Preconcentration of indapamide from human urine using molecularly imprinted solid-phase extraction.

A simple, sensitive, and selective molecularly imprinted solid-phase extraction and spectrophotometric method has been developed for the clean-up and preconcentration of indapamide from human urine. Molecularly imprinted polymers were prepared by a non-covalent imprinting approach using indapamide as a template molecule, 2-(trifluoromethyl) acrylic acid as a functional monomer, ethylene glycol dimethacrylate as a crosslinker, N,N-azobisisobutyronitrile as a thermal initiator and acetonitrile as a porogenic solvent. A non-imprinted polymer was also prepared in the same way, but in the absence of template. Molecularly imprinted polymer and non-imprinted polymer sorbents were dry-packed into solid-phase extraction cartridges. Eluates from cartridges were analyzed using a spectrophotometer for the determination of indapamide by referring to the calibration curve in the range 0.14-1.50 µg/mL. Preconcentration factor, limit of detection, and limit of quantification were 16.30, 0.025 µg/mL, and 0.075 µg/mL, respectively. A relatively high imprinting factor (9.3) was also achieved and recovery values for the indapamide spiked into human urine were in the range of 80.1-81.2%. In addition, relatively low within-day (0.17-0.42%) and between-day (1.1-1.4%) precision values were obtained as well. The proposed molecularly imprinted solid-phase extraction and spectrophotometric method was successfully applied to selective extraction, preconcentration, and determination of indapamide from human urine samples.

Quantitative determination of indapamide in pharmaceuticals and urine by high-performance liquid chromatography with amperometric detection.

A high-performance liquid chromatographic method with amperometric detection for the determination of the diuretic indapamide using a muBondapak C18 column is developed. The mobile phase consists of an acetonitrile-water mixture (45:55, 5 mM) in KH2PO4-K2HPO4 (pH 4.0). The compound is monitored at +1200 mV with an amperometric detector equipped with a glassy carbon working electrode. A liquid-liquid or solid-liquid extraction is performed prior to chromatographic analysis to avoid the interferences found in urine matrix. Percentages of recovery are 88.3 +/- 5.6 and 82.9 +/- 7.8 for liquid-liquid and solid-liquid extraction, respectively. The developed method has a linear concentration range from 25 to 315 ng/mL with a reproducibility in terms of relative standard deviation of 4% for a concentration level of 0.5 microgram/mL and a quantitation limit of 1 ng/mL. The method is applied to the determination of indapamide in tablets and urine obtained from hypertensive patients after the ingestion of Tertensif (indapamide 2.5 mg).

Bioavailability and pharmacokinetics of a fixed combination of delapril/indapamide following single and multiple dosing in healthy volunteers.

The study objective was to obtain detailed information on the bioavailability and pharmacokinetics of the new fixed combination of delapril and indapamide following single and multiple dosing. For this reason, the study was performed in two parts, separated by a medication-free period of at least 7 days. In the single dose part, one tablet, containing 30 mg delapril and 2.5 mg indapamide, was administered to 12 male volunteers; in the multiple dose part, the volunteers received one tablet of the test preparation, once daily over 7 days. Following single and on the last day of the multiple dosing regimen, blood samples were withdrawn and serum concentrations of delapril and its metabolites M1, M2 and M3 and whole blood concentrations of indapamide were quantified by means of HPLC methods. In addition, urine samples were collected following single and multiple dosing for evaluation of the cumulative amount of delapril and its metabolites M1-M3 excreted in urine. For the area under the curve, calculated from time 0 to infinity (AUC(0-infinity)) the study revealed, following single dosing, mean values of delapril and its metabolites M1, M2 and M3 of 281, 2178, 739 and 716 h.ng/ml, respectively; for indapamide the mean value was 1597 h.ng/ml. The corresponding mean values found after multiple dose administration were 272, 2071, 857 and 598 h.ng/ml for delapril and its metabolites, respectively and 1536 h.ng/ml for indapamide. Evaluation of the cumulative amount of delapril and its metabolites M1-M3 excreted in urine (Ae) demonstrated mean values following single dosing (observation period 36 h) of 705, 4521, 454 and 4203 micrograms, respectively; the corresponding values after multiple dose administration (observation period 24 h) of the test preparation were 655, 4679, 469 and 4801 micrograms, respectively. The most important pharmacokinetic parameters AUC(0-infinity) and Ae were statistically compared by analysis of variance (ANOVA) and 90% confidence intervals were calculated. It may be concluded from the results of this study, that the bioavailability and pharmacokinetic parameters of the test preparation after single dosing and after multiple doses correspond well. The undesired side effects observed are known to occur after administration of the test preparation. The occurrence was a little more frequent after multiple dose application in comparison with the single dose administration.

The disposition of 14C-indapamide in man.

The metabolism of 14C-indapamide labeled in the indoline ring was determined after a single oral administration of a solution (4.99 mg, 90.47 microCi) to four fasted adult male volunteers. 14C-Indapamide was rapidly absorbed, and peak blood concentrations of radioactivity occurred by 0.5 hour in three subjects and at 2 hours in one subject. The mean elimination half-lives of total radioactivity were 27.0 hours in blood and 24.5 hours in plasma. The concentration of total radioactivity in blood was 5.7 times greater than in plasma, indicating extensive binding to red blood cells. Unchanged drug, as analyzed in one subject, reached a peak concentration by 0.5 hour, and had a blood half-life of 15.8 hours. Radioactivity was primarily excreted in the urine, and more than 50 per cent of the administered radioactivity was eliminated by this route in 48 hours. By eight days, 92.8 per cent of the radioactivity was recovered, with 70.3 per cent in the urine and 22.5 per cent in the feces. 14C-Indapamide was shown to be extensively metabolized, with only 7.3 per cent of the dose excreted as unchanged drug in the urine. Systemic and renal clearances of total radioactivity were 12.8 +/- 1.3 and 8.6 +/- 0.8 ml/min, respectively, while the renal clearance of unchanged indapamide, determined for one subject, was substantially lower (1.71 ml/min).

Fluorometric assay for urinary indapamide.

A sensitive fluorescence method for the determination of indapamide was developed. Reaction of indapamide with sodium hydroxide at 100 degrees yielded a fluorescent product, and addition of formaldehyde to the fluorescent product increased its fluorescence intensity by a factor of three. The assay is sensitive to levels of indapamide of 0.025 microgram/ml in an aqueous solution, and a linear response between 0.025 and 2.0 microgram/ml was observed. The procedure was adapted to the analysis of intact indapamide in urine. Concentrations of indapamide of 0.05 microgram/ml can be detected in dogs given 20 mg of the drug.