Determination of 3-α-hydroxytibolone in human plasma by LC-MS/MS: application for a pharmacokinetic study after administration of a tibolone formulation.

A new method was developed for the quantitation of 3-α-hydroxy tibolone, in human plasma, after oral administration of a tablet formulation containing tibolone (2.5 mg). 3-α-Hydroxy tibolone was extracted by a liquid-liquid procedure, using cyproterone acetate as internal standard and chlorobutane as extraction solvent. After extraction, samples were submitted to a derivatization step with p-toluenesulfonyl isocyanate. A mobile phase consisting of acetonitrile and water (72:28 v/v) was used and chromatographic separation was achieved using Agilent XDB C18 column (100 × 4.6 mm i.d.; 5 µm particle size), at 40°C. Mass spectrometric detection was performed using atmospheric pressure chemical ionization in negative mode for 3-α-hydroxy tibolone and in positive mode for cyproterone acetate. The fragmentation transitions were m/z 510.2 → m/z 170.1 and m/z 417.0 → m/z 357.1 for 3-α-hydroxy tibolone and cyproterone acetate, respectively. Calibration curves were constructed over the range 100-30,000 pg/mL and the method was shown to be specific, precise and accurate, with a mean recovery rate of 94.2% for 3-α-hydroxy tibolone. No matrix effect or carry-over was detected in the samples. The validated method was applied in a pharmacokinetic study with a tibolone formulation in healthy female volunteers.

Quantitation of glucosamine sulfate in plasma by HPLC-MS/MS after administration of powder for oral solution formulation.

A rapid method for the quantification of glucosamine in human plasma using high-performance liquid chromatography coupled to tandem mass spectrometry was developed and validated. The sample preparation includes a simple deproteinization step, using D-[1-¹³C] glucosamine hydrochloride as an internal standard. Chromatographic separation was performed on an ACE Ciano column using isocratic elution with acetonitrile and aqueous 2 mM ammonium acetate containing 0.025% formic acid (80:20). Selected reaction monitoring was performed using the transitions m/z 180.1 → m/z 72.1 and m/z 181.0 → m/z 74.6 to quantify glucosamine and internal standard, respectively. The method was validated and proved to be linear, accurate and precise over the range 50-5000 ng/mL of glucosamine. Recovery rates higher than 90% were obtained for both glucosamine and internal standard. No matrix effect was detected in the samples. The validated method was successfully applied to a pharmacokinetic study after oral administration of a powder for oral solution formulation containing glucosamine sulfate.

Simultaneous quantitation of levodopa and 3-O-methyldopa in human plasma by HPLC-ESI-MS/MS: application for a pharmacokinetic study with a levodopa/benserazide formulation.

A sensitive and simple method was developed for the quantitation of levodopa and its metabolite 3-O-methyldopa, in human plasma, after oral administration of tablet formulations containing levodopa (200 mg) and benserazide (50 mg). The analytes were extracted by a protein precipitation procedure, using carbidopa as an internal standard. A mobile phase consisting of 0.2% formic acid and acetonitrile (94:6, v/v) was used and chromatographic separation was achieved using ACE C(18) column (50 mm×4.6 mm i.d.; 5 µm particle size). Selected reaction monitoring was performed using the fragmentation transitions m/z 198→m/z 107, m/z 212→m/z 166 and m/z 227→m/z 181 for levodopa, 3-O-methyldopa and carbidopa, respectively. Calibration curves were constructed over the range 50.0-6000.0 ng/mL for levodopa and 25.0-4000.0 ng/mL for 3-O-methyldopa. The method shown to be specific, precise, accurate and provided recovery rates higher than 85% for all analytes. No matrix effect was detected in the samples. The validated method was applied in a pharmacokinetic study with a levodopa/benserazide tablet formulation in healthy volunteers.