Original Article DEVELOPMENT AND VALIDATION OF A GRADIENT PROGRAM RP-HPLC METHOD FOR ESTIMATION OF MULTIPLE ACTIVE PHARMACEUTICAL INGREDIENTS IN AN ORAL SUSPENSION TASTE MASKED WITH AN ION EXCHANGE RESIN ROBINDRA K. PANDIT , VIVEK PANDEY * Department of Chemistry, School for Chemical Engineering and Physical Sciences, Lovely Professional University, Phagwara, Punjab, India * Corresponding author: Vivek Pandey; * Email: vivekpandey11sep@gmail.com Received: 29 Dec 2024, Revised and Accepted: 24 Apr 2025 ABSTRACT Objective: This study focuses on developing an effective Reverse Phase High-Performance Liquid Chromatography (RP-HPLC) method for the simultaneous analysis of Dextromethorphan Hydrobromide (DXM), Phenylephrine Hydrochloride (PEH), and Chlorpheniramine Maleate (CPM) in a taste-masked oral suspension. The method ensures rapid, precise, and accurate quantification of these Active Pharmaceutical Ingredients (APIs) while supporting formulation stability and regulatory compliance. Methods: A gradient High-Performance Liquid Chromatography (HPLC) method with a short 7.5-minute run time was optimized for the simultaneous analysis of DXM, PEH, and CPM in a complex suspension matrix. The taste masking was achieved using Indion 254 ion exchange resin, and its impact on drug release and assay accuracy was evaluated. Key method parameters, including resolution, plate count, and tailing factor, were optimized to ensure robust performance. The method was validated according to International Council for Harmonisation (ICH) guidelines, assessing specificity, precision, accuracy, and stability. Results: The developed DXM, PEH, and CPM method demonstrated excellent specificity, with no interference from the resin, excipients, or degradation products. Resolution values of more than 1.5 between ICH exceeded acceptance criteria, with plate counts more than 1500 and tailing factors within below 2. The method proved highly precise, with Relative Standard Deviation (RSD) values below 1%. It also ensured reliable quantification of Active Pharmaceutical Ingredients (APIs) in the presence of the taste-masking resin and under various stress conditions, confirming formulation stability. Conclusion: The developed HPLC method provides a rapid, precise, and reliable solution for analyzing APIs in a taste-masked oral suspension. Its efficiency and compliance with ICH guidelines make it a valuable tool for quality control, ensuring formulation consistency and patient safety. Keywords: ICH, BAGI, Development, Validation of reverse phase high-performance liquid chromatography (RP-HPLC), Assay, ICH guidelines, Dextromethorphan hydrobromide (DMH), Phenylephrine hydrochloride (PEH), Chlorpheniramine maleate (CPM), Ion exchange resin (IER), Blue applicability grade index (BAGI) and Oral suspension © 2025 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0/) DOI: https://dx.doi.org/10.22159/ijap.2025v17i4.53547 Journal homepage: https://innovareacademics.in/journals/index.php/ijap INTRODUCTION Simultaneous drug analysis presents considerable challenges due to differences in solubility, retention behaviour, and detector response of multiple Active Pharmaceutical Ingredients (APIs). Developing a robust Reverse-Phase High-Performance Liquid Chromatography (RP-HPLC) gradient method for Dextromethorphan Hydrobromide (DXM), Phenylephrine Hydrochloride (PEH), and Chlorpheniramine Maleate (CPM) in an oral suspension necessitates precise optimization to ensure resolution and accuracy. Taste-masking with ion exchange resins further complicates quantification by altering drug release and matrix composition. This study focuses on method development and validation, ensuring specificity, precision, and reproducibility to enable accurate estimation of APIs in a taste- masked formulation, thereby improving patient compliance [1-6]. Analyzing oral suspensions using High-Performance Liquid Chromatography (HPLC) involves significant technical challenges, including ensuring homogeneity and complete dissolution of APIs and excipients to prevent inconsistent results or system clogging. Sample filtration must be handled carefully to avoid analyte loss [7]. Selecting an appropriate mobile phase and HPLC column is critical to achieving effective resolution without inducing precipitation. Stability concerns arise due to APIs excipient interactions and degradation under analytical conditions [8-12]. Separating DXM, PEH and CPM, which exhibit varying polarities, requires careful optimization. A major challenge is achieving sufficient resolution, particularly between DXM and CPM, which may have overlapping retention times [13-18]. This can be mitigated by fine-tuning the mobile phase composition and employing a gradient elution approach using acetonitrile and water at specific pH values [19-23]. Additionally, since APIs may absorb UV light at different wavelengths, a Photodiode Array Detector (PDA) detector is crucial for comprehensive spectral analysis [24-27]. Excipients in oral suspensions can interfere with analyte peaks, necessitating optimization of sample preparation steps, such as filtration or dilution, to minimize interference and ensure accurate quantification [28-32]. Method validation, including linearity, accuracy, precision, and robustness, is essential for regulatory compliance and routine quality control [33-37]. Advances in analytical techniques, such as Ultra-Performance Liquid Chromatography (UPLC), have enhanced precision and efficiency, but rigorous validation is necessary to meet regulatory standards [38-41]. Oral suspensions are preferred for pediatric and geriatric patients due to ease of administration; however, the unpleasant taste of many APIs poses a significant barrier to compliance. Taste masking is critical in ensuring treatment adherence, with techniques including flavoring agents, coatings, and microencapsulation [42- 46]. Ion Exchange Resins (IERs) have emerged as a superior approach by forming tasteless drug-resin complexes that sequester the bitter drug from taste receptors [47-50]. Compared to flavoring agents, which may lose effectiveness over time, and encapsulation techniques, which can alter drug release profiles, IERs provide a more reliable and stable solution [51-54]. The International Council for Harmonisation (ICH) guidelines outline key validation parameters such as specificity, linearity, accuracy, precision, detection limit, quantitation limit, robustness, and system suitability [55-68]. Adhering to these guidelines ensures the reliability and reproducibility of analytical methods, enabling their application in routine quality control laboratories [69-72]. This study aims to International Journal of Applied Pharmaceutics ISSN- 0975-7058 Vol 17, Issue 4, 2025