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FI-chemiluminometric study of thiazides by on-line photochemical reaction.

Ciborowski M, Icardo MC, Mateo JV, Martinez Calatayud J.

Departamento de Quimica Analitica, Universidad de Valencia, Valencia, Spain.

The present manuscript deals with a simple and sensitive flow-injection method for the chemiluminescent determination of thiazides. The method is based on the on-line photodegradation and chemiluminescent determination of the resulting photo-fragments. The on-line photodegradation is performed in basic medium by using a photoreactor consisting of a 550cm long x 0.8mm ID piece of PTFE tubing helically coiled around an 8W low-pressure mercury lamp. The determination of the photo-irradiated thiazides is performed by a chemiluminescent oxidative reaction with Ce(IV) in sulphuric acid medium. A heterogeneous group of thiazides (indapamide, metolazone, hydroflumethiazide, chlorthalidone and bendroflumethiazide) has been studied. Hydrochlorothiazide was selected as a test substance. The "on-line" photochemical reaction approach allows the sensitive chemiluminescent determination of thiazides which do not present native chemiluminescence in the absence of sensitizers such as Rhodamine 6G. Linear calibration graphs were typically over the range 0.5-12 microgml(-1) (indapamide, metolazone, hydroflumethiazide and chlorthalidone); and over the range 0.5-5 microgml(-1) (hydrochlorothiazide). Limits of detection ranged between 0.005 microgml(-1) (hydrochlorothiazide) and 0.06 microgml(-1) (bendroflumethiazide). The relative standard deviation for the test substance was 2.0% for 2 microgl(-1) of the drug (n = 11) and the throughput was 65 h(-1) in all cases. The assessment of the photodegradation step on the molecular structure of thiazides was established by recording UV and fluorimetric spectra. The viability of the on-line photoinduced fluorescent determination of hydroflumethiazide and bendroflumethiazide was confirmed. The method was also applied to the determination of hydrochlorothiazide in commercially available formulation.

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Long-term adaptation of renal ion transporters to chronic diuretic treatment.

Kim GH.

Department of Internal Medicine and Institute of Biomedical Sciences, Hanyang University College of Medicine, Seoul, Korea. kimgh hanyang.ac.kr

Loop and thiazide diuretics are clinically useful to induce negative sodium balance. However, with chronic treatment, their effects tend to be blunted since the kidney adapts to diuretics. Molecular identification of the renal ion transporters has provided us with a new understanding of the mechanisms of intrarenal adaptation to diuretics at molecular levels. In the kidney, loop and thiazide diuretics are secreted from the proximal tubule via the organic anion transporter-1 (OAT1) and exert their diuretic action by binding to the Na-K-2Cl cotransporter type 2 (NKCC2) in the thick ascending limb and the Na-Cl cotransporter (NCC) in the distal convoluted tubule, respectively. Recent studies in animal models suggest that abundance of these ion transporters is affected by long-term diuretic administration. Downstream from the primary site of diuretic action, an increase in epithelial Na+ channel (ENaC) abundance is induced by chronic furosemide or hydrochlorothiazide treatment. This adaptation is consistent with previous reports showing cellular hypertrophy and increased Na+ absorption in distal tubular segments. The abundance of NKCC2 and NCC is increased by furosemide and hydrochlorothiazide, respectively. This compensatory upregulation suggests that either diuretic may activate the ion transporter within the primary site of action. In the proximal tubule, the abundance of OAT1 is increased by chronic treatment with furosemide or hydrochlorothiazide. This upregulation of OAT1 seems to be induced by substrate stimulation, lessening diuretic tolerance associated with long-term diuretic use. Copyright 2004 S. Karger AG, Basel

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A randomized trial of furosemide vs hydrochlorothiazide in patients with chronic renal failure and hypertension.

Dussol B, Moussi-Frances J, Morange S, Somma-Delpero C, Mundler O, Berland Y.

Service de Nephrologie-Hemodialyse-Transplantation, Hopital de la Conception, 147 Bd Baille, 13385 Marseille Cedex 5, France. bdussol mail.ap-hm.fr

BACKGROUND: Loop diuretics are the drugs of choice for the treatment of hypertension in chronic renal failure patients. However, the adaptive changes in the distal nephron and the short half-life of these drugs may decrease their long-term efficacy. Thiazides are not believed to be efficient in advanced renal failure, but this is debated. METHODS: We compared the efficacy of long-acting furosemide (60 mg/day) and hydrochlorothiazide (25 mg/day) in a double-blind, randomized crossover trial in seven patients with severe renal failure and hypertension (seven men, 54+/-10 years old). The primary end-points were sodium and chloride fractional excretions after 1 month of each diuretic and then after their combination. During the trial, other treatments and the diet were controlled. RESULTS: A trend towards an increase in the fractional excretion of sodium and of chloride was observed with furosemide, but the difference did not reach the level of statistical significance (P = NS). Hydrochlorothiazide significantly increased fractional excretion of sodium and chloride from 3.7+/-0.9 to 5.5+/-0.3 and from 3.9+/-0.19 to 6.5+/-0.3, respectively (P<0.05). The combination of the two diuretics had no additional effect on the increase in sodium and chloride fractional excretion. Furosemide, hydrochlorothiazide and the combination of the two diuretics decreased mean arterial blood pressure by the same extent from 112 to 97, 99 and 97 mmHg, respectively (P<0.05). CONCLUSIONS: Hydrochlorothiazide increased the fractional excretion of sodium and chloride more than furosemide did in hypertensive severe renal failure patients. Mean arterial blood pressure decreased by the same amount with both diuretics. Combining furosemide and hydrochlorothiazide did not increase the efficacy of hydrochlorothiazide.

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Fixed-dose combinations in the management of hypertension: defining the place of angiotensin receptor antagonists and hydrochlorothiazide.

Kjeldsen SE, Os I, Hoieggen A, Beckey K, Gleim GW, Oparil S.

Department of Cardiology, Ullevaal University Hospital, Oslo, Norway.

We discuss combination therapy with angiotensin receptor antagonists (angiotensin receptor blockers; ARBs) and thiazide diuretics in light of the independent actions of both types of agents, and the adverse effects of both agents independently and in the context of the physiologic synergy achieved in using these agents together. ARBs counteract many of the adverse events associated with the use of thiazide diuretics and have been shown to reduce the occurrence of new-onset diabetes mellitus. We also review outcome trials in patients with hypertension (such as LIFE [Losartan Intervention For Endpoint reduction in hypertension], VALUE [Valsartan Antihypertensive Long-term Use Evaluation], and SCOPE [Study on COgnition and Prognosis in the Elderly]), in which losartan, valsartan, and candesartan cilexetil were used in combination with hydrochlorothiazide. Fixed combination ARB/hydrochlorothiazide agents make sense as initial therapy for patients in whom BP is >20/10 mm Hg above goal.

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Aggressive antihypertensive therapy based on hydrochlorothiazide, candesartan or lisinopril as initial choice in hypertensive type II diabetic individuals: effects on albumin excretion, endothelial function and inflammation in a double-blind, randomized clinical trial.

Schram MT, van Ittersum FJ, Spoelstra-de Man A, van Dijk RA, Schalkwijk CG, Ijzerman RG, Twisk JW, Stehouwer CD.

[1] 1Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands [2] 2Department of Internal Medicine, VU University Medical Center, Amsterdam, The Netherlands.

We investigated the effects of aggressive antihypertensive therapy based on hydrochlorothiazide, candesartan or lisinopril on urinary albumin excretion, endothelial function and inflammatory activity in hypertensive type II diabetic individuals. A total of 70 hypertensive type II diabetic individuals were treated with three antihypertensive strategies in a randomized, double-blind, double-dummy design. Blood pressure was titrated to levels below 130/85 mmHg or a decrease in systolic pressure of 10% with a diastolic pressure below 85 mmHg. After titration, patients were treated for 12 months. Mean blood pressures changed from 157/93, 151/94 and 149/93 at baseline to 135/80, 135/82 and 131/80 mmHg after titration in the hydrochlorothiazide (n=24), candesartan (n=24) and lisinopril (n=22) groups. About 70% reached target blood pressures. However, only 45% had blood pressures <130/85 mmHg. Urinary albumin excretion and levels of soluble vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 decreased (GEE regression coefficients, -2.40 mg/24 h (P<0.001), -85 ng/ml (P=0.01) and -50 ng/ml (P=0.02)), but brachial artery endothelium-dependent and -independent vasodilation and levels of von Willebrand factor and C-reactive protein did not change (GEE regression coefficients, 0.21 mm (P=0.07), 0.04 mm (P=0.43), 0.04 IU/ml (P=0.33) and -1.15 mg/l (P=0.64)). No differences in outcome variables between treatment groups were observed. These data show that achievement of target blood pressures below 130/85 mmHg in hypertensive type II diabetes is difficult. Aggressive antihypertensive therapy can improve urinary albumin excretion, endothelial function and inflammatory activity in hypertensive type II diabetic individuals, regardless of the type of antihypertensive therapy used.Journal of Human Hypertension advance online publication, 13 January 2005; doi:10.1038/sj.jhh.1001812.

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