A Comprehensive Review to Develop & Validate An RP-HPLC Method for Simultaneous Estimation of Anti-Hypertensive Drugs in Bulk & Tablet Dosage Form

Hypertension, a major modifiable risk factor for cardiovascular morbidity and mortality, affects over one billion individuals globally. Its prevalence continues to rise due to increasing obesity, sedentary lifestyles, and dietary imbalances. Uncontrolled hypertension contributes significantly to ischemic heart disease, stroke, renal impairment, and heart failure. The management of hypertension typically requires long-term pharmacological therapy, and monotherapy often fails to achieve optimal blood pressure control in a large proportion of patients (1,2). The rationale for combination therapy lies in targeting multiple physiological pathways involved in blood pressure regulation. Combining drugs with complementary mechanisms such as angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), beta-blockers, calcium channel blockers, and diuretics enhances therapeutic efficacy while minimizing dose-related side effects. Such combinations are increasingly formulated as fixed-dose combinations (FDCs), improving patient adherence and clinical outcomes (3–5). The need for analytical methods capable of simultaneous estimation arises from the increasing development of FDCs. The analytical quantification of multiple active pharmaceutical ingredients (APIs) within a single formulation demands precise, accurate, and robust methods that can distinguish each compound without interference from excipients or degradation products. This is essential for ensuring drug quality, stability, and bioequivalence (6,7). Reverse-phase high-performance liquid chromatography (RP-HPLC) has emerged as the most versatile and reliable analytical technique in pharmaceutical analysis. Owing to its high resolution, reproducibility, and ability to handle complex mixtures, RP-HPLC is widely used for simultaneous estimation of multiple antihypertensive drugs in both bulk and dosage forms. Its adaptability to various mobile phases and stationary phases, along with compatibility with UV and PDA detection systems, makes it a preferred method for quantitative and qualitative analysis (8–10).The scope of this review is to provide a comprehensive understanding of the principles of RP-HPLC and its application in the simultaneous estimation of antihypertensive drugs. It also highlights recent advancements, method validation strategies, and analytical challenges encountered during multi-component analysis.

2. Anti-Hypertensive Drugs Used in Combination Therapy

2.1 Classification of Antihypertensive Drugs

Antihypertensive agents are broadly classified based on their pharmacological action. These include ACE inhibitors (such as enalapril and lisinopril), ARBs (such as losartan and valsartan), beta-blockers (such as atenolol and metoprolol), calcium channel blockers (such as amlodipine and nifedipine), and diuretics (such as hydrochlorothiazide and furosemide). Each class exerts its effect through distinct mechanisms, which often complement each other when used in combination therapy (11,12).

2.2 Commonly Combined Drugs

Fixed-dose combinations often include two or more of these classes. For example, ACE inhibitors or ARBs are commonly combined with diuretics to achieve synergistic effects in blood pressure reduction. Beta-blockers are sometimes paired with diuretics or calcium channel blockers to enhance cardiac protection. Calcium channel blockers, with their vasodilatory action, are effectively combined with ARBs or ACE inhibitors to counterbalance reflex tachycardia and improve overall tolerability (13,14). These multidrug regimens have proven effective in reducing cardiovascular events and improving long-term outcomes.

2.3 Physicochemical Properties Relevant to HPLC Analysis

Physicochemical properties such as pKa, solubility, and partition coefficient (logP) significantly influence chromatographic behavior. For instance, amlodipine exhibits moderate lipophilicity (logP ≈ 2.1) and a basic pKa, allowing good retention on C18 columns. In contrast, hydrochlorothiazide, being more polar, elutes faster under similar conditions. These differences necessitate optimized mobile phases to achieve resolution and peak symmetry. UV absorbance characteristics, typically between 220–280 nm for most antihypertensives, guide the choice of detection wavelength in RP-HPLC analysis (15–17).

3. Principles of Rp-Hplc For Pharmaceutical Analysis

3.1 Basics of HPLC

High-performance liquid chromatography (HPLC) operates on the principle of differential partitioning between a stationary phase and a mobile phase. Reverse-phase HPLC (RP-HPLC) employs a nonpolar stationary phase, typically octadecylsilane (C18), and a polar mobile phase, allowing nonpolar compounds to be retained longer. The separation depends on hydrophobic interactions, and modulation of mobile phase composition enables precise control over retention time and resolution (18).

3.2 Advantages of RP-HPLC

RP-HPLC offers several advantages over other chromatographic methods. It provides high efficiency, reproducibility, and selectivity, with excellent compatibility for water-soluble and lipophilic compounds. The technique allows simultaneous analysis of multiple analytes with minimal sample preparation. Moreover, RP-HPLC methods are easily validated for linearity, accuracy, precision, robustness, and limit of detection (LOD), meeting regulatory requirements for pharmaceutical analysis (19).

3.3 Components of an HPLC System

A standard HPLC system comprises a solvent reservoir, degasser, high-pressure pump, injector, analytical column, detector, and data-processing unit. The mobile phase is pumped at high pressure through the column packed with stationary phase particles, enabling efficient separation of analytes. The detector converts the chromatographic response into an electrical signal, producing a chromatogram that reflects analyte concentration and retention characteristics (20,21).

3.4 Detection Techniques for Antihypertensive Drugs

Detection methods in RP-HPLC depend on the analyte’s optical properties. UV-visible detection is the most commonly employed technique for antihypertensive drugs, owing to their strong chromophoric groups. Photodiode array (PDA) detectors provide additional advantages by enabling spectral analysis and peak purity assessment. In certain cases, fluorescence detection can enhance sensitivity for compounds with native fluorescence, though its application in antihypertensive analysis remains limited (22–24).

4. Literature Review on Simultaneous Estimation Methods

4.1 Reported RP-HPLC Methods for Combined Antihypertensive Drugs

Reverse-phase high-performance liquid chromatography (RP-HPLC) has emerged as the most reliable and reproducible analytical approach for the simultaneous estimation of antihypertensive drugs in both bulk and pharmaceutical dosage forms. Several researchers have optimized chromatographic conditions to achieve satisfactory separation, accuracy, and precision across diverse combinations of antihypertensive agents. Patel et al. (2019) developed and validated an RP-HPLC method for the simultaneous determination of amlodipine besylate and valsartan using a C18 column with an acetonitrile: phosphate buffer (pH 3.5) mobile phase (60:40 v/v), achieving detection at 238 nm and linearity in the range of 2–20 µg/mL. Similarly, Singh and Saini (2020) reported an RP-HPLC method for telmisartan and hydrochlorothiazide employing methanol and phosphate buffer (70:30 v/v) with retention times of 3.25 and 5.41 minutes, respectively, demonstrating accuracy within 99–101% [25]. A stability-indicating method was developed by Jain et al. (2021) for the simultaneous estimation of losartan potassium and amlodipine besylate, which effectively separated degradation products using a C18 column and a mobile phase comprising methanol and potassium dihydrogen phosphate buffer (55:45 v/v, pH 3.0) [26]. In another study, Shah et al. (2018) employed RP-HPLC for atenolol and chlorthalidone, with detection at 224 nm and mobile phase composition of acetonitrile:water (50:50 v/v) [27]. Furthermore, Nirmala et al. (2020) successfully established a method for olmesartan medoxomil and amlodipine besylate, achieving sharp peaks and satisfactory resolution under optimized chromatographic parameters (C18 column, acetonitrile:buffer 65:35 v/v) . Method validation in these studies followed ICH Q2(R1) guidelines, confirming linearity, precision, specificity, and robustness [28].

4.2 Comparative Evaluation of Existing Methods

The comparative evaluation of existing RP-HPLC methods reveals significant variability in chromatographic parameters such as mobile phase composition, column characteristics, and retention behavior. Most reported studies preferred C18 stationary phases, offering high efficiency and reproducibility due to their non-polar characteristics. However, the choice of mobile phase composition has varied significantly depending on the physicochemical properties of the analytes. Combinations of organic solvents such as acetonitrile and methanol with phosphate buffers of controlled pH (2.5–4.0) are commonly employed to ensure suitable peak symmetry and reduced tailing factors [29]. Retention time (t_R) for antihypertensive combinations generally ranges between 2.5 to 7.0 minutes, with methods optimized for shorter run times to enhance throughput. Sensitivity improvements have been achieved through the use of UV detection wavelengths between 230–250 nm, where both components exhibit adequate absorbance. Specificity studies across methods demonstrated the absence of interfering peaks from excipients, confirming method suitability for routine quality control applications [30]. While certain studies demonstrated excellent reproducibility and linearity, the sensitivity and resolution of analytes are often influenced by the selection of mobile phase ratios and flow rates. Adjustments in pH and ionic strength have shown a pronounced effect on the selectivity of drug peaks, indicating the criticality of method optimization for different formulations.

4.3 Limitations in Existing Literature

Although numerous RP-HPLC methods have been documented for simultaneous estimation of antihypertensive drugs, several limitations persist within the existing body of literature. Firstly, many reported methods lack stability-indicating capability, which is crucial for determining the degradation behavior of active pharmaceutical ingredients (APIs) under stress conditions [31]. Secondly, a majority of studies have been confined to binary drug combinations, with limited exploration of multi-component formulations that are increasingly prevalent in clinical practice. Furthermore, reproducibility across laboratories remains a challenge, primarily due to differences in column performance, buffer pH control, and solvent quality. Another limitation involves limited method robustness; small variations in temperature or mobile phase composition often result in significant changes in retention time and resolution, underscoring the need for more robust method validation. Sensitivity and specificity parameters also require improvement, especially for trace-level estimation in complex dosage forms [32]. Consequently, there is an emerging necessity for advanced, stability-indicating RP-HPLC methods that can simultaneously estimate multiple antihypertensive agents with high accuracy, sensitivity, and reproducibility. Incorporating Quality by Design (QbD) principles and chemometric optimization can further enhance method performance, ensuring compliance with current regulatory standards and improving analytical reliability [33].

5. Method Development for Simultaneous Estimation

5.1 Selection of Drugs for Estimation

The selection of anti-hypertensive drugs for simultaneous estimation is guided by their frequent co-administration in fixed-dose combinations (FDCs), synergistic pharmacological action, and clinical relevance in hypertension management. Commonly studied combinations include Amlodipine Besylate with Valsartan, Losartan Potassium with Hydrochlorothiazide, and Telmisartan with Amlodipine. These combinations offer enhanced therapeutic efficacy by targeting different pathways in blood pressure regulation, such as calcium channel blockade and angiotensin II receptor inhibition. Selecting such drugs necessitates evaluating their individual solubility, UV absorption characteristics, and compatibility under chromatographic conditions. The simultaneous estimation in a single chromatographic run minimizes analysis time and solvent consumption while improving accuracy and reproducibility in quality control laboratories [34].

5.2 Solvent and Mobile Phase Selection

The choice of solvent and mobile phase plays a crucial role in achieving optimal separation and peak symmetry in RP-HPLC. Typically, reversed-phase systems utilize a mixture of aqueous buffer and an organic modifier such as acetonitrile (ACN) or methanol (MeOH). The pH of the buffer system significantly affects the ionization state of the analytes and, consequently, their retention time and resolution. For antihypertensive drugs, phosphate buffers with pH ranging from 3.0 to 6.5 are commonly employed to stabilize ionizable groups and ensure reproducible retention. Acetonitrile is often preferred over methanol due to its lower viscosity, better elution strength, and shorter analysis time. However, methanol may be used for analytes requiring enhanced polarity or different selectivity. The optimal ratio of buffer to organic modifier is determined experimentally, considering factors such as peak sharpness, tailing factor, and resolution between co-eluting compounds [35].

5.3 Column Selection

Column selection is another vital parameter influencing chromatographic performance. C18 (octadecylsilane) columns are most widely used for RP-HPLC analysis of antihypertensive drugs due to their high hydrophobicity, reproducibility, and compatibility with various mobile phases [9]. Columns with dimensions of 250 mm × 4.6 mm and a particle size of 5 µm provide a suitable balance between resolution and analysis time. Smaller particle sizes (e.g., 3 µm or sub-2 µm) enhance efficiency but may require higher back pressure, thus necessitating the use of UHPLC systems. The stationary phase chemistry and surface area of the C18 column ensure strong nonpolar interactions with hydrophobic drug moieties, resulting in well-resolved and symmetric peaks. Column temperature stability and lifetime also contribute to consistent analytical performance across multiple runs [36].

5.4 Optimization of Chromatographic Conditions

Optimization of chromatographic parameters is achieved through a systematic approach involving the adjustment of flow rate, detection wavelength, injection volume, and temperature. Flow rate typically ranges between 0.8–1.2 mL/min, with optimization aimed at balancing resolution and run time . Detection wavelength is selected based on the maximum UV absorbance (λmax) of the drugs, often between 230–260 nm for antihypertensive compounds [37]. Spectral overlap studies are conducted to identify a common detection wavelength that allows simultaneous quantification without interference. The injection volume, generally between 10–20 µL, is optimized to ensure adequate signal response without overloading the column. Temperature control, usually maintained at 25–35°C, improves peak reproducibility and minimizes baseline fluctuations. These parameters are systematically evaluated using factorial design or response surface methodology (RSM) to achieve the best chromatographic separation with minimum peak tailing and maximum resolution [38].

5.5 Preparation of Standard and Sample Solutions

Accurate preparation of standard and sample solutions is essential for achieving reliable quantification in RP-HPLC analysis. Stock solutions of individual drugs are prepared in suitable solvents such as methanol or acetonitrile at known concentrations, followed by sonication to ensure complete dissolution. Working standards are then obtained by appropriate dilution of stock solutions with the mobile phase to achieve desired calibration levels, typically in the range of 10–100 µg/mL depending on the drug's linearity range. For tablet dosage forms, a specific quantity equivalent to the labeled amount of the drug is finely powdered, accurately weighed, and extracted with solvent under sonication or mechanical shaking. The solution is filtered through a 0.45 µm membrane filter before injection to remove particulate matter. The same diluent and mobile phase composition used in standard preparation are maintained in sample analysis to avoid matrix interference and ensure analytical reproducibility [39].

6. Validation of RP-HPLC Method (According To Ich Q2(R1) Guidelines)

Validation of an analytical method is a fundamental requirement to ensure reliability, precision, and reproducibility of the obtained results. The present study focuses on the validation of a reverse-phase high-performance liquid chromatography (RP-HPLC) method designed for the simultaneous estimation of selected antihypertensive drugs in bulk and combined tablet formulations. The validation process was carried out in accordance with the International Council for Harmonisation (ICH) guidelines Q2(R1), which define the parameters essential for confirming the suitability of an analytical method for its intended purpose [40].

6.1 Specificity and Selectivity

Specificity and selectivity refer to the method’s ability to accurately assess the analyte in the presence of other components such as excipients, degradation products, and impurities. The developed RP-HPLC method demonstrated excellent specificity, as no interference was observed at the retention times corresponding to the analytes of interest. Chromatographic peaks of each antihypertensive drug such as amlodipine besylate, losartan potassium, and fimasartan were well resolved with baseline separation from matrix components. This confirms that the developed method can unequivocally quantify the target analytes in complex pharmaceutical formulations without cross-interference from other constituents [41].

6.2 Linearity and Range

Linearity establishes the method’s ability to produce test results that are directly proportional to the concentration of analyte within a specified range. The calibration curves for all drugs exhibited strong linearity over the concentration ranges studied, with correlation coefficients (R²) consistently exceeding 0.999. Regression analysis of peak area versus concentration confirmed a linear response, thereby validating the quantitative reliability of the RP-HPLC system for a broad range of analyte concentrations [42].

6.3 Accuracy (% Recovery Studies)

Accuracy was evaluated through percentage recovery studies using standard addition techniques at three concentration levels (80%, 100%, and 120% of nominal concentration). The mean recovery values were found to be within the acceptable range of 98%–102%, demonstrating that the method is accurate for the intended analytical applications. The close agreement between the measured and true values indicates minimal systematic error and confirms that the analytical method can accurately determine the true concentration of the analytes in both bulk and formulated forms [43].

6.4 Precision

Precision, defined as the degree of repeatability under normal operating conditions, was assessed through repeatability and intermediate precision studies.
Repeatability was determined by analyzing multiple replicates of standard solutions within a single day, and the %RSD values were below 2%, signifying high intra-day precision. Intermediate precision (inter-day precision) was established by performing analyses on different days and by different analysts; the results confirmed that the %RSD values remained below 2%, signifying excellent reproducibility of the RP-HPLC method across time and personnel variability [44].

6.5 Limit of Detection (LOD) and Limit of Quantification (LOQ)

The sensitivity of the developed method was characterized through the determination of LOD and LOQ, which were calculated using the standard deviation of the response and the slope of the calibration curve according to the formulae LOD = 3.3σ/S and LOQ = 10σ/S. The LOD and LOQ values were sufficiently low to enable the quantification of trace levels of antihypertensive drugs, thereby confirming the high sensitivity of the RP-HPLC system for the proposed analysis [45].

6.6 Robustness

Robustness assesses the reliability of an analytical procedure when small deliberate variations are introduced in method parameters such as flow rate, mobile phase composition, and detection wavelength. The results indicated that minor changes in these parameters did not significantly affect the retention time, theoretical plates, or peak symmetry. The %RSD of peak area and retention time remained within the acceptable limits, confirming that the developed RP-HPLC method is robust and can withstand minor operational variations without compromising analytical performance [46].

6.7 System Suitability Parameters

System suitability testing was conducted to verify the performance characteristics of the chromatographic system prior to analysis. The parameters evaluated included the number of theoretical plates, tailing factor, and resolution between adjacent peaks. Theoretical plate counts exceeded the minimum requirement, indicating column efficiency, while the tailing factor was consistently below 2, demonstrating symmetric peak shape. The resolution between co-eluting peaks was greater than 2, signifying adequate separation. These results confirmed the chromatographic system’s suitability for routine analysis of antihypertensive drugs in combined dosage forms [47].

7. Application of The Developed Method

7.1 Analysis of Bulk Drugs

The analytical application of the developed Reverse Phase High-Performance Liquid Chromatography (RP-HPLC) method for bulk drugs represents a critical stage in validating the method’s selectivity, sensitivity, and robustness. In bulk drug analysis, the simultaneous estimation of antihypertensive agents such as amlodipine besylate, losartan potassium, telmisartan, and hydrochlorothiazide is essential due to their frequent co-formulation in fixed-dose combinations. The developed RP-HPLC method enables efficient resolution of these drugs with distinct retention times under optimized chromatographic conditions, typically involving a C18 column, mobile phase mixtures of acetonitrile or methanol with buffer (phosphate or acetate), and detection wavelengths ranging from 230–250 nm. The linearity of calibration curves in the bulk form usually extends across a concentration range of 5–100 μg/mL, with correlation coefficients (r²) greater than 0.999, demonstrating high reliability. Validation according to ICH Q2(R1) guidelines confirms that the method satisfies parameters of precision, accuracy, and robustness, rendering it applicable for the quantitative assessment of bulk drug substances before formulation [48].

7.2 Analysis of Tablet Dosage Forms

The developed RP-HPLC method demonstrates superior applicability for the simultaneous estimation of antihypertensive drugs in tablet dosage forms, ensuring both formulation quality and therapeutic consistency. In this context, the analytical procedure facilitates the accurate quantification of active pharmaceutical ingredients (APIs) in complex matrices without interference from excipients. Chromatographic separation is achieved under controlled conditions, maintaining retention time reproducibility and peak symmetry. Sample preparation typically involves sonication and filtration to ensure homogeneous extraction of APIs. Recovery studies conducted on tablet formulations reveal mean recovery values within 98–102%, reflecting method accuracy (10–13). System suitability parameters—including tailing factor (< 2.0), theoretical plates (> 2000), and resolution (> 2.0)—affirm the efficiency of the chromatographic system. The developed method’s ability to detect minor variations in dosage content provides a reliable analytical tool for routine quality control in the pharmaceutical industry (49).

7.3 Forced Degradation Studies (if applicable)

Forced degradation or stress testing forms an integral part of method validation to establish the stability-indicating nature of the RP-HPLC procedure. The antihypertensive drugs are subjected to various stress conditions, including acid and base hydrolysis, oxidative degradation, photolysis, and thermal stress, to assess their chemical stability. Degradation studies are crucial for identifying possible degradation products and ensuring that they are well resolved from the main analyte peaks. For instance, amlodipine and telmisartan exhibit susceptibility to acidic and oxidative degradation, whereas hydrochlorothiazide shows thermal instability. The method’s capacity to separate degradation products from the intact drugs with acceptable peak purity confirms its stability-indicating potential (50). Such validation strengthens its utility not only for routine analysis but also for stability testing of formulations during shelf-life evaluation.

7.4 Assessment of Assay and Content Uniformity

The developed RP-HPLC method is further validated through the assessment of assay and content uniformity, which are critical parameters in ensuring dose accuracy and formulation consistency. The assay results for antihypertensive drugs typically range between 98–102% of the labeled claim, indicating high precision and reliability of the analytical system (51). The content uniformity test, performed on multiple dosage units, ensures that each tablet contains the intended amount of the active ingredient within acceptable pharmacopeial limits (52). The low relative standard deviation (RSD < 2%) across samples demonstrates excellent repeatability. These findings confirm the suitability of the method for routine in-process and finished product quality control in industrial settings. Furthermore, the robustness studies evaluating deliberate variations in flow rate, mobile phase composition, and detection wavelength confirm the stability and reliability of the method across diverse analytical conditions (53).

FUTURE PERSPECTIVES

The development and validation of RP-HPLC methods for the simultaneous estimation of antihypertensive drugs continue to hold immense potential in the pharmaceutical and analytical sciences. With the ever-increasing demand for precision, reproducibility, and cost-effectiveness in routine analyses, the role of RP-HPLC methods extends beyond mere assay quantification toward broader applications in quality control, stability testing, and advanced analytical platforms. One of the most promising areas is the implementation of validated RP-HPLC methods in quality control laboratories. Such methods, once optimized, provide a robust analytical framework for the routine analysis of both bulk drug substances and finished dosage forms. Their high selectivity and reproducibility make them indispensable for ensuring batch-to-batch consistency and adherence to pharmacopeial standards. Furthermore, validated RP-HPLC techniques are essential in post-market surveillance, supporting the detection of substandard or counterfeit formulations and contributing to pharmaceutical quality assurance (54). Another emerging direction lies in the development of stability-indicating methods. RP-HPLC offers the capability to effectively separate degradation products from active pharmaceutical ingredients (APIs), thereby enabling comprehensive stability profiling. Stability-indicating RP-HPLC methods are critical for assessing drug integrity under various stress conditions, including thermal, photolytic, oxidative, and hydrolytic environments. Such advancements align with ICH Q1A(R2) guidelines for stability testing, supporting regulatory submissions and lifecycle management of antihypertensive formulations (55).

The applicability of these analytical methods to other drug combinations also offers wide-ranging opportunities. Antihypertensive therapy frequently involves fixed-dose combinations, where simultaneous quantification is necessary to maintain therapeutic efficacy and safety. Extending validated RP-HPLC methods to novel drug combinations, such as angiotensin receptor blockers (ARBs) with calcium channel blockers (CCBs) or diuretics, will further streamline multi-drug analysis. This adaptability underscores RP-HPLC’s role as a universal tool in modern combination therapy research (56).

Looking ahead, there is considerable scope for automation and integration with advanced detection systems, such as Ultra-Performance Liquid Chromatography (UPLC) and Liquid Chromatography-Mass Spectrometry (LC-MS). These advanced platforms offer enhanced resolution, reduced run times, and improved sensitivity. The transition from conventional RP-HPLC to these high-throughput systems represents a natural progression toward analytical modernization. Automation can minimize operator variability and improve throughput, while LC-MS coupling enables molecular-level identification, supporting trace impurity profiling and pharmacokinetic evaluations (57). Therefore, the evolution of RP-HPLC methodology in the estimation of antihypertensive drugs is poised to strengthen analytical reliability, regulatory compliance, and innovation in pharmaceutical research. By integrating novel detection technologies, these methods can be transformed into comprehensive analytical solutions tailored to the demands of next-generation drug development and quality assurance (58).

CONCLUSION

The review emphasizes that RP-HPLC is a powerful and indispensable analytical tool for the simultaneous estimation of antihypertensive drugs in bulk and combined dosage forms. Its high selectivity, reproducibility, and precision make it ideally suited for routine quality control and regulatory compliance in the pharmaceutical industry. Validation according to ICH Q2(R1) guidelines confirms that RP-HPLC methods meet stringent analytical performance requirements, including accuracy, precision, linearity, and robustness. Despite widespread adoption, challenges persist regarding method transferability, stability indication, and multi-component quantification. The incorporation of Quality by Design (QbD) principles and chemometric optimization can enhance method reliability and reproducibility across laboratories. Moreover, the integration of advanced technologies such as UPLC and LC-MS expands the analytical scope of RP-HPLC, allowing for faster, more sensitive, and structurally informative analyses. Future developments should focus on establishing stability-indicating methods, improving automation, and broadening applicability to newer drug combinations. Overall, the RP-HPLC method represents a benchmark in pharmaceutical analysis, ensuring therapeutic consistency, patient safety, and the effective monitoring of antihypertensive formulations throughout their life cycle.

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