Deposition of Aerosolized Lucinactant in Nonhuman Primates.

Background: Lucinactant for inhalation is an investigational noninvasive, aerosolized surfactant replacement therapy for treatment of preterm neonates with respiratory distress syndrome. Lucinactant for inhalation consists of lyophilized lucinactant and the Aerosurf® Delivery System (ADS). The objective of this study was to characterize the total and regional pulmonary deposition of lucinactant delivered by the ADS in nonhuman primates (NHPs). Methods: Lucinactant was radiolabeled by the addition of technetium-99m (99mTc)-sulfur colloid. The radiolabeled aerosol was characterized and validated using a Mercer cascade impactor. An in vivo deposition study was performed in three cynomolgus macaques. Radiolabeled lucinactant was aerosolized using the ADS and delivered via nasal cannula under 5 cm H2O nasal continuous positive airway pressure (nCPAP) for 5-9 minutes. A two-dimensional planar image was acquired immediately after aerosol administration, followed by a three-dimensional single-photon emission computed tomography (SPECT) image and a second planar image. The images were analyzed to determine the pulmonary (lungs) and extrapulmonary (nose + mouth, trachea, stomach) distribution. The SPECT data were used to determine regional deposition. Results: The radiolabed lucinactant aerosol had a mass median aerodynamic diameter = 2.91 µm, geometric standard deviation (GSD) = 1.81, and an activity median aerodynamic diameter = 2.92 µm, GSD = 2.06. Aerosolized lucinactant was observed to deposit in the lungs (11.4%), nose + mouth (79.9%), trachea (7.3%), and stomach (1.4%). Analysis of the SPECT image demonstrated that the regional deposition within the lung was generally homogeneous. Aerosolized lucinactant was deposited in both the central (52.8% ± 1.2%) and peripheral (47.2% ± 1.2%) regions of the lungs. Conclusion: Aerosolized lucinactant, delivered using the ADS via constant flow nCPAP, is deposited in all regions of the lungs demonstrating that surfactant can be aerosolized and delivered noninvasively to NHPs.

Assessing the antifungal activity, pharmacokinetics, and tissue distribution of amphotericin B following the administration of Abelcet and AmBisome in combination with caspofungin to rats infected with Aspergillus fumigatus.

The purpose of this study was to assess the antifungal activity, pharmacokinetics, and tissue distribution of amphotericin B (AmpB) following the administration of Abelcet and AmBisome alone and in combination with Caspofungin to rats infected with Aspergillus fumigatus. Aspergillus fumigatus inoculum (2.1-2.5 x 10(7) colony forming units [CFU]) was injected via the jugular vein; 48 h later male albino Sprague-Dawley rats (350-400 g) were administered either a single intravenous (i.v.) dose of Abelcet (5 mg AmpB/kg; n = 6), AmBisome (5 mg AmpB/kg; n = 6), Caspofungin (3 mg/kg; n = 5), Abelcet (5 mg AmpB/kg) plus Caspofungin (3 mg/kg) (n = 6), AmBisome (5 mg AmpB/kg) plus Caspofungin (3 mg/kg) (n = 7), or physiologic saline (non-treated controls; n = 6) once daily for 4 days. Antifungal activity was assessed by organ CFU concentrations and plasma galactomannan levels. Plasma and tissue samples were taken from each animal for AmpB pharmacokinetic analysis and tissue distribution determinations. Abelcet treatment significantly decreased total fungal CFU concentrations recovered in all the organs added together by 73% compared to non-treated controls. Ambisome treatment significantly decreased total fungal CFU concentrations recovered in all the organs added together by 69% compared to non-treated controls. Caspofungin treatment significantly decreased total fungal CFU concentrations recovered in all the organs added together by 80% compared to non-treated controls. Abelcet plus Caspofungin treatment significantly decreased total fungal CFU concentrations recovered in all the organs added together by 81% compared to non-treated controls. Ambisome plus Caspofungin treatment significantly decreased total fungal CFU concentrations recovered in all the organs added together by 98% compared to non-treated controls. Abelcet treatment significantly decreased plasma galactomannan levels by 50 and 75% 96 h following the initiation of treatment in the absence and presence of Caspofungin co-therapy, respectively. AmBisome treatment significantly decreased plasma galactomannan levels by 73 and 78% 96 h following the initiation of treatment in the absence and presence of Caspofungin co-therapy, respectively. Co-administration of Caspofungin with Abelcet and AmBisome did not significantly alter the plasma concentration-time profile, pharmacokinetic parameters, and tissue distribution of AmpB. Taken together, our findings suggest that an alternative mechanism, possibly at the cellular level rather than altered AmpB disposition, may be an explanation for the differences in organ CFU concentrations following Abelcet plus Caspofungin versus AmBisome plus Caspofungin administration.

The experience is CLEAR.

Conventional amphotericin B has been the 'gold standard' for antifungal efficacy, but nephrotoxicity problems limit its clinical utility. In the late 1990s, three lipid-based formulations of amphotericin B were introduced, all of which offered comparable efficacy and reduced renal complications. However, to date, robust safety and comparative efficacy data have been sparse. This paper briefly reviews the available clinical data on amphotericin B lipid complex (ABLC). Also, in detail, it reviews the findings of Collaborative Exchange of Antifungal Research (CLEAR), the most extensive dataset on systemic antifungal treatment with the lipid-based agent ABLC.

Molecular imaging of brain localization of liposomes in mice using MALDI mass spectrometry.

Phospholipids have excellent biocompatibility and are therefore often used as main components of liposomal drug carriers. In traditional bioanalytics, the in-vivo distribution of liposomal drug carriers is assessed using radiolabeled liposomal constituents. This study presents matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) as an alternative, label-free method for ex-vivo molecular imaging of liposomal drug carriers in mouse tissue. To this end, indocyanine green as cargo and two liposomal markers, 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine conjugated with monodisperse polyethylene glycol (PEG36-DSPE) were incorporated into liposomal carriers and administered to mice. We used MALDI MSI of the two lipid markers in both positive and negative ion mode for visualization of liposome integrity and distribution in mouse organs. Additional MSI of hemoglobin in the same tissue slice and pixel-by-pixel computational analysis of co-occurrence of lipid markers and hemoglobin served as indicator of liposome localization either in parenchyma or in blood vessels. Our proof-of-concept study suggests that liposomal components and indocyanine green distributed into all investigated organs.

Reutilization of surfactant phosphatidylglycerol and lysophosphatidylcholine by adult rabbits.

Adult rabbits reutilize the phosphatidylcholine (PC) of surfactant much less efficiently than developing rabbits (22% vs. 95%). Comparisons of reutilization efficiency of other components of surfactant in adult rabbits have not been determined. We injected adult rabbits intratracheally with [3H]dipalmitoylphosphatidylcholine (DPPG) mixed with [14C]lysophosphatidylcholine (lysoPC) and natural surfactant or [14C]DPPC mixed with [3H]dipalmitoylphosphatidylglycerol (DPPG) and natural surfactant. Recovery in the alveolar wash and lamellar bodies of labelled DPPC, lysoPC and DPPG was determined at different times after injection. By plotting the ratio of [3H]DPPG to [14C]DPPC in the alveolar wash versus time after injection we found that phosphatidylglycerol was reutilized with an efficiency of only 0-7% which was much less than the reutilization of PC in these animals. At early times after injection, adult rabbits injected with [14C]lysoPC had a ratio of [14C]PC in their alveolar wash to lamellar bodies that was larger than 1.0. By comparison, 3-day old rabbits injected intratracheally with [14C]lysoPC had a ratio of [14C]PC in alveolar wash to lamellar bodies less than 1.0 at the earliest times measurable. Thus adult rabbits demonstrate a pathway for accumulation of PC in their alveolar space prior to its appearance in lamellar bodies. This was not detected in developing rabbits. As in developing rabbits, adult rabbits reutilize the phosphatidylglycerol of surfactant less efficiently than the PC of surfactant.

Lymphatic uptake and biodistribution of liposomes after subcutaneous injection. II. Influence of liposomal size, lipid compostion and lipid dose.

The present paper reports on the results of a systematic study on liposome variables potentially affecting lymphatic disposition and biodistribution of liposomes after sc injection. Liposomal size was found to be the most important factor influencing lymphatic uptake and lymph node localization of sc administered liposomes. Lymphatic uptake from the s.c. injection site of small liposomes (about 0.04 microm) was relatively high (76% of the injected dose (%ID)) as compared to large, non-sized liposomes, which remained almost completely at the site of injection. Small liposomes were less efficiently retained by regional lymph nodes than larger liposomes. Liposomal lipid composition did not influence lymphatic uptake with one exception: Lymphatic uptake was decreased in case of neutral liposomes composed of (DPPC). Lymph node localization was substantially enhanced by inclusion of phosphatidylserine (PS) into the liposomal bilayers. Saturation of lymphatic uptake and lymph node localization did not occur over a large liposomal lipid dose range, illustrating the efficient performance of lymph nodes in capturing s.c. administered particles.

Tumor accumulation of novel RES-avoiding liposomes.

For passive targeting of liposomes to tumor tissues, we earlier developed reticuloendothelial system (RES)-avoiding liposomes modified with a uronic acid derivative, palmityl-D-glucuronide (PGlcUA) (Namba, Y., Sakakibara, T., Masada, M., Ito, F. and Oku, N. (1990) Chem. Pharm. Bull. 38, 1663-1666). In this present study, we examined the blood clearance and biodistribution of PGlcUA-liposomes (dipalmitoylphosphatidylcholine/cholesterol/PGlcUA = 40:40:20 as a molar ratio) in normal and tumor-bearing mice. Liposomes containing dipalmitoylphosphatidylglycerol (DPPG) instead of PGlcUA was also examined as a control. When [3H]inulin-encapsulated PGlcUA-liposomes and DPPG-liposomes were intravenously injected into normal mice, approx. 50% of the 3H radioactivity was recovered from the liver, the bulk of RES, at 12 h after administration of DPPG-liposomes, while only approx. 20% of it was found there when PGlcUA-liposomes were administered. Radioactivity remaining in the plasma at 12 h after injection was 5-fold higher when PGlcUA-liposomes were injected than when DPPG-liposomes were used. Biodistribution of liposomes in tumor-bearing mice was also examined. Mice were inoculated with 10(7) S180 cells into the hind leg. After 1 week, liposomes were injected. Radioactivity of [3H]inulin originally encapsulated in the PGlcUA-liposomes accumulated in the tumor to an extent 3-4-fold higher than that of the marker in DPPG-liposomes. Liver/tumor ratio of the radioactivity was 12 for DPPG-liposomes and only 2 for PGlcUA-liposomes. This latter value is the lowest of various liposome formulations ever reported.

Planar lipid bilayers on solid supports from liposomes--factors of importance for kinetics and stability.

One method to create planar lipid bilayers on solid substrates involves the transfer of lipids from liposomes to the support. We have varied the composition of liposomes systematically using factorial experimental designs and analyzed the adsorption behaviour of lipids from these liposomes onto solid supports. The hydrophilic supports were either used plain or modified with a monolayer of a lipid mixture, exposing hydrophobic groups. The monolayer-covered supports were used to identify factors important for adhesion and stability. Lipid adsorption kinetics was primarily studied on plain silicon supports in an ellipsometric cell or on a silicon nitride surface in a resonant mirror system (IAsys), using the systematic approach. Saturated phospholipids were essential for the required stability. Mixtures of dipalmitoylphosphatidylcholine, dipalmitoylphosphatidylglycerol, dipalmitoylphosphatidylethanolamine and cholesterol in combination with proteins were investigated in further detail as regards kinetics. The propensity to form a supported planar bilayer could be manipulated by the presence of calcium ions.

Comparative toxicity and concentrations of intravitreal amphotericin B formulations in a rabbit model.

PURPOSE: To determine the toxicity of various doses of intravitreal amphotericin B deoxycholate, amphotericin B lipid complex (ABLC), and liposomal amphotericin B (L-AmB). METHODS: Fifty-two rabbits were divided into two treatment groups (groups A and B). Thirteen treatments were administered intravitreally to the 104 rabbit eyes. Treatments included a control plus 10, 20, 30, and 50 micro g amphotericin B deoxycholate, ABLC, and L-AmB. Eye examinations were performed before injection and on day 11 for group A and on day 18 for group B. At death, on days 13 and 21 in groups A and B, respectively, vitreous humor was aspirated and concentrations of amphotericin B were determined by high performance liquid chromatography (HPLC), followed by enucleation for histologic studies. RESULTS: Significantly more eyes treated with ABLC showed development of vitreal opacities than developed in eyes treated with amphotericin B deoxycholate or L-AmB (P < 0.05). Vitreal band formation was significantly higher in ABLC-treated eyes than in those treated with L-AmB, (P = 0.039). Vitreal inflammation was greater in eyes treated with L-AmB (75%), amphotericin B deoxycholate (78%), and ABLC (91%) than with the control (50%; P = 0.08). Retinal ganglion cell loss was greater in eyes treated with amphotericin B deoxycholate (81%), L-AmB (91%), and ABLC (97%) than with the control (38%; P = 0.003). Amphotericin B concentrations were measurable for all doses of the three formulations. CONCLUSIONS: Based on histologic data, increasing doses of all three agents appear to be associated with increasing toxicity, however based on ophthalmologic data, L-AmB appears to be less toxic than either amphotericin B deoxycholate or ABLC.

Interactions of liposomes and platelets.

Rats were injected intravenously with liposomes of various compositions and sizes and blood platelet count measured. It was found that negatively-charged liposomal systems produced a transient reduction in platelet count in the first 5 minutes after injection which recovered by 60 minutes post-injection. This effect was most striking for multilamellar vesicles (MLV's) containing phosphatidylglycerol (PG). Dose levels of 25 mg/kg of MLV's containing 10 mole% PG caused the platelet count to drop from a control value of 1,086 +/- 21 X 10(9)/l to 193 +/- 14 X 10(9)/l by 2 minutes post-injection, an 82% decline. This thrombocytopenic effect was observed to diminish as vesicle size or vesicle dose was decreased. Positively-charged liposomes produced a less pronounced transient reduction in platelet count while neutral liposomes caused only a mild, transient platelet decline. This transient thrombocytopenic effect was not blocked by common anticoagulants and fibrinolytic agents but was prevented by liposomal pretreatment. Radiolabeled platelet studies revealed that transient sequestration of platelets occurs in the liver and spleen 2 minutes after PG:EPC:CHOL MLV injection with a normalization of platelet distribution by 60 minutes post-injection. In vitro studies, using an automated blood counter, suggest a transient association of liposomes and platelets occurring following injection. Liposomally-induced transient thrombocytopenia suggests a role for platelets in the biodistribution of liposomes.

Amphotericin B lipid complex: in visceral leishmaniasis.

Amphotericin B lipid complex is a lipid formulation of amphotericin B, an antifungal drug with activity against Leishmania spp. Amphotericin B lipid complex appears to enhance uptake of amphotericin B by infected macrophages in patients with visceral leishmaniasis (VL). In randomised, open-label, dose-ranging studies, short-course treatment with once-daily amphotericin B lipid complex (5-15 mg/kg total cumulative dose over 5 days), administered by intravenous infusion, produced high rates of apparent (day 19) [93-100%] and definitive (6 months) [79-100%] cures in Indian patients with antimonial-resistant VL. Amphotericin B lipid complex appeared to be as effective as liposomal amphotericin B or the conventional deoxycholate formulation in a randomised, open-label study conducted in India in a mixed population of patients with previously untreated or antimonial-resistant VL. In patients with HIV infection and VL, amphotericin B lipid complex 3 mg/kg/day for 5 or 10 days appeared to be as effective as meglumine antimonate 20 mg/kg/day for 28 days in a small randomised pilot study in southern Europe. Amphotericin B lipid complex was generally well tolerated in patients with VL. Infusion-related reactions were the most common adverse events associated with amphotericin B lipid complex.

Antiviral activity of phosphatidyl-dideoxycytidine in hepatitis B-infected cells and enhanced hepatic uptake in mice.

Dideoxycytidine (ddC) inhibits the replication of hepatitis B virus (HBV) but its clinical use is limited by peripheral neuropathy. We synthesized dioleoylphosphatidyl-ddC (DOP-ddC), a phospholipid prodrug of ddC which forms lipid bilayers and is readily incorporated into liposomes. The 90% effective dose (ED90) of DOP-ddC was 18 microM vs. 7 microM for ddC. However, in HBV-infected human hepatoma cells (2.2.15 cells), DOP-ddC was less toxic in vitro. When liposomal DOP-[5,6-3H]ddC was administered intraperitoneally to mice, drug levels in liver were 40 times greater than [5,6-3H]ddC when expressed as area under curve. Liposomal DOP-ddC also provided higher levels of drug in lymph nodes and spleen, important accessory sites of HBV replication. Plasma levels of drug remained above the ED90 six times longer with DOP-ddC than with ddC. DOP-ddC levels in sciatic nerve, the major site of toxicity, were not significantly different from levels observed with free ddC. The phospholipid prodrug approach is a general one which may readily be applied to other antiviral nucleosides for HBV.

Liposomal modification with uronate, which endows liposomes with long circulation in vivo, reduces the uptake of liposomes by J774 cells in vitro.

For overcoming rapid removal of liposomes from the bloodstream, we developed reticuloendothelial system (RES)-avoiding liposomes modified with a uronic acid derivative, palmityl-D-glucuronide (PGlcUA). In this current study, we examined the in vitro interaction of PGlcUA-liposomes with J774 cells derived from mouse macrophages. Liposomal association with J774 cells at 37 degrees C did not increase compared with the binding at 4 degrees C when liposomes were modified with PGlcUA. RES-avoiding ability was not specifically endowed by glucuronate but by uronates in general, since palmityl-D-galacturonide showed a similar effect on liposomal clearance in vivo and liposomal uptake in vitro. These facts indicate that modification of the liposomal surface with uronic acid derivatives endows liposomes with a long circulation time in the bloodstream by reducing their uptake by macrophages.

Accelerated clearance of a second injection of PEGylated liposomes in mice.

We recently reported that the firstly injected PEGylated liposomes dramatically affected the rate of blood clearance of secondly injected PEGylated liposomes in rats in a time interval of injection dependent manner [J. Control. Release (2003)]. Mice are frequently used in evaluations of the therapeutic efficacy of PEGylated liposomal formulations, but the pharmacokinetics of repeatedly injected PEGylated liposomes in mice is not fully understood. In this study, therefore, we examined in mice the effect of the repeated injection of PEGylated liposomes on their pharmacokinetics. An intravenous pretreatment with PEGylated liposomes produced a striking change in the biodistribution of the second dose which was given several days after the first injection. The first dose resulted in a reduction in the circulation half-life of the second dose. The degree of alteration was dependent on the time interval between the injections. The rapid clearance of the second dose was strongly related to hepatic clearance (CLh). This finding suggests that a considerable increase in hepatic accumulation accounts for this phenomenon. But, no liver injury or an increase in the number of Kupffer cells were detected in histopathological evaluations. Collectively, although the multiple injections of the PEGylated liposomes had no obvious physical effects, such as inflammation, their pharmacokinetic behavior was clearly altered in mice. The results obtained here have important implications not only with respect to the design and engineering of liposomes for human use, but for evaluating the therapeutic efficacy of liposomal formulations in experimental animal models as well.

Peritoneal penetration of amphotericin B lipid complex and fluconazole in a pediatric patient with fungal peritonitis.

Fungal peritonitis is a rare event in patients receiving peritoneal dialysis. This case report describes the blood and dialysate concentrations of fluconazole and amphotericin B following intravenous administration in a 5-month-old infant with Candida albicans peritonitis receiving continuous cyclic peritoneal dialysis. Fluconazole rapidly and efficiently penetrated the peritoneal fluid achieving concentrations that exceed the minimal inhibitory concentration (MIC) for most Candida species. In contrast, the amount of amphotericin B in the dialysate was below the limit of quantification despite measurable blood concentrations. This suggests that fluconazole represents a better choice for antifungal therapy because of its excellent peritoneal penetration.

Lucinactant for the prevention of respiratory distress syndrome in premature infants.

Respiratory distress syndrome (RDS) is the leading cause of neonatal morbidity and mortality in premature infants. It is caused by surfactant deficiency and lung immaturity. Lucinactant is a synthetic surfactant containing sinapultide, a bioengineered peptide mimic of surfactant-associated protein B. A meta-analysis of clinical trials demonstrates that lucinactant is as effective as animal-derived surfactants in preventing RDS in premature neonates, and in vitro studies suggest it is more resistant to oxidative and protein-induced inactivation. Its synthetic origin confers lower infection and inflammation risks as well other potential benefits, which may make lucinactant an advantageous alternative to its animal-derived counterparts, which are presently the standard treatment for RDS.

Pharmacokinetics of temoporfin-loaded liposome formulations: correlation of liposome and temoporfin blood concentration.

Liposomal formulations of the highly hydrophobic photosensitizer temoporfin were developed in order to overcome solubility-related problems associated with the current therapy scheme. We have incorporated temoporfin into liposomes of varying membrane composition, cholesterol content, and vesicle size. Specifically, two phosphatidyl oligoglycerols were compared to PEG2000-DSPE with respect to the ability to prolong circulation half life of the liposomal carrier. We measured the resulting pharmacokinetic profile of the liposomal carrier and the incorporated temoporfin in a rat model employing a radioactive lipid label and (14)C-temoporfin. The data for the removal of liposomes and temoporfin were analyzed in terms of classical pharmacokinetic theory assuming a two-compartment model. This model, however, does not allow in a straightforward manner to distinguish between temoporfin eliminated together with the liposomal carrier and temoporfin that is first transferred to other blood components (e. g. plasma proteins) before being eliminated from the blood. We therefore additionally analyzed the data based on two separate one-compartment models for the liposomes and temoporfin. The model yields the ratio of the rate constant of temoporfin elimination together with the liposomal carrier and the rate constant of temoporfin elimination following the transfer to e. g. plasma proteins. Our analysis using this model demonstrates that a fraction of temoporfin is released from the liposomes prior to being eliminated from the blood. In case of unmodified liposomes this temoporfin release was observed to increase with decreasing bilayer fluidity, indicating an accelerated temoporfin transfer from gel-phase liposomes to e. g. plasma proteins. Interestingly, liposomes carrying either one of the three investigated surface-modifying agents did not adhere to the tendencies observed for unmodified liposomes. Although surface-modified liposomes exhibited improved pharmacokinetic properties with regard to the liposomal carrier, an enhanced temoporfin loss and elimination from the PEGylated-liposomes was observed. This effect was more pronounced for PEGylated liposomes than for the two oligo-glycerols. Our combined experimental-theoretical approach for in vivo plasma re-distribution of liposomal drugs may help to optimize colloidal drug carrier systems.

Nanodiscs as a therapeutic delivery agent: inhibition of respiratory syncytial virus infection in the lung.

There is increasing interest in the application of nanotechnology to solve the difficult problem of therapeutic administration of pharmaceuticals. Nanodiscs, composed of a stable discoidal lipid bilayer encircled by an amphipathic membrane scaffold protein that is an engineered variant of the human Apo A-I constituent of high-density lipoproteins, have been a successful platform for providing a controlled lipid composition in particles that are especially useful for investigating membrane protein structure and function. In this communication, we demonstrate that nanodiscs are effective in suppressing respiratory syncytial viral (RSV) infection both in vitro and in vivo when self-assembled with the minor pulmonary surfactant phospholipid palmitoyloleoylphosphatidylglycerol (POPG). Preparations of nanodiscs containing POPG (nPOPG) antagonized interleukin-8 production from Beas2B epithelial cells challenged by RSV infection, with an IC50 of 19.3 µg/mL. In quantitative in vitro plaque assays, nPOPG reduced RSV infection by 93%. In vivo, nPOPG suppressed inflammatory cell infiltration into the lung, as well as IFN-γ production in response to RSV challenge. nPOPG also completely suppressed the histopathological changes in lung tissue elicited by RSV and reduced the amount of virus recovered from lung tissue by 96%. The turnover rate of nPOPG was estimated to have a halftime of 60-120 minutes (m), based upon quantification of the recovery of the human Apo A-I constituent. From these data, we conclude that nPOPG is a potent antagonist of RSV infection and its inflammatory sequelae both in vitro and in vivo.

In vitro and in vivo entrapment of bupivacaine by lipid dispersions.

Intravenous lipid emulsion is recommended as treatment for local anesthetic intoxication based on the hypothesis that the lipophilic drug is entrapped by the lipid phase created in plasma. We compared a 15.6 mM 80/20 mol% phosphatidyl choline (PC)/phosphatidyl glycerol (PG)-based liposome dispersion with the commercially available Intralipid® emulsion in a pig model of local anesthetic intoxication. Bupivacaine-lipid interactions were studied by electrokinetic capillary chromatography. Multilamellar vesicles were used in the first in vivo experiment series. This series was interrupted when the liposome dispersion was discovered to cause cardiovascular collapse. The toxicity was decreased by an optimized sonication of the 50% diluted liposome dispersion (7.8 mM). Twenty anesthetized pigs were then infused with either sonicated PC/PG liposome dispersion or Intralipid®, following infusion of a toxic dose of bupivacaine which decreased the mean arterial pressure by 50% from baseline. Bupivacaine concentrations were quantified in blood samples using liquid chromatography/mass spectrometry. No significant difference in the context-sensitive plasma half-life of bupivacaine was detected (p=0.932). After 30 min of lipid infusion, the bupivacaine concentration was 8.2±1.5 mg/L in the PC/PG group and 7.8±1.8 mg/L in the Intralipid® group, with no difference between groups (p=0.591). No difference in hemodynamic recovery was detected between groups (p > 0.05).

Effects of a novel ultrasound contrast agent with long persistence on right ventricular pressure: Comparison with SonoVue.

This work investigated the effect of infusion of a self-made ultrasound contrast agent with long persistence (named ZHIFUXIAN) on rat right ventricular pressure and made a preliminary evaluation on the relative safety of the novel microbubbles. Normal saline, SonoVue and ZHIFUXIAN were injected through caudal vein at the total volume of 0.5ml for each injection. The right ventricular systolic pressure (RVSP) and end-diastolic pressure (RVEDP) were monitored and the changes of the pressure were compared with baseline readings. RVSP increased when saline, SonoVue or ZHIFUXIAN were injected, the greatest change being after SonoVue (about 2mmHg), but there was no statistical significance compared with baseline (P>0.05). There was no significant difference in RVSP between saline, SonoVue and ZHIFUXIAN at any time point. Also, there was no significant difference in RVEDP between groups at each time point and between different time points in each group. The results indicate that the self-made microbubbles effect on right ventricular hemodynamics is equivalent to that of normal saline at the same volume needed for effective enhanced imaging, demonstrating that it does not produce changes in right ventricular blood pressure under the study conditions. Pathological examination also showed it had no obvious influence on lung, liver and kidney.