Simultaneous determination of aliskiren and hydrochlorothiazide in tablets and spiked human urine by ion-pair liquid chromatography

An alternative method for analysis of aliskiren (ALI) and hydrochlorothiazde (HCT) in combined dosage forms by ion-pair reversed phase high performance liquid chromatography was developed and validated. The pharmaceutical preparations were analyzed using a C18 column (250 mm x 4.6 mm, 3 microm) with a mobile phase consisting of 25% methanol, 50% sodium monobasic phosphate aqueous solution containing 6 mM tetrabutylammonium bromide and 25% water at pH 7.2. Isocratic analysis was performed at a flow rate of 1 mL/min and a column temperature of 30 degrees C under direct UV detection at 210 nm. Paracetamol was used as internal standard. The validation was performed according to the ICH guidelines. The proposed method was linear over the concentration range of 0.250 to 60 and 0.1 to 10 microg/mL for ALI and HCT, respectively. The limits of detection and quantitation (LOD and LOQ) were 0.075 and 0.198 microg/mL, respectively, for ALI and 0.04 and 0.062 microg/mL, respectively, for HCT. The method proved to be specific, sensitive, precise and accurate with mean recovery values of 101.1 +/- 0.32% and 100.9 +/- 0.41% for ALI and HCT, respectively. The method robustness was evaluated by means of an experimental design. The proposed method was applied successfully to spiked human urine samples with mean recoveries of 98.8 +/- 0.36% and 98.1 +/- 0.21% for ALI and HCT, respectively.

Development and validation of an LC method for simultaneous determination of amiloride hydrochloride and hydrochlorothiazide in human urine

An HPLC method with photometric detection has been developed for determination of a binary mixture of amiloride hydrochloride and hydrochlorothiazide in human urine using chlorthalidone as the internal standard. Reversed-phase chromatography was performed at room temperature on a cyanopropyl column with the mobile phase consisting of a 10 mM KH2PO4 solution (pH 4.5)-methanol (70 + 30, v/v) at a flow rate of 1 ml/min. The detector was set at 214 nm. The total analysis time was 10 min. The method was validated in terms of accuracy, precision, absolute recovery, freeze-thaw stability, bench-top stability, and re-injection reproducibility. The procedure shows good accuracy, repeatability, and selectivity. Moreover, the method was applied directly to urine that had not undergone prior treatment. The intra- and interday coefficients of variation for all compounds were below 4%, and the method was highly accurate, with a relative error for all compounds that was below 8%. No interference from endogenous compounds in urine samples was found. The proposed method, which is rapid, simple, and does not require any separation steps, has been successfully applied to the assay of human urine containing amiloride hydrochloride and hydrochlorothiazide.

Measurement of glomerular filtration rate in the conscious rat

INTRODUCTION

Glomerular filtration rate (GFR) is an important parameter for studying drug-induced impairments on renal function in rats. The GFR is calculated from the concentration of creatinine and blood urea nitrogen (BUN) in serum and in urine, respectively. Following current protocols serum and urine samples must be taken from the same animal. Thus, in order to determine time-dependent effects it is necessary to use for each time point one separated group of animals. We developed a statistical test which allows analyzing the GFR from two different groups of animals: one used for repeated serum and the other one used for repeated urine analysis.

METHODS

Serum and urine samples were taken from two different sets of rats which were otherwise treated identically, i.e. drug doses, routes of administration (per os or per inhalation) and tap water loading. For each dose group GFR mean, standard deviation and statistical analysis to identify differences between the dose groups were determined.

RESULTS

After determination of the optimal time points for measurements, the effect on GFR of the three reference compounds, furosemide, hydrochlorothiazide and formoterol, was calculated. The results showed that the diuretic drugs furosemide and hydrochlorothiazide decreased the GFR and the antidiuretic drug formoterol increased the GFR, as counter regulation on urine loss or urine retention, respectively.

DISCUSSION

A mathematical model and the corresponding algorithm were developed, which can be used to calculate the GFR, and to test for differences between groups from two separated sets of rats, one used for urine, and the other one for serum analysis. This new method has the potential to reduce the number of animals needed and to improve the quality of data generated from various groups of animals in renal function studies.

Multidrug Resistance–Associated Protein 4 Is Involved in the Urinary Excretion of Hydrochlorothiazide and Furosemide

The role of ATP-binding cassette transporters in the urinary excretion of diuretics was investigated. Significant ATP-dependent uptake of hydrochlorothiazide (HCT) and furosemide was observed in membrane vesicles that expressed multidrug resistance-associated protein 4 (MRP4) and breast cancer resistance protein (BCRP). Unlike taurocholate uptake, S-methylglutathione had no effect on the ATP-dependent uptake of both compounds by MRP4. The functional importance of MRP4 and BCRP in the urinary excretion of HCT and furosemide was investigated using gene knockout mice. The renal clearance of HCT and furosemide was reduced significantly but not abolished in Mrp4 knockout mice compared with wild-type mice (9.0 +/- 0.9 versus 15 +/- 2 ml/min per kg for HCT and 1.9 +/- 0.3 versus 2.7 +/- 0.1 ml/min per kg for furosemide), and the amount of HCT that was associated with the kidney specimens was greater in Mrp4 knockout mice (21 +/- 3 versus 13 +/- 1 nmol/g kidney). In contrast, Bcrp makes only a negligible contribution because the urinary excretion was unchanged in Bcrp knockout mice. Our results suggest that Mrp4, together with other unknown transporters, accounts for the luminal efflux of HCT and furosemide from proximal tubular epithelial cells.

Hydrochlorothiazide efficacy and polymorphisms in ACE, ADD1 and GNB3 in healthy, male volunteers

OBJECTIVE

The antihypertensive effect of thiazide diuretics has recently been associated with genetic variation in the angiotensin I-converting enzyme (ACE), alpha-adducin (ADD1) and the G protein subunit beta3 (GNB3). Analysis of short-term diuretic effects may provide insight into the mechanisms behind these findings.

METHODS

A total of 103 male volunteers took 25 and 100 mg hydrochlorothiazide (HCT) after a placebo day, each. We measured volume, sodium, chloride, potassium, calcium excretion, blood pressure and heart rate.

RESULTS

Excretion and cardiovascular parameters were highly constant between the 2 placebo days. The resting heart rate was 2-3 beats/minute (bpm) higher per ACE insertion allele on all 4 study days. The HCT-induced excretion of sodium, chloride and volume was independent of the genotypes. The additional potassium excretion induced by 100 mg HCT was 44+/-21, 33+/-27 and 16+/-26 mmol (mean+/-SD, p<0.001) in ACE II, ID and DD carriers and the same trend was observed after 25 mg HCT. As a second finding, the 100 mg HCT-induced calcium retention was 0.2+/-1.2, 0.7+/-0.8 and 1.7+/-2.1 mmol in ADD1 Gly/Gly, Gly/Trp and Trp/Trp carriers (p=0.002) and the same trend existed after 25 mg HCT.

CONCLUSION

The effects of genetic polymorphisms were stronger with the higher diuretic dose. ACE insertion allele carriers appeared to be more prone to hypokalaemia than deletion allele carriers. ADD1 Trp460 carriers may especially benefit from the calcium-sparing effect of thiazides. Both associations should be further studied in long-term treatment with thiazide diuretics.

Electrochemical study of hydrochlorothiazide and its determination in urine and tablets

A voltammetric study of hydrochlorothiazide (HCTZ) at glassy carbon electrode was carried out. The drug in Britton-Robinson buffer (pH 3.3) is oxidized at +1040mV, giving rise to a well-defined peak. Cyclic voltammetric study indicates that the oxidation process is irreversible and diffusion-controlled. A sensitive, simple and time-saving differential pulse anodic voltammetric procedure has been developed. The procedure has been applied for the drug determination in human urine with no prior extraction and in commercial tablets. The proposed method has been validated. The limit of detection for the standard solution was 5.0ngml(-1) and for the drug in urine was 14.0ngml(-1). The results obtained from the analysis of commercial tablets were compared statistically with those obtained from the USP 26 high-performance liquid chromatographic (HPLC) method.

Determination of hydrochlorothiazide and rutin in Chinese herb medicines and human urine by capillary zone electrophoresis with amperometric detection

In this paper, capillary zone electrophoresis with amperometric detection (CZE-AD) was firstly applied to the simultaneous determination of rutin (RT) and hydrochlorothiazide (HCT) in compound Chinese herb medicines and human urine samples. The two analytes could be perfectly analyzed within 12 min and showed significant current responses at carbon electrode under the optimum conditions. It was found that the linear range of HCT was from 2.0 x 10(-6) to 1.0 x 10(-4) mol l(-1) and that of RT was from 1.0 x 10(-6) to 1.0 x 10(-4) mol l(-1). Their sensitivity was determined by linear regression and calculated as 7.02 x 10(4) and 2.17 x 10(5) nA l mol(-1), respectively, and their detection limits were 5.0 x 10(-7) and 2.0 x 10(-7) mol l(-1), respectively (S/N=3). Above results demonstrated that this method was of high sensitivity, good repeatability, high selectivity and could be used in metabolic kinetics studies of medicines. Satisfactory results were obtained when this method was used to simultaneously analyze the amounts of RT and HCT in one general compound Chinese herb medicine-Zhen Ju jiang Ya Pian and human urine samples.

Simple method for determination of hydrochlorothiazide in human urine by high performance liquid chromatography utilizing narrowbore chromatography

A simple high performance liquid chromatographic (HPLC) method utilizing narrowbore chromatography was developed for the determination of hydrochlorothiazide in human urine. A mobile phase of 0.1% aqueous acetic acid--acetonitrile (93:7, v/v) pH 3 was used with a C18 analytical column and ultraviolet detection (UV). The method demonstrated linearity from 2 to 50 micrograms ml-1 using 50 microliters of urine with a detection limit of 1 microgram ml-1. The method was utilized in a study evaluating if racial differences are present in the pharmacokinetic and pharmacodynamic effects of hydrochlorothiazide.

3-Bromomethyl-propyphenazone as a new derivatization reagent for high performance liquid chromatography of captopril and hydrochlorothiazide with UV-detection

3-Bromomethyl-propyphenazone (BMP) was used as a derivatization reagent for the detection and quantification of captopril (CAP) and hydrochlorothiazide (HCT) by high performance liquid chromatography using Zorbax C8 column, and 0.05M sodium acetate, acetonitrile, methanol (14:17:4; pH 6.5) as mobile phase system with UV-detection at 254 nm. The cited reagent reacts with the mercapto and amino groups of CAP and HCT in acetone using anhydrous potassium carbonate as hydrobromide acceptor. The reaction was completed within 30 min for CAP and 60 min for HCT with heating at 105 +/- 5 degrees C in mini-reaction vial. The linear concentration ranges for both CAP and HCT were 8 to 160 and 6 to 140 ng per injection, respectively. The derivatized captopril was synthesized and confirmed with spectral analysis. This method was applied for determination of spiked captopril in human urine after extraction with Extrelut-20 column using ethyl acetate:isopropanol (85:15 v/v) as eluant.

[The phenomenon of resistance to a thiazide diuretic in acute kidney failure]

The resistance to hypothiazid (hydrochlorothiazide) during the development of acute renal insufficiency (ARI) induced by glycerin injection was studied in rat experiments. Natriuretic, kaliuretic, and hydrouretic activity of the diuretic decreased two days after injection of a glycerin solution. In this period hypothiazid excretion with the urine was least. Ten days later, despite the restoration of the water- and electrolyte-excretion function of the kidneys and normalization of hypothiazid excretion with the urine, the natriuretic effect of the drug was still very poor. This is indirect evidence of the long-term affection of the receptors for the thiazid diuretics during the development of ARI. The affection remains even after the excretory function of the kidneys is restored. The high correlation between the cumulative excretion of hypothiazid with the urine and natriuresis encountered in intact animals was weaker in rats with acute renal insufficiency.

Effect of hydrochlorothiazide on the pharmacokinetics of enalapril in hypertensive patients with varying renal function

An open, randomised, cross-over study was performed to investigate the pharmacokinetics of enalaprilat, administered as 20 mg enalapril both as monotherapy and in combination with hydrochlorothiazide (HCTZ 12.5 mg). Three groups of 6 hypertensive patients were enrolled [untreated diastolic blood pressure (DBP) 90-115 mm Hg]; normal renal function [glomerular filtration rate (GFR) > 81 ml min-1 1.73 m-2], mild renal impairment (GFR 51-80 ml min-1 1.73 m-2), and moderate renal impairment (GFR 31-50 ml min-1 1.73 m-2). The pharmacokinetics of enalaprilat and enalaprilat plus HCTZ correlated predictably with renal impairment with increased plasma concentrations and decreased urinary elimination at lower values of GFR. The coadministration of HCTZ had no significant effect on the pharmacokinetics of enalaprilat in any group. We conclude that although the pharmacokinetics of both enalaprilat and HCTZ are related to renal function, HCTZ has no significant effect on the pharmacokinetics of enalaprilat and that dosage adjustment for both regimens should be based on renal function.

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.

Fully automated methods for the determination of hydrochlorothiazide in human plasma and urine

LC assays utilizing fully automated sample preparation procedures on Zymark PyTechnology Robot and BenchMate Workstation for the quantification of hydrochlorothiazide (HCTZ) in human plasma and urine have been developed. After aliquoting plasma and urine samples, and adding internal standard (IS) manually, the robot executed buffer and organic solvent addition, liquid-liquid extraction, solvent evaporation and on-line LC injection steps for plasma samples, whereas, BenchMate performed buffer and organic solvent addition, liquid-liquid and solid-phase extractions, and on-line LC injection steps for urine samples. Chromatographic separations were carried out on Beckman Octyl Ultrasphere column using the mobile phase composed of 12% (v/v) acetonitrile and 88% of either an ion-pairing reagent (plasma) or 0.1% trifluoroacetic acid (urine). The eluent from the column was monitored with UV detector (271 nm). Peak heights for HCTZ and IS were automatically processed using a PE-Nelson ACCESS*CHROM laboratory automation system. The assays have been validated in the concentration range of 2-100 ng ml-1 in plasma and 0.1-20 micrograms ml-1 in urine. Both plasma and urine assays have the sensitivity and specificity necessary to determine plasma and urine concentrations of HCTZ from low dose (6.25/12.5 mg) administration of HCTZ to human subjects in the presence or absence of losartan.

Carbonic anhydrase-immobilized precolumn for selective on-line sample pretreatment in high-performance liquid chromatographic determination of certain sulphonamide drugs

Carbonic anhydrase (CA)-immobilized aminopropyl silica precolumn was developed for direct injection determination of certain sulphonamide drugs in biological fluids by column-switching (CS) high-performance liquid chromatography. Under the optimized conditions, only the sulphonamide drugs with an unsubstituted sulphonamide group were retained on the CA precolumn and separated on a reversed-phase analytical column. Of these, the retention of hydrochlorothiazide (HCT), chlorothiazide, acetazolamide, furosemide (FS) and chlorthalidone was almost quantitative. The peak area of HCT was proportional to the concentration in the range of 1-100 nmol/mL with relative standard deviations of 3.7% (5 nmol/mL) and 0.7% (100 nmol/mL). This CS system was applied to urine and plasma samples spiked with HCT and FS. Endogenous components of these were effectively removed, and HCT and FS were selectively retained on the CA precolumn. Almost quantitative recoveries and reproducibility were obtained.

Simple determination of hydrochlorothiazide in human plasma and urine by high performance liquid chromatography

The diuretic drug hydrochlorothiazide (HCT) is used mainly for treatment of mild to moderate hypertension and is usually administered with other drugs. An assay for the determination of HCT in human plasma and urine by high performance liquid chromatography (HPLC) has been developed. Samples were purified by solvent extraction and analysed by reversed phase HPLC with ultraviolet detection, using hydroflumethiazide as the internal standard; plasma was eluted using gradient elution and urine was analysed isocratically. The method is simple to perform, is sensitive (detection limit 0.01 micrograms/mL in plasma and 0.2 micrograms/mL for urine); it showed good reproducibility (3-8%). A great number of drugs did not interfere with the assay and the method was used for pharmacokinetic studies in healthy subjects, but samples from patients can also be analysed with high selectivity.

High-performance liquid chromatographic determination of diuretics in urine by micellar liquid chromatography

The use of micellar liquid chromatography for the determination of diuretics in urine by direct injection of the sample into the chromatographic system is discussed. The retention of the urine matrix at the beginning of the chromatograms was observed for different sodium dodecyl sulphate (SDS) mobile phases. The eluent strengths of a hybrid SDS-methanol micellar mobile phase for several diuretics were compared and related to the stationary phase/water partition coefficient with a purely micellar mobile phase. The urine band was appreciably narrower with a mobile phase of 0.05 M SDS-5% methanol (v/v) at 50 degrees C (pH 6.9). With this mobile phase the determination of bendroflumethiazide and chlorthalidone was adequate. Acetazolamide, ethacrynic acid, furosemide, hydrochlorothiazide and probenecid were overlapped by the urine matrix, and the retention of amiloride and triamterene was too long.

The influence of gastrointestinal transit on drug absorption in healthy volunteers

1. The effect of variability of gastric emptying and oro-caecal transit on the absorption of a multicomponent solution of frusemide, atenolol, hydrochlorthiazide and salicylic acid has been studied in six healthy subjects. Each subject was studied on five separate occasions: three times under basal conditions, once following metoclopramide and once following codeine pretreatment in an attempt to speed and slow transit respectively. 2. Inter-subject variability of gastric emptying, oro-caecal transit and the rate and extent of drug absorption was considerable. 3. The absorption of salicylic acid appeared rate-limited by gastric emptying but the rate and extent of frusemide, atenolol and hydrochlorthiazide absorption were unrelated to measures of gastric emptying or oro-caecal transit. 4. Codeine phosphate caused a two-fold delay in oro-caecal transit but did not influence gastric emptying while metoclopramide had no significant effect on either function. 5. Metoclopramide and codeine had no significant effect on the rate or extent of absorption of any of the study drugs. 6. Within the limits of this experiment, oro-caecal transit time did not appear to be an important determinant of frusemide, atenolol, hydrochlorothiazide or salicylic acid absorption. Other factors must account for the observed variability in drug absorption.

Effects of a non-absorbable osmotic load on drug absorption in healthy volunteers

1. We have studied the effects of a non-absorbable osmotic load on the absorption of a multicomponent solution of frusemide, atenolol, hydrochlorothiazide and salicylic acid in six healthy volunteers. 2. Each subject was studied on up to four separate occasions. The drugs were administered in one of four solutions: a) a mannitol/electrolyte solution, b) a double-strength mannitol/electrolyte solution, c) a glucose/electrolyte solution and d) water. Lactulose or sulphasalazine were added as oro-caecal transit markers. Lactulose was included in the mannitol- and glucose-based solutions, adding a further non-absorbable osmotic load, and sulphasalazine was added to the water, adding little osmotic load. 3. The absorption of atenolol and hydrochlorothiazide was two- to three-times less from all lactulose-containing solutions than from the sulphasalazine-containing solution. The absorption of frusemide and salicylic acid was similar from all four solutions. 4. The largest non-absorbable osmotic load impaired the absorption of atenolol and hydrochlorothiazide most and the incorporation of glucose only partly restored absorption. 5. These results suggest that transmucosal water movement is an important determinant of atenolol and hydrochlorothiazide absorption but is less relevant for the absorption of frusemide and salicylic acid. Furthermore, these data demonstrate a previously unrecognised interaction between a commonly prescribed laxative--lactulose, and atenolol and hydrochlorothiazide.

Screening for diuretics in human urine by gas chromatography-mass spectrometry with derivatisation by direct extractive alkylation

A rapid, sensitive and reliable gas chromatographic-mass spectrometric (GC-MS) screening procedure for diuretics in human urine has been developed. The procedure uses derivatisation by extractive methylation directly from the urine. The suitability of a number of phase transfer reagents and solvents were studied for the detection of sixteen diuretics. The results obtained indicate that the screening procedure employing tetrahexylammonium hydrogensulphate at pH 12 with methyl iodide in toluene at room temperature was the most effective. This method gives selectivity and sensitivities down to 0.03-0.1 microgram/ml and provides a substrate suitable for GC-MS confirmation without further manipulation. The application of the method is demonstrated by the screening of urine for bumetanide, ethacrynic acid, acetazolamide, chlorothiazide and hydrochlorothiazide.

Optimization of selectivity in micellar chromatographic procedures for the determination of drugs in urine by direct injection

Selectivity was optimized for the determination of drugs in urine by direct injection micellar chromatography through changes in specific mobile phase parameters. The rôle of mobile phase pH and the type of surfactant used for mobile phase preparation was investigated. The retention of the urine matrix was found to be minimal between pH 5.5 and 7.5. The non-ionic surfactant, polyoxyethylene 23 lauryl ether (Brij 35), was found to be the surfactant of choice for the separation of drugs from urine. Favourable retention of both the urine background and the analyte was achieved with this surfactant. Micellar mobile phases of optimal composition were used to develop chromatographic procedures for the determination of furosemide, hydrochlorothiazide and propranolol in urine. Good accuracy (98-102% of drug recovered), precision (1-4% RSD) and linearity were obtained for all methods. Limits of detection for all drugs were adequate.

Mobile phase versus stationary phase approaches to the direct injection of biological fluids in liquid chromatography

The liquid chromatographic analysis of drugs in urine through direct injection without any sample pretreatment was extended to micellar chromatography with nonionic surfactants, the Pinkerton ISRP column and the shielded hydrophobic phase (Hisep) column. The feasibility of using each was demonstrated through the determination of the diuretic, hydrochlorothiazide, in urine. Good separation, recovery, precision and linearity, and adequate limits of detection were obtained for this analysis with all three techniques. The advantages and limitations of the mobile phase approach of micellar chromatography and the two stationary phase approaches are discussed for the direct injection of urine as well as other biological fluids.

Pharmacokinetic and pharmacodynamic interactions between furosemide and hydrochlorothiazide in nephrotic patients

We examined the response of 8 patients with nephrotic syndrome (creatinine clearance 70.4 +/- 16.0 ml/min) to oral furosemide (F; 40 mg) in the absence (control) and in the presence of oral hydrochlorothiazide (HCT; 100 mg). In the 24-hour period after oral F, HCT was shown to increase urine volume and urinary sodium and chloride excretion. Increment was most significant during the 12- to 24-hour period. Enhancement of the diuresis with HCT was associated neither with a significant increase in the area under the curve of plasma F concentration nor an increase in urinary F excretion. Urinary excretion of glucuronidated F, one of the main metabolites of F, however, was decreased with HCT. In summary, HCT significantly enhanced the response to F in nephrotic patients.

Influence of time intervals for cholestyramine dosing on the absorption of hydrochlorothiazide

Ten healthy adult men participated in a study to evaluate appropriate dosing schedules of cholestyramine to minimize its effect on the absorption of hydrochlorothiazide (HCTZ). A single 8 gm dose of cholestyramine 2 hours before or after HCTZ, 75 mg po, significantly decreased the amount of HCTZ excreted unchanged in the urine over 24 hours (Ae(0-24)) by 65% (P less than 0.01) and 26% (P less than 0.05), respectively, in four subjects. Six subjects randomly received three different schedules: control, single dose of cholestyramine 4 hours after HCTZ, and multiple doses of cholestyramine (-24, -12, and +4 hours) after HCTZ. There were no significant differences in HCTZ kinetics between the control group and the subjects who received a single dose of cholestyramine. Multiple doses of cholestyramine significantly altered HCTZ kinetics, including reductions in Ae(0-24) by 35% (P less than 0.02), AUC(0-infinity) by 32% (P less than 0.01), and Cmax by 31% (P less than 0.01). We conclude that the best dosing schedule for cholestyramine is 4 hours after HCTZ, but there will still be at least a 30% to 35% decrease in the absorption of HCTZ.

High-performance liquid chromatographic assay for hydrochlorothiazide in human urine

A high-performance liquid chromatographic assay was developed for the quantitative determination of hydrochlorothiazide (HCT) in human urine. Reversed-phase separation of HCT and the internal standard, trichloromethiazide (TCMT), was accomplished on a 300 X 3.9 mm mu Bondapak Phenyl column. Following solvent extraction, concentrations of HCT as low as 0.25 micrograms/ml in urine were quantified by UV detection at 280 nm. Detector response (peak-area ratio of HCT to TCMT) was linear to 50 micrograms/ml. No interferences were observed in the extracts obtained from drug-free urine nor from several antihypertensive agents which are commonly co-administered with HCT. This method has been routinely employed in bio-availability studies evaluating a variety of formulations as well as characterizing the pharmacokinetics of this drug from urinary excretion data.

The development of reliable compliance tests for antihypertensive drugs

Many tests for measuring compliance have been proposed, but in most cases compliance rates have been determined without taking into account the factors influencing the interval during which a drug can be detected by a qualitative test after having been taken by the patient. The drug half-life, often used for determining the time at which the sample is collected, is inadequate for obtaining conclusive test results. A procedure is described for the determination of urine collection intervals during which reliable information on compliance can be obtained, using oxprenolol, hydrochlorothiazide, and pindolol as examples.

Exaggerated natriuretic and calciuric responses to hydrochlorothiazide in renal hypercalciuria but not in absorptive hypercalciuria

Patients with hypercalciuria have been reported to have an exaggerated response to hydrochlorothiazide (HCTZ), implying a renal tubular defect in solute reabsorption. To determine whether this disturbance is generalized or unique to a particular pathogenetic type of hypercalciuria, we measured the increments in urinary sodium (delta Na), calcium (delta Ca), and magnesium after a 100-mg dose of oral HCTZ in 10 normal subjects and 31 patients with different types of hypercalciuric nephrolithiasis. Eleven patients with renal hypercalciuria had significantly greater delta Na (P less than 0.005) and delta Ca (P less than 0.005) than the normal subjects. Ten patients with absorptive hypercalciuria and 10 patients with fasting hypercalciuria without parathyroid stimulation had delta Na and delta Ca indistinguishable from those of normal subjects. In all groups, urinary HCTZ and basal 24-h urinary Na did not differ. The results suggest that the unique natriuretic and calciuric responses to HCTZ occur only in renal hypercalciuric patients with secondary hyperparathyroidism. The data support a renal tubular defect in renal hypercalciuric in contrast to other diagnostic categories of hypercalciuric nephrolithiasis.

Accuracy of indirect measures of medication compliance in hypertension

The purpose of this study was to identify the most accurate indirect measure of medication compliance in primary hypertension through comparison with a recently developed direct measure of the antihypertensive agent, hydrochlorothiazide. A convenience sample of 40 subjects was seen by the investigator twice in an office setting and once in their homes. Data were collected by an interview schedule, blood pressure measurement, pill counts, urine analysis, and hospital record review. Patient interview was the most sensitive and accurate measure of compliance; this measure correctly classified 85% of patients as to compliant or noncompliant.

Bioequivalence study of a new tablet formulation of triamterene and hydrochlorothiazide

A three-treatment, single-dose, crossover bioequivalence study was conducted in healthy volunteers to compare urinary drug recovery following administration of hydrochlorothiazide tablets, the currently marketed capsule formulation of triamterene and hydrochlorothiazide (Dyazide), and a new tablet preparation of these active ingredients (Maxzide). No significant differences were observed in the urinary recovery of hydrochlorothiazide after the administration of hydrochlorothiazide tablets and Maxzide tablets. However, only about one-half as much hydrochlorothiazide was recovered following the administration of Dyazide capsules. Similarly, the urinary recovery of triamterene and the sulfate ester of hydroxy-triamterene after administration of Dyazide capsules was approximately one-half the levels observed after giving the new tablet formulation. The clinical consequences of the limited bioavailability of the active ingredients of Dyazide are discussed.

Simplified detection of hydrochlorothiazide in urine by thin-layer chromatography

A new thin-layer chromatographic procedure for the detection of the antihypertensive/diuretic drug hydrochlorothiazide in human urine is described. The sensitivity of the method, 5 micrograms/mL, makes it useful to both the clinician interested in determining patient compliance and the toxicologist who must identify or confirm hydrochlorothiazide ingestion. The rapidity of analysis typically allows the screening of 25 urine samples within one hour.

Comparative bioavailability and pharmacokinetics of hydrochlorothiazide from oral tablet dosage forms, determined by plasma level and urinary excretion methods

The bioavailability and pharmacokinetics of two hydrochlorothiazide products were compared following single 50 mg oral doses to 20 healthy male volunteers. Plasma and urine were assayed for hydrochlorothiazide by a specific and sensitive HPLC method. Plasma profiles of hydrochlorothiazide were adequately described by a triexponential function. The bioavailability of hydrochlorothiazide from the two brands did not differ significantly as judged by the values of Cmax, tmax, AUC0 leads to infinity, mean residence time, variance of residence time, and urinary excretion of unchanged drug. Close similarity was observed between urinary excretion rates and concentrations of drug in plasma.

On-line direct liquid introduction interface for micro-liquid chromatography/mass spectrometry: application to drug analysis

We describe an integrated micro-liquid chromatograph/mass spectrometer (micro-LC/MS) system capable of performing routine determinations for 1--10 ng of drugs and their metabolites extracted from biological fluids. The micro-LC is constructed from conventional "high-performance" liquid-chromatographic instrumentation by using commercially available components. The mass spectrometer is operated in the chemical ionization mode. The direct liquid introduction micro-LC/MS interface can be constructed from commercially available materials. Chromatographic and mass spectral results demonstrate the ability of the micro-LC and micro-LC/MS system to separate and determine multiple components in standards of trace concentrations and in equine urinary extracts. The stability and sensitivity of this micro-LC/MS system are demonstrated through determinations of trichlormethiazide.

Pharmacokinetics of hydrochlorothiazide in fasted and nonfasted subjects: a comparison of plasma level and urinary excretion methods

The bioavailability of hydrochlorothiazide from 50-mg oral tablet doses was examined in healthy male volunteers under fasting and nonfasting conditions. Bioavailability was examined from plasma levels and urinary excretion of unchanged drug. The pharmacokinetics of hydrochlorothiazide in plasma could be described in terms of a triexponential function, and the mean drug half-lives determined from the three exponents were 1.0, 2.2, and 9.0 hr. Changing the accompanying fluid volume has no significant effect on hydrochlorothiazide absorption in fasted subjects. Plasma drug levels were significantly reduced in non-fasted individuals, compared with those in fasted individuals. A similar trend was observed in the urinary excretion of hydrochlorothiazide, but differences between treatments were not significant (p greater than 0.05). Mean 48-hr urinary recovery of hydrochlorothiazide was 70.5% of the dose in nonfasted subjects, and 73.5 and 75.0% of the dose in fasted subjects receiving the drug with 20 and 250 ml of water, respectively. The cumulative urinary excretion of hydrochlorothiazide correlated poorly (r = 0.27) with areas under plasma drug level curves, although the correlation between the means of these values for each of the three treatments was high (r = 0.996).. Close similarity was observed between urinary excretion rates of hydrochlorothiazide and the time course of drug concentrations in plasma.

High-pressure liquid chromatographic determination of chlorothiazide and hydrochlorothiazide in plasma and urine: preliminary results of clinical studies

High-pressure liquid chromatographic procedures were developed for the determination of chlorothiazide and hydrochlorothiazide in plasma and urine. The plasma assay incorporates a preextraction procedure that eliminates interference by endogenous substances. Chromatography is carried out on an octadecyl reversed-phase column. Mobile phases are 15% methanol in 0.01 M acetic acid for plasma and 4% acetonitrile in 0.01 M sodium perchlorate, adjusted to pH 4.6, for urine. At a flow rate of 2.5 ml/min, the retention times for chlorothiazide and hydrochlorothiazide are 3.5 and 4.6 min for plasma and 10.5 and 13.5 min for urine, respectively. Preliminary results of a clinical study in fasting male volunteers showed that the plasma levels and urinary excretion rate of chlorothiazide peaked at 1-2 hr following a 500-mg oral dose and subsequently declined irregularly. On the other hand, the plasma levels and urinary excretion rate of hydrochlorothiazide peaked at 2-3 hr following a 50-mg oral dose and subsequently declined in biphasic fashion. Urinary excretion rates of both chlorothiazide and hydrochlorothiazide closely resemble their concentration profiles in plasma.

Can simple clinical measurements detect patient noncompliance?

Measurement of patient compliance is essential if management of low compliance is to be performed efficiently. We assessed the value of several easily obtained clinical assessments compared to quantitative pill counts among 134 newly treated hypertensive male steelworkers during the first 6 months of their treatment with antihypertensive medication. Patient's self-reports obtained on structured interview correlated best with pill count compliance (r = 0.74, p less than 0.0001). Patients overestimated their compliance by an average of 17% but 90% of those who admitted to being noncompliant were found so. Qualitative urinary chlorthalidone and hydrochlorothiazide levels and changes in serum potassium, uric acid, and blood pressure also correlated with pill count compliance but were less accurate than interviews. Assessment of the patient's "health beliefs" and a variety of sociodemographic and health traits and perceptions did not provide useful information on compliance. Interviewing the patient is a simple and useful approach in assessing compliance with antihypertensive therapy.

Qualitative and quantitative analysis of hydrochlorothiazide in equine plasma and urine by high-performance liquid chromatography

A sensitive, quantitative method has been developed for the determination of hydrochlorothiazide in equine plasma and urine. Thin-layer chromatography is used to screen for the presence of the drug in unknown samples. The TLC screening methods described provide minimum detection limits of 50 ng/mL in plasma and 25 ng/mL in urine. A silica micro chromatography column is used to clean up ethyl acetate extracts for HPLC analysis and mass spectral confirmation. An internal standard, trichloromethiazide, is used to derive quantitative data at concentrations as low as 25 ng/mL for plasma disappearance curves and urinary excretion rates.

Liquid-chromatographic detection of thiazide diuretics in urine

We describe a liquid-chromatographic procedure for detection in urine of all thiazide drugs currently used clinically. Urine is treated initially with NaBH4 to convert any chlorothiazide present to hydrochlorothiazide. The urine is acidified with NaH2PO4 (1.0 mol/L, pH 5), and thiazides are extracted with ethyl acetate. Interfering substances are then removed in two washes with 0.1 mol/L Na2HPO4 at pH 8. The ethyl acetate is evaporated and the residue redissolved in mobile phase. Thiazides are assayed by reversed-phase chromatography, with detection by ultraviolet absorption. Analytical recovery of thiazides ranged from 53 to 93%. Urines from 48 patients were so studied, and the results were compared with results by the currently used spectrophotometric method. The two methods agreed for 56% of samples. Evaluation of the discrepancies by review of patients' histories clearly showed liquid chromatography to have correctly identified seven of eight positive urines that the spectrophotometric method failed to detect. Ultraviolet scanning incorrectly identified as positive two samples, whereas liquid chromatography did not falsely identify any urines as positive. Our method was more sensitive and more specific than the spectrophotometric method.

Correlation of urinary excretion with in vitro dissolution using several dissolution methods for hydrochlorothiazide formulations

Four different hydrochlorothiazide formulations were prepared, and cumulative urinary hydrochlorothiazide excretion was determined in a crossover study using six volunteers. A comparison of in vivo results showed that one formulation (Forumulation D) was significantly different from the others at 2, 3, 4, 5, 8, and 14 hr. A dissolution study was conducted on each formulation using the flask, USP basket, and magnetic basket methods at agitation speeds of 50, 100, and 150 rpm. Formulation D was significantly different from other formulations when determined using the USP basket method at 150 rpm and a sampling time of 10 min; the USP basket method at 100 rpm and a sampling time of 100 min; the flask method at 100 rpm and sampling times of 30, 40, 60, and 120 min; and the flask method at 150 rpm and sampling times of 30 and 40 min. Significant in vitro and in vivo correlations were found using a regression analysis and F test. With a correlation coefficient and 95% confidence intervals, it was established that the USP basket method at 150 rpm was the best predictor of urinary hydrochlorothiazide excretion among the dissolution methods tested.

Estimating compliance with diuretic therapy: urinary hydrochlorothiazide-creatinine ratios in normal subjects

We gave 21 healthy young men 100 mg of hydrochlorothiazide daily to determine whether or not urinary detection of the drug was feasible as a measure of compliance on a standard antihypertensive regimen. All subjects took the drug daily for 6 days, after which they were divided into four groups with differing patterns of medication administration. Urine hydrochlorothiazide and creatinine measurements were obtained to validate the urinary hydrochlorothiazide-creatinine ratio (UHCR) as an accurate quantitative index of compliance. The subjects achieved a constant level of UHCR of 13 +/- 3.0 within 48 hours of hydrochlorothiazide administration. The UHCR levels decreased to 5.0 +/- 0.8 48 hours after discontinuation of the drug (p less than 0.001). UHCR values in the range of 13 +/- 6 indicate that the subject has ingested hydrochlorothiazide 24 hours previously. The UHCR is a potentially useful means of assessing compliance in hypertensive patients taking hydrochlorothiazide.

Pharmacokinetics of hydrochlorothiazide in patients with congestive heart failure

1. Hydrochlorothiazide (HCT, 50-75 mg) was administered orally to seven patients with cardiac failure. 2. Plasma levels and urinary concentration of HCT were determined by GLC. 3. The gastrointestinal uptake of the diuretic in three patients was reduced to approximately half that seen in healthy controls. 4. Plasma halflife of HCT was correlated with endogenous creatinine clearance. 5. Pharmacokinetics of HCT are considerably changed in cardiac failure.

High performance liquid chromatographic analysis of hydrochlorothiazide in serum and urine

We report a high performance liquid chromatographic method for the analysis of hydrochlorothiazide in 500microliter of serum of 25 microliter of urine. The between-day precision of the analysis (CV 5.0-7.0%) is acceptable, as is the recovery of hydrochlorothiazide (90-96%) and trichloromethiazide (96%) added to serum. No drug or drug metabolite interferences have been noted. The method represents a considerable improvement over existing techniques described in the literature.

Malabsorption of hydrochlorothiazide following intestinal shunt surgery

Hydrochlorothiazide 775mg was administered orally to 5 patients who had undergone intestinal shunt operations for obesity 1.5 to 6 years previously. Postoperative weight loss averaged 53.4kg. The concentrations of hydrochlorothiazide in plasma and urine were determined with gas/liquid chromatography. The mean area under the plasma concentration time curve during 9h in 4 of the patients was 889ng/ml.h. Mean total urinary recovery of hydrochlorothiazide amounted to 23.0mg in the 5 patients, which corresponds to approximately half that seen in healthy volunteers. The gastrointestinal hydrochlorothiazide appears to be substantially reduced after intestinal shunt surgery.

Quantitative determination of thiazides in urine by a sensitive colorimetric method

Chloriothiazide and hydrochlorothiazide may be determined in urine by the Bratton-Marshall reaction after extracting with ethyl acetate and treating the extract with Florisil. Such treatment reduces the background color of the urine sample and eliminates interferences. The modified procedure is thus sensitive enough to determine both drugs in 24 hour urine specimens from patients receiving therapeutic doses orally.

[Fluorometric determination of hydrochlorothiazide in body fluids by direct measurement of thin-layer chromatographic plates (author's transl)]

Two fluorometric methods for analysis of hydrochlorothiazide (HCT) are described utilizing direct measurement of thin-layer plates. The first method employs a modification of the Bratton-Marshall reaction and is therefore applicable to all aromatic primary amines. Following diazotation and azocoupling of the HCT hydrolysis product, a fluorescent group is added to the compound. For this purpose N-(1-naphthyl)ethylenediamine is first coupled with 4-chloro-7-nitrobenzo-2,1,3-oxadiazole. In the second method, the intrinsic fluorescence of underivatized HCT, following its extraction from plasma, urine or saliva, is used. It is shown that the sensitivity of this method is sufficient for estimating the kinetics following oral administration of 25 mg HCT.

Identification of selected antihypertensive drugs by thin-layer chromatography

A thin-layer chromatographic procedure is described for the qualitative identification of several antihypertensive drugs including certain thiazide diuretics spironolactone, triamterene, methyldopa and their metabolites. Utilization of new solvent developing systems and spray detecting reagents provides a method useful for the identification of these compounds in biologic fluids at low therapeutic concentrations. Sensitivity limits for these antihypertensive drugs are given, and alternate techniques to provide confirmatory analyses are also presented.