Renal secretion of hydrochlorothiazide involves organic anion transporter 1/3, organic cation transporter 2, and multidrug and toxin extrusion protein 2-K.

Hydrochlorothiazide (HCTZ) is the most widely used thiazide diuretic for the treatment of hypertension either alone or in combination with other antihypertensives. HCTZ is mainly cleared by the kidney via tubular secretion, but the underlying molecular mechanisms are unclear. Using cells stably expressing major renal organic anion and cation transporters [human organic anion transporter 1 (hOAT1), human organic anion transporter 3 (hOAT3), human organic cation transporter 2 (hOCT2), human multidrug and toxin extrusion 1 (hMATE1), and human multidrug and toxin extrusion 2-K (hMATE2-K)], we found that HCTZ interacted with both organic cation and anion transporters. Uptake experiments further showed that HCTZ is transported by hOAT1, hOAT3, hOCT2, and hMATE2-K but not by hMATE1. Detailed kinetic analysis coupled with quantification of membrane transporter proteins by targeted proteomics revealed that HCTZ is an excellent substrate for hOAT1 and hOAT3. The apparent affinities (Km) for hOAT1 and hOAT3 were 112 ± 8 and 134 ± 13 µM, respectively, and the calculated turnover numbers (kcat) were 2.48 and 0.79 s-1, respectively. On the other hand, hOCT2 and hMATE2-K showed much lower affinity for HCTZ. The calculated transport efficiency (kcat/Km) at the single transporter level followed the rank order of hOAT1> hOAT3 > hOCT2 and hMATE2-K, suggesting a major role of organic anion transporters in tubular secretion of HCTZ. In vitro inhibition experiments further suggested that HCTZ is not a clinically relevant inhibitor for hOAT1 or hOAT3. However, strong in vivo inhibitors of hOAT1/3 may alter renal secretion of HCTZ. Together, our study elucidated the molecular mechanisms underlying renal handling of HCTZ and revealed potential pathways involved in the disposition and drug-drug interactions for this important antihypertensive drug in the kidney.

First identification of a diuretic, hydrochlorothiazide, in hair: Application to a doping case and interpretation of the results.

An athlete contested an adverse analytical finding involving hydrochlorothiazide, and requested our laboratory for testing his hair. As there is no reference in the literature about identification of hydrochlorothiazide in hair, several volunteers were first enrolled (4 after a single 25 mg administration and 10 with daily therapeutic treatment). A specific method was developed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS. Hair samples were decontaminated with dichloromethane and 30 mg were incubated in buffer at pH 7.0 for 15 hours at 50°C. Then, 5 mL ethyl acetate was added for extraction. Linearity was observed for hydrochlorothiazide concentrations ranging from 5 to 2000 pg/mg. The limit of quantification was 5 pg/mg. The coefficients of variation (CVs) of repeatability and matrix effect were lower than 20%. Analysis of the 0-2-cm segment of the 4 volunteers having received a single dose, collected 1 month after administration, was negative at the limit of quantification. The hair of the 10 patients (proximal 2 cm) on daily treatment was positive with concentrations ranging from 12 to 1845 pg/mg, with no correlation between daily dose and concentration. The athlete's hair tested positive for hydrochlorothiazide at 36 pg/mg in the segment corresponding to the period of the urinary control. Since a single exposure to hydrochlorothiazide is not detectable in hair and based on the results of the patients on daily treatment, the concentration found in the athlete has been interpreted as corresponding to repeated exposures, where it was not possible to establish the dosage and the frequency.

Hydrochlorothiazide binding to human serum albumin induces some compactness in the molecular structure of the protein: A multi-spectroscopic and computational study.

The interaction between hydrochlorothiazide (HCTZ), a diuretic drug, with human serum albumin (HSA) was investigated by different biophysical approaches such as UV absorption, circular dichroism (CD), Fourier transform infrared (FT-IR), and fluorescence spectroscopy in 50 mM sodium phosphate buffer, pH 7.4. The results of fluorescence titration experiments revealed that HCTZ strongly quenches the intrinsic fluorescence of HSA through a static quenching mechanism. Binding constants and the number of binding sites were calculated using Stern-Volmer plots. Thermodynamic analysis of the binding data elucidated that hydrogen bonding and van der Waals interactions played the major role in the binding process. Computation of the protein surface hydrophobicity (PSH) index using 1-anilinonaphtalene-8-sulfonate indicated that considerable decrement in PSH value of the protein happened upon drug binding. The binding site of HCTZ in HSA was identified using warfarin and ibuprofen as site markers, a result confirmed by molecular docking study. The results of CD experiments showed that some alterations occurred in the structure of the protein upon ligation. Also, the results of FT-IR experiments were in good agreement with CD experiments. It looks like that both secondary and tertiary structures of HSA have been affected upon HCTZ binding.

Self dispersing mixed micelles forming systems for enhanced dissolution and intestinal permeability of hydrochlorothiazide.

Mixed micelles provide promising strategy for enhancing dissolution and permeability of drugs. However, their fluid nature limited the stability of the loaded drug and hindered the development of stable oral dosage form. Accordingly, the objective was to develop solid self dispersing mixed micelle forming systems (MMFS) for enhanced dissolution and intestinal permeability of hydrochlorothiazide. Pseudoternary phase diagrams were constructed using sodium cholate, lecithin with either poloxamer 407 or PEG 4000 to determine the composition of MMFS. Both polymer free and poloxamer or PEG containing MMFS were prepared as homogenous matrices or as solid self dispersing powder. The later was developed by adsorption of MMFS on avicel-aerosil mixture. Differential scanning calorimetry provided an evidence for existence of hydrochlorothiazide as molecular dispersion in the MMFS. Dispersing polymer free, PEG 4000 or poloxamer based MMFS in aqueous medium produced micelles having size values of 119, 52.6 and 28nm, respectively. The zeta potential values were -61.8, -59.5 and -19.5mV for the same systems, respectively. Preparation of solid self dispersing MMFS enhanced the dissolution rate of hydrochlorothiazide. The intestinal absorption of hydrochlorothiazide from its aqueous solution and polymer incorporating mixed micellar systems was monitored using in situ rabbit intestinal perfusion technique. The permeability results showed a clear trend for enhanced membrane transport of the drug after being incorporated into poloxamer containing mixed micellar system. The study thus introduced a versatile easily formulated solid self dispersing system with high potential for solving the dissolution and permeability problems of class IV drugs.

Transethnic meta-analysis suggests genetic variation in the HEME pathway influences potassium response in patients treated with hydrochlorothiazide.

Hypokalemia is a recognized adverse effect of thiazide diuretic treatment. This phenomenon, which may impair insulin secretion, has been suggested to be a reason for the adverse effects on glucose metabolism associated with thiazide diuretic treatment of hypertension. However, the mechanisms underlying thiazide diuretic-induced hypokalemia are not well understood. In an effort to identify genes or genomic regions associated with potassium response to hydrochlorothiazide, without a priori knowledge of biologic effects, we performed a genome-wide association study and a multiethnic meta-analysis in 718 European- and African-American hypertensive participants from two different pharmacogenetic studies. Single-nucleotide polymorphisms rs10845697 (Bayes factor=5.560) on chromosome 12, near to the HEME binding protein 1 gene, and rs11135740 (Bayes factor=5.258) on chromosome 8, near to the Mitoferrin-1 gene, reached genome-wide association study significance (Bayes factor >5). These results, if replicated, suggest a novel mechanism involving effects of genes in the HEME pathway influencing hydrochlorothiazide-induced renal potassium loss.

Multimedia fate modeling and comparative impact on freshwater ecosystems of pharmaceuticals from biosolids-amended soils.

This study modeled the impact on freshwater ecosystems of pharmaceuticals detected in biosolids following application on agricultural soils. The detected sulfonamides and hydrochlorothiazide displayed comparatively moderate retention in solid matrices and, therefore, higher transfer fractions from biosolids to the freshwater compartment. However, the residence times of these pharmaceuticals in freshwater were estimated to be short due to abiotic degradation processes. The non-steroidal anti-inflammatory mefenamic acid had the highest environmental impact on aquatic ecosystems and warrants further investigation. The estimation of the solid-water partitioning coefficient was generally the most influential parameter of the probabilistic comparative impact assessment. These results and the modeling approach used in this study serve to prioritize pharmaceuticals in the research effort to assess the risks and the environmental impacts on aquatic biota of these emerging pollutants.

Diphenyl diselenide supplementation reduces biochemical alterations associated with oxidative stress in rats fed with fructose and hydrochlorothiazide.

The study evaluated whether a diet containing diphenyl diselenide (PhSe)2, a synthetic antioxidant, could reduce the biochemical alterations induced by chronic consumption of highly enriched fructose diet and/or hydrochlorothiazide (HCTZ). Rats were fed a control diet (CT) or a high fructose diet (HFD), supplemented with or not HCTZ (4.0g/kg) and/or (PhSe)2 (3ppm) for 18weeks. HFD intake increased significantly plasma glucose, fructosamine, triglycerides and cholesterol levels. (PhSe)2 supplementation significantly reduced triglycerides and cholesterol but could not restore them to control levels. The combination of HFD and HCTZ significantly altered plasma glucose, fructosamine, triglycerides and cholesterol levels which were not restore by (PhSe)2 supplementation. Lipid peroxidation, protein carbonyl formation, vitamin C level and catalase activity decreased after HFD, HCTZ or HFD plus HCTZ ingestion. Remarkably (PhSe)2 supplementation restored the oxidative stress parameters. HCTZ decreased renal superoxide dismutase (SOD) activity, which was restored to control levels by (PhSe)2. Furthermore, the association of HFD and HCTZ decreased plasma potassium levels and aggravated HCTZ-induced hypomagnesemia and hypertriglyceridemia. Here we provided evidence of the involvement of oxidative stress and metabolic disorders in a rat model of HFD associated or not with HTCZ. (PhSe)2 supplementation reduced the oxidative stress and this compound should be considered for the treatment of biochemical disturbances and oxidative stress in other animal models of metabolic disorders.

Iatrogenic hyperhomocysteinemia in patients with metabolic syndrome: a systematic review and metaanalysis.

Metabolic syndrome (MetS) is associated with increased cardiovascular mortality and its management incorporates hypolipidemic, antidiabetic and antihypertensive drugs. However, several classes of these drugs, such as biguanides, fibrates and hydrochlorothiazide have been reported to raise circulating total homocysteine (tHcy) levels. During the last decades, numerous large-scale epidemiological studies have identified Hcy as a moderate independent cardiovascular risk factor. Therefore, drug-induced hyperhomocysteinemia in MetS patients may add one cardiovascular risk factor in these high-risk patients. The present systematic review summarizes data from studies which investigated the effects of the above-mentioned drugs on tHcy, and calculates the treatment effect of each drug class on tHcy levels. We also discuss the underlying pathophysiology and the issues that should be addressed in the future.

Lack of a primary physicochemical determinant in the direct transport of drugs to the brain after nasal administration in rats: potential involvement of transporters in the pathway.

The objectives of this study were to evaluate the relative contribution of the direct pathway in overall brain transport for 17 model drugs with different physicochemical properties after nasal administrations and to identify factors that govern the fraction of the dose transported to the brain via the direct pathway (F(a, direct)). When the model drugs were nasally administered to rats, 5 of the 17 model drugs were delivered to a significant extent to the brain via the direct pathway. Multiple linear regression analyses showed that the correlation between various physicochemical properties and F(a, direct) was not statistically significant, indicative of a lack of primary physicochemical determinants in the direct transport pathway. Transporters such as rOAT3 and rOCT2 were expressed at significant levels in rat olfactory epithelia, and uptakes of standard substrates were significantly decreased in HEK293 cells expressing rOAT3 and rOCT2 in the presence of the five model drugs that were delivered to appreciable extents to the brain via the direct pathway. Therefore, these observations indicate that carrier-mediated transport may play a role in the brain delivery of drugs from the nose via the direct transport pathway.

Detection of urinary markers for thiazide diuretics after oral administration of hydrochlorothiazide and altizide-relevance to doping control analysis.

In sports, thiazide diuretics are used to flush out previously taken prohibited substances with forced diuresis and in sports where weight classes are involved to achieve acute weight loss. Thiazide diuretics include compounds which are very unstable and hydrolyse in aqueous media. Because information regarding the urinary detection of the hydrolysis products is limited, urinary excretion profiles for the hydrolysis product 4-amino-6-chloro-1,3-benzenedisulphonamide were established in 6 healthy volunteers after oral administration of altizide (15 mg per tablet) and hydrochlorothiazide (25mg per tablet). Additionally, the excretion profile of chlorothiazide, a metabolite of altizide and hydrochlorothiazide, was also determined. A quantitative liquid-chromatographic tandem mass spectrometric method to detect the 4 substances was developed and validated. The result of this work shows that altizide is eliminated within 48 h in urine whereas hydrochlorothiazide was detectable after 120 h. Chlorothiazide was determined to be a minor metabolite of altizide and hydrochlorothiazide and could be detected up to 120 h. The hydrolysis product, 4-amino-6-chloro-1,3-benzenedisulphonamide, was detectable 120 h after administration, with concentrations at least 10 times higher than the parent drug. Concentrations ranged between 41-239 and 60-287 ng/mL after altizide and hydrochlorothiazide administration, respectively. The study shows that 4-amino-6-chloro-1,3-benzenedisulphonamide is an important target compound for the long time detection of thiazide diuretics in urine.

Telmisartan/Hydrochlorothiazide: a review of its use as fixed-dose combinations in essential hypertension.

Fixed-dose combinations of telmisartan and hydrochlorothiazide (HCTZ) [Micardis Plus, Micardis HCT, PritorPlus] are available in many countries for the treatment of patients with essential hypertension. Combining the angiotensin II receptor antagonist (angiotensin II receptor blocker [ARB]) telmisartan with the thiazide diuretic HCTZ provides antihypertensive therapy with complementary mechanisms of action. In the US and EU, telmisartan/HCTZ is approved for patients whose hypertension is not adequately controlled with telmisartan monotherapy; US labelling for the fixed-dose combination also includes inadequate control of blood pressure (BP) with HCTZ monotherapy.The antihypertensive efficacy of once-daily telmisartan/HCTZ has been demonstrated in several large, randomized trials in patients with stages 1 and 2 hypertension. The addition of HCTZ to telmisartan achieved significant reductions in BP in nonresponders to telmisartan monotherapy, and the antihypertensive efficacy of telmisartan/HCTZ was similar to or significantly greater than that of various comparator agents. Moreover, in studies that used ambulatory BP monitoring, telmisartan/HCTZ provided consistent 24-hour BP reductions throughout morning, daytime and night-time periods. The BP-lowering efficacy over the entire 24-hour dose administration interval is consistent with the pharmacokinetic profile of telmisartan, which has the longest elimination half-life among currently available ARBs and a unique chemical structure. Adverse events with telmisartan/HCTZ in clinical trials were typically mild and transient, and no unexpected events occurred that had not been previously reported with either telmisartan or HCTZ. Extensive tolerability data are available for telmisartan, in particular from the ONTARGET study, the largest clinical outcomes trial with an ARB. As such, fixed-dose combinations of telmisartan/HCTZ provide an effective, rational and generally well tolerated treatment option for the management of patients with hypertension.

pH-dependent functional activity of P-glycoprotein in limiting intestinal absorption of protic drugs 1. Simultaneous determination of quinidine and permeability markers in rat in situ perfusion samples.

A simple, specific and sensitive reversed-phase high performance liquid chromatographic (RP-HPLC) method with UV absorbance detection was developed and validated for simultaneous determination of quinidine, verapamil and passive permeability markers, in samples obtained from rat intestinal in situ single-pass perfusion studies. Chromatography was carried out on C18 column with mobile phase comprising of acetate buffer (pH 5.0) and methanol in the ratio of 40:60 (v/v) pumped at a flow rate of 0.6 ml/min and UV detection was employed at 230 and 275 nm. The average retention times for hydrochlorthiazide, frusemide, quinidine, propranolol, and verapamil were 4.9, 5.8, 6.9, 8.9 and 11.3 min, respectively. The calibration curves were linear (R(2)>0.9995) in the selected range for each analyte. The method is specific and sensitive with limit of quantification as 25 ng/ml for quinidine and verapamil. The intra- and inter-day accuracy and precision were found to be good for all the five analytes. The method was found to be reliable in permeability determination and to estimate pH-dependent P-glycoprotein (P-gp)-mediated efflux transport of quinidine. Weak bases quinidine, propranolol and verapamil showed pH-dependent permeability, where quinidine permeability increased by 3.6-fold when the luminal pH was changed from pH 4.5-7.4. Inhibition of P-gp by verapamil (200 microM) indicated that about 68% and only 35% of passive transport of quinidine was attenuated by P-gp-mediated efflux at pH 4.5 and 7.4, respectively. In conclusion, low passive transport rates of weakly basic P-gp substrates at lower pH, may lead to more accessibility of these molecules to P-gp within enterocytes thus resulting in pH-dependent functional activity of P-gp as protic drugs moves along the gastrointestinal tract.

Na+ competes with K+ in bumetanide-sensitive transport by Malpighian tubules of Rhodnius prolixus.

We examined the effects of bathing saline Na+/K+ ratio, bumetanide and hydrochlorothiazide on fluid and ion transport by serotonin-stimulated Malpighian tubules of Rhodnius prolixus. Previous pharmacological and electrophysiological studies indicate that a bumetanide-sensitive Na+/K+/2Cl- cotransporter is the primary route for basolateral ion entry into the cell during fluid secretion. The goal of this study was to resolve the apparent conflict between relatively high secretion rates by tubules bathed in K+-free saline and the evidence that Na+/K+/2Cl- cotransporters described in other systems have an absolute requirement for all three ions for translocation. Our measurements of fluid secretion rate, ion fluxes and electrophysiological responses to serotonin show that fluid secretion in K+-free saline is bumetanide sensitive and hydrochlorothiazide insensitive. Dose-response curves of secretion rate versus bumetanide concentration were identical for tubules bathed in K+-free and control saline with IC50 values of 2.6 x 10(-6) mmol l(-1) and 2.9 x 10(-6) mmol l(-1), respectively. Double-reciprocal plots of K+ flux versus bathing saline K+ concentration showed that increasing Na+ concentration in the bathing fluid increased Kt but had no effect on Jmax, consistent with competitive inhibition of K+ transport by Na+. We propose that the competition between Na+ and K+ for transport by the bumetanide-sensitive transporter is part of an autonomous mechanism by which Malpighian tubules regulate haemolymph K+ concentration.

Development and validation of a stability-indicating HPLC method for the simultaneous determination of losartan potassium, hydrochlorothiazide, and their degradation products.

Losartan potassium was the first in a new class of potent angiotensin II receptor antagonists which are well-tolerated in the treatment of hypertension. Losartan potassium is the active ingredient in tablets COZAAR and is combined with diuretic co-active hydrochlorothiazide (HCTZ) in tablets HYZAAR for increased efficacy. Losartan potassium has one main impurity and two primary degradates. HCTZ has one major degradate as well as two common process impurities. Historically, separate methods have been used for the analysis of each active and their respective impurities and degradates. The ultimate goal of this work was to develop and validate a single high-performance liquid chromatography method selective for the eight main components of tablets HYZAAR. A single method was developed to afford simultaneous quantitation of actives and degradates for each of the two existing formulations. Each method is presented herein and demonstrated to be suitable for quantitation to 0.1% levels of all relevant degradates, as well as 100% levels of respective drug substances.

Characterization of the thiazide-sensitive Na(+)-Cl(-) cotransporter: a new model for ions and diuretics interaction.

The thiazide-sensitive Na(+)-Cl(-) cotransporter (TSC) is the major pathway for salt reabsorption in the apical membrane of the mammalian distal convoluted tubule. When expressed in Xenopus laevis oocytes, rat TSC exhibits high affinity for both cotransported ions, with the Michaelis-Menten constant (K(m)) for Na(+) of 7.6 +/- 1.6 mM and for Cl(-) of 6.3 +/- 1.1 mM, and Hill coefficients for Na(+) and Cl(-) consistent with electroneutrality. The affinities of both Na(+) and Cl(-) were increased by increasing concentration of the counterion. The IC(50) values for thiazides were affected by both extracellular Na(+) and Cl(-). The higher the Na(+) or Cl(-) concentration, the lower the inhibitory effect of thiazides. Finally, rTSC function is affected by extracellular osmolarity. We propose a transport model featuring a random order of binding in which the binding of each ion facilitates the binding of the counterion. Both ion binding sites alter thiazide-mediated inhibition of transport, indicating that the thiazide-binding site is either shared or modified by both Na(+) and Cl(-).

Antioxidant properties of indapamide, 5-OH indapamide and hydrochlorothiazide evaluated by oxygen-radical absorbing capacity and electron paramagnetic resonance.

The aim of these experiments was to investigate the radical scavenging properties of three diuretics: indapamide (IND) and its major metabolite, 5-OH indapamide (5-OH IND), compared to a reference diuretic, hydrochlorothiazide (HTZ). Electron Paramagnetic Resonance (EPR) was used to determine the scavenging abilities of these compounds on enzymatically produced superoxide radical anion, with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) used as a spin-trap. These experiments revealed that IND and specially 5-OH IND were effective superoxide radical anion scavengers at 0.2 mg/ml. In the second part of these studies, allophycocyanin was used as an indicator of free radical mediated protein damage. In the assay, 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH) was used as a peroxyl radical generator, Trolox (a water-soluble analogue of vitamin E) as a control standard, and the loss of allophycocyanin fluorescence was monitored. The antioxidant effects of the diuretics were expressed in oxygen-radical absorbing capacity (ORAC), where one ORAC unit equals the net protection produced by 1 microM Trolox. HTZ showed no protection up to 100 microM final concentration, whereas IND and 5-OH IND showed linear correlation with respect to concentration when expressed in ORAC units: 5-OH IND induced the highest protection against peroxyl radical. The above observations suggested that IND and 5-OH IND are potent radical scavengers, with the metabolite 5-OH IND having a superior antioxidant potency than IND. By contrast, HTZ had no effect. These radical scavenging properties of 5-OH IND may be of clinical interest for vascular protection and may help to protect the heart from oxidative injury.

Saturable accumulation and diuretic activity of hydrochlorothiazide in the isolated perfused rat kidney.

The role of tubular accumulation in renal disposition and diuretic efficacy of hydrochlorothiazide was studied in the isolated perfused rat kidney. Hydrochlorothiazide resulted in a dose-dependent increase in the fractional excretion of sodium, chloride and potassium, and in urinary flow and pH. Renal clearance of the drug was low as a result of a low extraction ratio and extensive nonionic back-diffusion. Hydrochlorothiazide was subject to saturable tubular secretion, following Michaelis-Menten kinetics. Parameters obtained after nonlinear regression analysis were a maximum tubular transport velocity of 42 +/- 6 micrograms/min, a Michaelis-Menten constant of secretion of 38 +/- 11 micrograms/ml and a fraction of excreted drug reabsorbed passively of 0.49 +/- 0.03. The thiazide diuretic accumulated extensively in kidney tissue due to active cellular uptake (maximum capacity of renal accumulation of 500 +/- 270 micrograms/g; affinity constant of renal accumulation of 28 +/- 16 micrograms/ml) and passive diffusion. Plots were constructed of the sodium excretion rate versus hydrochlorothiazide perfusate concentration or the renal excretion rate. The perfusate plot could be described by the sigmoid Emax model, while a simplification of the model had to be used for the response curve in urine because a maximum effect was not observed. The apparent maximum effect resulting from the perfusate concentration-response curve and the discrepancy with the renal excretion rate-response curve indicates that the diuretic effect of hydrochlorothiazide is restricted by saturable accumulation and secretion.

Effect of diuretic drugs on creatinine clearance determination.

Diuretic drugs have been reported to alter the glomerular filtration rate and possibly the creatinine excretion by the kidneys. We evaluated the effects of single doses of diuretic drugs on creatinine clearance determination. Ten healthy volunteers were randomized to receive either oral hydrochlorothiazide, oral furosemide, intravenous furosemide, or no treatment in a cross-over fashion during four separate test days with 6-day washout periods. Urine and blood specimens were collected during 24 h after the treatments. Specimens were assayed for creatinine, and the creatinine clearance corresponding to the 4-, 6-, 12-, and 24-h urine collections were calculated. Analysis of variance did not show a statistically significant effect of the diuretic regimens on creatinine clearance over these periods. This study demonstrates that single doses of diuretic drugs do not have significant effect on creatinine clearance determination using urine collected during 4-24-h periods.

[HPLC used in the validation of simple methods for research of degradation products in essential drug tablets]. / Validation par HPLC de méthodes simples pour la recherche de produits de dégradation dans les comprimés de médicaments essentiels.

HPLC have been used to validate simple methods to be employed in developing countries (DC) for the quality control of drugs. As the important lack of analytical material in DC, colorimetric methods have been used. These are subjected to visual appreciation of the color intensity. Two essential drugs have been selected: aspirin, hydrochlorothiazide. For each compound, standardization of concentration's degradation product by colorimetry and HPLC have been achieved in proximity of the restricted norms of pharmacopoeia. These results have been applied to tablets exposed to stressed conditions (t(0) = 60 and humidity = 75%). The results obtained by colorimetric method were similar to HPLC's ones.

Hydrochlorothiazide versus spironolactone: long-term metabolic modifications in patients with essential hypertension.

The metabolic side effects of thiazide diuretics are believed to be responsible for the failure of thiazide diuretics to reduce cardiovascular morbidity in patients with hypertension. However, the decrease in the incidence of osteoporotic fractures that are associated with thiazide administration may be relevant in elderly patients with arterial hypertension. Spironolactone (SP) appears not to influence the metabolic risk profile of the patient with hypertension, and no studies have examined its effect on calcium metabolism. Therefore, in 22 patients with mild to moderate essential hypertension, the authors performed a parallel, randomized, double-blind, placebo-controlled study that compared the effects on serum urate and lipid, potassium, magnesium, and calcium metabolism of hydrochlorothiazide (HC) (mean [+/- SD] dose, 72 +/- 26 mg/d) and SP (144 +/- 53 mg/d) during a 52-week period. As compared with placebo, HC significantly increased serum urate and total cholesterol concentrations, and decreased serum potassium levels. SP did not affect serum urate or cholesterol levels but increased serum potassium concentrations. Neither diuretic significantly modified magnesium metabolism. Little changes were seen in serum calcium levels during HC or SP treatment, whereas urinary calcium excretion was significantly decreased by HC (mean decrease, 45%; P less than .01) or SP (40%; P less than .01). The authors conclude that SP, in addition to its potassium-sparing properties, has a calcium-sparing effect that may be beneficial for patients in whom reduction of urinary calcium excretion has a therapeutic value.