Combination Drug Analysis: Challenges and Approaches in HPLC Method Development

Combination drug therapy has emerged as a pivotal strategy in the management of chronic and multifactorial diseases, offering synergistic therapeutic effects, enhanced patient adherence, and a reduced risk of adverse reactions. High-Performance Liquid Chromatography (HPLC) remains a critical analytical tool for the precise qualitative and quantitative evaluation of such formulations, owing to its high sensitivity, selectivity, and reliability. Nevertheless, the concurrent analysis of multiple active pharmaceutical ingredients (APIs) presents notable challenges, including co-elution, varying physicochemical properties, matrix complexities, and stability-related concerns. Regulatory frameworks demand the implementation of thoroughly validated and scientifically sound analytical methods to guarantee product safety, efficacy, and quality. This review comprehensively addresses the methodological challenges encountered in HPLC analysis of combination drugs and examines advanced strategies such as Quality by Design (QbD), innovative detection technologies, and refined sample preparation techniques to optimize analytical outcomes. In addition, this review features selected case studies that illustrate the practical implementation of HPLC methodologies in the analysis of complex combination drug regimens, including antihypertensive, antidiabetic, and antimicrobial therapies. It further examines emerging technological advancements poised to transform analytical practices—such as the integration of hyphenated techniques (e.g., LC-MS/MS, UHPLC), automation systems, artificial intelligence-driven data processing, and eco-friendly (green) analytical approaches. Collectively, these innovations signify a paradigm shift in the analytical landscape, steering towards more efficient, sustainable, and intelligent method development. This comprehensive analysis serves as a critical reference for pharmaceutical analysts, research scientists, and regulatory authorities engaged in the rigorous development, validation, and optimization of HPLC methods for combination drug products.