Simultaneous determination of timolol maleate in combination with some other anti-glaucoma drugs in rabbit aqueous humor by high performance liquid chromatography–tandem mass spectroscopy

An innovative electrochemical sensor for brinzolamide detection in athletes' urine using a mercury-phen complex: a step forward in anti-doping

Brinzolamide (BRZ) is an antiglaucoma drug also used by athletes for doping purposes; therefore, it is prohibited by the World Anti-Doping Agency. Consequently, the presence of BRZ or its metabolites in athletes' urine constitutes a violation of anti-doping rules. The current work presents a novel electrochemical method that assesses the effectiveness of mercury oxide nanoparticles (HgO-NPs) and a mercuric chloride-1,10-phenanthroline complex (HgCl2-Phen complex) as sensors for BRZ analysis. A comparative analysis revealed that the synthesized HgCl2-Phen complex exhibited superior sensitivity and efficiency in determining BRZ levels. The properties of the modifiers were extensively characterized using elemental analysis, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM). Furthermore, electrochemical characterization was conducted using square wave voltammetry (SWV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The electrode showed a good response for SWV evaluations of BRZ in a concentration range of 0.1 to 6.0 μmol L-1, with very low limits of detection (0.01 μmol L-1) and quantitation (0.031 μmol L-1). The method's applicability was validated by detecting BRZ in urine samples from healthy human volunteers and in pharmaceutical eye drops. Additionally, the practical effectiveness of the method was assessed using the blue applicability grade index (BAGI). The key advantages of this sensor include its simple manufacturing process, as well as its remarkable sensitivity and selectivity.

Colorimetric Concurrent Determination of Ultra-Trace Amounts of Pilocarpine and Timolol as Anti-Glaucoma Drugs in Binary Mixtures Using a Multivariate Calibration Approach Based on the Aggregation of Gold Nanoparticles

BACKGROUND

To study the ultra-trace simultaneous determination of drugs, the colorimetric method in combination with chemometrics can be used.

OBJECTIVE

In this study, a simple, rapid, and sensitive UV-Vis spectrophotometric method using gold nanoparticles (AuNPs) was introduced for the simultaneous determination of ultra-trace amounts of pilocarpine (PIL) and timolol (TIM) in binary mixtures and biological samples.

METHODS

AuNPs interacted with components and the aggregation mode of NPs occurred, and, finally, the color change of the solution (red to gray) was observed with the naked eye without the most modern and expensive instruments. The characterization of AuNPs was evaluated by transmission electron microscopy (TEM) and dynamic light scattering (DLS).

RESULTS

The validation of the colorimetric way was studied in the concentration range of 100-800 and 100-600 μg/L with good linearity equal to 0.9772 and 0.9891 for PIL and TIM, respectively. The limit of detection (LOD) was found to be 165.00 and 92.40 μg/L, where the limit of quantitation (LOQ) was 500.00 and 280.00 μg/L for PIL and TIM, respectively. The effect of some factors such as interaction time, the concentration of components, and the volume of buffer on absorbance was investigated. Partial least squares (PLS) as an efficient multivariate calibration method was combined with colorimetry for the simultaneous determination of PIL and TIM in binary mixtures. The optimum number of latent variables was selected by k-fold cross-validation based on minimum mean square error prediction (MSEP), and the number of components equal to 1 with MSEP of 1.085 and 0.763 was considered for PIL and TIM, respectively. The mean recovery was obtained at 100.20 and 101.55% for PIL and TIM, respectively.

CONCLUSIONS

The colorimetric method can be introduced as a proper option for the simultaneous determination of components in pharmaceutical formulations and other samples.

HIGHLIGHTS

A colorimetric method using AuNPs was proposed. The PLS method was coupled with a colorimetric method for the ultra-trace simultaneous estimation of PIL and TIM in binary mixtures. Ultra-trace amounts of PIL and TIM were also determined in biological samples. The proposed method is simple, fast, and less expensive than chromatography methods.

A Simple Validated LC-UV Method for the Simultaneous Determination of Brimonidine and Brinzolamide in the Presence of Brinzolamide's Degradation Product (Major Metabolite) in Rabbit Aqueous Humor

A sensitive, specific, reliable and low-cost LC-UV method has been developed and validated for simultaneous quantification of brimonidine tartrate (BM) and brinzolamide (BZ) in rabbit aqueous humor (AH) in the presence of N-desethyl-brinzolamide (NDBZ); BZ is a major degradation product, and it is also considered to be its major metabolite. Dorzolamide hydrochloride (DZ) was used as an internal standard (IS). The analytes were extracted from rabbit AH samples by a simple pre-treatment utilizing ZnSO4.7H2O as a deproteinizing agent. The analytes were separated on a cyanopropyl Waters column (4.6 × 200 mm, 5 μm) with an isocratic mobile phase consisting of 25 mM ammonium acetate pH 4.5 (adjusted with 85% phosphoric acid):methanol:acetonitrile (94:4.5:1.5, v/v) at a flow rate of 1.0 mL min-1. The detection was done at 254 nm. The lower limit of quantification in rabbit AH was 100.0 ng mL-1. The method was validated according to EMA guidelines. The method was confirmed to be accurate, precise and linear over a range of 100.0-1000.0 ng mL-1 for BM and BZ. The method developed herein is simple, safe, eco-friendly, rapid and accurately applied for the quantification of BM and BZ, along with the successful separation of NDBZ, which is considered as a potential irritant degradation product of BZ.

Adaptation of the AbsoluteIDQ p180 kit to the analysis of metabolites in the human aqueous humor

The aim of this study was to use the commercial kit AbsoluteIDQ p180 (Biocrates) for the quantification of metabolites in aqueous humor (AH), as well as to determine the optimal volume of AH that is necessary to obtain reliable and reproducible results. Different volumes of AH (10 µl, 20 µl, and 30 µl) were tested. Of the 188 metabolites measurable with the Biocrates kit, 69 were detected in AH. Depending on the volume used, 41, 51, and 63 metabolites were measured using 10 µl, 20 µl, and 30 µl of AH, respectively. The repeatability of the measurements improved with increasing AH volume. Considering only those metabolites that were obtained with a CV < 15%, 34 metabolites at 10 µl, 41 at 20 µl, and 44 at 30 µl AH were received. On this basis, it can be concluded that the tested method can be successfully applied to analyze metabolites in the human AH. To achieve the most comprehensive detection range and highest repeatability of measurements, it is recommended to use 30 µl AH.

Development and Validation of Facile RP-HPLC Method for Simultaneous Determination of Timolol Maleate, Moxifloxacin Hydrochloride, Diclofenac Sodium and Dexamethasone in Plasma, Aqueous Humor and Pharmaceutical Products

The present study aimed to develop a validated RP-HPLC method for the simultaneous determination of timolol maleate (TM), moxifloxacin hydrochloride (MOXI), diclofenac sodium (DS) and dexamethasone (DEXA) in human plasma, bovine aqueous humor and pharmaceutical preparations. The chromatographic separation was studied using the C18 column. The chromatographic conditions, such as composition, pH, the flow rate of mobile phase, the temperature of column, wavelength of absorption and injection volume of the sample, were studied. The method was validated to confirm specificity, linearity and accuracy in accordance with an International Conference on Harmonization guidelines. The optimum conditions for separation included mobile phase 0.05 M monobasic phosphate buffer: acetonitrile (65:35 v/v), pH of buffer adjusted to 6.2 and the flow rate of 1 mL/minute. The optimum temperature of the column was found to be 35°C, absorption wavelength 265 nm and injection volume 50 μL. The baseline separation of all four drugs with good sensitivity, resolution, and a less than 15 min run time was achieved. The retention time of TM, MOXI, DS and DEXA were 4.3,5.7,9.9 and 13.5 minutes respectively. The limit of detection (LOD) values were 6.2, 4.8, 0.8 and 1.2 ng/mL for TM, MOXI, DS and DEXA, respectively, whereas their respective limit of quantification (LOQ) values was: were 42.6, 26.8, 5.6 and 6.2 ng/mL. The coefficient of variation for intra-day and inter-day were in the range of 0.32-1.57 and 1.29-3.07%, respectively. The method was found to be sensitive, precise and accurate in human plasma and bovine aqueous humor and can be applied for the quantification of these compounds in plasma, aqueous humor and pharmaceuticals.

Metabolomics Analysis of Aqueous Humor Based on Liquid Chromatography-Mass Spectrometry

Aqueous humor (AH) is a transparent fluid that fills the anterior segment of the eye. The composition and level of metabolites in AH are important for understanding its physiology and changes caused by the occurrence of eye disease. A simple method for the preparation and analysis of AH samples was developed using the liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) technique. The analyses were performed using two types of chromatography: reversed-phase liquid chromatography-mass spectrometry (LC-RP-MS) and hydrophilic interaction liquid chromatography-mass spectrometry (LC-HILIC-MS), in the sample prepared by one protocol.

Brimonidine

Brimonidine is a highly selective 2-adrenoceptor agonist that lowers intraocular pressure (IOP) by decreasing aqueous humor production and increasing aqueous humor outflow via the uveoscleral route. Brimonidine is used to treat glaucoma and other eye conditions. Brimonidine is a topical medication that is used mainly to treat open-angle glaucoma and ocular hypertension in the eyelids. The purpose of this chapter is to provide a comprehensive discussion of Brimonidine's nomenclature, physiochemical properties, preparation methods, identification procedures, and numerous qualitative and quantitative analytical techniques, as well as its ADME profiles and pharmacological effects. In addition, the chapter contains numerous approaches for separating brimonidine from other medications in combination formulations utilizing chromatographic techniques and other spectroscopic approaches.

Full Factorial Design for Development and Validation of a Stability-Indicating RP-HPLC Method for the Estimation of Timolol Maleate in Surfactant-Based Elastic Nano-Vesicular Systems

A novel isocratic stability-indicating chromatographic method was developed, optimized and validated using Design-Expert® following ICH guidelines for the quantification of Timolol maleate (TM). The intrinsic stability of TM was assessed by force degradation studies, which concluded no extensive degradation except under alkaline and oxidative conditions. TM was quantified accurately in the surfactant-based elastic vesicular system by separating it on Hypersil BDS C8 column using triethylamine in H2O (0.15%v/v; pH 3.0) and acetonitrile (ACN; 65:35%v/v). The influence of variable factors like mobile phase pH, injection volume (μL), flow rate (mL/min) and ACN content (%) on method responses were assessed using a full factorial design. The method was linear between 0.05 and 10 μg/mL with an R2 value of 0.9993. Limit of detection and limit of quantification were found to be 0.90 and 27.2 ng/mL. The method was specific, with recovery in plain drug solution of 89-92% and elastic nanovesicles of 90-93%. The experimental model was significant (P < 0.0001) as indicated by deliberate changes in the method analyzed through analysis of variance. The total drug content in elastic nanovesicles was estimated to be 9.53 ± 0.01 mg/20-mL dispersion and entrapment efficiency was 44.52 ± 0.73%. The developed method was rapid, economic and precise for the quantification of TM in bulk and vesicular system.

Development and validation of a fast ultra-high-performance liquid chromatography tandem mass spectrometry method for determining carbonic anhydrase inhibitors and their metabolites in urine and hair

A new, rapid, sensitive, and comprehensive ultra‐high‐performance liquid chromatography tandem mass spectrometry (UHPLC–MS/MS) method for quantifying diuretics (acetazolamide, brinzolamide, dorzolamide, and their metabolites) in human urine and hair was developed and fully validated. Twenty‐five milligrams of hair were incubated with 500‐μl M3® buffer reagent at 100°C for 1 h for complete digestion. After cooling, 1‐μl supernatant was injected onto chromatography system. Urine samples were simply diluted before injection. The chromatographic run time was short (8 min) through a column with a mobile phase gradient. The method was linear (determination coefficients always higher than 0.99) from limit of quantification (LOQ) to 500 ng/ml in urine and from LOQ to 10 ng/mg in hair. LOQs ranged from 0.07 to 1.16 ng/ml in urine and from 0.02 to 0.15 ng/mg in hair. No significant ion suppression due to matrix effect was observed, and process efficiency was always higher than 80%. Intra‐ and inter‐assay precision was lower than 15%. The suitability of the methods was tested with six urine and hair specimens from patients treated with acetazolamide, dorzolamide, or brinzolamide for ocular diseases or systemic hypertension. Average urine concentrations were 266.32 ng/ml for dorzolamide and 47.61 ng/ml for N‐deethyl‐dorzolamide (n = 3), 109.27 ng/ml for brinzolamide and 1.02 ng/ml for O‐desmethyl‐brinzolamide (n = 2), and finally, 12.63 ng/ml for acetazolamide. Average hair concentrations were 5.94 ng/mg for dorzolamide and 0.048 ng/mg for N‐deethyl‐dorzolamide (n = 3), 3.26 ng/mg for brinzolamide (n = 2), and 2.3 ng/mg for acetazolamide (n = 1). The developed method was simple and fast both in the extraction procedures making it eligible in high‐throughput analysis for clinical forensic and doping purposes.

Single quad mass analyzer coupled UPLC method for impurity profile of Brimonidine tartrate and Timolol maleate: Application in their binary mixture ophthalmic formulation

The main objective of the study is to develop a suitable and rapid UPLC/PDA method by coupling online to Quadrupole Dalton analyzer (QDa), a mass detector for the identification and impurity profiling of Brimonidine Tartrate (BRIM)/Timolol maleate (TIMO) in the ophthalmic formulation. Chromatographic separation was achieved on ethylene bridged hybrid octadecylsilane column having 1.7μm particle size in gradient mode using high pure heptafluorobutyric acid as a buffer (A) and water, methanol, and acetonitrile (B) as mobile phase with a flow rate of 0.3mlmin^-1. Based on the spectral maxima, BRIM and its impurities were monitored at 248nm, and TIMO and its impurities were monitored at 295nm. During evaluation of stress conditions and stability data unknown degradants are observed and identified as m/z 218.01 (DP1) and m/z 390.03 (DP2) using QDa-ESI+ scanning mode technique. The performance of the method was systematically validated according to ICH Q2 (R1) guidelines and the method shown very good sensitivity (≥0.5μg.mL^-1) and linearity (r²≥0.999) with consistent recoveries and less than 5% RSD for all compounds. Hence, the proposed UPLC/PDA/QDa method is a simple, sensitive and comprehensive technique where identification and quantification can be done. It gives for complete impurity profile evaluation of BRIM/TIMO in the ophthalmic formulation during quality control in the pharmaceutical industry.

The application of continuous wavelet transform based on spectrophotometric method and high-performance liquid chromatography for simultaneous determination of anti-glaucoma drugs in eye drop

In this study, a fast, low-cost, accurate, and precise spectrophotometric method based on the continuous wavelet transform (CWT) was assayed to determine dorzolamide (DOR) and timolol (TIM) in an eye drop sample simultaneously. Different wavelet families were investigated to select the best family for analyzing the DOR and TIM. The Mexican hat wavelet (MHW) family with the wavelength of 281 nm and Gaussian wavelet family (gaus2) in the wavelength of 267 nm were found for the simultaneous analysis of DOR and TIM, respectively. Mean recovery values of synthetic mixtures were found 97.44%±2.63 and 99.18%±4.00 for DOR and TIM, respectively. The root mean square errors (RMSE) of DOR and TIM were achieved 0.5550 and 0.3306, respectively. Eye drop as a real sample was analyzed by spectrophotometry coupled with the CWT technique, as well as high-performance liquid chromatography (HPLC) as a reference method. The obtained results were compared with each other by the one-way analysis of variance (ANOVA) test and there was no significant difference between them.

Co-delivery of brinzolamide and miRNA-124 by biodegradable nanoparticles as a strategy for glaucoma therapy

Co-delivery nanoparticles with characteristics of intracellular precision release drug have been generally accepted as an effective therapeutic strategy for eye diseases. In this study, we designed a new co-delivery system (miRNA/NP-BRZ) as a lasting therapeutic approach to prevent the neuro-destructive after the long-term treatment of glaucoma. Neuroprotective and intraocular pressure (IOP) response were assessed in in vivo and in vitro models of glaucoma. At the meaning time, we describe the preparation of miRNA/NP-BRZ, drug release characteristics, intraocular tracing, pharmacokinetic and pharmacodynamics study and toxicity test. We found that miRNA/NP-BRZ could remarkably decrease IOP and significantly prevent retinal ganglion cell (RGC) damages. The new formula of miRNA-124 encapsulated in PEG-PSA-BRZ nanoparticles exhibits high encapsulation efficiency (EE), drug-loading capacity (DC), and stable controlled-release efficacy (EC). Moreover, we also verified that the miRNA/NP-BRZ system is significantly neuroprotective and nontoxic as well as lowering IOP. This study shows our co-delivery drug system would have a wide potential on social and economic benefits for glaucoma.

Review on analytical studies of some pharmaceutical compounds containing heterocyclic rings: brinzolamide, timolol maleate, flumethasone pivalate, and clioquinol

Background

The heterocyclic compounds are extremely important with wide array of synthetic, pharmaceutical, and industrial applications. Heterocyclic-containing compounds have been reported for their broad spectrum of biological activities including antibacterial, antifungal, antiviral, antiprotozoal, and anthelmintic activity.

Main text

Several techniques have been used for the quantitation of heterocyclic compounds in pharmaceutical samples such as high-performance liquid chromatography (HPLC) either equipped with UV-visible or fluorescence, in addition to liquid chromatography-mass spectroscopy, UV-visible spectrophotometry, and electrochemical techniques. This article reviewed several published methods that have been applied to detect and quantify some pharmaceutical drugs containing heterocyclic compounds focusing on four drugs: brinzolamide, timolol maleate, flumethasone pivalate, and clioquinol.

Conclusion

From literature reviews, HPLC is the most widely used analytical technique for the quantitative analysis of the four selected drugs.

Analysis of pharmaceuticals and small molecules in aqueous humor

Aqueous humor (AH) is a transparent fluid found in the anterior chamber of the eye. The circulating AH nourishes the cornea and lens and removes the metabolic waste moving through the ocular chambers and drains from the eye to the venous blood. Analysis of drugs in AH is necessary to evaluate their pharmacokinetics parameters, which may be crucial to avoid potential adverse effects. Analysis of endogenous components of AH may help to understand its physiology as well as changes evoked by pathological situation. This review describes analytical methods used for determination of pharmaceuticals and small endogenous molecules in AH, focusing on sample preparation procedures and analytical techniques. Studies on human and animal samples are included. After inspection and filtering of records found in PubMed about 100 research papers were selected to review. In these articles AH samples of human and rabbit origin were studied most often. Sample evaporation and reconstitution in smaller solvent volume was the most popular method for analyte pre-concentration. Acetonitrile, methanol or mixture of both solvents were used most often for protein precipitation.

A validated stability-indicating HPLC method for determination of brimonidine tartrate in BRI/PHEMA drug delivery systems

BACKGROUND

A simple, rapid and accurate stability-indicating reverse phase high performance liquid chromatography (RP-HPLC) was developed and validated for the determination of brimonidine tartrate in brimonidine tartrate/poly(2-hydroxyethyl methacrylate) (BRI/PHEMA) drug delivery contact lenses and pharmaceutical formulations.

RESULTS

Optimum chromatographic conditions for separating brimonidine tartrate from other impurities in the leaching liquor of BRI/PHEMA drug delivery contact lenses or pharmaceutical formulations have been achieved by using a Diamonsil C18 column (150 mm × 4.6 mm, 5 μm) as a stationary phase and a mixture solution of phosphate buffer (10 mM, pH3.5) containing 0.5% triethlamine and methanol (85:15, v/v) as a mobile phase at a flow rate of 1 mL/min. The theoretical plates for the brimonidine tartrate measurement were calculated to be 8360 when detection was performed at 246 nm using a diode array detector. The proposed method was validated in accordance with ICH guidelines with respect to linearity, accuracy, precision, robustness, specificity, limit of detection and quantitation. Regression analysis showed a good correlation (R² > 0.999) for brimonidine tartrate in the concentration range of 0.01-50 μg/mL. The peak purity factor is ≥980 for the analyte after all types of stress tests, indicating an excellent separation of brimonidine tartrate peak from other impurities. The measurement course could be completed within 10 min, which was very quick, effective and convenient.

CONCLUSIONS

Overall, the proposed stability-indicating method was suitable for routine quality control and drug analysis of brimonidine tartrate in BRI/PHEMA drug delivery contact lenses and other pharmaceutical formulations.