Development and Validation of an RP-HPLC Method for the Estimation of Glimepiride in Compliance with Quality Assurance Standards

First introduced back in 1995, glimepiride improves upon glycaemic control and manages type 2 diabetes mellitus (T2DM) as it is a member of the second-generation sulfonylurea (SU) class of drugs. Type 2 diabetes is a metabolic disorder of sorts. It is becoming more common globally. Glimepiride stimulates the secretion of insulin granules from pancreatic beta cells by way of blocking ATP-sensitive potassium channels (KATP channels) as well as causing depolarization of the cells. Compared to glipizide, another second-generation SU drug, glimepiride has a longer duration of action. Because it has more substitutions than other second-generation SUs, it is occasionally categorised as a third-generation SU. In clinical trials, glimepiride was linked to a decreased risk of weight gain and hypoglycaemia when compared to other SUs. [1,2]. Glimepiride, also known as 3-ethyl-4-methyl-N-(1-(4-(2-(methylamino)-2-oxoethyl) phenyl) sulfonyl)-2-oxo-2,5-dihydro-1H-pyrrole-1-carboxamide, is a second-generation sulfonylurea antidiabetic agent. Because of its capacity to increase the secretion of insulin from pancreatic β-cells, it is frequently prescribed for the treatment of Type 2 diabetes mellitus. [3,4,5]. Glimepiride exhibits lipophilic properties and has moderate solubility in methanol and ethanol, but limited solubility in water. These physicochemical characteristics render it amenable to detection via reverse-phase chromatography. Because it only needs a small amount (usually 1–4 mg per tablet) and has a narrow therapeutic index, it is very important to measure it accurately in pharmaceutical quality control.[6]

Figure no. 1: Structure of Glimepiride

Glimepiride is metabolized in the liver to form two main metabolites: M1 (cyclohexyl hydroxymethyl derivative) and M2 (carboxyl derivative). M1 is formed via oxidative biotransformation by the CYP2C9 enzyme, and it's pharmacologically active. M2 is formed from M1 by cytosolic enzymes and is pharmacologically inactive.[7]

was first approved by the U.S. Food and Drug Administration (FDA) in 1995 under the brand name Amaryl®, developed by Aventis Pharmaceuticals (now part of Sanofi) [8]. Since its approval, it has gained regulatory clearance from several major agencies, including the European Medicines Agency (EMA) and the Central Drugs Standard Control Organization (CDSCO), India, for oral administration either as monotherapy or in combination with other hypoglycaemic agents.[9]

Glimepiride is officially recognized in multiple pharmacopoeias, including the United States Pharmacopeia (USP) and the Indian Pharmacopoeia (IP), where it is listed under oral hypoglycaemic agents for quality control and assay purposes. The drug continues to be a cornerstone in diabetes therapy due to its efficacy, safety, and once-daily dosing advantage [10]

1. 1. Mechanism of Action:

Glimepiride, a sulfonylurea, lowers blood sugar by stimulating the release of insulin from pancreatic beta cells and improving insulin sensitivity in peripheral tissues. It works by closing ATP-sensitive potassium channels in beta cells, leading to depolarization, calcium influx, and subsequently, insulin exocytosis.[9]

2. MATERIALS AND METHODS:
   1. Chemicals and reagents:

The R&D Department of Axiom Analytical Services, Rau, Indore, supplied the Glimepiride API, which Rusan Pharma Ltd., Pithampur, Indore produced. Rankem Laboratory Chemicals provides HPLC-grade water, whereas Advent Chembio Pvt. Ltd. provides HPLC-grade acetonitrile.

1. 2. HPLC apparatus and conditions:

The chromatographic analysis was carried out using a Waters Alliance 2695 HPLC system equipped with a Photodiode Array (PDA) Detector 2998 and controlled through Empower 3 software. The system included an automatic injector and a quaternary gradient pump capable of delivering precise and reproducible solvent flow.

The separation of Glimepiride was achieved on a Waters Xterra ODS C18 column (150 mm × 4.6 mm, 5 µm particle size). The mobile phase consisted of Water and Acetonitrile in the ratio of 60:40 (v/v). The flow rate was maintained at 0.8 mL/min, and the detection was performed at a wavelength of 228 nm. The injection volume was set to 10 µL, and the run time for each analysis was 15 minutes. The chromatographic process was carried out at ambient temperature.

3. Preparation of Standard and Sample Solutions (25 ppm)
   1. Standard preparation:

Accurately weighed 25 mg of Glimepiride was transferred into a 100 mL volumetric flask. Dissolved using 70 mL of methanol and sonicated. Final volume was made up to 100 mL with methanol, yielding a concentration of 250 µg/mL (250 ppm).

1. 2. Sample preparation:

Accurately weighed 25 mg of Glimepiride was transferred into a 100 mL volumetric flask. Dissolved using 70 mL of methanol and sonicated. Final volume was made up to 100 mL with methanol, yielding a concentration of 250 µg/mL (250 ppm).

4. Method development: The creation of an effective RP-HPLC method for Glimepiride started with the goal of obtaining a sharp, symmetrical peak that has minimal tailing, a suitable retention time, and high resolution in a short analysis time. Different chromatographic conditions were carefully adjusted to achieve these objectives, including the composition of the mobile phase, the flow rate, the wavelength for detection, and the type of column used.

At first, experiments were performed with various mixtures of water and acetonitrile in ratios ranging from 90:10 to 50:50 (volume to volume).  However, the initial results did not meet the desired standards for peak symmetry and retention time. Later, a water: acetonitrile ratio of 60:40 (v/v) was found to produce a clear, sharp peak with minimal tailing and a good number of theoretical plates. A Waters Xterra ODS C18 column (150 × 4.6 mm, 5 µm) was chosen because it offers better retention for compounds with moderate lipophilicity, such as Glimepiride.  The flow rate was adjusted to 0.8 mL/min, which provided a good balance between peak resolution and the overall run time. Detection was performed at 228 nm, as this wavelength allowed for a strong absorbance signal from Glimepiride, improving the sensitivity of the method. An injection volume of 10 µL was used, and the total runtime was 10 minutes. Under these conditions, Glimepiride consistently eluted at 2.993 minutes.

1. 3. The optimized chromatographic conditions were as follows:

Figure no. 2: Optimized chromatogram of Glimepiride

4. Method validation:

The developed RP-HPLC method for Glimepiride was validated as per the International Conference on Harmonisation (ICH) Q2(R1) guidelines. The method was assessed for system suitability, specificity, linearity, accuracy, precision, and ensuring it is reliable for routine analysis.

1. 1. System suitability:

The system's suitability was evaluated by injecting a blank sample and five copies of the standard solution. Key parameters such as retention time, theoretical plates (N), tailing factor (T), and the percentage RSD of peak area were all found to be within the acceptable limits, confirming that the system was functioning properly for further validation steps.

Acceptance criteria:

• Should be consistent (±2%)
• Not more than 2.0 (USP)
• Not less than 2000 (USP)
• Not more than 2.0%

1. 2. Specificity/Selectivity: Specificity was evaluated by injecting blank, standard, and sample solutions. The chromatograms of these solutions were compared to ensure there were no interfering peaks in the blank chromatogram at the retention time of the analyte peak observed in both the standard and sample chromatograms. This comparison confirmed the specificity of the method.

• 3. Linearity: To ensure linearity, six different concentrations of the standard solution, ranging from 120 to 900 μg/mL, were analysed along with blank samples and the standard. A calibration curve was created by plotting the concentrations against the corresponding peak areas. Regression analysis was then performed. If the correlation coefficient fell within the acceptable range, it confirmed that the procedure produced linear results.
• Correlation coefficient (R²) ≥ 0.999

Table: Linearity of Glimepiride

• 4. Precision: Each sample was prepared separately under the identical analytical conditions, and precision was achieved by injecting blank, standard, and six sample solutions. Record the peak region for all injections and calculate percent assay and % RSD. If the test and RSD percentages were both within the acceptable range, the procedure was accurate.
• % Assay: 98%–102% 
• % RSD < 2.0%

• 5. Accuracy (recovery): By injecting blank, standard, and sample solutions in triplicate of the desired concentration at several different concentrations—50%, 100%, and 150%—accuracy was achieved. An unknown amount of sample (API) and a known amount of standard (API) were combined to create a sample solution. Determine the amount of API recovered from each level by measuring the peak areas. Determine the average recovery percentage and RSD percentage for every stage. If the mean percent recovery and the percentage RSD were found to be within acceptable limits, the approach was considered accurate.
• Recovery: 98%–102%
• % RSD < 2.0%

Figure no.3.Chromatogram 50%

Figure no.3.Chromatogram 50%