A highly sensitive spectrofluorimetric method for the determination of bilastine in human plasma: Application of content uniformity testing.

Bilastine, a new second generation antihistaminic drug, has been widely used for relieving symptoms of allergic rhinitis and urticaria without a sedative effect. A simple, cost-effective, and highly sensitive fluorimetric method was developed for the estimation of bilastine in human plasma, in addition to its pure state and tablets. The suggested method depended on binary complex formation of eosin with bilastine in a buffered medium at pH 4.2. The formed complex resulted in quantitative quenching of eosin emission at 538 nm after excitation at 335 nm. This method demonstrates a broad range of linearity, spanning from 200 to 1000 ng/mL, and exhibits exceptional sensitivity, with a limit of detection and quantitation of 30.85 and 93.48 ng/mL, respectively. In addition, this spectrofluorimetric method may be employed to determine the amount of bilastine in human plasma and tablets with satisfactory accuracy and excellent precision. Furthermore, the content uniformity of bilastine in commercially available tablets was successfully tested by this approach. Compared with the reference method, there were no significant variations in terms of precision or accuracy. In conclusion, the proposed protocol is highly recommended to quantitatively estimate bilastine in different quality control settings.

Spectrofluorimetric Protocol for Estimation of Commonly Used Antispasmodic Drotaverine. Fluorescence Quenching Study.

A fast, simple, accurate, precise, and cheap fluorimetric protocol has been proposed for analysis of a phosphodiesterase-IV inhibitor, namely drotaverine hydrochloride. Fluorimetric protocol is based on estimating the decrease in the eosin Y fluorescence intensity by quantitative addition of drotaverine at pH 3.1 (acetate buffer). An ion pair complex is formed, which leads to quenching in the fluorescence intensity of the dye without need of prior extraction at 534 nm (λex. 339 nm). Different reaction perimeters which influence the production of complex (ion pair between drotaverine and eosin) were deeply investigated and optimized. The developed fluorimetric protocol is capable for quantitative estimation of drotaverine in linear range of 0.4 to 2.5 µg mL-1. After method validation in respect to ICH guidelines, it was applied to determine drotaverine in its commercial preparation. By comparing with other reported method, the developed and validated fluorimetric protocol is capable for estimation of drotaverine in commercial preparation with good accuracy and excellent precision.

Selective Spectrofluorimetric Protocol for Determination of Commonly Used Gram-negative Bactericidal Drug in Combined Pharmaceutical Dosage Forms and Human Plasma.

Gram-negative bacteria cause infections such as skin infection, meningitis, and pneumonia in human being. Gram-negative bacteria are highly resistant to most availaible bactericidal drugs. One of the most commonly used Gram-negative bactericidal drug is Polymyxin B sulfate (PMS). In addition, it is used in cases of highly resistant Gram-negative bacterial infections. The widespread of PMS necessitate the development of an exceedingly sensitive and selective fluorimetric assay for its determination in pure form, different pharmaceutical dosage forms, and human plasma. The presented method is used to determine PMS in their dosage form (vials) and combined pharmaceutical formulations (skin and eye ointments) with a high degree of accuracy and selectivity. The described procedure relies on the structure of a derivative of a high degree of fluorescence called dihydropyridine, via the condensation of the amino moiety of PMS with two equivalents of acetylacetone in the presence of formaldehyde and Teorell buffer (pH = 3). The fluorescent product was measured at 471 nm (λex = 402 nm). The linearity ranged from 100-3000 ng mL-1 of PMS with an excellent r2 of 0.9998. LOD and LOQ were 27.16 ng mL-1 and 82.30 ng mL-1, respectively. Owing to the developed method's high selectivity, it was successfully utilized for assay of PMS, in the ointment, in the presence of oxytetracycline as an active ingredient. Furthermore, the procedure applied for the estimation of parenteral PMS in human plasma with very good mean recovery 97.42 ± 1.46.

Novel environment friendly TLC-densitometric method for the determination of anti-coronavirus drugs "Remdesivir and Favipiravir": Green assessment with application to pharmaceutical formulations and human plasma.

A great demand for discovering new therapeutic solutions has been considered all over the world for managing the rapidly progressing COVID-19 pandemic. Remdesivir (REM) and Favipiravir (FAV) are introduced as promising newly developed antiviral agents against the corona virus as evidenced by the clinical findings. Hence, the optimization of an analytical method for their simultaneous determination acquires potential importance in quality control labs and further confirmatory investigations. Herein, a green, sensitive, and selective densitometric method has been proposed and validated for determination of REM and FAV in pharmaceutical formulations and spiked human plasma on normal phase TLC plates. A solvent mixture of ethyl acetate-methanol-ammonia (8:2:0.2 by volume) has been chosen as developing mobile phase system. Well resolved spots have been detected at 235 nm with retardation factors (Rf) of 0.18 and 0.98 for REM and FAV, respectively. A validation study has been carried out in the light of ICH guidelines. Remdesivir and FAV have shown excellent sensitivities with quantitation limits down to 0.12 and 0.07 µg/band, respectively. The developed method has been successfully applied to tablet formulations and spiked plasma with excellent recoveries ranged from 97.21 to 101.31%. The greenness of the method has been evaluated using the standards of greenness profile and Eco-Scale. It has passed the four greenness profile quadrants and achieved 80 score in Eco-Scale.

Facile spectrofluorimetric quantitation of octreotide, a synthetic peptide, in its pure form and pharmaceutical formulation; evaluation of the method's greenness.

A new, rapid, highly sensitive, and affordable spectrofluorimetric approach has been constructed and validated for the determination of octreotide in its authentic form and pharmaceutical dosage form. Octreotide is an important synthetic analog of the naturally occurring somatostatin hormone. The developed spectrofluorimetric approach is actually dependent on the measurement of octreotide native fluorescence at emission wavelength of 342 nm after excitation at 218 nm. At optimal reaction conditions, the calibration curve has been constructed over the concentration range 200-2000 ng ml-1 , with excellent linearity. The limits of detection and quantitation values were found to be 55 and 169 ng ml-1 , respectively. The developed approach has been effectively used to determine octreotide in its pharmaceutical ampoules, without interference from the excipients in the dosage form. The developed approach is simple, time-saving, and does not require multiple pretreatment steps for samples, costly apparatus, or dangerous materials. As a result, it can be used to detect and quantify octreotide acetate in quality control laboratories.

Salvage parenteral antibiotics for multidrug-resistant (MDR) Gram-negative bacteria; a fluorescamine-based technique for ultrasensitive spectrofluorimetric measurement of Polymyxins; human plasma application.

Polymyxins (PMS), namely Colistin (CS) and polymyxin B (poly B), are antimicrobial drugs that have been recently used to treat multiresistant Gram-negative bacteria infections and their resurgence, owing to a lack of new antibiotics. A speedy, simple, and ultrasensitive spectrofluorimetric screening of PMS in pharmaceutical formulations and biological fluids was urgently required from this point forwards. A reaction between fluorescamine and the aliphatic amino moiety found in both drugs was performed in a slightly alkaline borate buffer (pH 8.5) resulted in highly fluorescent products measured at λem 460 (after λex 390.5 nm). Linear calibration curves were constructed over the concentration range 70-1800 ng ml-1 and 100 to 1400 ng ml-1 , with slope values of 0.273 and 0.286, correlation coefficients of 0.9998 and 0.9997, and determination coefficient of 0.9997 and 0.9994 for poly B and CS, respectively. The ultrasensitivity of the proposed method was demonstrated by the very low limit of quantification values of 67.56 ng ml-1 and 94.89 ng ml-1 for poly B and CS, respectively. The cited drugs were successfully determined in their intravenous market preparations by the prescribed method. Moreover, due to the high sensitivity, the suggested method was used to assay the investigated drugs in biological fluids.

Spectrofluorimetric determination of the anti-Covid 19 agent, remdesivir, in vials and spiked human plasma.

Following the sudden widespread of the novel coronavirus (COVID-19) which first appeared in Wuhan city. Remdesivir (REM) was the first medicine licensed by the US Food and Drug Administration (FDA) for COVID-19 infected hospitalized patients. Hence, there was an urgent demand for the optimization of efficient selective and sensitive methods to be developed for the determination of REM in pharmaceuticals as well as biological samples. A sensitive and simple green spectrofluorimetric method has been developed to determine REM in pharmaceutical formulation, in addition to, spiked human plasma. The technique involves measuring the native fluorescence of REM in distilled water at 410 nm followed by excitation at 241 nm, giving a linear relationship over the range 50.00-500.00 ng/mL, and then improving the sensitivity of REM through micellar formation using 2.00% w/v sodium dodecyl sulfate (SDS). A linear relationship has been obtained over the range 10.00-350.00 ng/mL having detection and quantitation limits of 2.34 and 7.10 ng/mL, respectively. Different analytical parameters have been carefully studied. A validation study has been conducted successfully in accordance with the FDA and the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) guidelines. The developed methods' greenness was assessed utilizing a greenness profile and analytical eco-scale standards. Both methods were discovered to be environmentally friendly and could be successfully used for the determination of the studied drugs in pharmaceutical formulation and human plasma with good accuracy and high precision. As a result, the developed spectrofluorimetric methods could be ideally suited for determination of REM in quality control and medicinal laboratories.

Sensitivity improvement for spectrofluorimetric determination of commonly used antifungal drug 'nystatin': application for oral suspension.

In this paper, two simple, rapid and highly sensitive spectrofluorimetric methods were developed and validated for nystatin determination in its pure form and pharmaceutical dosage form (oral suspension). The first method was based on measuring the nystatin native fluorescence after dilution with isopropyl alcohol at 407 nm (excitation 303 nm). The fluoresence intensity was linearly dependant on the nystatin concentration within the specified range 50-500 ng ml-1 . The second was based on micellar enhancement of nystatin fluorescence using sodium dodecyl sulphate (SDS). In the presence of 2% w/v SDS, an ~1.9-fold enhancement could be achieved in the relative fluorescence intensity of nystatin. The linear range for the second method was 20-100 ng ml-1 . The limits of quantification and detection were found to be 43.23 ng ml-1 and 14.27 ng ml-1 (Method I), 6.08 ng ml-1 and 2.0 ng ml-1 (Method II). According to percentage recoveries and relative standard deviations (RSDs) obtained, the proposed methods were precise (RSDs were less than 2%), reproducible, and accurate and could be successfully applied for quantitative estimation of nystatin in its dosage form. The statistical results of this method were compared with that of the reported method and showed excellent agreement with respect to accuracy and precision.

A novel spectrofluorimetric method for determination of lomefloxacin adopting on zinc(II) chelation strategy: Application in human plasma.

A new sensitive and instantaneous spectrofluorimetric method for efficient determination of lomefloxacin (LMX) in its pure, dosage form and human plasma was designed. The developed method depends on formation of a metal-chelation compound of LMX as a ligand with zinc(II) in a buffer of acetate (pH 5.5). The following parameters; type of metal, concentration of metal, pH, type of buffer and diluting solvent were optimized. After carefully investigation; 0.2 mM zinc, 2.0 ml acetate buffer (pH 5.5) and water as diluting solvent were set as optimum reaction conditions. Under these conditions, a large increase in the intensity of the fluorescence of LMX was attained at 450 after excitation at 284 nm. The limits of detection and quantification were 5.8 and 1.9 ng ml-1 , respectively, with linearity range of 10.0 to 500.0 ng ml-1 . The binding mode of LMX and zinc(II) ion (Zn2+ ) was found to be 2:1, respectively, and confirmed by Job's plot method. Furthermore, it extended to the analysis of LMX in the spiked plasma of humans with percentage recovery (98.70 ± 0.97 to 100.30 ± 1.69%, n = 3).

Green spectrofluorimetric determination of salmeterol xinafoate in its pure forms, medicinal commercial formula, and human plasma: Application for stability studies.

A natural, accurate, extremely rapid, and precise spectrofluorometric method has been developed and validated for determination of salmeterol (SAL) xinafoate in its medicinal commercial form and spiked human plasma. The native SAL fluorescence has been measured at 415 nm (after 340 nm as excitation) in distilled water. Different factors affecting the native fluorescence consistency of SAL were surveyed and optimized. The suggested procedure was capable of SAL determination over concentrations ranging 200-2000 ng.mL-1 with excellent correlation coefficient of 0.9995. The limits of detection and quantification were estimated as 44.44 ng mL-1 and 134.66 ng mL-1 , respectively. The method has good accuracy and precision. The green spectrofluorometric method was used for determination of SAL in its commercial preparations and the results were in accordance with other reported methods regarding accuracy and precision. Moreover, the proposed procedure was enforced for stability indicating assay of SAL and for SAL determination in spiked human plasma. Nearly no cost, high sensitivity, and wide application make the proposed method ideally suited for analysis of SAL in quality control laboratories.

The first spectrofluorimetric approach for quantification of colistin sulfate and its prodrug colistimethate sodium in pharmaceutical dosage form and human plasma.

A new, accurate, nonextractive, and sensitive fluorimetric approach was proposed and validated for the first time estimation of colistin sulfate and its inactive prodrug colistimethate sodium in its bulk form, pharmaceutical formulations, and human plasma. The approach relied on condensation between acetylacetone/formaldehyde and the primary amino moiety of nonfluorescent colistin in Teorell and Stenhagen buffer (pH 2.8) by the Hantzsch reaction to form a highly fluorescent dihydropyridine derivative. The fluorescent product was measured at 460 nm (λex  = 402 nm). A plot of relative fluorescence intensity (RFI) versus concentration was rectilinear over the range 200-4000 ng ml-1 with excellent correlation (r) and determination (r2 ) coefficients of 0.9999 and 0.9998, respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were 40.91 and 123.99 ng ml-1 , respectively. The present procedure was useful for determination of colistin sulfate either in powder form for suspension or in its parenteral prodrug colistimethate sodium in vial formulation. The investigated approach was applied for in vitro quantification of this drug in spiked human plasma, with a per cent mean recovery of 98.24 ± 1.34. The proposed method is reliable, selective, and does not require tedious sample pretreatment steps, expensive instrumentation, or harmful reagents, all of which make it ideally suited for use in quality control laboratories.

Effect of Drug Combination on Omeprazole Metabolism by Cytochrome P450 2C19 in Helicobacter pylori Eradication Therapy.

Helicobacter pylori (H. pylori) infection is common and can result in gastric and duodenal ulcers, and in some cases, gastric lymphoma and cancer. Omeprazole (OMP)-in combination with clarithromycin (CLR), amoxicillin (AMX), tinidazole (TND), or metronidazole (MET)-is used in double or triple combination therapy for eradication of H. pylori. However, the roles of the drugs other than OMP are not clearly understood. Therefore, in the present study, we aimed to investigate any effects of these drugs on OMP metabolism by wild-type CYP2C19 using spectroscopy and enzyme kinetics. The dissociation constants (Kd) for CYP2C19 with OMP, CLR, AMX, TND, and MET were 8.6, 126, 156, 174, and 249 µM, respectively. The intrinsic clearance of OMP was determined to be 355 mL/min/µmol of CYP2C19. Metabolism of OMP was significantly inhibited by 69, 66, 28, and 40% in the presence of CLR, TND, AMX, and MET, respectively. Moreover, the combination of CLR and TND resulted in 76% inhibition of OMP metabolism, while the combination of AMX and MET resulted in 48% inhibition of OMP metabolism. Both combinations of drugs not only have antibacterial effects, but also enhance the effect of OMP by inhibiting its metabolism by CYP2C19. These results indicate that drug-drug interactions of co-administered drugs can cause complex effects, providing a basis for OMP dose adjustment when used in combination therapy for H. pylori eradication.

Spectrofluorimetric determination of certain adrenergic agonist drugs in their pure forms and pharmaceutical formulations: Content uniformity test application.

A new, simple, sensitive and rapid spectrofluorimetric method has been developed for determination of certain adrenergic agonists such as isoxsuprine hydrochloride, ritodrine hydrochloride and etilefrine hydrochloride in their pure forms and pharmaceutical dosage forms. The method depends on micellar enhancement of the native fluorescence of investigated drugs by using 2% w/v sodium dodecyl sulfate (SDS) as an anionic surfactant. The enhanced fluorescence intensity of investigated drugs was measured at 305 nm after excitation at 278 nm. The interaction of studied drugs with SDS was studied, and the enhanced fluorescence intensity was exploited to develop an assay method for the determination of investigated drugs. The relative fluorescence intensity-concentration plots were rectilinear over the range 0.15-3.00 µg ml-1 , with low quantification limits of 0.132, 0.123 and 0.118 µg mL-1 for isoxsuprine, ritodrine and etilefrine, respectively. The proposed method was successfully applied for determination of studied drugs in their pharmaceutical formulations. Moreover, the high sensitivity of the proposed method allows performing the content uniformity testing of the studied drugs in their tablets by using the official United States Pharmacopeia (USP) guidelines. Statistical comparisons of the results with those of the reported methods revealed excellent agreement and indicated no significant difference in accuracy and precision.

Spectrofluorimetric determination of thioridazine and flupentixol in dosage forms; application to content uniformity test.

A reliable, sensitive, cheap and non-extractive spectrofluorimetric method has been developed and validated for determination of thioridazine and flupentixol based on ternary complex formation with eosin and lead(II) in the presence of methylcellulose as surfactant at pH 3.2. Under the optimum conditions, the quantitative quenching effect of investigated drugs on the native fluorescence of eosin has been investigated. The quenching of the eosin fluorescence was measured at 517 nm after excitation at 462 nm. The different experimental parameters affecting the development and stability of the reaction products were carefully studied and optimized, and the results were satisfactory. The calibration plots were constructed over the range of 0.5-3.0 µg mL(-1) . The developed method was successfully applied for determination of investigated drugs in commercial tablets without interference from common excipients. It was further applied for content uniformity testing of flupentixol in its tablets. Statistical comparisons of the results with those of the reference methods revealed excellent agreement and indicated no significant difference in accuracy and precision. Copyright © 2015 John Wiley & Sons, Ltd.

Full green assay of parenteral dosage forms of polymyxins utilizing xanthene dye: application to content uniformity testing.

Due to the lack of other treatment options, a rebirth of polymyxins is urgently required. Colistin (also called polymyxin E) and polymyxin B are the only two examples of this antibiotic class that were effectively employed in such critical situations. In the present work, both of the two studied medications were quantified via a simple, green, and non-extracting spectrophotometric approach based on the formation of ion-pair complexes with Erythrosine B. Without using any organic solvents, the pink color of the created complexes was detected at wavelength = 558 nm. To achieve the highest intensity of absorbance, optimum conditions were established by the screening of many experimental factors such as pH, buffer volume, the volume of Erythrosine B, and the time consumed to undergo the reaction. For Colistin and Polymyxin B respectively, Beer-Lambert's law was observed at the concentration ranges of 1-6, 1-9 µg mL- 1. The technique was approved and validated following ICH recommendations. Lastly, the suggested approach has been successfully implemented to quantify the cited medications colorimetrically, for the first time, in their parenteral dosage forms with excellent recoveries. Also, Content uniformity testing was implemented.

Condensation methodology for quantification of Polymyxin B fluorimetrically: application to pharmaceutical formulations and greenness assessment.

The appearance of multidrug-resistant Gram-negative bacterial infections, along with the lack of newly discovered antibiotics, resulted in the return to old antimicrobial medications like Polymyxins. As a result, the suggested technique aims to develop a fast, environmentally friendly, and sensitive fluorimetric method for quantifying Polymyxin B. The investigated approach depends on generating a highly fluorescent derivative by a condensation pathway between the studied drug and ninhydrin in the presence of phenylacetaldehyde and then estimated spectrofluorimetrically. After the reaction conditions were well optimized, the fluorescent product was estimated at emission wavelength (λem) = 475.5 nm (following excitation at a wavelength (λex) = 386 nm. The developed calibration plot displayed rectilinear throughout the following range (0.2-3 µg mL- 1), and the calculated limit of detection and quantification were 0.062 µg mL- 1 and 0.187 µg mL- 1, respectively. As a consequence, the drug's ophthalmic and intravenous pharmaceutical forms were both successfully quantified with an excellent degree of recovery. Finally, the methodology's greenness was assessed utilizing Analytical Eco-Scale scores.

The first spectrofluorimetric protocol for sensitive quantitative analysis of bromocriptine in its pure and pharmaceutical forms: evaluation of the greenness of the method.

Bromocriptine mesylate, a dopamine D2 receptor agonist, has been quantitatively determined using a sensitive, precise, quick, and affordable spectrofluorimetric method. The proposed method relies on the estimation of bromocriptine native fluorescence after the optimization of different factors to improve its inherently weak fluorescence through the use of a sodium dodecyl sulphate micellar system (2% w/v). Following excitation at 238 nm, the enhanced fluorescence intensity of bromocriptine was determined at 418 nm. As compared to its native fluorescence, the bromocriptine fluorescence intensity has been greatly enhanced by about 15 fold by employing the micellar system. The plot of intensity of fluorescence versus bromocriptine concentration was linear in the range of 50-600 ng mL-1. The method was found to have a high sensitivity, as indicated by the low limit of detection and limit of quantitation values (14.57 and 44.16 ng mL-1 respectively). Without the interference of any excipient, this method was effectively employed to quantify bromocriptine in its pharmaceutical dosage form.

New validated spectrofluorimetric protocol for colistin assay through condensation with 2,2-dihydroxyindan-1,3-dione: application to content uniformity testing.

A new, cost-effective and sensitive spectroscopic assay for the quantification of Colistin Sulfate (CS) and its prodrug colistimethate sodium (CMS) has been developed and validated. The validated technique depends on the condensation of the studied drug with 2,2-dihydroxyindan-1,3-dione (ninhydrin) and phenylacetaldehyde using Teorell and Stenhagen buffer (pH = 6) to yield a fluorescent product that is estimated at emission wavelength (λ em = 474 nm) after excitation wavelength (λ ex = 390 nm). The reaction's affecting factors were carefully studied and adjusted accurately. Over the following range (0.4-2.4 µg mL-1), the produced calibration plot looked rectilinear, and the estimated limits of detection and quantification (LOD and LOQ) were 0.051 & 0.154 µg mL-1 respectively. The recommended approach was utilized to evaluate market products containing the investigated drug. Moreover, content uniformity testing was employed as a new procedure not found in the previously reported fluorimetric technique.

Green innovative fluorescence approach for the feasible and reliable assay of thiol-containing drugs; captopril as a model.

In the present study, a novel spectrofluorimetric approach was designed for the analysis of captopril as a thiol-containing compound. The approach is based on the formation of a ternary fluorescent compound between the target thiol compound, ortho-phthaldehyde, and a suitable primary amine-containing compound. The produced 1-thio-alkyl-isoindole derivative exhibited very high emission activity in a faintly alkaline aqueous solution that could be monitored at 448 nm (excitation at 334 nm). 2-Amino-6-methyl-6-hydroxy-heptane was selected as the primary amine candidate that gave the high fluorescence intensity with the stability of the formed product. At the optimal experimental condition, the intensity of fluorescence of the formed product was linearly related to the concentration of captopril in 20-450 ng mL-1 range. Commercial pharmaceutical tablets were analyzed, and the obtained results agreed with those of the published method regarding precision and accuracy. The mechanism of the reaction was discussed. In addition, the greenness of the approach was rated following eco-scale criteria.

A highly sensitive fluorimetric protocol based on isoindole formation for determination of gabapentin.

A new, simple, highly sensitive and selective spectrofluorimetric method was developed for determination of gabapentin through its derivatization with o-phthalaldehyde in the presence of 2-mercaptoethanol. The resulting product was highly fluorescent and its emission intensity was measured at 431 nm after excitation at 335 nm. The effect of different experimental parameters on the formation and stability of the fluorescent product was carefully studied and optimized. The fluorescence-concentration plot was rectilinear over the range of 25-125 ng mL-1. The lower detection and quantification limits were 3.4 mL-1 and 11.2 ng mL-1, respectively. The procedure was fully validated according to the guidelines of the International Conference on Harmonization. The proposed method was successfully applied for the determination of the investigated drug in its pharmaceutical capsules and the results were in agreement with those of the reported method, in terms of the accuracy and precision. The low cost of analysis and high sensitivity make the proposed method ideally suited for analysis of the investigated drug in quality control laboratories.