ABSTRACT
The purpose of the present study was to develop a standard protocol for imidapril hydrochloride bioequivalence testing. For this reason, a specific LC-MS method was developed and validated for the determination of imidapril in human plasma. A solid-phase extraction cartridge, Sep-pak C18, was used to extract imidapril and ramipril (an internal standard) from deproteinized plasma. The compounds were separated using a XTerra MS C18 column (3.5 microm, 2.1 x 150 mm) and acetonitrile-0.1% formic acid (67:33, v/v) adjusted to pH 2.4 by 2 mmol/L ammonium formic acid, as mobile phase at 0.3 mL/min. Imidapril was detected as m/z 406 at a retention time of ca. 2.3 min, and ramipril as m/z 417 at ca. 3.6 min. The described method showed acceptable specificity, linearity from 0.5 to 100 ng/mL, precision (expressed as a relative standard deviation of less than 15%), accuracy, and stability. The plasma concentration-versus-time curves of eight healthy male volunteers administered a single dose of imidapril (10 mg), gave an AUC12hr of imidapril of 121.48 +/- 35.81 ng mL(-1) h, and Cmax and Tmax values of 32.59 +/- 9.76 ng/mL and 1.75 +/- 0.27 h. The developed method should be useful for the determination of imidapril in plasma with sufficient sensitivity and specificity in bioequivalence study.
Subject(s)
Angiotensin-Converting Enzyme Inhibitors/pharmacokinetics , Imidazolidines/pharmacokinetics , Administration, Oral , Angiotensin-Converting Enzyme Inhibitors/administration & dosage , Angiotensin-Converting Enzyme Inhibitors/blood , Area Under Curve , Biological Availability , Chromatography, High Pressure Liquid , Drug Stability , Humans , Imidazolidines/administration & dosage , Imidazolidines/blood , Male , Reproducibility of Results , Sensitivity and Specificity , Spectrometry, Mass, Electrospray Ionization , TabletsABSTRACT
The purpose of the present study was to develop a standard protocol for loperamide hydrochloride bioequivalence testing. For this purpose, a simple rapid and selective LC-MS method utilizing a single quadrupole mass spectrometer was developed and validated for the determination of loperamide hydrochloride in human plasma, and we followed this with a bioavailability study. Methyl tert-butylether (MTBE) was used to extract loperamide hydrochloride and ketoconazole (internal standard (IS)) from an alkaline plasma sample. LC separation was performed on a Zorbax RX C18 column (5 microm, 2.1 mm x 150 mm) using acetonitrile-water-formic acid (50:50:0.1 (v/v)) as a mobile phase. The retention times of loperamide hydrochloride and IS were 1.2 and 0.8 min, respectively. Quadrupole MS detection was by monitoring at m/z 477 (M + 1) corresponding to loperamide hydrochloride and at m/z 531 (M + 1) for IS. The described assay method showed acceptable precision, accuracy, linearity, stability, and specificity. The bioavailability of loperamide hydrochloride was evaluated in eight healthy male volunteers. The following pharmacokinetic parameters were elucidated after administering a single dose of four 2mg capsules of loperamide: the area under the plasma concentration versus time curve from time 0 to 72 h (AUC72 h) 19.26 +/- 7.79 ng h/ml; peak plasma concentration (Cmax) 1.18 +/- 0.37 ng/ml; time to Cmax (Tmax) 5.38 +/- 0.74 h; and elimination half-life (t1/2) 11.35 +/- 2.06 h. The developed method was successfully used to study the bioavailability of a low dose (8 mg) of loperamide hydrochloride.
