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The purpose of this research is to evaluate the effect of self-micelle formation and incorporation of lipid in the formulation on absorption of ginsenosides Rg1 and Rb1 from intestinal tract in rats. Ginsenosides Rg1 and Rb1 were extracted from Panax notoginseng saponins (PNS). The critical micellar concentration (CMC) of PNS in deionzied water was determined to be 0.339 mg/ml. At normal physiological ionic strengths, PNS was salted out from the solution above the CMC. The particle size of the micelle grows as PNS concentration increases. By in situ injection to a closed loop of the rat jejunum, AUC0-6h obtained after administration of low concentration solution (12 mg/ml) was 3.61 times for ginsenoside Rg1 and 3.84-folds for ginsenoside Rb1 compared with high concentration solution (120 mg/ml). The release rate of ginsenosides in aqueous medium was too slow to complete in 24h, especially for Rb1. The data suggested that the self-micelle formation tendency in ginsenosides might prevent them from permeation or absorption through the cell membrane of gastrointestinal (GI) tract. To inhibit the formation of micelles, lipid was incorporated in the PNS formulation. The intraduodenal bioavailability in rats showed that the bioavailability was enhanced remarkably relative to the aqueous solution. AUC 0-infinity of ginsenoside Rg1 and Rb1 in the lipid-based formulation were 207.52+/-53.95 and 1961.72+/-686.60 microg ml(-1) h, compared with 7.87+/-2.85 and 148.58+/-36.73 microg ml(-1) h, respectively from its aqueous solution. These findings suggested a new strategy to increase the absorption of amphiphilic saponins.

The purpose of this study was to investigate the transport mechanisms and causes of low bioavailability of leuprolide. The everted gut sac technique and Caco-2 cell monolayer were used to examine: (1) transport properties, enzyme degradation and apparent permeation coefficient (Papp); (2) the influence of trypsin inhibitor, EDTA, chitosan and alginate on drug transport; and (3) the effect of animal species on the intestinal transport. Results showed flux increased with increasing concentration of drug, showing a passive diffusion pathway. The enzyme degradation in rabbit gut was the highest. The Papp of (4.19 +/- 1.33) x 10(-5) cm/s in rat gut was the largest and the Papp of (5.20 +/- 0.20) x 10(-7) cm/s in Caco-2 cell the smallest. At a low concentration of drug, trypsin inhibitor had strong enhancement effect on the Papp by protecting enough drug for permeation. Chitosan had no effect on the activity of alpha-chymotrypsin. The increase in Papp was due to opening of the tight junctions and interaction with cells. In conclusion, both inhibition of proteolytic enzymes and opening the tight junctions to allow for paracellular transport improved the intestinal absorption. At low drug concentration, reduction of enzyme degradation is the most important factor.

The objective of the present work was to investigate the effect of chitosan concentration and lipid type on the characteristics of chitosan-coated liposomes and their interactions with leuprolide. Liposomes from lipid of high purity and low purity were prepared and coated by chitosan. Physical properties, drug entrapment efficiency, and stability upon dilution were respectively compared. Results showed that the particle size increment of liposomes from low purity lipid was larger than that from high purity lipid, indicating a thicker coating layer. The high zeta potential of particles from low purity lipid was thought to play an important role in the resistance to flocculation. As to particles from high purity lipid, polymer bridging caused flocculation at low polymer concentration while at high concentration, the adsorbed chitosan molecule led to steric stabilization. Drug entrapment efficiency decreased as chitosan was added to liposomes, showing the disturbance of bilayers. Upon dilution, the leakage of leuprolide from low purity liposomes was larger than that from high purity liposomes. In conclusion, low purity lipid possessed more negative charge and formed thicker adsorptive layer by stronger electrostatic attraction with chitosan. The interaction between chitosan and the polar head groups on the surface of phospholipid bilayers may interfere with leuprolide entrapped in liposomes and result in the leakage of leuprolide.

The present study was undertaken to investigate the incorporation of lipophilic polypeptide, cyclosporin A (CsA) into lecithin vesicular system and to compare its pharmacokinetics behavior with Sandimmun Neoral® (CsA-NEO). Lecithin vesicles of cyclosporin A (CsA-VES) were prepared by the rotary evaporation method, treated further with sonication. Studies were carried out to characterize the vesicles on physical properties, content, entrapment efficiency, particle size, polydispersity and Zeta potential. Pharmacokinetic behaviors were studied in rabbits at dose of 30 mg/kg. Results showed CyA vesicles were spherical particles, with content of 3.137±0.060% mg/ml, entrapment efficiency of 98.91±0.80%, particle size of 63.89±4.75 nm, polydispersity of 43.2±6.1% and Zeta potential of −13 mV. The best model fitting experimental data was a two-compartment open model with first-order kinetics. The relative bioavailability of CsA-VES versus CsA-NEO was 105±21% ( n =6) and statistical analysis demonstrated both preparations were bioequivalent. In conclusion, lecithin vesicles are promising carriers in the oral delivery of CsA, considering their absorption enhancement effect and low-toxic property.

Two kinds of vesicles with and without the presence of sodium cholate (flexible vesicles and conventional vesicles) were prepared, using cyclosporin A as model drug. When applied onto the excised abdominal skin of mice non-occlusively, the enhancing effects of vesicles on the penetration of cyclosporin A were assessed by an in vitro permeation technique. The effect of sodium cholate micelles was also studied. In vivo study was carried out by topical application of vesicles onto the mice skin and drug serum concentration was detected. Results showed that after 8 h of administration, flexible vesicles transported 1.16 microg of cyclosporin A through per cm(2) mice skin and amounted to 1.88 microg 24 h later. The residual amount in the skin was 1.78+/-0.51 microg/cm(2). However, flexible vesicles failed to transport measurable amount of drug through pre-hydrated skin while deposited 2.39+/-0.26 microg/cm(2) into the skin. Conventional vesicles failed to transfer cyclosporin A into the receiver while accumulated 0. 72+/-0.19 microg/cm(2) of drug in the skin. Furthermore, 1 and 40% sodium cholate micelles precluded the transport of cyclosporin A. In vivo studies indicated that with the application of flexible vesicles, serum drug concentration of 53.43+/-9.24 ng/ml was detected 2 h later. After the stratum corneum of mouse skin has been destroyed by shaving, flexible vesicles transferred large amount of drug into blood, up to 187.32+/-53.21 ng/ml after 1 h of application. Conventional vesicles failed to deliver measurable amount of drug into the blood under normal skin condition. In conclusion, flexible vesicle is better than conventional vesicle as the carrier for transdermal delivery of cyclosporin A. Penetration and fusion have been suggested to be two major functional mechanisms. Hydration is detrimental to the enhancement effect. Stratum corneum constitutes main barrier to the transport of lipophilic cyclosporin A.

Aim To compare pharmacokinetics of intravenous breviscapine liposomes in Beagle dogs, rabbits and rats. Methods Six Beagle dogs, 6 rabbits and 12 rats were intravenously administrated with breviscapine liposomes and commercial injection (breviscapine solution) by the crossover design (two periods), respectively. Plasma concentration of scutellarin, the main active component in breviscapine, at different time intervals was determined by reverse phase-HPLC. The pharmacokinetic parameters including area under the curve (AUC), clearance (CL (s) ) and volume of distribution ( V (c) ) were calculated. Results The plasma concentration–time profiles were fitted to a two-compartment model. Breviscapine liposomes exhibited significant difference from injection in CL (s) and AUC, examined by a one-way analysis of variance (ANOVA). With regard to both breviscapine liposomes and commercial injection (free breviscapine), the logarithm values of AUC, CL (s) and V (c) were all related to the logarithm of the body weight by the allometric equation: Y = a × W b . Conclusion The allometric equation might be applied to extroplate dosage for human from animal data and also for dosage adjustment of breviscapine liposomes in order to achieve same AUC as commercial injection. Compared with the breviscapine solution, breviscapine liposomes delivered more scutellarin into the plasma.

Pharmacokinetics and lactone/carboxylate equilibrium of 9-Nitrocamptothecin (9-NC) were compared after intravenous (i.v.) and intramuscular (i.m.) injection at a dose of 1.5mg/kg 9-NC solution. The concentrations of three different forms of 9-NC, namely lactone, carboxylate and total 9-NC, were measured by HPLC analysis. Injection routes were demonstrated to have significant effect on pharmacokinetics of 9-NC. Compared with i.v. injection route, mean residence time (MRT) of 9-NC three forms was significantly prolonged following i.m. route (p0.05). The AUC(0-infinity) ratios of i.m. to i.v. route were calculated to be 102+/-43%, 273+/-221% and 150+/-62% for lactone, carboxylate and total 9-NC, respectively. Compared with i.v. injection route, although AUC(0-infinity) was barely changed, MRT of lactone 9-NC was dramatically prolonged 4.5-fold after i.m. injection, which may account for the reported improved antitumor efficacy. However, the results of the present study also demonstrated that i.m. injection route increased both AUC(0-infinity) and MRT of carboxylate 9-NC more significantly. Since the carboxylate form of CPT analogs including 9-NC is associated with their unwanted toxicity, i.m. injection route might lead to severe toxicity compared with i.v. route. Lactone/carboxylate equilibrium was also significantly influenced by injection routes. Based on the AUC(0-infinity) measurements, the lactone 9-NC constituted 50+/-8% and 32+/-7% of circulating total 9-NC after i.v. or i.m. administration, respectively (p0.01).

Aim To investigate distribution of breviscapine in brain after intravenous (i.v.) injection of liposomes. Methods Breviscapine liposomes were prepared by rotary evaporation–sonication method. Particle size, encapsulation efficiency and stability of liposomes were respectively examined. In vitro drug release was investigated in 0.9% sodium chloride at 37 °C. Rats were divided into two groups. Liposomes were given to one group and commercial injection ( Injectio Breviscapine ) was given to the other at a single dose of 28.1 mg kg −1 i.v., respectively. Scutellarin in rat brain at different sampling time was determined by RP-HPLC. The brain concentration–time curves of breviscapine liposomes and commercial injection were constructed and pharmacokinetic parameters were calculated and compared by statistic analysis. Results The average liposome diameter was 735 ± 59 nm and encapsulation efficiency was 85.1 ± 2.3%. The average accumulative release percentage of breviscapine liposomes in 0.9% sodium chloride was less than 30% within 24 h. The mean concentration–time curves of breviscapine liposomes and commercial injection were both fitted to one-compartment model. There are significant difference of parameter T 1/2 and AUC 0–360 between liposome and commercial injection ( p T 1/2 of breviscapine liposomes and commercial injection were 23.13 ± 7.71 and 6.27 ± 1.84 min, respectively. The brain AUC ratio of breviscapine liposomes to commercial injection was 443.4 ± 92.3%. Conclusion Compared with the commercial injection, liposomes delivered more drugs into the brain and have longer elimination time.

The purpose of the study was to investigate the absorption behavior of lecithin vesicles of cyclosporin A (CsA-VES), prepared by the rotary evaporation method and treated further with sonication. The everted gut sac technique and in situ circulation method were used to examine: (1) relationship between the CsA-VES absorption velocity and the CsA-VES content; (2) the influence of the intestinal mucus, blank vesicles, concentration of Na(+), energy inhibitor and P-gp inhibitor on the absorption of CsA-VES; and (3) the respective accumulated content of CsA in the incubating medium and the sacs after incubation with Sandimmum Neoral((R))(CsA-NEO) and CsA-VES. Our results showed there was a saturated absorption of CsA. Most CsA-VES accumulated in the mucus before it reached the intestinal tissue. There was no significant difference in the accumulated absorption content in the incubating medium and the sacs of CsA-NEO and CsA-VES. The addition of blank vesicles and concentration of Na(+) had no significant influence on the accumulated absorption of CsA (P>0.05). The energy inhibitor and P-gp inhibitor influenced the accumulated absorption of CsA significantly (P