simple and sensitive HPLC method for fluorescence quantitation of doxorubicin in micro-volume plasma: applications to pharmacokinetic studies in rats

A validated HPLC method was developed to determine the doxorubicin concentration in a small volume of rat plasma [60 microL] with convenient fluorescence detection. Sample preparation includes a simple one-step liquid-liquid extraction using a minimum amount of organic solvent, with extraction recovery more than 95%. The analysis was accomplished using PerfectSil C18 column maintained at 35 [degree]C and a mobile phase consisted of acetonitrile and water [32:68, v/v; pH=2.6]. The flow-rate was kept at 1 mL/min and the column effluent was monitored with a fluorescence detector at an excitation and emission wavelength of 470 and 555 nm, respectively. The detection limit was 5 ng/mL. No analytical interference was observed from endogenous components in the rat plasma. This method was feasibly applied to the pharmacokinetic study of 5 mg/Kg of doxorubicin after the intravenous administration to rats

Preparation and characterization of stable Nanoliposomal formulation of fluoxetine as a potential adjuvant therapy for drug-resistant tumors

Chemotherapy research highly prioritizes overcoming the multidrug resistance [MDR] in human tumors. Liposomal formulation of fluoxetine, as a fourth generation chemosensitizer, was constructed and characterized for percent entrapment, release profile, morphology, particle size, zeta potential and stability. Liposomes were prepared using different active loading techniques. The influence of different formulation variables such as loading methodology, type of main lipid, addition of PEGylated lipid and cholesterol percentage was evaluated to achieve required entrapment efficiency, in vitro release behavior and stability. The studied parameters had significant effect on physicochemical characteristics of the nanocarriers. High fluoxetine encapsulation efficiency [83% +/- 3%] and appropriate particle size [101 +/- 12 nm] and zeta potential [-9 +/- 2 mv] were achieved for PEGylation liposomes composed of DSPE-PEG, DSPC and cholesterol at respective molar ratio of 5:70:25. An in vitro fluoxetine release of about 20% in 48 h was observed from optimum formulation. Atomic force microscopy [AFM] studies confirmed homogeneous distribution of particles and spherical shape with smooth surface. The optimum formulation was stable for 9 days when incubated at 37 [degree sign]C. The results of this study are very encouraging for application of the developed fluoxetine liposomal formulation in drug-resistant tumor models

Metabolite parameters as an appropriate alternative approach for assessment of bioequivalence of two verapamil formulations

A bioequivalence study of two verapamil formulations [generic verapamil tablets and Isoptin tablets] was performed by comparing pharmacokinetic parameters of the parent drug and its major metabolite, norverapamil following a single dose administration of 80 mg verapamil hydrochloride in 22 healthy volunteers according to a randomized, two-period, crossover-design study. Moreover, the feasibility of proving bioequivalence of verapamil oral dosing form by means of norverapamil pharmacokinetic parameters was evaluated. Concentrations of verapamil and norverapamil were quantified in plasma using a validated high-performance liquid chromatography [HPLC] with fluorescence detection. The 90% CIs for the log-transformed ratios of verapamil C[max] [maximum plasma concentration] and AUC [area under the plasma concentration-versus-time curve from time zero to the infinity] were 73 to 101 and 80 to 103. respectively. Similarly, the corresponding ranges for norverapamil were 80-100 and 84-103, respectively. According to the parent drug data, the 90% confidence intervals around the geometric mean ratio of AUC happened to fit within preset bioequivalence limits of 80-125%, whereas those for C did not. The 90% confidence intervals for both C[max] and AUC of norverapamil met preset bioequivalence limits. The AUC and C[max] of metabolite, when compared to parent drug, showed a much lower degree of variability and the 90% confidence intervals of the metabolite were therefore narrower than those of the parent drug. These observations indicate that bioequivalence studies using metabolite, norverapamil. could be a more suitable and preferable approach to assess bioequivalence of verapamil formulations due to its much lower variability and therefore lower number of volunteers that are required to conduct the study