degradation products outlined. ABSTRACT In the present study, degradation behaviour of abacavir sulfate was evaluated in solution and solid stress conditions. Solution state studies resulted in formation of eleven degradation products; of which two were also formed on solid stress. The same were separated by high performance liquid chromatography. They were characterized using liquid chromatography‐high resolution mass spectrometry, liquid chromatography‐multistage mass spectrometry and hydrogen/deuterium exchange mass spectrometry data. Additionally, seven degradation products were isolated and subjected to 1D and 2D nuclear magnetic resonance studies for their structural confirmation.

Stability behavior of antiretroviral drugs and their combinations. 7: Comparative degradation pathways of lamivudine and emtricitabine and explanation to their differential degradation behavior by density functional theory

HighlightsComparative forced degradation studies conducted on lamivudine and emtricitabine.Degradation products were detected and identified using HPLC and LC‐HRMS studies, respectively.Relative degradation kinetics of both the drugs was studied.Differential degradation kinetics was explained with the help of DFT. Abstract The interest in this study was to establish comparative degradation behavior of lamivudine (3TC) and emtricitabine (FTC) under solution and solid state stress conditions. Structurally, the two drugs differ only in terms of additional fluorine at 5 position in FTC. Along with the known degradation products of both the drugs, one additional degradation product was observed in each case, which was characterized by mass spectrometry. Both the drugs degraded via the same route, but at a differential rate in acid, base and oxidative stress conditions. The variable rate of degradation in acid and base conditions was justified by the application of density functional theory (DFT).

Quantitation of memantine hydrochloride bulk drug and its tablet formulation using proton nuclear magnetic resonance spectrometry

The use of quantitative nuclear magnetic resonance spectrometry for the determination of non‐UV active memantine hydrochloride with relative simplicity and precision has been demonstrated in this study. The method was developed on a 500 MHz NMR instrument and was applied to determination of the drug in a tablet formulation. The analysis was performed by taking caffeine as an internal standard and D2O as the NMR solvent. The signal of methyl protons of memantine hydrochloride appeared at 0.75 ppm (singlet) relative to the signal of caffeine (internal standard) at 3.13 ppm (singlet). The method was found to be linear (r2 = 0.9989) in the drug concentration range of 0.025 to 0.80 mg/ml. The maximum relative standard deviation for accuracy and precision was <2. The limits of detection and quantification were 0.04 and 0.11 mg/ml, respectively. The robustness of the method was revealed by changing nine different parameters. The deviation for each parameter was also within the acceptable limits. The study highlighted possibility of direct determination of memantine hydrochloride in pure form and in its marketed tablet formulation by the use of quantitative NMR, without the need of derivatization, as is the requirement in HPLC studies. Copyright

Forced degradation of lafutidine and characterization of its non-volatile and volatile degradation products using LC-MS/TOF, LC-MSn and HS-GC-MS

Lafutidine was subjected to forced degradation under hydrolysis, oxidation, thermal and photolysis conditions, in accordance with ICH guidelines Q1A(R2) and Q1B. Thirteen non-volatile and one volatile degradation products (DPs) were formed under different stress conditions. Among them, DPs IV, V, VII and IX were formed under acidic stress conditions, while DPs I, X and XIII were formed under basic stress conditions. Oxidative stress resulted in the generation of DPs II, III and VI. DPs XII and XIII were formed under photoacidic conditions, while DPs VIII and XI were formed under both photoacidic and photoneutral conditions. The single volatile DP was formed only under acidic stress. In order to characterize the non-volatile DPs, the complete mass fragmentation pathway of the drug was established with the help of MS/TOF and MSn studies, followed by LC-MS/TOF and on-line H/D exchange experiments. Twelve out of thirteen non-volatile DPs were characterized successfully. The structure of DP-I could not be elucidated, as it did not ionize in both ESI and APCI modes. The lone volatile DP was characterized using GC-MS data and correlation with mass information in NIST library. Finally, the degradation pathway and mechanisms for the formation of the DPs were postulated.

Stability behaviour of antiretroviral drugs and their combinations. 8: Characterization and in-silico toxicity prediction of degradation products of efavirenz

Graphical abstract Figure. No Caption available. HighlightsSolution state stress studies were conducted on efavirenz.Comprehensive mass fragmentation pattern of the drug was outlined.Twelve degradation products detected by HPLC and identified using LC‐HRMS and NMR studies.Degradation pathway of the efavirenz was established.In‐silico toxicity of all the degradation products was evaluated by TOPKAT. ABSTRACT Efavirenz (EFV), an antiretroviral drug, was evaluated for its degradation behaviour in solution state. A total of twelve degradation products were detected on high performance liquid chromatography (HPLC) analyses. Initially, comprehensive mass fragmentation pattern of the drug was established by direct injection and collection of high resolution mass spectrometry (HRMS) and multi‐stage tandem mass spectrometry (MSn) data. Subsequently, LC‐HRMS studies were carried on the stability samples containing the degradation products. Eleven degradation products were isolated and subjected to 1D and 2D nuclear magnetic resonance (NMR) studies for their structural confirmation. The collated information was utilized for the characterization of all the degradation products and hence in outlining the comprehensive degradation pathway of the drug. In‐silico toxicity of the degradation products was evaluated by TOPKAT analyses.

Stability behaviour of antiretroviral drugs and their combinations. 6: evidence of formation of potentially toxic degradation products of zidovudine under hydrolytic and photolytic conditions

This study explored the comprehensive degradation behaviour of zidovudine (ZDV) under solution and solid stress conditions. In total, nine degradation products were detected by high performance liquid chromatography (HPLC). The same were tentatively characterized with the help of high resolution and multistage mass spectrometry. Among them, five degradation products were also enriched and isolated with the help of semi-preparative HPLC and subjected to 1D and 2D nuclear magnetic resonance and/or infrared spectrometric studies to confirm their structures. The characterization of all the degradation products helped in outlining the comprehensive degradation pathway of ZDV. A significant finding was the formation of 3′-amino-3′-deoxythymidine (AMT) upon base hydrolysis as well as photolysis of the drug. This product is a known catabolite of the drug with a high degree of toxicity. Also, a few other degradation products formed during the study were predicted to have potential toxicity.

Characterization of forced degradation products of torasemide through MS tools and explanation of unusual losses observed during mass fragmentation of drug and degradation products through density functional theory

Graphical abstract Figure. No Caption available. HighlightsStressing of the drug under ICH prescribed conditions followed by HPLC separation of the degradation products.Characterization of three degradation products by LC–MS tools.Establishment of comprehensive mass fragmentation pattern of the drug and DPs.Explanation of unusual losses of S, HS•, SO, SO2, HSO2•, CO, CHO• and C5H3NOS and rearrangement processes with the help of DFT. Abstract Mass spectrometry tools (HRMS/LC‐HRMS, MSn, and/or on‐line H/D exchange) were employed to establish mass fragmentation pattern of torasemide and to characterize its degradation products. During collision‐induced dissociation, multiple rearrangement processes and unusual losses of sulfur (S), sulfanyl (HS•), sulfur dioxide (SO2), sulphinic acid radical (HSO2•), sulfur monoxide (SO), carbon monoxide (CO), formyl radical (CHO•) and C5H3NOS were observed. The same were successfully explained by study of energy profiles, established by application of density functional theory (DFT).