Thromboelastographic and pharmacokinetic profiles of micro- and macro-emulsions of propofol in swine.

PURPOSE: Compared with traditional macroemulsion propofol formulations currently in clinical use, microemulsion formulations of this common intravenous anesthetic may offer advantages. The pharmacokinetics and coagulation effects as assessed by thromboelastography of these formulations were characterized in swine. METHODS: Yorkshire swine (20-30 kg, either sex, n=15) were sedated, anesthetized with isoflurane, and instrumented to obtain a tracheostomy, internal jugular access and carotid artery catheterization. Propofol (2 mg/kg, 30 s) was administered as a macroemulsion (10 mg/ml; Diprivan; n=7) or a custom (2 mg/kg, 30 s) microemulsion (10 mg/ml; n=8). Arterial blood specimens acquired pre- and post-injection (1 and 45 min) were used for thromboelastography. Arterial blood specimens (n=12 samples/subject, 60 min) were serially collected, centrifuged and analysed with solid-phase extraction with UPLC to determine propofol plasma concentrations. Non-compartmental pharmacokinetic analysis was applied to plasma concentrations. RESULTS: No changes were noted in the thromboelastographic R time (p=0.74), K time (p=0.41), alpha angle (p=0.97), or maximal amplitude (p=0.71) for either propofol preparation. Pharmacokinetic parameters k (p=0.45), t(1/2) (p=0.26), C(o) (p=0.89), AUC(0-infinity) (p=0.23), CL (p=0.14), MRT (p=0.47), V(ss) (p=0.11) of the two formulations were not significantly different. CONCLUSION: The microemulsion and macroemulsion propofol formulations had similar pharmacokinetics and did not modify thromboelastographic parameters in swine.

Pi-Pi complexation of bupivacaine and analogues with aromatic receptors: implications for overdose remediation.

The interaction of the important but often overdosed local anesthetic bupivacaine, its structural analogs 2,6-dimethylaniline, and N-methyl-2,6-dimethylacetanilide, and cocaine, with several electron deficient aromatic moieties were studied primarily by proton NMR and UV-visible spectroscopy. In solution, the anesthetic, its analogs and cocaine are electron donors and form pi-pi charge transfer complexes with strong aromatic acceptors, as monitored by the upfield changes induced in the NMR chemical shifts (delta) and red-shifted UV-vis wavelength (lamda max) absorbance of the acceptors. The equilibrium binding constant, K, was determined from the 1H NMR charge transfer induced chemical shift changes and used to calculate the free energy (deltaG) for complex formation of three acceptor-donor pairs. HPLC results indicate that the concentrations of free bupivacaine, its analogs and of cocaine are reduced from solution via binding to aromatic-functionalized silica.

Effect of the composition of lecithin/n-propanol/isopropyl myristate/water microemulsions on barrier properties of mice skin for transdermal permeation of tetracaine hydrochloride: in vitro.

Effect of composition of lecithin water-in-oil and oil-in-water microemulsion on in vitro transdermal permeation of tetracaine hydrochloride was studied on mice model. The results were compared with an aqueous solution of tetracaine hydrochloride (2.7 mg/ml). In vitro skin flux and permeability coefficients were obtained using the Franz diffusion cell. Differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM) were used to study the mechanism of action of the microemulsion. Micrographs of TEM and CLSM studies were analyzed by using Image Pro Plus image software. Skin flux of tetracaine hydrochloride was found to be dependent on the composition of lecithin/n-propanol/isopropyl myristate/water microemulsions. At lower Km ratio (i.e. 0.5:1 and 0.8:1) of microemulsion, the rate of permeation of tetracaine hydrochloride was higher when compared to the microemulsion of higher Km ratio (1:1 and 1.5:1). Image analysis of TEM micrograph, 6h after application of lecithin microemulsion, showed 3.5+/-0.75-fold (p<0.001) increase in the intercellular space in the epidermis and 3.8+/-0.4-fold (p<0.001) enhancement in upper dermis. CLMS results show that sweat gland and hair follicles also provided path for permeation of the drug through the skin.

Surface modification of silica core-shell nanocapsules: biomedical implications.

In this article we present the synthesis of oil core silica shell nanocapsules with different shell thicknesses. The surface of the nanocapsules was modified with polyethyleoxide (PEO) and succinic anhydride. Two biomedical tests were then used to study the biocompatibility properties of these nanocapsules with different surface treatments, hemolysis and thromboelastography (TEG). PEO surface modification greatly reduced the damaging interactions of nanocapsules with red blood cells (RBCs) and platelets and attenuated particle size effects. It was found that the blood toxicity of charged particles increased with the acid strength on the surface. Experiments toward the assessment of detoxification of these nanocapsules in model drug overdose concentrations are currently underway.

Mass spectral fragmentation of the intravenous anesthetic propofol and structurally related phenols.

Propofol (2,6-diisopropyl phenol) is a widely used intravenous anesthetic. To define its pharmacokinetics and pharmacodynamics, methods for its quantitation in biological matrixes have been developed, but its pattern of mass spectral fragmentation is unknown. We found that fragmentation of the [M - H](-) ion (m/z 177) of propofol in both APCI MS/MS and ESI MS/MS involves the stepwise loss of a methyl radical and a hydrogen radical from one isopropyl side chain to give the most intense product ion, [M -H - CH(4)](-), at m/z 161. This two-step process is also the preferred mode of fragmentation for similar branched alkyl substituted phenols. This mode of fragmentation of the [M - H](-) ion is supported by three independent lines of evidence: (1) the presence of the intermediary [M - H - CH(3)](-) radical ion under conditions of reduced collision energy, (2) the determination of the mass of the predominant [M - H - CH(4)](-) product ion by high resolution mass spectrometry, and (3) the pattern of product ions resulting from further fragmentation of the [M - H - CH(4)](-) product ion. Phenols with a single straight chain alkyl substituent, in contrast, undergo beta elimination of the alkyl radical irrespective of the length of the alkyl chain, yielding the most intense product ion at m/z 106. This product ion represents a special case of a stable intermediary radical for the two-step process described for branched side chains, because further elimination of a hydrogen radical from the beta carbon is not possible.

AOT water-in-oil microemulsions as a penetration enhancer in transdermal drug delivery of 5-fluorouracil.

In vitro transdermal permeation of 5-fluorouracil (antineoplastic), a hydrophilic drug encapsulated in AOT/water/isopropylmyristate water-in-oil microemulsions (MEs), were studied using a modified Keshary and Chien diffusion cell. AOT (aerosol-OT or sodium bis(2-ethylhexyl) sulfosuccinate) is an anionic surfactant, which forms 'water-in-oil' ME in non-aqueous medium. The effect of water and AOT concentrations in MEs to the transdermal permeation of 5-fluorouracil through hairless mouse skin was investigated. MEs with 5:95 weight ratio of AOT:isopropylmyristate, containing 0.9, 1.8, 2.7 and 3.6% w/w of water have showed 1.68-, 2.36-, 3.58- and 3.77-fold increases in the skin flux of 5-fluorouracil (5-FU) respectively, compared to the aqueous solution of drug. The MEs with 5:95, 9:91 and 13:87 weight ratio of AOT:isopropyl myristate at fixed water content W0=15 (W0=[H2O]/AOT]) gave 3.58-, 5.04- and 6.3-fold enhancement of drug. In addition, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to examine the effect of ME on lipid alkyl chain, hydration level, and corneocyte cells of the stratum corneum (SC). Results reveal that the ME interacts with a component of the SC and perturbs its architectural structure. The extent of perturbation in the SC depends on the concentration of water and AOT in the ME. Preliminary dermal toxicity studies indicate that the AOT/water/isopropylmyristate ME be safe for the transdermal permeation of 5-FU.

A new method for the quantitation of propofol in human plasma: efficient solid-phase extraction and liquid chromatography/APCI-triple quadrupole mass spectrometry detection.

Propofol (2,6-diisopropyl phenol) is widely used for the induction and maintenance of anesthesia. Analyses of its pharmacokinetics require simple and sensitive methods for quantitation of propofol in human plasma. Previously reported HPLC and GC methods are limited by cumbersome extraction steps. We describe a novel method that combines sample preparation by solid-phase extraction (SPE) with hydrophilic-lipophilic balance cartridges and analysis with a sensitive LC-APCI-triple quadrupole mass spectrometry (MS/MS) method for better quantitation. The absolute recovery of the analyte was greater than 96%. The limit of quantification for propofol in plasma at a signal-to-noise ratio of 10 was 5 ng/ml. The precision of the assay yielded coefficients of variation ranging from 2.9 to 5.3% and an accuracies of 99-105%. Our method advances the quantitative analysis of propofol in human plasma by combining simple, rapid and efficient SPE with specific and sensitive quantitation by HPLC with APCI-MS/MS detection.

Pluronic microemulsions as nanoreservoirs for extraction of bupivacaine from normal saline.

We hypothesized that custom-designed microemulsions would effectively scavenge compounds from bulk media. Pluronic-based oil-in-water microemulsions were synthesized that efficiently reduced the free concentration of the local anesthetic bupivacaine in 0.9% NaCl. Both the molecular nature and concentration of the constituents in the microemulsions significantly affected extraction efficiencies. Pluronic F127-based microemulsions extracted bupivacaine more efficiently than microemulsions synthesized using other Pluronic surfactants (L44, L62, L64, F77, F87, F88, P104). Extraction was markedly increased by addition of fatty acid sodium salts due to greater oil/water interface area, increased columbic interaction between bupivacaine and fatty acids sodium salt, and greater surface activity. These data suggest that oil-in-water microemulsions may be an effective agent to treat cardiotoxicity caused by bupivacaine or other lipophilic drugs.

A physiologically-based pharmacokinetic model of drug detoxification by nanoparticles.

Nanoparticles (NPs) may be capable of reversing the toxic effects of drug overdoses in humans by adsorbing/absorbing drug molecules. This paper develops a model to include the kinetic effects of treating drug overdoses by NPs. Depending on the size and the nature of the NPs, they may either pass through the capillary walls and enter the tissue space or remain only inside the capillaries and other blood vessels: models are developed for each case. Furthermore, the time scale for equilibration between the NP and the blood will vary with the specific type of NP. The NPs may sequester drug from within the capillaries depending on whether this time scale is larger or smaller than the residence time of blood within the capillary. Models are developed for each scenario. The results suggest that NPs are more effective at detoxification if they are confined to the blood vessels and do not enter the tissues. The results also show that the detoxification process is faster if drug uptake occurs within the capillaries. The trends shown by the model predictions can serve as useful guides in the design of the optimal NP for detoxification.

Treatment of Local Anesthetic-Induced Cardiotoxicity Using Drug Scavenging Nanoparticles.

Because of its ability to create structures of nanoscale dimension with large aggregate particle surface area-to-volume ratios, nanotechnology offers new opportunities to treat drug poisonings. Emulsion-based nanoparticles (diameter: 118.4 nm) extracted bupivacaine from the aqueous phase in a physiological salt solution and attenuated the drug's cardiotoxicity in guinea pig heart to a greater extent than did a macroemulsion (432.0 nm). Additionally, nanoparticles sequestered bupivacaine from the aqueous phase of human blood and merit further investigation in animal models of intoxication.

Hepatoprotective activity of two plants belonging to the Apiaceae and the Euphorbiaceae family.

The different extracts of Apium graveolens Linn. (Apiaceae) and Croton oblongifolius Roxb. (Euphorbiaceae) were tested for their hepatoprotective activity against CCl(4) induced hepatotoxicity in albino rats. The degree of protection was measured by using biochemical parameters like serum transaminases (SGOT and SGPT), alkaline phosphatase, total protein and albumin. The methanolic extracts showed the most significant hepatoprotective activity comparable with standard drug silymarin. Other extracts namely petroleum ether and acetone also exhibited a potent activity.