Simultaneous quantification of amiloride and hydrochlorothiazide in human plasma by liquid chromatography-tandem mass spectrometry

Mapping Advantages and Challenges in Analytical Development for Fixed Dose Combination Products, a Review

Formulations containing more than one active ingredient are increasingly gaining popularity due to advantages with regard to patient convenience as well as reduced cost of production, packaging, and transportation. Such fixed-dose combinations (FDCs) demand for enhanced analytical methodologies and tools to efficiently achieve quality control of these complex products as compared to the conventional products containing only one active constituent. Highly efficient analytical methods can measure multiple constituents at once, improving their quality control. This review article discusses the challenges in the development of such methods due to the similarities or differences in the chemical identity of the participating drug molecules in an FDC. The latest developments in multiple analyte determination using various analytical techniques (HPLC, LC-MS, NMR, IR, powder XRD and DSC) are discussed, with a focus on special considerations in each case. The article discusses challenges with sample preparation of complex FDC products, and the use of Chemometrics and Quality by Design to develop efficient analytical methods. Lastly, an equation-based approach is proposed and demonstrated to arrive at a parameter referred to as "percentage efficiency gain" that would be useful in directly accessing the relevance and commercial benefits of a simultaneous method vis-a-vis separate methods for individual components.

Diuretics in Different Samples: Update on the Pretreatment and Analysis Techniques

Diuretics are drugs that promote the excretion of water and electrolytes in the body and produce diuretic effects. Clinically, they are often used in the treatment of edema caused by various reasons and hypertension. In sports, diuretics are banned by the World Anti-Doping Agency (WADA). Therefore, in order to monitor blood drug concentration, identify drug quality and maintain the fairness of sports competition, accurate, rapid, highly selective and sensitive detection methods are essential. This review provides a comprehensive summary of the pretreatment and detection of diuretics in various samples since 2015. Commonly used techniques to extract diuretics include liquid-liquid extraction, liquid-phase microextraction, solid-phase extraction, solid-phase microextraction, among others. Determination methods include methods based on liquid chromatography, fluorescent spectroscopy, electrochemical sensor method, capillary electrophoresis and so on. The advantages and disadvantages of various pretreatment and analytical techniques are elaborated. In addition, future development prospects of these techniques are discussed.

Screening and elucidation of fragmentations of 23 diuretics in dietary supplements using UHPLC-Q-Orbitrap

Diuretics are used to treat the edematous state in cases of renal insufficiency, nephrotic syndrome, liver cirrhosis, and heart failure. These compounds are used by athletes to lose weight and are included in the list of prohibited substances by the World Anti-Doping Agency. They are also used by obese and overweight people for losing weight, and there are a number of recent reports on the contamination of dietary supplements with diuretics. Due to the alluring online marketing and blogging, there is an extensive misuse of products that are illegally adulterated with diuretics, which has seriously increased health risks. Therefore, it is essential to develop an analytical method for the detection of adulterants in such substances. In this study, 23 diuretics, categorized into four groups, namely, thiazide diuretics (e.g., bendroflumethiazide), loop diuretics (e.g., bumetanide), potassium-sparing diuretics (e.g., amiloride), and carbonic anhydrase inhibitors (e.g., acetazolamide), were analyzed using ultrahigh-performance liquid chromatography-quadrupole orbitrap (UHPLC-Q-Orbitrap). Their fragmentation was elucidated based on the MS/MS data. The 124 products were screened by the UHPLC-Q-Orbitrap (LC-HRMS) method, and the confirmed compounds were quantitated by a previously established LC-MS/MS method. Approximately 5% of the samples were found to be illegally contaminated with diuretics at a concentration of 0.051-162 mg/g. The high selectivity and sensitivity of the UHPLC-Q-Orbitrap (LC-HRMS) method, in combination with the established fragmentation, offer a new approach for the rapid and accurate screening of diuretics in adulterated products, which would be ultimately beneficial for the public health.

Validated LC-MS/MS method for the simultaneous determination of enalapril maleate, nitrendipine, hydrochlorothiazide, and their major metabolites in human plasma

Hypertension is a major risk factor for atherosclerosis and ischemic heart disease. Most hypertensive patients need a combination of antihypertensive agents to achieve therapeutic goals. A rapid, sensitive, and selective liquid chromatography-tandem mass spectrometric method was developed and validated for simultaneous determination of enalapril maleate (ENA) and its major metabolite enalaprilat (ENAT), nitrendipine (NIT) and its major metabolite dehydronitrendipine (DNIT), and hydrochlorothiazide (HCT) in human plasma using felodipine as an internal standard (IS). The drugs were extracted from plasma using one-step protein precipitation. Chromatographic separation was performed on a Symmetry C₁₈ column, with water and acetonitrile (10:90, v/v) as mobile phase. The detection was carried out using multiple reaction monitoring mode and coupled with electrospray ionization source. Multiple reaction monitoring transitions were m/z 377.1 → 234.1 for ENA, m/z 349.2 → 206.1 for ENAT, m/z 361.2 → 315.1 for NIT, m/z 359 → 331 for DNIT, m/z 295.9 → 205.1 for HCT, and m/z 384.1 → 338 for felodipine (IS). The method was linear over concentration ranges of 1-200, 20-500, 5-200, 2-100, and 5-200 ng/mL for ENA, ENAT, NIT, DNIT, and HCT, respectively, with r² ≥ 0.99. Method validation was performed according to U.S. Food and Drug Administration guidelines. The validated method showed good sensitivity and selectivity and could be applied for therapeutic drug monitoring and bioequivalence studies.

Photostability study of multicomponent drug formulations via MCR-ALS: The case of the hydrochlorothiazide-amiloride mixture

The kinetics and photodegradation mechanism of the pharmaceutical mixture of hydrochlorothiazide (HCT) and amiloride (AML) has been studied in depth using a chemometric approach. Water solutions of HCT and AML, separately or in binary mixtures, were irradiated with forced light at different pH values (3, 7, 9 and 12). Multivariate Curve Resolution - Alternating Least Squares (MCR-ALS) modelling has been applied to the experimental data recorded by UV spectrophotometry and HPLC-UV/MS. 78 data sets were collected and their chemometric processing has allowed the simultaneous determination of the behaviour of the two drugs in the mixture when exposed to light and the dependence of their photodegradation kinetics on pH. MCR-ALS has been applied using three different implementations. Soft-MCR-ALS and hybrid Hard/Soft-MCR-ALS have been used to resolve the experimental data and to get the equilibrium and kinetic parameters of the investigated chemical processes. A third implementation of the MCR-ALS method has been used in the analysis of the incomplete data sets obtained when UV spectrophotometric and HPLC-UV/MS data were simultaneously analysed, using a row- and column-wise incomplete augmented data matrix arrangement. In these matrices, information from HPLC-UV detector was used as a bridge between the data recorded by UV spectrophotometry (acid-base and kinetic reactions monitoring) and the data obtained by HPLC-MS.

A Randomized Trial of Distal Diuretics versus Dietary Sodium Restriction for Hypertension in Chronic Kidney Disease

BACKGROUND

Distal diuretics are considered less effective than loop diuretics in CKD. However, data to support this perception are limited.

METHODS

To investigate whether distal diuretics are noninferior to dietary sodium restriction in reducing BP in patients with CKD stage G3 or G4 and hypertension, we conducted a 6-week, randomized, open-label crossover trial comparing amiloride/hydrochlorothiazide (5 mg/50 mg daily) with dietary sodium restriction (60 mmol per day). Antihypertension medication was discontinued for a 2-week period before randomization. We analyzed effects on BP, kidney function, and fluid balance and related this to renal clearance of diuretics.

RESULTS

A total of 26 patients (with a mean eGFR of 39 ml/min per 1.73 m²) completed both treatments. Dietary sodium restriction reduced sodium excretion from 160 to 64 mmol per day. Diuretics produced a greater reduction in 24-hour systolic BP (SBP; from 138 to 124 mm Hg) compared with sodium restriction (from 134 to 129 mm Hg), as well as a significantly greater effect on extracellular water, eGFR, plasma renin, and aldosterone. Both interventions resulted in a similar decrease in body weight and NT-proBNP. Neither approaches decreased albuminuria significantly, whereas diuretics did significantly reduce urinary angiotensinogen and β2-microglobulin excretion. Although lower eGFR and higher plasma indoxyl sulfate correlated with lower diuretic clearance, the diuretic effects on body weight and BP at lower eGFR were maintained. During diuretic treatment, higher PGE2 excretion correlated with lower free water clearance, and four patients developed mild hyponatremia.

CONCLUSIONS

Distal diuretics are noninferior to dietary sodium restriction in reducing BP and extracellular volume in CKD. Diuretic sensitivity in CKD is maintained despite lower diuretic clearance.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

DD-study: Diet or Diuretics for Salt-sensitivity in Chronic Kidney Disease (DD), NCT02875886.

Hybrid Systems Based on Talc and Chitosan for Controlled Drug Release

Inorganic matrices and biopolymers have been widely used in pharmaceutical fields. They show properties such as biocompatibility, incorporation capacity, and controlled drug release, which can become more attractive if they are combined to form hybrid materials. This work proposes the synthesis of new drug delivery systems (DDS) based on magnesium phyllosilicate (Talc) obtained by the sol–gel route method, the biopolymer chitosan (Ch), and the inorganic-organic hybrid formed between this matrix (Talc + Ch), obtained using glutaraldehyde as a crosslink agent, and to study their incorporation/release capacity of amiloride as a model drug. The systems were characterized by X-ray diffraction (XRD), Therma analysis TG/DTG, and Fourier-transform infrared spectroscopy (FTIR) that supported the DDS’s formation. The hybrid showed a better drug incorporation capacity compared to the precursors, with a loading of 55.74, 49.53, and 4.71 mg g⁻¹ for Talc + Ch, Talc, and Ch, respectively. The release assays were performed on a Hanson Research SR-8 Plus dissolver using apparatus I (basket), set to guarantee the sink conditions. The in vitro release tests showed a prolongation of the release rates of this drug for at least 4 h. This result proposes that the systems implies the slow and gradual release of the active substance, favoring the maintenance of the plasma concentration within a therapeutic window.

Determination of Tryptophan and Its Major Metabolites in Fluid from the Anterior Chamber of the Eye in Diabetic Patients with Cataract by Liquid Chromotography Mass Spectrometry (LC-MS/MS)

Tryptophan (TRP) is to an essential amino acid and its catabolites are significant to human health. By using ultra-high-performance liquid chromatography coupled to electrospray ionization triple quadrupole mass spectrometry (UHPLC-ESI-MS/MS), levels of three major components of kynurenic pathway namely tryptophan (TRP), kynurenic acid (KYNA) and kynurenine (KYN) in fluid from the anterior chamber of the eye were determined. The analysis was carried out on a Synergi 4 μ Fusion-RP column using gradient elution mode. For quantitative determination, l-tryptophan-amino-15N, 99 ATOM % 15N was used as an internal standard. The method was linear in the concentration range 4–2000 ng mL⁻¹ for TRP, KYNA and KYN. The mean recoveries measured at four concentration levels for TRP, KYN and KYNA included the following ranges 94.3–96.1; 91.0–95.0; and 96.0–97.6%, respectively. The intra-day precision parameters were smaller than 4.4, 6.4 and 5% respectively. The developed method was applied to study the level of TRP, KYNA and KYN in eye fluid for the retrospective case series which included 28 patients suffering from cataracts and diabetes (n = 8). The experimental data was subjected to statistical analysis. The Mann-Whitney U-test revealed clear differences in the level of TRP catabolites and the ratios of TRP/KYN representing the activities of specific enzyme of kynurenine pathway in examined groups of patients. A level of probability p < 0.05 was used throughout a paper to denote statistically significant differences between the groups.