Cell cultures in the investigation of thiazide phototoxicity

The NHIK 3025 cell line (Norsk Hydro Institutt for Kreftforskning), a human in situ carcinoma of the cervix cell line, was used to investigate the thiazides bemetizide, bendroflumethiazide, benzylhydrochlorothiazide, bumetanide, butizide, chlortalidone, furosemide, hydrochlorothiazide, hydroflumethiazide, indapamide, piretanide, polythiazide, trichlormethiazide and xipamide for their potential phototoxic properties. Cell death following UVA irradiation and dependent on test substance concentration was observed in the presence of all the tested substances except chlortalidone, furosemide, indapamide and xipamide. Bendroflumethiazide was phototoxic at concentrations of 0.05mM and higher; bemetizide, benzylhydrochlorothiazide, bumetanide and hydroflumethiazide were phototoxic at 0.25mM and higher and butizide, hydrochlorothiazide, piretanide, polythiazide and trichlormethiazide were phototoxic at 0.5mM and higher. Received: 20 March 1997 / Accepted: 5 May 1997     

Diuretics: from classical carbonic anhydrase inhibitors to novel applications of the sulfonamides

The widely clinically used benzothiadiazines and high ceiling diuretics, such as hydrochlorothiazide, hydroflumethiazide, quinethazone, metolazone, chlorthalidone, indapamide, furosemide and bumetanide, contain SO(2)NH(2) moieties acting as an effective zinc-binding function in carbonic anhydrases (CAs, EC 4.2.1.1) inhibitors. These drugs were launched in a period when only isoform CA II was known and considered physiologically/pharmacologically relevant. Although acting as moderate-weak inhibitors of CA II, all these drugs considerably inhibit other CA isozymes known nowadays to be involved in critical physiologic processes, among the 16 CAs present in vertebrates. Some low nanomolar (or even subnanomolar) inhibitors against such isoforms were recently detected, such as metholazone against CA VII, XII and XIII, chlorthalidone against CA VB, VII, IX, XII and XIII, indapamide against CA VII, IX, XII and XIII, furosemide against CA I, II and XIV, and bumethanide against CA IX and XII. The X-ray crystal structure of the CA II-indapamide adduct was also reported recently, revealing interesting aspects useful for the drug design of CA inhibitors. It has also been proposed that the recently observed beneficial effect of indapamide for the treatment of patients with hypertension and type 2 diabetes might be due to its potent inhibition of CA isoforms present in kidneys and blood vessels, which would thus explain both the blood pressure lowering effects as well as organ-protective activity of the drug. Thus, these old drugs may be useful as leads for new applications.     

Identification and pharmacological properties of binding sites for the atypical thiazide diuretic, indapamide

[3H]Indapamide bound to a single class of binding sites in pig renal cortex membranes with a dissociation constant Kd = 35 +/- 13 nM and a binding site density Bmax = 40 +/- 9 pmol/mg of protein. [3H]Indapamide binding was inhibited by the carbonic anhydrase inhibitor, acetazolamide, and by thiazide diuretics with the following rank order of potency: chlorothiazide greater than hydrochlorothiazide approximately metolazone greater than hydroflumethiazide. The effect of the latter drugs to inhibit [3H]indapamide binding was not related to their activity as thiazide diuretics, but was significantly correlated with their inhibitory effect on carbonic anhydrase II. These results suggest that the major renal binding site of [3H]indapamide is a membrane form of carbonic anhydrase. Inhibition of carbonic anhydrase may play a role in the antihypertensive effect of indapamide.     

Defect of the potassium transport process in the kidney of spontaneously hypertensive rats.

We investigated the natriuretic and kaliuretic effect of distal tubular diuretics in saline-loaded spontaneously hypertensive Wistar rats (SHR) from three different sources and normotensive Wistar rats (NWR). Orally administered early distal tubular diuretics (hydrochlorothiazide, chlorthalidone, metolazone, indapamide and cicletanine) caused much less potassium excretion in SHR than in NWR, whereas the magnitude of concurrent natriuresis was similar in both NWR and SHR. The intriguing renal handling of potassium excretion was exemplified by hydrochlorothiazide, for which enhanced kaliuresis was dose dependent in NWR but not in SHR. The doses tested ranged from 1 to 100 mg/kg, p.o. Amiloride, a late distal tubular diuretic, was also evaluated for its effect on sodium and potassium excretion in NWR and SHR. Amiloride produced potassium retention more effectively in NWR than in SHR, although the magnitude of natriuresis was similar. The difference between SHR and NWR with regard to potassium-retaining activity of amiloride was consistent at all doses tested (1-30 mg/kg, p.o.). In conclusion, it was suggested that SHR appear to have a genetic defect in potassium transport in the distal nephron.     

Screening procedure for detection of diuretics and uricosurics and/or their metabolites in human urine using gas chromatography-mass spectrometry after extractive methylation

A gas chromatography-mass spectrometry (GC-MS)-based screening procedure was developed for the detection of diuretics, uricosurics, and/or their metabolites in human urine after extractive methylation. Phase-transfer catalyst remaining in the organic phase was removed by solid-phase extraction on a diol phase. The compounds were separated by GC and identified by MS in the full-scan mode. The possible presence of the following drugs and/or their metabolites could be indicated using mass chromatography with the given ions: m/z 267, 352, 353, 355, 386, and 392 for thiazide diuretics bemetizide, bendroflumethiazide, butizide, chlorothiazide, cyclopenthiazide, cyclothiazide, hydrochlorothiazide, metolazone, polythiazide, and for canrenoic acid and spironolactone; m/z 77, 81, 181, 261, 270, 295, 406, and 438 for loop diuretics bumetanide, ethacrynic acid, furosemide, piretanide, torasemide, as well as the uricosurics benzbromarone, probenecid, and sulfinpyrazone; m/z 84, 85, 111, 112, 135, 161, 249, 253, 289, and 363 for the other diuretics acetazolamide, carzenide, chlorthalidone, clopamide, diclofenamide, etozoline, indapamide, mefruside, tienilic acid, and xipamide. The identity of positive signals in such mass chromatograms was confirmed by comparison of the peaks underlying full mass spectra with reference spectra. This method allowed the detection of the abovementioned drugs and/or their metabolites in human urine samples, except torasemide. The limits of detection ranged from 0.001 to 5 mg/L in the full-scan mode. Recoveries of selected diuretics and uricosurics, representing the different chemical classes, ranged from 46% to 99% with coefficients of variation of less than 21%. After ingestion of the lowest therapeutic doses, furosemide was detectable in urine samples for 67 hours, hydrochlorothiazide for 48 hours, and spironolactone for 52 hours (via its target analyte canrenone). The procedure described here is part of a systematic toxicological analysis procedure for acidic drugs and poisons.     

Direct vascular actions of hydrochlorothiazide and indapamide in isolated small vessels.

The mechanism by which thiazides lower peripheral resistance is unresolved. The aim of this study was to investigate the mechanisms of the acute vasodilator action of hydrochlorothiazide and the 'thiazide-like' diuretic indapamide on human, guinea pig and rat small arteries. Vessels were mounted on a myograph and the relaxation profile of both drugs and interactions with K+ channels and the vascular eicosanoid system were studied. Neither drug had any relaxant effect in rat mesenteric vessels and indapamide did not relax human arteries. Hydrochlorothiazide in both human and guinea pig vessels produced significantly more relaxation of noradrenaline than K(+)-constricted vessels (P less than 0.001). Relaxation to hydrochlorothiazide was reduced in the presence of charybdotoxin. Maximal-induced hydrochlorothiazide relaxation was reduced by 64% in human arteries (P less than 0.001) and by 91% in guinea pig vessels (P less than 0.001). Incubation with glibenclamide and indomethacin had no effect on the relaxant activity of hydrochlorothiazide and indapamide. Indapamide-induced relaxation was unaffected in the presence of charybdotoxin. These results show marked differences in the acute vasodilator action of hydrochlorothiazide and indapamide. There appears to be involvement of Ca(2+)-activated K+ channels in the acute vasorelaxant activity of hydrochlorothiazide.     

Indapamide: Clinical Pharmacology,Therapeutic Efficacy in Hypertension,and Adverse Effects

Indapamide will soon be marketed in the United States as an oral antihypertensive agent and diuretic. Its molecular structure includes both a polar sulfamoyl chlorobenzamide moiety and a lipid-soluble methylindoline molety. It differs chemically from the thiazides in that it does not possess the thiazide ring system and it contains only one sulfonamide group. Indapamide is rapidly and well absorbed after oral Ingestion, and it has a long terminal half-life in whole blood which permits once daily administration. Indapamide is extensively metabolized by the liver with excretion of unchanged drug accounting for approximately 5% of the total dose. Although indapamide is thought to exert its antihypertensive effect by its diuretic action, several investigations employing laboratory animal preparations have documented a direct vascular action. It has been categorized as a calcium channel blocking agent and this may account for a portion of its antihypertensive effectiveness. In both the treatment of edema and as an antihypertensive agent, indapamide appears to be comparable to hydrochlorothiazide, chlorthalidone and furosemide and seems to have no clinically important advantage over these agents. Side effects associated with indapamide are minimal and appear to be comparable to those observed with other antihypertensive diuretics. Based on few published studies, indapamide appears to be a useful long acting antihypertensive and diuretic agent that is well tolerated and associated with minimal biochemical abnormalities or side effects.     

Diuretics with carbonic anhydrase inhibitory action: a patent and literature review (2005 – 2013)

Introduction: The benzothiadiazines and high ceiling diuretics (hydrochlorothiazide, hydroflumethiazide, quinethazone, metolazone, chlorthalidone, indapamide, furosemide and bumetanide) contain primary sulfamoyl moieties acting as zinc-binding groups in the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). These drugs are widely used clinically and were recently shown to weakly inhibit isoforms CA I and II, but to possess stronger activity against isoforms involved in other important pathologies, for example, obesity, cancer, epilepsy and hypertension.

Areas covered: The class of clinically used diuretics, with CA inhibitory properties, is the main topic of the review. A patent literature review covering the period from 2005 to 2013 is presented.

Expert opinion: This section presents an overview of the patent literature in the sulfonamide diuretic field. Most of the patents deal with the combination of diuretic sulfonamide CA inhibitors with other agents useful in the management of cardiovascular diseases and obesity. Such combinations exert a better therapeutic activity compared to similar diuretics that do not inhibit CAs, raising the question of the polypharmacological and drug repositioning effects of these old drugs. These effects seem to be due to the potent inhibition of such drugs against CA isoforms present in kidneys and blood vessels, which explain both the blood pressure lowering effects as well as organ-protective activity of the drugs. An explanation of these data is provided by the fact that inhibition of the renal CAs leads to a large increase of the nitrite excretion in urine, suggesting that renal CAs are involved in nitrite reabsorption in humans. Important lessons for the drug design of sulfonamide CA inhibitors (CAIs) can be drawn from these data.     

Aspects on pharmacokinetics of some diuretics

Abstract: This review summarizes the present knowledge of some commonly used diuretics. Bendroflumethiazide and bumetanide are completely absorbed from the gut while the uptake of hydrochlorothiazide, chlorthalidone and furosemide averages about 65%. The degree of uptake of amiloride and spironolactone is unknown but exceeds 50%. Plasma t 1/2 of bumetanide and furosemide are approximately 1 h. The clinically important phase of the plasma concentration of bendroflumethiazide has a t 1/2 of 3 h, although a slower phase with a t 1/2 of 9 h has been described. Hydrochlorothiazide and amiloride, often used in combination, both have a t 1/2 of about 10 h. Canrenone, an active metabolite of spironolactone, has a t 1/2 of 15–20 h. Chlorthalidone is eliminated very slowly with a t 1/2 of about two days. This is partly caused by an extensive binding to carbonic anhydrase in the erythrocytes. The protein binding of bendroflumethiazide, bumetanide, canrenone and furosemide is approximately 95%. The binding of chlorthalidone and hydrochlorothiazide is about 75 and 40% respectively. All mentioned diuretics except spironolactone are in part eliminated renally, mainly via tubular secretion. This is the major elimination route for amiloride and hydrochlorothiazide, while it constitutes one third to two thirds for bendroflumethiazide, bumetanide and furosemide. Spironolactone is exclusively eliminated as metabolites.     

Comparative cardiovascular effects of loop-acting, thiazide-type and potassium-sparing diuretics in spontaneously hypertensive rats

Studies were carried out in conscious, chronically-cannulated, spontaneously hypertensive (SH) rats to determine the comparative cardiovascular actions of a series of diuretic compounds. The effects of three oral doses of hydrochlorothiazide, trichlormethiazide, chlorthalidone, metolazone, spironolactone, triamterene, amiloride, furosemide, ethacrynic acid, MK-447, hydrochlorothiazide + amiloride, and MK-447 + amiloride on blood pressure and heart rate were monitored continuously for four hr and again 24 hr post-dose. Thiazides, thiazide derivatives and antikaliuretic diuretics exerted little or no antihypertensive effects, while the loop-acting diuretics (except ethacrynic acid) and combinations markedly reduced blood pressure. Antihypertensive responses to furosemide, MK-447 and the diuretic combinations were associated with either stable heart rate or paradoxical bradycardia, but not compensatory tachycardia. Heart rate remained relatively unaltered by individual doses of the remaining compounds.     

氯噻酮和氢氯噻嗪应用比较的研究进展

噻嗪类利尿剂作为抗高血压一线药物,氯噻酮和氢氯噻嗪是这一类药物中较常使用的利尿剂。近年来,氯噻酮、氢氯噻嗪引起了众多研究者的关注,有证据显示氯噻酮在治疗高血压的疗效及减少心血管事件方面优于氢氯噻嗪,但氯噻酮还远没有氢氯噻嗪应用广泛。针对氯噻酮得不到广泛应用的原因,从临床应用、药动学、临床药效学等方面比较二者在减少心血管事件中的效果,并对氯噻酮、氢氯噻嗪各自复方制剂的研究进展进行了综述。     

Hydrochlorothiazide: is it a wise choice?

INTRODUCTION: Hydrochlorothiazide (HCTZ) has not been shown to reduce mortality or cardiovascular events when given as a single agent. In fact, HCTZ increased cardiovascular death and coronary artery disease (CAD) compared to placebo and usual care in 2 randomized trials, yet it is the most prescribed diuretic in the United States (U.S.). The Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure does not recommend one thiazide diuretic over another. However, there are more clinical data for chlorthalidone and indapamide than HCTZ. AREAS COVERED: This review summarizes the differences between HCTZ, chlorthalidone and indapamide for pharmacological profile, surrogate marker data and clinical trial data. EXPERT OPINION: The use of the term 'thiazide diuretic' should be replaced with 'non-thiazide sulfonamide diuretic' for chlorthalidone and indapamide. Furthermore, chlorthalidone and indapamide, rather than HCTZ, should be recommended due to the lack of evidence and potential harm of the latter.     

'In vitro' study of chemotherapeutic activity of sulphimidazole on some sensitive and metronidazole-resistant Trichomonas vaginalis strains.

Trichomonacidal treatment based on 5-nitroimidazoles is problematic both when Metronidazole, the drug of choice, is ineffective owing to the presence of resistant strains and when bacterial aerobic infections are present. Sulphimidazole (SIZ) possesses two distinct functional groups: one sulphonamide, the other 5-nitroimidazole. Since SIZ is active against aerobic and anaerobic bacteria, we set out to discover whether, in view of the presence of the 5-nitroimidazole group, it could also be effective against Trichomonas vaginalis. Twelve strains of T. vaginalis were cultured in Modified Thioglycate Medium in anaerobic conditions; subsequently, their growth was monitored in the presence of Metronidazole (MZ), SIZ, Sulphamethoxazole (SMX), Trimethoprim (TMP) and their associations. Eight strains proved to be sensitive to Metronidazole (minimum lethal concentration=0.5 microgml(-1)) and four to be resistant (minimum lethal concentration=40-60 microgml(-1)). SIZ was active against both the sensitive and the Metronidazole-resistant strains (minimum lethal concentrations=0.5-1 and 10 microgml(-1), respectively), thus showing that the chemotherapeutic activities of the two functional groups coexisting in SIZ remain unimpaired.     

Flow injection chemiluminescent determination of amiodarone in pharmaceutical preparations using photogenerated tris(2,2'-bipyridyl)ruthenium(III)

A flow injection configuration was developed and evaluated for the chemiluminescent determination of amiodarone. The method is based on the reaction of the drug with tris(2,2'-bipyridyl)ruthenium(III), which was generated through the on-line photo-oxidation of tris(2,2'-bipyridyl)ruthenium(II) with peroxydisulfate. Under the optimum experimental conditions, a linear calibration graph was obtained over the range 3.0-60.0 microg ml(-1) with a detection limit of 0.28 microg ml(-1). The proposed method allows 120 injections h(-1) with excellent repeatability and precision (R.S.D. less than 0.5% and 2.8%, respectively) and a reagent consumption of only 0.37 micromol (0.27 mg) of Ru(bpy)(3)Cl(2) x 6H(2)O per determination. The method was successfully applied to the determination of amiodarone in commercial pharmaceutical formulations.     

Hydrochlorothiazide and bendroflumethiazide in low doses–a comparative trial

Abstract: The effect and tolerability of hydrochlorothiazide 12.5 mg and bendroflumethiazide 2.5 mg were compared in 36 previously untreated hypertensives in a double-blind randomized multicenter trial. The results show a significant blood pressure reduction with both hydrochlorothiazide 12.5 mg and bendroflumethiazide 2.5 mg both at month 6 and 12 compared with month 0. Serum potassium was not significantly changed after twelve months of therapy with either of the thiazide compared with month 0. There was no significant difference between hydrochlorothiazide and bendroflumethiazide with respect to the hypotensive effect, the effect on potassium and uric acid in serum, fasting blood glucose, or any other variable studied. Few subjective side effects were reported.     

Flow-injection inhibition chemiluminescence determination of indapamide based on luminol-ferricyanide reaction

A novel and sensitive chemiluminescence (CL) method for the determination of indapamide coupled with flow-injection analysis (FIA) technique is developed in this paper. It is based on the inhibition effect of the studied drug on the chemiluminescence emission of luminol-potassium ferricyanide system. Under the optimum conditions, the decreased CL intensity is proportional with the concentration of indapamide in the range of 1 x 10(-8) to 1.0 x 10(-6) g ml(-1). The detection limit is 3.4 x 10(-9) g ml(-1) (3sigma). A complete analysis could be performed in 45 s including washing and sampling, giving a throughout of about 90 h(-1). The relative standard deviation (R.S.D.) for 11 parallel measurements of 1.0 x 10(-7) g ml(-1) indapamide is 3.0%. The proposed method has been applied for the determination of indapamide in its pharmaceutical formulations. The results obtained compared well with those by an official method. The possible inhibition mechanism of indapamide on luminol-potassium ferricyanide CL system was discussed briefly.     

Flow-injection chemiluminescent determination of cefprozil using Tris (2,2'-bipyridyl) ruthenium (II)-permanganate system

A rapid and sensitive chemiluminescence (CL) method using flow-injection (FI) has been developed for the determination of a second generation cephalosporin, cefprozil. The method is based on the CL reaction of cefprozil with acidic potassium permanganate and tris (2,2'-bipyridyl) ruthenium (II), Ru (bipy)3(2+). The CL intensity is greatly enhanced when quinine sulfate is used as a sensitizer. After optimization of the different experimental parameters, a calibration graph was obtained over a concentration range of 0.1-3.0 microg ml(-1) with minimum detectability of 0.005 microgml(-1) (S/N=3). The correlation coefficient was 0.9998 (n=6) with a relative standard deviation (%R.S.D.) of 1.63% for 2.0 microgml(-1). The proposed method was successfully applied to commercial tablets. The average percentage recovery (n=6) was 99.9+/-1.40.     

Antihypertensive action of indapamide. Comparative studies in several experimental models.

1-(4-Chloro-3-sulfamylbenzamido)-2-methyl-indoline (indapamide), after single oral dose administration, showed antihypertensive activity in genetically hypertensive rats, DOCA/saline hypertensive rats, unilaterally-nephrectomised DOCA/saline hypertensive rats and dogs made hypertensive by renal encapsulation. The activity was observed at doses as low as 1-3 mg/kg and lasted at least 48 h. Increasing the dose level considerably prolonged the duration of action but did not substantially enhance the maximum antihypertensive effect. In genetically hypertensive rats indapamide was 30-300 times more potent than furosemide, spironolactone and chlorthalidone. Indapamide had no effect on blood pressure in normotensive rats. In concentrations of 1 X 10(-5) to 1 X 10(-3) g/ml, indapamide antagonised contractions of arterial and venous strips to angiotensin, epinephrine and norepinephrine revealing a direct vascular action. Indapamide has a prolonged saluretic action which in combination with the direct vascular effects may well account for its antihypertensive activity.     

Simple and rapid determination of adenosine in human synovial fluid with high performance liquid chromatography-mass spectrometry

A simple, fast, sensitive and selective reversed-phase high performance liquid chromatography-mass spectrometry coupling with an electrospray ionization (ESI) interface method is described for the determination of adenosine in human synovial fluid. This method involved the use of the [M + H](+)ions of adenosine and 2-chloroadenosine (internal standard for the assay) at m/z 268 and 302 in positive ion mode with selective ion monitoring (SIM). Separation was carried out on a 2.0 x 150 mm Shimadzu VP-ODS column by using an isocratic elution with a mobile phase consisting of water (94%),methanol (5%) and formic acid (1%). No interference with the components of the biological matrix was observed in the determination conditions. The calibration curve was linear in the range of 0.2-140 microgml(-1). The limits of quantification (LOQ) and detection (LOD) were 0.2 and 0.03 microgml(-1), respectively. The standard recoveries were between 93.3 and 104.0%. The method was successfully applied to determination of adenosine in some synovial fluids of patients affected by rheumatoid arthritis.     

氯沙坦单用、与吲哒帕胺或氢氯噻嗪合用对高血压患者血压、血钾、血尿酸的影响

目的: 分析评价氯沙坦单用、与吲哒帕胺或氢氯噻嗪合用对高血压患者血压、血钾、尿酸的影响.方法: 选择60例轻、中度原发性高血压患者,分为3组,每组20例.氯沙坦组;氯沙坦 吲哒帕胺组;氯沙坦 氢氯噻嗪组.观察8wk,检测各组治疗前后的血压、血钾、血尿酸的变化.结果: 与治疗前相比,治疗后3组血压下降效果明显(P＜0.01);氯沙坦组和氯沙坦 氢氯噻嗪组血尿酸治疗后明显降低(分别为P＜0.01,P＜0.05),氯沙坦 吲哒帕胺组无明显变化(P＞0.05);3组治疗前后血钾无明显变化(P＞0.05).结论: 氯沙坦有降低尿酸的作用,与吲哒帕胺或氢氯噻嗪合用有协同降压作用,并可改善单用吲哒帕胺或氢氯噻嗪所引起的血钾下降、血尿酸升高的不良反应.