0% READ
FULL TEXT
INTRODUCTION
Hydrochlorothiazide (HCTZ) is a thiazide diuretic that is commonly administered to treat hypertension and related illness such as edema caused by heart failure or renal problems. It acts by inhibiting salt and chloride reabsorption in the kidney’s distal convoluted tubules, increasing diuresis and thus lowering blood pressure. HCTZ has been cornerstone of hypertension therapy for decades due to its efficacy, safety profile, and affordable cost (Herman et al., 2023). Combination therapy with HCTZ and other antihypertensives, such as Angiotensin Receptor Blockers (ARBs), Angiotensin II receptor blockers (ACE) inhibitors, and beta blockers, is commonly used to improve blood pressure control, particularly when monotherapy fails to meet therapeutic goals. Clinical data supports up the superiority of combination regimens over monotherapy in lowering systolic and diastolic blood pressure (MacDonald et al., 2017). Combination therapy with HCTZ and other antihypertensives, such as ARBs, ACE inhibitors, and beta blockers, is commonly used to improve blood pressure control, particularly when monotherapy fails to meet therapeutic goals. Clinical data supports up the superiority of combination regimens over monotherapy in lowering systolic and diastolic blood pressure. With the increased use of fixed dose combinations, developing accurate, precise, and robust analytical methodologies has become essential to pharmaceutical quality control and clinical pharmacokinetics evaluation. Chromatographic techniques such as High-Performance Liquid Chromatography (HPLC) and Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) are frequently used for the simultaneous measurement of HCTZ with co-formulated medicines in tablet and plasma, resulting in high sensitivity and specificity (Liu et al., 2007). Furthermore, emerging approaches combine current validation strategies and environmentally friendly consideration in order to meet regulatory requirements and ensure environmental sustainability (Al‐Asmar et al., 2025). A chemometric design (central composite design) was used to optimized parameters such as mobile phase composition and flow rate. Herby boosting separation and analytical efficiency. The proven method is appropriate for bioavailability and pharmacokinetic studies in clinical and pharmaceutical research (Ganna et al., 2022). Precise therapeutic monitoring, impurity profiling, stability studies and pharmacokinetic investigation in both research and clinical contexts.
Importance of Combination Therapy
Fixed-dose combinations of ARBs with HCTZ have demonstrated greater efficacy in lowering systolic and diastolic blood pressure than ARB monotherapy, with similar rates of adverse events, indicating that low-dose HCTZ adds significant antihypertensive benefit without compromising tolerability (Ma et al., 2021). Guidelines and clinical data underline the justification for combining drugs with different mechanisms, such as renin-angiotensin system blockers and diuretics, to improve blood pressure control while minimizing side effects. When combined with an ACE inhibitor or ARB, diuretic-induced hypokalaemia can be reduced (Gradman, 2010).
Triple combinations of ARBs, calcium channel blockers, an HCTZ have resulted in significantly greater blood pressure reductions and higher rates of target achievement compared to dual therapies, demonstrating the benefits of multi-mechanism regimens in patients with more severe or difficult-to-control high blood pressure. Single pill fixed dose combinations enhance adherence and simplify drugs, which can lead to sustained 24-hr blood pressure management and better overall clinical results than numerous independent drugs or monotherapy approaches (Volpe and Tocci, 2012). The Central Drug Standard Control Organization (CDSCO)-approved fixed-dose combinations of HTCZ are listed in Table 1 (Central Drugs Standard Control Organization [CDSCO]).
| Combination | Approved Year | Medication class com bination | Treatment for |
|---|---|---|---|
| HCTZ+Benazepril | 2004 | Angiotensin-converting enzyme inhibitor (ACEI)+ Angiotensin-II receptor blocker+Thiazide | Mild to moderate hypertension |
| HCTZ+Captopril | 1997 | Heart Failure, Raised blood pressure | |
| HCTZ +Enalapril | 2001 | Heart Failure, Raised blood pressure | |
| HCTZ +Fosinopril | 2004 | Raised blood pressure | |
| HCTZ +Lisinopril | 2002 | Heart Failure, Raised blood pressure | |
| HCTZ +Moexipril | 2007 | Raised blood pressure | |
| HCTZ +Quinapril | 2005 | Raised blood pressure | |
| HCTZ +Candesartan | 2012 | Raised blood pressure | |
| HCTZ +Irbesartan | 2012 | Raised blood pressure | |
| HCTZ +Losartan | 2010 | Raised blood pressure | |
| HCTZ +Olmesartan | 2016 | Raised blood pressure | |
| HCTZ +Telmisartan | 2014 | Raised blood pressure | |
| HCTZ +Valsartan | 2012 | Raised blood pressure | |
| HCTZ +Bisoprolol | 2000 | β-Blocker+Thiazide | Raised blood pressure |
| HCTZ +Metoprolol | 2004 | Raised blood pressure | |
| HCTZ +Amiloride | 1987 | Potassium-sparing diuretic thiazide | Raised blood pressure |
| HCTZ +Triamterene | 1987 | For the management of fluid retention (edema) or Raised blood pressure (hypertension) | |
| HCTZ +Spironolactone | 1979 | Mineralocorticoid receptor antagonist+Thiazide | Raised blood pressure |
| HCTZ +Olmesartan +Amlodipine | 2016 | Angiotensin-II receptor blockers calcium channel blockers+Thiazide | Raised blood pressure |
| HCTZ+Valsartan+Amlodipine | 2013 | Raised blood pressure | |
| HCTZ+Candesartan Cilexetil | 03.01.2002 | Angiotensin-II receptor blocker+ Thiazide | Essential hypertension (not for initial therapy) |
| HCTZ +Losartan Potassium | 08.06.1999 | Angiotensin-II receptor blocker or ACEI+Thiazide | For treatment of mild to moderate hypertension |
| HCTZ +Telmisartan IP | 14.05.2013 | ACEI or angiotensin-II receptor blockers+ Thiazide | Use as adjunct medication to manage high blood pressure |
| HCTZ+Amlodipine Besylate | 23.11.2011 | Potassium-sparing diuretic thiazide | For treatment of hypertension in patients who are not controlled |
| HCTZ+Ramipril | 26.08.1996 | ACEI+ Thiazide | Mild to moderate hypertension in patients |
| HCTZ +Benazapril HCL | 21.05.1998 | ACEI+ Thiazide | Mild to moderate hypertension only |
| HCTZ +Lisinopril | 23.11.1995 | ACEI+ Thiazide | Raised blood pressure |
METHODOLOGY
From an analytical and quality control perspective, robust, stability-indicating analytical methods capable of the reliable, precise, and validated simultaneous estimation of HCTZ with co-formulated drugs in both pharmaceutical dosage forms and biological matrices are essential to ensure the assay accuracy, content uniformity, impurity profiling, and stability evaluation of combination products, especially given HCTZ’s susceptibility to degradation under hydrolytic, oxidative, and photolytic conditions, which mandates the assurance of product quality and safety throughout the shelf life (Bakshi and Singh, 2002). Variations in physicochemical parameters, such as polarity, pKa, and UV absorption characteristics, worsen analytical problems in multi-component compositions, needing optimal chromatographic separation and selective detection (Blessy et al., 2014). Table 2. provides an overview of the various analytical methods reported in the literature for the simultaneous estimation of Hydrochlorothiazide (HCTZ) in combined dosage formulations.
| Sl. No. | Drug Estimated | Technique | Description of method | Application | Ref |
|---|---|---|---|---|---|
| 1 | Telmisartan+HCTZ | Stability indicating RP-LC with internal standard | C18 (25 cm) Column 50 mM ammonium acetate buffer (pH 5.5) and acetonitrile (70:30 v/v) mobile phase with flow rate of 1.0 mL/min detection at 260 nm column temperature of 30ºC. | Applied for assay content and quality control | (Rane et al., 2008) |
| 2 | Losartan +HCTZ | HPLC-ESI-MS/MS (Negative ion mode, MRM) | Human plasma using liquid-liquid extraction followed by HPLC-ESI-MS/MS in negative ion MRM mode, with valsartan and chlorthalidone as internal standards. | Applied for bioequivalence studies. | (Salvadori et al., 2009) |
| 3 | Valsartan+HCTZ | HPTLC with UV detection | Precoated silica gel 60F254 as the stationary phase. The mobile phase consisted of chloroform: methanol: toluene: glacial acetic acid (6:2:1:0.1v/v/v/v) Densitometric detection was carried out at 260 nm. | Applied for assay content and quality control | (Shah et al., 2009) |
| 4 | Irbesartan+ HCTZ | Stability-indicating RP-LC with internal standard. | C18 (25 cm) column, 50 mM ammonium acetate buffer (pH 5.5) and acetonitrile (70:30 v/v) mobile phase with flow rate of 1.5 mL/min. Detection at 235 nm, column temperature of 30ºC and Methylparaben internal standard. | Applicable for assay, forced degradation, and routine quality control | (Rane et al., 2010) |
| 5 | Candesartan cilexetil+ HCTZ | LC-MS/MS (Negative ion mode) with Liquid-Liquid Extraction | Sample preparation involved liquid-liquid extraction using 100µL Human plasma, followed by LC separation and tandem mass spectrometric detection in negative ion mode; run time of 2.5 min, calibration ranges of 1-160 ng/mL for candesartan cilexetil and 2-160ng/mL for HCTZ. | Applied for pharmacokinetic studies | (Bharathi et al., 2012) |
| 6 | Ramipril +HCTZ | LC-MS/MS with ESI (Positive and Negative modes) using LLE | Human plasma using liquid-liquid extraction with methyltert-butyl ether dichloromethane (85:15). Chromatographic separation was achieved on an enable C18G column (150x4.6 mm, 5 µm) using methanol 1:0.1% formic acid in water (85:15) at a flow rate of 0.5 mL/min. Detection was performed by triple quadrupole MS in MRM mode with positive ionization for ramipril and negative ionization for HCTZ using carbamazepine as internal standard. | Applied for pharmacokinetic studies | (Patel et al., 2014) |
| 7 | Aliskiren +HCTZ | Stability indicating RP-HPLC | Phenyl column, 0.030 M ammonium acetate-acetonitrile (60:40 v/v) mobile phase with flow rate of 0.40 mL/min and detection at 280 nm. | Applied for assay content uniformity and quality control | (Karvelis et al., 2014) |
| 8 | Lisinopril+HCTZ | LC-MS/MS (Negative ion mode, MRM) | Human plasma using solid phase extraction was Water Oasis HLB cartridge, followed by chromatographic separation on a Hypersil Gold C18 (50x3.0 mm, 5 µm) column. The mobile phase consisted of acetonitrile and 5.0mM ammonium for mate (pH 4.5) in the ratio 85:15v/v. Detection was performed using tandem mass spectrometry in multiple reaction monitoring mode with labeled internal standards. | Applied to pharmacokinetic studies. | (Shah et al., 2017) |
| 9 | Amlodipine+Valsartan+ HCTZ | LC-MS/MS with Solid Phase Extraction (SPE) | In human plasma using solid phase extraction on Qasis HLB cartridges (100 µL plasma) Chromatographic separation was achieved on a chromolith RP 18e (100X4.6mm) column under isocratic condition with a total run time of 2.5 min. Detection was performed by tandem mass spectrometry using deuterated internal standard. | Applied to a bioequivalence study | (Shah et al., 2009) |
| 10 | Candesartan +HCTZ | HPLC method | Hypersil BDS C18 column (150x4.6x5µm) using mobile phase consisting of phosphate buffer pH 5.4 and acetonitrile (65:35) at flow 1.0 mL/min Detection was carried out at 232nm. | Applied for quality control method. | (Gaurkhede and Chandewar, 2018) |
| 11 | Telmisartan and HCTZ impurities | RP-HPLC(Gradient)with Analytical QbD | Intersil ODS-3V column(150x4.6 mm, 3.5 µm), gradient elution with 0.02M KH2PO4(pH 3.5) and water: Acetonitrile (100:900v/v), flow 1 mL/min, 40ºC detection at 230 nm. Design of Experiments (DoE) used to identify critical quality attributes and establish method design space. | Applied to forced degradation studies. | (Palakurthi et al., 2020) |
| 12 | Fimasartan, fimasartan-amide, amlodipine+ HCTZ | LC-MS/MS | Analysing rate plasma with an Agilent 6470 triple-quadrupole LC-MS/MS instrument. Chromatographic separation was achieved using a Synergi Polar RP column (150x4.6 mm, 4 µm) using an isocratic mobile phase of water acetonitrile (30:70 v/v) containing 0.1% formic acid at a flow rate of 0.20 mL/min. Detection was carried out in Multiple Reaction Monitoring (MRM) mode. | Applied to pharmacokinetic inter action and toxicokinetic studies of triple combination antihypertensive therapy and evaluation of Panax ginseng extract effects | (Jeon et al., 2022) |
| 13 | losartan potassium and HCTZ | RP-HPLC (Stability-indicating, Analytical QbD) | The X-Bridge C18 column (150x4.6mm,3.5 µm) used a gradient elution of 0.3%formic acid (A) and acetonitrile: methanol 80:20 (B). Flow 1.3 mL/min, 40ºC, injection 10μL. Method development followed AQbD principles: ATP definition, bibliographic survey, screening with Plackett-Burman (11 factors, 2 levels), optimization with central composite design (4 factors, 5 levels), and modeling of response surfaces. | Applied for quality control method | (Rocha and Lourenço, 2023) |
| 14 | Dilitiazem, Propranolol+HCTZ | Mixed-mode RP-HPLC (Analytical QbD) | Mixed-mode stationary phase. Separation achieved in more than 8min under isocratic elution. Method development followed Analytical Quality by Design (QbD) principle with risk assessment 2- level fractional factorial screening and central composite design optimization. Method operable design established using Monte Carlo simulation and capability analysis. | Applied to in vitro release sample from 3D printed tablet | (Samara et al., 2024) |
DISCUSSION AND SUMMARY
HCTZ is a commonly prescribed thiazide diuretics that is frequently combined with antihypertensive agent such as ARBs (telmisartan, losartan, valsartan etc), ACE inhibitors (ramipril, lisinopril) calcium channel blockers (amlodipine) and renin inhibitors (aliskiren) in view of its widespread clinical use, pharmaceutical research has focused on developing reliable, sensitive and robust analytical method for determining HCTZ in conjunction with co-administered drugs. The reviewed research article shows considerable advancements in chromatographic and hyphenated analytical techniques for pharmaceutical dosage forms as well as biological matrices. Traditional RP-HPLC as well as HPTLC procedures are still frequently used for routine quality control of combined dosage forms because they are simple, relatively inexpensive and have acceptable precision and accuracy. Several methods including C18 columns isocratic elution UV detection (235-280 nm and internal standards like methylparaben, have demonstrated excellent linearity, low relative standard deviation (<2%) and significant recovery, making them suitable for formulation analysis and content uniformity testing. In contrast-MS/MS - based approaches are widespread in bioanalytical applications, particularly for pharmacokinetics bioequivalence and drug - drug interaction studies. these approaches provide superior sensitivity, selectivity and lower limits of quantification often in the ng/mL or sub-ng/mL range albeit using small plasma volume (≈100 µL). Both liquid - liquid and solid phase extraction technique were used successfully incorporating isotope labelled or structurally related internal standards increasing methods robustness. A significant breakthrough noted by various studies is the rising emphasis on stability - indicating approaches. The tandem application of photodiode array and mass spectroscopy improved peak purity evaluation and structural elucidation of degradation products, including unidentified impurity species resulting from excipient - drug interaction. Further, the use of analytical Quality by Design (AQbD) concepts constituents an evaluation from traditional one- factor - at -a time technique. AQbD- based methodologies improved their robust-ness, regulatory flexibility and lifecycle’s reliability by incorporating Design of Experiments (DoE), risk assessment and design space establishment. An overview of the conceptual framework of analytical approaches for HCTZ in fixed-dose combinations is depicted in Figure 1. These methodologies were effectively used to both traditional formulations and emerging technologies, such as 3D- printed pharmaceutical dosage forms, proving adaptability to innovative drug delivery system. Overall, the data highlight the progression of analytical approaches forms simple routine evaluation to highly sophisticate, stability- indicating, and regulatory - compliant techniques they can support both product developed and clinical research.
Research Gaps
In conclusion, the studied methodologies provide a solid analytical framework for quality assurance, regulatory evaluation of HCTZ containing fixed dose combinations. Nonetheless, the available literature suggests a research deficit in the development of AQbD-oriented, stability indicating and environmentally sustainable analytical methods capable of estimating HCTZ in combination with routinely co-formulated antihypertensive drugs. In particular, there has been little attention on systematic method optimization using design space concepts and validation of technique suitable for routine quality control.
CONCLUSION
This study focuses on the analytical methodologies developed for simultaneous quantification of HCTZ with diverse antihypertensive drugs in pharmaceutical formulations and biological matrices. Conventional HPLC and HPTC producer remain important in routine quality control because to their simplicity, accuracy, and cost effectiveness. Meanwhile, LC-MS/MS technologies have become indispensable in bioanalytical applications, providing the sensitivity and selectivity required for pharmacokinetics, bioequivalence and interaction studies. The growing use of stability -indicating methods and AQbD- driven analytical development fits recent regulatory demands while ensuring method robustness across the product lifecycle. Furthermore, the application of this analytical approach to modern drug delivery system, such as fixed - dose combination drugs and 3D- printed tablets, illustrates their adaptability and future utility.
To summarise, the reviewed approaches provided a solid analytical platform for the quality assurance, regulatory evaluation, and clinical investigation of HCTZ - containing combined dosage forms. The further integration of AQbD principles and advanced detections techniques is anticipated to improve analytical performance and support changing landscape of pharmaceutical research.