Many registration agencies and other organizations define how to calculate the elimination rate constant (kel) value. No validation procedures have been introduced to verify the correct selection of the concentration-time (C-T) points used for the kel calculation. The purpose of this paper is to discover whether kel analysis can be subjected to the condensed validation procedure and what acceptance criteria should be adopted for such a procedure. For the analysis, data collected during bioequivalence studies of 4 drugs were selected, including 2 highly lipophilic drugs (itraconazole, atorvastatin) and 2 weakly lipophilic drugs (trimetazidine, perindopril). Pharmacokinetic calculations were performed with the use of WinNonlin Professional v 5.3. Internal validation of the kel analysis using leave-one-out cross-validation was performed. The present analysis proves that the C-T selection process for the kel calculations cannot be automated. In each of the analysed data series there were such C-T sequences that did not meet even one of the validation criteria. This paper proposes 3 validation criteria which need to be met in order to confirm the optimal selection of C-T data to calculate kel: Q 2≥0.6, R2≥ 0.85, Q 2-R2<0.3, were Q 2 - squared cross-validated correlation coefficient, R2 - coefficient of determination). Application of the validation procedure for the kel analysis under discussion proves the accuracy of the calculations, even if repeated kel analysis is based on a different sequence of points in the elimination phase.

To evaluate the changes in myocardial enzymes and plasma epirubicin concentration following administration by micro-pump (MP) and intravenous drip (ID) in breast cancer patients.11 self-controlled breast cancer patients were recruited for a trial with epirubicin administration by MP for 48 h and by ID for 1 h during 2 cycles of treatment. Plasma concentration of epirubicin at different time points was determined using LC-MS/MS. The levels of myocardial enzymes before and after chemotherapy were compared. Another group of patients receiving epirubicin by ID (n=4) or MP (n=9) were monitored for 4 months.8 patients completed the self-controlled study. The peak concentration of epirubicin in the MP group and the ID group were 21.84±18.85 ng/mL and 294.80±225.54 ng/mL, respectively. The MP group had a longer duration (54~60 h) of plasma concentration of epirubicin not less than 10 ng/mL than that of the ID group (8~14 h). There was significant difference for the alteration of myocardial enzymes before and after chemotherapy (p<0.05) in the ID group, whereas the MP group showed no significant difference (p>0.05). The increased range of myocardial enzymes after chemotherapy in the ID group was larger than that of the MP group and the difference was significant (p<0.05). There is an increased cardiotoxicity in patients receiving epirubicin by ID during the 4-month trial.Administration of epirubicin by MP maintained an effective drug concentration for a longer period of time than by ID. The higher peak plasma concentration observed following epirubicin administration by ID may lead to cardiac toxicity.

Since the first non-peptide Ang II receptor antagonist was originally reported, it has become the most common target in the development of new treatments for hypertension. In recent years, all components of the classical RAS have been reported in the prostate, these results suggest the possibility that ARB is a novel therapeutic class of agents for prostate cancer. In this study, a new compound 2-(4-((2-propyl-5-nitro-1H-benzo[d]imidazol-1-yl) methyl)-1H-indol-1-yl) benzoic acid was synthesized and evaluated as a novel angiotensin II AT1 receptor antagonist by radioligand binding assays, anti-hypertensive assays in vivo and oral acute toxicity test. MTT assays and tests in nude mice were used to demonstrate its anti-tumor activity. This new compound showed high affinity to AT1 receptor and anti-hypertensive activity in spontaneously hypertensive rats and renal hypertensive rats. Moreover, in human prostate cancer cells and in athymic nude mice bearing human prostate cancer cells, we observed this new compound had an efficient antiproliferative activity in vitro and anti-tumor activity in vivo. The preliminary pharmacological characteristics with oral acute toxicity test suggested that this new compound can be considered as a candidate for both anti-hypertensive and anti-tumor drug.

Nicotine, the main pharmacologically active component in tobacco and cigarette, has some toxic effects and also high potential for addiction. In this study, the effect of artichoke (Cynara scolymus L.) and zeolite nano-materials on urinary excretion of nicotine and consequently elimination of systematically absorbed nicotine was investigated. A simple, valid and highly sensitive high performance liquid chromatography method has been developed for determination of nicotine in rat urine according to guidelines for bioanalysis.It was found that nano-zeolites can cause increase in urinary concentration of nicotine due to its high surface adsorption. Artichoke leaf extract can cause increase in urinary excretion of nicotine in longer post administration times. It was observed that co-administration of nanozeolites and the leaf extract has the synergetic effect on increasing the urinary excretion of nicotine.

A simple HPLC with fluorescence detection method was developed for determination and pharmacokinetic study of Etoposide in dog plasma.Plasma sample pretreatment involved liquid-liquid extraction of 500 µL plasma. The chromatographic separation was carried out on a Gemini C18 column with a mixture of methanol (A) and water (B) (0~5 min, volume of A was 45-50%, 5~10 min, volume of A was 50-90%) used as mobile phase at a flow rate of 0.4 ml/min.These results indicated that the accuracy and precision of the current assay were within the recommendations for assay validation as stipulated in "Guidance for Industry: Bioanalytical Method Validation". Etoposide nanoparticles and injection pharmacokinetic parameters were as follows: T1/2, 2.26 (0.71) and 1.74 (0.43) h;Cmax, 13.24 (5.32) and 8.12 (3.61) µg/ml; AUC0-t, 41.32 (7.33) and 16.53 (4.12) µg · ml - 1 · h; AUC0-∞, 49.54 (9.62) and 19.64 (8.22) µg · ml - 1 · h; MRT, 3.13 (0.54) and 2.06 (0.33) h and CL 7.35 (1.53) and 12.61 (2.22), respectively.This method was fully validated and successfully applied to a preclinical pharmacokinetic study of Etoposide in dogs after i. v. drip administration.

To better understand the pharmacokinetics and potential advantages of a levothyroxine oral solution vs. tablets and soft gel capsules.4 randomized, 2-treatment, single-dose (600 mcg levothyroxine), 2-way crossover bioequivalence studies in 84 healthy subjects were analyzed. Samples were collected before dosing and until 48-72 h post-dose to calculate noncompartmental baseline-adjusted pharmacokinetic parameters: maximum concentration, time to maximum concentration, and area-under-the-concentration-time-curve from 0 to 48 h and from 0 to 2 h.Mean pharmacokinetic parameters (±standard deviation) for tablets, capsules and solution, respectively, were: area-under-the-concentration-time-curve from 0 to 2 h (ng*h/mL)=68.4±32.8, 64.4±24.4, 99.1±22.7; area-under-the-concentration-time-curve from 0 to 48 h (ng*h/mL)=1 632±424, 1 752±445, 1 862±439; maximum concentration (ng/mL)=67.6±20.9, 68.0±15.9, 71.4±16.0; time of maximum concentration (hours)=2.25±0.99, 2.38±1.58, 1.96±1.07. Overall rate and extent of exposure were not statistically different between formulations, but a faster onset of absorption for the solution was suggested (greater area-under-the-concentration-time-curve from 0 to 2 h and faster time to maximum concentration by an average of 30 min).Levothyroxine rate and extent of exposure are similar between tested formulations. The solution appears however to reach systemic circulation quicker as dissolution is not needed before absorption starts. The solution's greater early exposure and a faster time to maximal concentration of around 30 min may be of benefit to minimize drug-food interactions and deserves further investigations.

The purpose of this study was to determine EriB in plasma by using the method of HPLC and collect the preclinical pharmacokinetic parameters of EriB.The analysis involved a simple liquid-liquid extraction. After making alkaline with NaOH, plasma was extracted with diethyl ether and the organic extract was then evaporated. From there, the residue was reconstituted in to the mobile phase. Chromatographic separation was achieved on the C18 column using acetonitrile and 0.1% triethylamine as mobile phase delivered at 1.0 ml/min. The UV detector wavelength was set at 233 nm. Standard curves were linear over the concentration range of 50-2 500 ng/ml.The mean predicted concentrations of the quality control (QC) samples deviated by less than 3% from the corresponding nominal values; the intra-assay and inter-assay precision of the assay were within 10% relative standard deviation. The extraction recovery of EriB was more than 80%.The developed method has been applied to the pharmacokinetic study of EriB in rats.

The aim of this study was to synthesize and determine the biological activity of new derivatives of 4-fluorobenzoic acid and tetrahydroacridine towards inhibition of cholinesterases. Compounds were synthesized in condensation reaction between 9-aminoalkyl-tetrahydroacridines and the activated 4-fluorobenzoic acid. Properties towards inhibition of acetyl- and butyrylcholinesterase were estimated according to Ellman's spectrophotometric method. Among synthesized compounds the most active were compounds 4a and 4d. These compounds, in comparison with tacrine, were characterized by the similar values of IC50. Among all obtained compounds, 4d presented the highest selectivity towards inhibition of acetylcholinesterase. Molecular modeling studies revealed that all derivatives presented similar extended conformation in the gorge of acetylcholinesterase, however, there were 2 main conformations in the active center of butyrylcholinesterase: bent and extended conformation.

The effect of repeated administration of centhaquin to pregnant rats on postnatal development, and expression of ETA and ETB receptors was determined. Pregnant rats were treated daily with either saline or centhaquin for 2 weeks. Male rat pups were sacrificed on day 1, 7, 14 and 28 of birth. Brain, kidney and heart were removed to study the expression of ETA and ETB receptor protein levels. Body weight of pregnant rats increased steadily in both vehicle and centhaquin groups. Expression of ETA receptors in the heart and kidney was similar in vehicle and centhaquin treated postpartum rats, but was significantly increased in the brain of centhaquin treated postpartum rats. No change in expression of ETB receptors was observed. In postnatal rats, mean body weight and weights of the brain, kidney and heart increased proportionally with advancing age and were similar in vehicle and centhaquin groups. The expression of ETA receptors in the brain, heart and kidneys was similar in vehicle and centhaquin groups. ETB receptor expression significantly (p<0.001) decreased by 72% and 70% on day 28 compared to rats of age 1, 7 and 14 days in control and centhaquin groups, respectively. Centhaquin treated rats showed similar expression of ETA and ETB receptors compared to vehicle treatment. This study suggests that repeated administration of centhaquin was well tolerated by pregnant rats that gave birth to normal pups. Centhaquin did not affect postnatal development of rats and had similar expression of ETA and ETB receptors compared to control pups.