Effects of particle size on the pharmacokinetics of puerarin nanocrystals and microcrystals after oral administration to rat

Puerarin, which is extracted from traditional Chinese medicine, is widely used in clinic in China and mainly used as a therapeutic agent to cardiovascular diseases. Owing to its poor water solubility and adverse drug reactions caused by cosolvents after intravenous administration, the development of oral formulation is urgently needed. Nowadays, nanocrystals technique has become a preferred way to develop oral dosage form. In this study, we used high pressure homogenization (HPH) to prepare puerarin nanocrystals and microcrystals with different sizes ranged from 525.8 nm to 1875.6 nm and investigated the influence of particle size on pharmacokinetics. The nanocrystals and microcrystals prepared were characterized using DLS, DSC, XRD and SEM, and we found that the crystalline state of puerarin was changed during the preparation process and the drug was dispersed into HPMC. In the pharmacokinetic study, we observed an increasing of C_max and AUC and a decreasing of CL/F with the decreasing of particle size. The AUC of the puerarin nanocrystals (525.8 nm) was 7.6-fold of that of raw puerarin suspension, with an absolute bioavailability of 21.44%. From the above results, we can conclude that nanocrystal technique is an efficient technology to improve the oral bioavailability of puerarin.     

Studies on Effect of Piperine on Oral Bioavailability of Ampicillin and Norfloxacin

Ampicillin and Norfloxacin are used to treat variety of bacterial infections. These two drugs have low oral bioavailability. Co-administration of Piperine (20mg/kg), an alkaloid from Piper nigrum L. enhanced oral bioavailability of Ampicillin and Norfloxacin in animal model. This is reflected in various pharmacokinetic measurements like Cmax, Tmax, AUC and t½ of the above antibiotics in animal model.     

Concentration of adipogenic and proinflammatory cytokines in the bone marrow supernatant fluid of osteoporotic women

Osteoporosis is characterized by low bone mass, microarchitectural deterioration of bone tissue leading to increased bone fragility, and a resulting susceptibility to fractures. Distinctive environmental bone marrow conditions appear to support the development and maintenance of the unbalance between bone resorption and bone formation; these complex bone marrow circumstances would be reflected in the fluid surrounding bone marrow cells. The content of regulatory molecules in the extracellular fluid from the human bone marrow is practically unknown. Since the content of cytokines such as adiponectin, leptin, osteoprogeterin (OPG), soluble receptor activator of nuclear factor κB ligand (s‐RANKL), tumor necrosis factor α, and interleukin 6 (IL‐6) may elicit conditions promoting or sustaining osteoporosis, in this work we compared the concentrations of the above‐mentioned cytokines and also the level of the soluble receptors for both IL‐6 and leptin in the extracellular fluid from the bone marrow of nonosteoporotic and osteoporotic human donors. A supernatant fluid (bone marrow supernatant fluid [BMSF]) was obtained after spinning the aspirated bone marrow samples; donors were classified as nonosteoporotic or osteoporotic after dual‐energy X‐ray absorptiometry (DXA) measuring. Specific commercially available kits were used for all measurements. The cytokines' concentration in BMSF showed differently among nonosteoporotic and osteoporotic women; this last group was characterized by higher content of proinflammatory and adipogenic cytokines. Also, osteoporotic BMSF differentiated by decreased leptin bioavailability, suggesting that insufficient leptin action may distinguish the osteoporotic bone marrow. © 2010 American Society for Bone and Mineral Research     

Bioanalytical approaches,bioavailability assessment,and bioequivalence study for waiver drugs: In vivo and in vitro perspective

Evidence of differences in bioavailability from different oral formulations of the same therapeutic agents had become obvious by the early 1960s. The consequent 40 years have produced the body of scientific belief, debate, and policy on the subject of bioequivalence. The motivating force behind many of these events has been the continued interest of the food and drug administration (FDA) to improve the manner in which these studies are conducted, the quality of the data generated from such studies, and the methods by which they are evaluated. Bioanalytical data used to support regulatory submission needs to be accurate and reproducible. In order to have confidence in the reliability of the data, it is important that the analytical method used to generate it is well characterized and fully validated. However, bioavailability assessment (BA) and bioequivalence (BE) studies are necessary in filing of the data towards the drug approval. This review article describes the methods for assessing bioavailability and bioequivalence; and bioanalytical approaches of pharmaceuticals in vivo and in vitro and also a waiver of BA/BE studies based on the biopharmaceutical classification (BCS) system.     

Nutritional bioavailability to rats of selenium in Brazil nuts and mushrooms

Weanling male rats were fed a selentum (Se)-deficient Torula yeast diet for 4 to 9 weeks followed by either continued depletion or repletion for 4 to 6 weeks with Se as sodium selenite, extracted Brazil nut meal, or dried mushroom powder. The Se in the Brazil nut meal (Bertholletia excelsa) was fully as available as that in sodium selenite when judged by the ability of dietary Se to restore plasma and liver glutathione peroxidase activities or Se levels. By these same criteria, the Se in cultivated commercial mushrooms (Agaricus bisporus) or wild mushrooms (Boletus edulis) was of very poor bioavailability. Addition of mushroom powder to a diet containing selenite did not interfere with the ability of the selenite to restore hepatic glutathione peroxidase activity during repletion. These results demonstrate the great differences that can occur in the bioavailability of Se from different foods and point out the need to develop suitable Se bioavailability assays in humans.     

Plasma concentrations and relative bioavailability of naftidrofuryl from different salt forms

The relative bioavailability of the vasodilator naftidrofuryl from formulations containing its oxalate or citrate salt has been estimated using a specific HPLC assay, and a less specific fluorimetric assay, to measure plasma drug concentrations. The conclusions of the study were the same irrespective of the assay employed. The relative rate, but not the extent, of bioavailability of naftidrofuryl from the citrate salt (peak 1096 ng ml-1 at 0.76 h) was marginally greater (p = 0.003) than that from the oxalate salt (peak 922 ng ml-1 at 0.94 h). The degree of intersubject variability was similar after administration of either salt form. The mean half-life of naftidrofuryl was 1.8 h and its mean residence time was 2.5 h.     

Bioinequivalence of a generic brand of diazepam

Twenty-six healthy male volunteers received a single 10 mg dose of diazepam on two occasions in a crossover bioequivalence study comparing the reference product (Valium) and a generic formulation (NeoCalme). Concentrations of diazepam and its metabolite, desmethyldiazepam, were determined during 264h after each dose. Peak plasma diazepam concentrations were significantly lower for NeoCalme vs Valium (247 vs 394 ng ml-1, p less than 0.001) and reached significantly later after the dose (1.62 vs 0.98 h, p less than 0.001). Total area under the plasma concentration curve (AUC) was also significantly lower for NeoCalme (6614 vs 7552 ng ml-1 x h, p less than 0.001), although AUC ratios for NeoCalme divided by Valium satisfied the '75-75' guidelines. Findings for desmethyldiazepam were similar. Thus, diazepam absorption from the generic brand of diazepam is significantly slower than from Valium, which in turn could lead to therapeutic inequivalence.     

Relative bioavailability of almitrine bismesylate in humans

Bioavailability and bioequivalency studies of almitrine bismesylate from U.S. manufactured film coated, waxed, 50 mg tablets were compared in 34 normal healthy volunteers to 50 mg European film coated, waxed and unwaxed, tablets and a 0.5 per cent (w/v) oral reference solution of almitrine bismesylate in d,l malic acid. The U.S. manufactured formulations were 85.88 and 87.85 per cent of the calculated mean area under the individual concentration-time curve for almitrine bismesylate reference solution compared to 88.40 and 88.86 per cent for the waxed and unwaxed film coated European tablets, respectively. The mean peak plasma concentrations for the U.S. formulations were 176.3 ng ml-1 and 180.1 ng ml-1 compared to 196.3 and 200.1 ng ml-1 for the waxed and unwaxed European formulations, respectively. Mean time to peak plasma concentrations for the two U.S. formulations and the waxed and unwaxed European formulations were 3.22, 3.33, 3.06, and 3.26 h, respectively. In addition, the oral reference solution yielded a mean peak plasma concentration of 222.8 ng ml-1 and a mean time to peak plasma concentration of 2.68 h. Analysis of variance and multiple range comparisons (p less than 0.05) indicated that the tablet formulations were bioequivalent. The results of this study show that the U.S. formulated almitrine bismesylate tablets exceed 85 per cent relative bioavailability with respect to the oral reference solution and are bioequivalent compared to the marketed standard European tablet formulations.     

Development of a carcinogenic potency index for dermal exposure to viscous oil products

Polycyclic aromatic compounds (PACs) present in oil streams and formulated products are important determinants of possible carcinogenicity. Following dermal exposures the transport of the PACs from oil (the carrier) into the skin is a factor that may affect macromolecular (DNA) adduct formation and thus determine carcinogenicity. We have developed a mathematical model, which describes the flux into the skin for a representative carcinogenic PAC, benzo(a)pyrene. The model is based on measurements of the amount of benzo(a)pyrene bound to skin DNA or blood observed in mouse skin painting studies. The degree of adduct formation from a particular oil product, which we term the Bioavailability Index (BI), was shown to be a function of both the viscosity of the oil product, which affected the transport of the PAC through the carrier, and the aromaticity, which affected the partition of PAC between the carrier and the skin. Literature data were analysed from mouse skin painting studies with mineral oils of known carcinogenicity. A linear relationship was shown between the amount of DNA adduct formation, expressed as alkylation frequency, and the arithmetic product of the total (3–6) ring PAC content and the BI, which we have termed the Carcinogenic Potency Index (CPI). Comparison of literature data on DNA alkylation frequencies for oil products and their carcinogenicity indicated that oils giving rise to an alkylation frequency below a certain threshold (ca. 1 adduct in 10⁸ nucleotides) are non-carcinogenic to mouse skin. This threshold level can be translated into a value for the CPI, below which the genotoxic carcinogenic risk arising from skin contact with the oil product is considered to be negligible. The CPI for bitumens is well below this value, being both due to the low BI from bitumen, but more so, due to their low PAC content. For some bitumens diluted with solvents, i.e. cutback-bitumens, the CPI may exceed this value, indicating a possible carcinogenic risk for some of the cutback-bitumens. The main determining factor is the PAC content which is principally determined by the nature of the diluent used. Received: 16 December 1998 / Accepted: 16 February 1999     

Pharmacokinetics of (−)-epicatechin in rabbits

The aim of this study was to investigate the pharmacokinetics of (−)-epicatechin (EC) in rabbits after intravenous, intraperitoneal, and oral administration. A two-compartment model was used to describe the pharmacokinetics of EC after intravenous administration. EC showed dose-independent pharmacokinetics after intravenous administration. In addition, the area under the concentration-time curve was proportional to the dose over the range 5–25 mg/kg. After intraperitoneal administration of 25 mg/kg, a high percentage of EC escaped from first-pass hepatic elimination. After oral administration of 50 mg/kg, there was a great variation in the pharmacokinetics, and the mean oral bioavailability of EC was 4%. There was no significant difference in the elimination rate constants in all treatments (p>0.05). In conclusion, after intravenous, intraperitoneal, and oral administration of EC, the EC exhibits dose-independent pharmacokinetics in rabbits. The first-pass effect did not participate in the low oral bioavailability. Base on the results of the present study, the other factors may contribute the low oral bioavailability.