Green-modified micellar liquid chromatography for isocratic isolation of some cardiovascular drugs with different polarities through experimental design approach.

Bilayer pseudo-stationary phase micellar liquid chromatography (MLC) was developed for simultaneous isocratic isolation of hydrochlorothiazide, as a basic-polar (hydrophilic) cardiovascular drug, as well as triamterene and losartan potassium, as acidic-nonpolar (hydrophobic) cardiovascular drugs. Utilizing a deep eutectic solvent (DES), as a novel green mobile phase additive in combination with acetonitrile (ACN) and acetic acid (ACA), drastically improved the chromatographic behavior of the drugs. Concentration of sodium dodecyl sulphate (SDS), as well as volume percentages of ACN, DES, and ACA were optimized by using a central composite design. The optimal composition of the mobile phase (0.12 mol L-1 SDS, 5% ACN, 4% DES, and 2% ACA) was chosen through the desirability function. The chromatographic peaks of both hydrophilic and hydrophobic drugs, respectively, emerged at high and low retention time values in the shortest total analysis time of 20 min (at a flow rate of 2 mL min-1). Analytical characterization of the developed approach was investigated through Food and Drug Administration (FDA) guidelines. Applicability of the method was evaluated by analysing of human plasma samples which were directly injected into the system.

Selective recognition of Triamterene in biological samples by molecularly imprinted monolithic column with a pseudo template employed.

Melamine (MAM) was employed as a pseudo template to prepare a molecularly imprinted polymer monolithic column which presents the ability of selective recognition to Triamterene (TAT), whose structure was similar to that of MAM. Methacrylic acid and ethylene glycol dimethacrylate were applied as functional monomer and cross-linker, respectively, during the in situ polymerization process. Chromatographic behaviors were evaluated, the results indicated that the molecularly imprinted polymer monolithic column possessed excellent affinity and selectivity for TAT, and the imprinting factor was high up to 3.99 when 7:3 of ACN/water v/v was used as mobile phase. In addition, the dissociation constant and the binding sites were also determined by frontal chromatography as 134.31 µmol/L and 132.28 µmol/g, respectively, which demonstrated that the obtained molecularly imprinted polymer monolith had a high binding capacity and strong affinity ability to TAT. Furthermore, biological samples could be directly injected into the column and TAT was enriched with the optimized mobile phase. These assays gave recovery values higher than 91.60% with RSD values that were always less than 3.5%. The molecularly imprinted monolithic column greatly simplified experiment procedure and can be applied to preconcentration, purification, and analysis of TAT in biological samples.

Simultaneous analysis of hydrochlorothiazide, triamterene and reserpine in rat plasma by high performance liquid chromatography and tandem solid-phase extraction.

A tandem solid-phase extraction method (SPE) of connecting two different cartridges (C(18) and MCX) in series was developed as the extraction procedure in this article, which provided better extraction yields (>86%) for all analytes and more appropriate sample purification from endogenous interference materials compared with a single cartridge. Analyte separation was achieved on a C(18) reversed-phase column at the wavelength of 265 nm by high-performance liquid chromatography (HPLC). The method was validated in terms of extraction yield, precision and accuracy. These assays gave mean accuracy values higher than 89% with RSD values that were always less than 3.8%. The method has been successfully applied to plasma samples from rats after oral administration of target compounds.

Bioequivalence evaluation of a triamterene-hydrochlorothiazide generic product: a new bioequivalence index for fixed-dose combinations.

In this study, an open, double-blind, randomized, two-period, two-group crossover design was conducted in 14 healthy volunteers to study the bioequivalence of a fixed-dose generic product. After administration of test or reference products to each volunteer, both active ingredients were determined simultaneously in plasma samples using a developed and validated HPLC-UV method, and pharmacokinetic parameters, including C(max), T(max), AUC(0-t) , AUC(0∞), terminal elimination rate constant (λz), volume of distribution in steady state (Vd(ss)), mean residence time (MRT), clearance (Cl), terminal elimination rate constant (Kel) were determined in each subject using the standard non-compartmental approach. Statistical comparison showed that the test and reference products were bioequivalent in terms of both the rate and extent of bioavailability of both active ingredients. Finally, a new parameter named range overlap index (ROI) was introduced for the first time in this study in order to judge about the overall bioequivalence of the combination products. This parameter indicates the extent in which the two CI90% ranges of each parameter for two active ingredients overlap with each other. The ROI is suggested to be equal or more than 50% for two combination products in order to be known as bioequivalent. The ROI values of the bioequivalence-indicating parameters were 61.90%, 84.6%, and 76.0% for C(max), AUC(0--->12), and AUC(0--->∞), respectively, which are indicative for bioequivalence in all the cases.

Multicommuted flow-through fluorescence optosensor for determination of furosemide and triamterene.

Multicommutation implemented with flow-through optosensors is a very promising area of research. This recent approach benefits from the advantages of both methods and results in high sensitivity, selectivity, and speed, and little waste generation. This paper reports the simultaneous determination of furosemide and triamterene, two widely used diuretics, by measurement of their native fluorescence. The system has been proved to be useful for determination of both analytes in pharmaceutical preparations and for determination of triamterene in human urine and serum. A minicolumn filled with Sephadex SPC-25 microbeads was used to achieve separation of both analytes before detection in a flow-through cell filled with the same resin. The sensor is linear in the range 50-1200 and 0.4-8 ng mL(-1) with detection limits of 15 and 0.1 ng mL(-1) for furosemide and triamterene, respectively.

Determination of triamterene and leucovorin in biological fluids by UV derivative-spectrophotometry and partial least-squares (PLS-1) calibration.

The resolution of binary mixtures of triamterene (TAT) and leucovorin (LV) by application of first-derivative spectrophotometry and by application of Partial Least Squares calibration (PLS-1) was performed. Triamterene is determined in presence of leucovorin directly in the absorption spectra at 358 nm, and leucovorin is determined in the first-derivative spectra at 305.6 nm, zero-crossing of the triamterene. The mean recovery values in urine samples were 102 and 97% for TAT and LV, respectively. Partial Least Squares calibration (PLS-1) multivariate calibration of spectrophotometric data, have been applied to the determination of these compounds in serum and in urine without pretreatment of the samples. The absorption spectra of samples of serum or urine, spiked with triamterene and/or leucovorin, were used to perform the optimization of the calibration matrices by PLS-1 method. Mean recovery values were of 107 and 108% for TAT and LV in serum samples, and 98 and 91% for TAT and LV in urine samples.

The effect of diflunisal on the elimination of triamterene in human volunteers.

A major metabolic pathway for triamterene (a potassium sparing diuretic) is aromatic hydroxylation followed by sulphate conjugation. Diflunisal (a salicylate anti-inflammatory agent) also undergoes sulphate conjugation of its phenolic group as a major pathway. We investigated the possible effect of diflunisal on the elimination of triamterene (competition for phenolic sulphonation) in six healthy volunteers by studying the disposition of single doses of triamterene (100 mg) taken alone and in the presence of steady-state levels of diflunisal. Diflunisal coadministration (500 mg b.i.d.) had no effect on the pharmacokinetics of triamterene itself. However, plasma AUC of p-hydroxytriamterene sulphate was greater (4.6 times), and its renal clearance lower (0.24 times), in the presence of diflunisal. There was no change in the formation clearance or protein binding of p-hydroxytriamterene sulphate in the presence of diflunisal. The data point to competition for renal excretory pathways rather than sulphonation capacity. This interaction could have clinical relevance since p-hydroxytriamterene sulphate is pharmacologically active.

[The pharmacokinetics of different drug forms of nifedipine when used singly and in a course as monotherapy and in combination with Cordanum and triampur preparations in patients with arterial hypertension]. / Izuchenie farmakokinetiki razlichnykh lekarstvennykh form nifedipina pri odnokratnom i kursovom primenenii v monoterapii i v sochetanii s preparatami kordanum i triampur u bol'nykh s arterial'noi gipertoniei.

Pharmacokinetics of three drugs derived from nifedipine: corinfar, corinfar retard, and SL adalate in the cases of a single and course administration in patients with arterial hypertension and the effect of cordanum and triampur on pharmacokinetics of corinfar retard in combined repeated administration have been studied. The studies were carried out in 6 groups of patients with arterial Hypertension, each group included 10 patients. Nifedipine concentration in blood plasma was determined using a special HPLC procedure within 24 h after administration of the drugs at a dose 20 mg. A pharmacokinetic characteristics of new drug adalate SL with two-step liberation of nifedipine. A possibility of autoinhibition was noted for corinfar and adalate SL in course therapy. A conclusion was made that cordanum and triampur did not affect the pharmacokinetics of corinfar retard.

[A pharmacokinetic study of korinfar-retard in monotherapy and in combination with cordanum and triampur in patients with arterial hypertension]. / Izuchenie farmakokinetiki korinfara-retard v monoterapii i v sochetanii s kordanumom i triampurom u bol'nykh s arterial'noi gipertenziei.

The long-acting corinfar formulation, corinfar-retard tablets, 20 mg (AWD, Germany), was studied for pharmacokinetics in single and course use in 40 patients with arterial hypertension, as well as for its effects of cordanum and triampur. Patients' plasma corinfar was measured by high performance liquid chromatography. There were no changes in the pharmacokinetics of the agent when it was used in its course use. Cordanum and triampur was demonstrated to have no effects on the pharmacokinetics of corinfar during their application.

The identification and quantitation of triamterene in blood and urine from a fatal aircraft accident victim.

Triamterene, a diuretic drug used in combination with other drugs for the treatment of hypertension, was found in the blood and urine of a fatal aircraft accident victim. The extraction and identification of triamterene is difficult. It exhibits poor extraction efficiency using some standard base-extraction procedures, and the parent drug is unsuitable for analysis using gas chromatography. In this case, a thin-layer chromatography solvent system and high-performance liquid chromatography were used to identify and quantitate triamterene in blood and urine. Triamterene is a strong absorber in the ultraviolet region and has an unusual UV spectrum, which simplifies the identification and quantitation of this substance by high-performance liquid chromatography.

Absorption and disposition of a new low-dose combination formulation of hydrochlorothiazide and triamterene.

Two studies are reported that assess the bioequivalence of a new half-strength drug combination containing 25 mg hydrochlorothiazide and 37.5 mg triamterene compared to a full-strength formulation containing 50 mg hydrochlorothiazide and 75 mg triamterene. The first study (I) compared the absorption and disposition of the two drugs after administration of two tablets of the half-strength product as a single dose compared to a single dose of the full-strength product. The second study (II) assessed the bioavailability of the new product given as a single tablet on two occasions separated by an interval of 12 h compared to the full-strength product given as a single dose. Urine parameters in the first study indicated bioequivalence of the half-strength to the full product for both rate and extent of absorption. When given in divided doses, the half-strength product demonstrated bioequivalence to the full-strength product for extent of absorption. Additional data from the second study suggest that absorption of triamterene is greater when given in smaller divided doses and when given at night.

Clinical experience with a new combination formulation of triamterene and hydrochlorothiazide (Maxzide) in patients with mild to moderate hypertension.

The results of an investigation to assess the clinical responses of patients with mild to moderate hypertension to a new combination formulation containing 75 mg triamterene and 50 mg hydrochlorothiazide are reported. One hundred fifty-six subjects entered the investigation. Subjects were divided into three groups, depending on whether they took two (group 1) or four capsules per day of a currently available formulation of triamterene and hydrochlorothiazide (Dyazide), or no antihypertensive medication prior to the start of the study. These medications were continued for an additional two weeks to generate baseline data. Thereafter, subjects received one tablet of the new combination formulation for four weeks. Seventy of the 156 participants received the new formulation for an additional period of at least 20 weeks. Observations during the study included sitting and standing pulse and blood pressure, weight, and serum electrolytes, uric acid, creatinine, and blood urea nitrogen levels. The results of the investigation indicated that subjects transferred to the new combination drug maintained normal serum electrolyte values, including potassium, with no or minor changes in the levels of uric acid, creatinine, and blood urea nitrogen. Reductions in systolic and diastolic blood pressure were observed in all three study groups, including subjects receiving two or four capsules of Dyazide per day in the two-week baseline period. We conclude that mild to moderately hypertensive subjects taking no medication or either two or four capsules of Dyazide per day may be transferred safely to the new combination product of triamterene and hydrochlothiazide.

Liquid chromatographic analysis of triamterene and its major metabolite, hydroxytriamterene sulfate, in blood, plasma, and urine.

The first rapid and highly sensitive high-performance liquid chromatographic (HPLC) assay for triamterene, hydroxytriamterene, and hydroxytriamterene sulfate is reported. Plasma samples were processed by protein precipitation, while urine was used untreated. Three different solvent systems were used to analyze (a) triamterene in plasma (30% acetonitrile, pH 4.0; internal standard: furosemide; sensitivity limit: 1 ng/mL); (b) hydroxytriamterene and hydroxytriamterene sulfate in plasma (12% acetonitrile, pH 5.5; internal standard: cefamandole; sensitivity limits: 20 and 2 ng/mL, respectively) and (c) triamterene, hydroxytriamterene, and hydroxytriamterene sulfate in urine (13% acetonitrile, pH 5.3; internal standard: hydroflumethiazide; sensitivity limits: 0.04 microgram/mL, 0.5 microgram/mL, and 0.1 microgram/mL, respectively). Fluorescence detection of compounds was performed at 365-nm excitation and 440-nm emission wavelengths. Recovery of triamterene and its metabolites from plasma was complete, and calibration curves were linear. Intraday variation was less than 6% except for the lowest plasma concentration. The assay procedure has already been used in several pharmacokinetic studies.

Triamterene kinetics and dynamics in cirrhosis.

Triamterene is extensively metabolized by the liver and undergoes important presystemic elimination in normal subjects after oral doses. We examined triamterene disposition in eight healthy controls and seven patients with cirrhosis and ascites. A specific and sensitive HPLC assay was used to measure concentrations of triamterene and of its major metabolite p-hydroxy-triamterene sulfate (OH-T-S). Apparent oral clearance of triamterene in controls averaged 1617 +/- 219 ml/min. Plasma concentration of OH-T-S was 7.2 +/- 1.1 times that of the parent compound (estimated by the ratio AUCOH -T-S/ AUCtriamterene ). Urinary recovery of OH-T-S accounted for 45% of the triamterene dose. There was 92% reduction in apparent oral clearance of triamterene (134 +/- 42 ml/min) in patients with cirrhosis. The ratio AUCOH -T-S/ AUCtriamterene fell to 0.55 +/- 0.2, and urinary recovery of OH-T-S accounted for only 15% of the dose. These changes in triamterene kinetics in patients with cirrhosis resulted in prolongation of its natriuretic effect, which lasted for up to 48 hr, whereas it was only 8 hr in the controls. These observations reinforce the concept that cirrhosis is associated with a markedly impaired disposition of drugs that have a large first-pass effect.

[Pharmacokinetics of triamterene in healthy subjects and patients with liver and kidney function disorders]. / Pharmakokinetik von Triamteren bei Probanden und Patienten mit Leber- und Nierenfunktionsstörungen.

The knowledge about the pharmacokinetics of triamterene (TA) was limited until recently. The metabolic pathway of TA is the formation of p-hydroxytriamterene (OH-TA), which is subsequently conjugated with active sulfate to form p-hydroxytriamterene sulfuric acid ester (OH-TA-ester). The phase-II-metabolite is surprisingly pharmacologically active. TA and its metabolites were measured concomitantly by a specific and sensitive tlc-method. The i.v. kinetics of TA were determined after application of a newly developed lactic acid solution of the drug. Comparing these data with results after oral application of TA the bioavailability of TA was 52% and the extent of absorption 83%. The bioavailability of different dosage forms was correlated with in vitro-tests. In liver disease the pharmacokinetics of TA are markedly altered. While in cirrhosis the hydroxylation of TA was decreased, the biliary excretion of this agent was strongly reduced in hepatitis. In renal disease the excretion of TA and OH-TA-ester was reduced proportional to the reduction of endogenous creatinine clearance. In older patients the elimination of TA was impaired.

Pharmacokinetics of triamterene.

The knowledge about the pharmacokinetics of triamterene (TA) was limited until recently. The metabolic pathway of TA is the formation of p-hydroxytriamterene (OH-TA), which is subsequently conjugated with active sulfate to form p-hydroxytriamterene sulfuric acid ester (OH-TA-ester). The phase-II-metabolite is surprisingly pharmacologically active. TA and its metabolites were measured by a specific and sensitive tlc-method concomitantly. The i.v. kinetics of TA were determined after application of a newly developed lactic acid solution of the drug. Comparing these data with results after oral application of TA the bioavailability of TA was 52% and the extent of absorption 83%. The bioavailability of different dosage forms was correlated with in vitro tests. In liver disease the pharmacokinetics of TA are markedly altered. While in cirrhosis the hydroxylation of TA was decreased, the biliary excretion of this agent was strongly reduced in hepatitis. In renal disease the excretion of TA and OH-TA-ester was reduced according to endogenous creatinine clearance. In older patients the elimination of TA was impaired.

Pharmacokinetics of triamterene and its metabolite in man.

The pharmacokinetic profiles of triamterene and hydroxytriamterene sulfuric acid ester, the major metabolite of triamterene, were studied in six normal male volunteers using a newly developed specific HPLC analytical method. Following a 100 mg oral dose of triamterene, the plasma concentration time course of the sulfate conjugate parallels that of triamterene in all subjects, but concentrations of the metabolite were more than 10 times higher than unchanged triamterene concentrations at identical sampling times. Interestingly, the renal clearance of the sulfate conjugate was less than that of triamterene. These characteristic features of triamterene disposition were fitted to a compartment model incorporating a first-pass metabolic process. Unbound fractions of triamterene and metabolite in plasma were 0.39 and 0.10 (mean of 6 subjects), respectively. The low unbound fraction of the metabolite in plasma most probably accounts for the low renal clearance of the sulfate conjugate as compared with triamterene.

Altered hydroxylation rate of triamterene in patients with liver cirrhosis.

After oral administration of triamterene to four patients with liver cirrhosis the triameterene (TA) metabolism was altered. The ratio of AUCs of p-hydroxy-triamterene-sulfuric acid ester (OH-TA-ester)/triamterene (TA) was 1.0 +/- 1.0 in cirrhotic patients compared with 7.5 +/- 3.9 in control patients (p less than 0.025). Cumulative urinary excretion of TA was higher and that of OH-TA-ester lower in patients with liver cirrhosis compared with patients without liver disease. The results indicate that the metabolism of TA is influenced by liver cirrhosis. The extent of impairment of the metabolism of TA is correlated to reduced galactose-elimination capacity. This may be an indicator of reduced redox potential of the liver cell.