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.

Development and Validation of Novel RP-HPLC Method for the Simultaneous Estimation of Capecitabine and Thymoquinone in the Biodegradable Nanoparticles using Full Factorial Design

An innovative RP-HPLC technique was devised to simultaneously quantify thymoquinone (TQ) and capecitabine (CAP) in newly designed polymeric nanoparticles. A unique chromatographic approach was created, optimized and validated using Design-Expert® (design of experiment) in compliance with ICH requirements. A 24 factorial design examined the influence of variables on method responses. The method found linear between 0.25 and 16 μg/mL, with an R2 value of 0.999. The detection and quantification limits for CAP were 0.05 and 0.16 μg/mL, respectively, and 0.12 and 0.38 μg/mL for TQ, respectively, and 97-100% recovery in plain drug solution and 100-102% in nanoformulation were achieved. A purposeful modification examined by analysis of variance revealed that the experimental model was significant (P = 0.0001). The total drug content in nanoformulation was 8.68 mg, and the entrapment efficiency was 84.79%. Based on the findings, it is possible to infer that the use of the Quality by Design methodology resulted in the development of a more accurate technique capable of producing consistent, dependable, high-quality data and precise in quantifying CAP and TQ in bulk and nanoparticulate systems.

Drilling into "Quality by Design" Approach for Analytical Methods

The need for consistency in analytical method development reinforces the dependence of pharmaceutical product development and manufacturing on robust analytical data. The Analytical Quality by Design (AQbD), akin to the product Quality by Design (QbD) endows a high degree of confidence to the method quality developed. AQbD involves the definition of the analytical target profile as starting point, followed by the identification of critical method variables and critical analytical attributes, supported on risk assessment and design of experiment tools for the establishment of a method operable design region and control strategy of the method. This systematic approach moves away from reactive troubleshooting to proactive failure reduction. The objective of this review is to highlight the elements of the AQbD framework and provide an overview of their implementation status in various analytical methods used in the pharmaceutical field. These methodologies include but are not limited to, high-performance liquid chromatography, UV-Vis spectrophotometry, capillary electrophoresis, supercritical fluid chromatography, and high-performance thin-layer chromatography. Finally, a critical appraisal is provided to highlight how regulators have encouraged AQbD principles application to boost the prevention of method failures and a better understanding of the method operable design region (MODR) and control strategy, ultimately resulting in cost-effectiveness and regulatory flexibility.

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.

Analytical Quality by Design-Based Robust RP-HPLC Method for Quantitative Estimation of Pregabalin and Etoricoxib in Fixed-Dose Combination Tablet Formulation

Background

The Central Drugs Standard Control Organization approved a bilayered, uncoated, fixed-dosage combination tablet formulation containing pregabalin (75 mg) and etoricoxib (60 mg) in November 2019 to control prolonged back pain with neuropathic components.

Objective

This research aims to create an analytical quality by design-assisted reversed phase (RP)-HPLC method for quantifying pregabalin and etoricoxib in tablet formulation.

Methods

The best chromatographic conditions were a Phenomenex C8 column (250 × 4.6 mm, 5.6 μm) and a mobile phase of 0.35% orthophosphoric acid –acetonitrile (1 + 1, by volume). A flow rate of 1 mL/min was used with a detection wavelength of 220 nm.

Results

The optimized reversed phase HPLC method was successfully validated by the International Conference on Hormonization guideline Q2(R1). Moreover, the percentage assay of pregabalin and etoricoxib tablet formulation was 99.05 and 100.02% w/w, respectively, using the validated RP-HPLC method.

Conclusion

The newly developed analytical quality by design-assisted RP-HPLC method has several advantages, including shortened analytical time (2.65 min and 7.45 min pregabalin and etoricoxib, respectively), efficient separation in terms of well-defined peaks, and a simple mobile phase combination.

Highlights

The use of analytical quality by design principles and the design of the experiment tool allowed the detection of influential parameters critical for achieving the most favourable chromatographic conditions for accurately quantifying individual drugs using the RP-HPLC method. The compliance of the results with the ICH criteria validated the method. As a result, adopting the analytical quality by design methodology ensured the development of a more robust method that can generate consistent, dependable, and quality data throughout the process while also saving time.

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.