LC-MS/MS determination of 4-hydroxynimesulide, an active metabolite of nimesulide and application to bioequivalence study in Indian subjects

A simple and highly sensitive bioanalytical method was developed and validated for simultaneous quantification of nimesulide (NSD) and its active metabolite 4-hydroxy-nimesulide (M1) in human plasma by liquid chromatography-tandem mass spectrometer (LC-MS/MS) and applied in a bioequivalence study performed on Indian subjects. The bioanalytical method was carried out by LC-MS/MS with celecoxib (CXB) as an internal standard (IS) using liquid-liquid extraction technique. The chromatographic separation was performed on a reversed-phase Agilent eclipse plus C18 (75 mm × 4.6 mm, particle size 3.5 µm) column with a mobile phase of acetronitrile and water containing 5 mM ammonium formate (9:1, v/v). Method validation and clinical sample were analysed as per USFDA and EMA guidelines and results met the acceptance criteria. The lower limit of quantitation of NSD and M1 was found 10 ng/mL with a large linearity range from 10 to 6000 ng/mL for both NSD and M1 using only 100 µL of plasma and reported no matrix effect. The multiple reaction monitoring transitions of m/z 307.20 → 229.20, m/z 323.00 → 245.00 and m/z 380.20 → 316.20 were used to measure NSD, M1 and CXB (IS), respectively. The assay method was successfully applied for the simultaneous quantification of both NSD and M1 in plasma samples after oral administration of nimesulide 100 mg tablet in healthy human subjects.

Limustin®, a non-innovator tacrolimus formulation, yields reduced drug exposure in pediatric renal transplant recipients

The aim of this study was to evaluate the bioavailability of two oral tacrolimus formulations, the innovator Prograf(®) and a formulation commercialized in Mexico with the brand name Limustin(®), in children. Stable Mexican pediatric renal transplant recipients received the product authorized by their social security provider, being either Prograf(®) or Limustin(®). At steady state, blood samples were drawn and tacrolimus blood concentration against time curves was constructed. CYP3A5 genotype was also determined. There was no significant difference in dose or in trough concentrations between formulations. However, AUC and Cmax were significantly higher with Prograf(®). The lower tacrolimus bioavailability with Limustin(®) was observed in both expressers and non-expressers of the functional CYP3A5 protein. Dose-normalized AUC values in expressers were 12.7 ± 11.9 and 48.7 ± 20.4 ng·h/mL/mg for Limustin(®) and Prograf(®), whereas in non-expressers, dose-normalized AUC was 54.4 ± 49.1 and 110.4 ± 42.9 ng·h/mL/mg for Limustin(®) and Prograf(®), respectively (p < 0.05). Pharmaceutical quality analysis showed that Limustin(®) dissolution at 120 min was 31.1 ± 6.2% while Prograf(®) dissolution was 100 ± 4.8%. Furthermore, the mean percentage of labeled amount of Limustin(®) and Prograf(®) was 91.0 ± 3.1% and 100.0 ± 0.7%, respectively. Hence, Limustin(®) exhibits pharmaceutical characteristics dissimilar to the innovator that likely explain the reduced tacrolimus exposure in children. We consider Limustin(®) is not adequate for pediatric use.

Characterization of a quaternary liquid system improving the bioavailability of poorly water soluble drugs

The aim of this work is the characterization of the quaternary system composed of water, triacetin (oil), ethanol (alcohol), and Tween 80 (surfactant), as its results enable the enhancement of the bioavailability of nimesulide, a poorly water soluble nonsteroidal antiinflammatory drug widely employed in the pharmaceutical field. Particular attention is devoted to the surfactant-free ternary system, as it proved able to solubilize nimesulide as well, and the absence of a surfactant is desirable in order to keep the preparation as tolerable as possible. Both bulk and interfacial properties of this system are investigated, and a mathematical model to calculate the interface composition of a three-component two-phase system is developed. This model is based on Gibbs' theory on interfaces, which considers an arbitrary mathematical dividing surface so that the two phases continue uniformly up to it, although interface regions have no sharply defined boundaries. We find that both the quaternary and the ternary systems investigated show a miscibility lacuna and that, in the surfactant-free ternary system, an increase of the ethanol weight fraction is reflected as an impoverishment of the ethanol interfacial molar fraction.