Solubility and stability of tetrazepam in mixed micelles

Biocompatible phospholipid-based mixed micelles for posaconazole ocular delivery: Development, characterization, and in - vitro antifungal activity

Current study intended to prepare and evaluate phospholipid-based, mixed micelles (MMs) to improve the ocular delivery of posaconazole (POS), a broad-spectrum antifungal drug. For this, MMs based on egg phosphatidylcholine (EPC), as the main component, in combination with various bile salts (sodium cholate (NaC), sodium deoxycholate (NaDC), sodium taurocholate (NaTC)) or non-ionic surfactants (Pluronic® F-127, Pluronic® F-68, Tween 80, Labrasol® ALF, and d-a-tocopheryl polyethylene glycol 1000 succinate (TPGS)) were prepared. Particle size, polydispersity index, zeta potential and entrapment efficiency were evaluated to optimize the composition and preparation method of the MMs. Finally, morphology, stability, in vitro release pattern, and in vitro antifungal activity of the optimized formulation were investigated. Among the prepared MMs, vesicles composed of EPC: TPGS with a molar ratio of 70:30, prepared by the thin-film hydration method, showed more appropriate features. Among the prepared MMs, vesicles composed of EPC: TPGS with a molar ratio of 70:30 showed more appropriate features, including an entrapment efficiency (EE) greater than 80%, spherical shape morphology, an average particle size of about 58 nm, desirable stability over a month, slow-release without a noticeable initial burst, and a significantly higher in vitro antifungal activity in comparison with the drug suspension. Therefore, this formulation was selected as the optimal MMs and could be considered as a promising carrier for topical ocular delivery of POS.

Production and isolation of pharmaceutical drug nanoparticles

Nanosizing of pharmaceutical drug particles is one of the most important drug delivery platforms approaches for the commercial development of poorly water-soluble drug molecules. Though nanosizing of drug particles has been proven to greatly enhance drugs dissolution rate and apparent solubility, nanosized materials have presented significant challenges for their formulation as solid dosage forms (e.g. tablets, capsules). This is due to the strong Van der Waals attraction forces between dry nanoparticles leading to aggregation, cohesion, and consequently poor flowability. In this review, the broad area of nanomedicines is overviewed with the primary focus on drug nanocrystals and the top-down and bottom-up methods used in their fabrication. The review also looks at how nanosuspensions of pharmaceutical drugs are generated and stabilised, followed by subsequent strategies for isolation of the nanoparticles. A perspective on the future outlook for drug nanocrystals is also presented.

Mixed micelles loaded with the 5-benzylidenethiazolidine-2,4-dione derivative SKLB023 for efficient treatment of non-alcoholic steatohepatitis

Background: SKLB023, a novel 5-benzylidenethiazolidine-2,4-dione based-derivative, specifically inhibits inducible nitric oxide synthase and shows promise for treating non-alcoholic steatohepatitis (NASH). However, its poor water solubility and low bioavailability limits its clinical use. Here the drug was loaded into phosphatidylcholine-bile salt-mixed micelles (PBMM/SKLB023) to overcome these limitations. Methods: PBMM/SKLB023 was developed using a simple co-precipitation method, and formulation parameters were optimized. The pharmacokinetics of PBMM/SKLB023 were investigated in Wistar rats, and therapeutic efficacy was assessed in a mouse model of NASH induced by a diet deficient in methionine- and choline. Results: PBMM/SKLB023 particles were 11.36±2.08 nm based on dynamic light scattering, and loading the drug into micelles improved its water solubility 300-fold. PBMM/SKLB023 inhibited proliferation and activation of HSC-T6 cells more strongly than free SKLB023. PBMM/SKLB023 showed longer mean retention time and higher bioavailability than the free drug after intravenous injection in Wistar rats. In the mouse model of NASH, PBMM/SKLB023 alleviated hepatic lipid accumulation, inflammation, and fibrosis to a significantly greater extent than free SKLB023. Conclusion: PBMM/SKLB023 shows therapeutic potential for treating NASH and liver fibrosis.

Mixed Micelles Loaded with Bile Salt: An Approach to Enhance Intestinal Transport of the BCS Class III Drug Cefotaxime in Rats

BACKGROUND AND OBJECTIVES

Cefotaxime is a class III drug according to the Biopharmaceutical Classification System due to low intestinal permeability based on poor oral bioavailability. Bile salt compounds have been shown to be effective additive for drug permeation through several biological membranes. The main purpose of this study was to investigate the ability of a mixed micelles made of phosphatidylcholine, sodium deoxycholate, and loaded with a cefotaxime-3α,7α-dihydroxy-12-keto-5β-cholanate complex to enhance the oral bioavailability of cefotaxime in rats.

METHODS

Thin-film hydration method was used to prepare cefotaxime-loaded mixed micelles using different bile salt concentrations (0.87-25 mM of sodium deoxycholate). Overall, micelle sizes ranging from 86.9 to 155.6 nm were produced with negative zeta potential values from -15.9 to -19.5 mV and drug loading from 10.5 to 18.9 %. The oral bioavailability of cefotaxime in mixed micellar formulation was assessed and the pharmacokinetic parameters were compared with cefotaxime-3α,7α-dihydroxy-12-keto-5β-cholanate complex and cefotaxime aqueous solution. 24 Male Wistar rats were randomly allocated into four groups (n = 6, per group) to receive the following: (1) a single intravenous dose of cefotaxime (25 mg/kg) in sterilized normal saline solution for injection; (2) a single oral dose of mixed micelles (100 mg/kg of cefotaxime) in phosphate buffered saline administered by oral gavage; (3) a single oral dose of cefotaxime-3α,7α-dihydroxy-12-keto-5β-cholanate complex (100 mg/kg of cefotaxime) in phosphate buffered saline administered by oral gavage; (4) a single oral dose of free cefotaxime (100 mg/kg) in aqueous solution administered by oral gavage. Blood samples were collected for up to 24 h and cefotaxime analyzed using a validated HPLC assay.

RESULTS

Pharmacokinetic data showed that the oral bioavailability of cefotaxime in mixed micelles was found to be 4.91 % higher compared to the cefotaxime in aqueous solution (1.30 %). Maximum concentration (C _max) of cefotaxime in mixed micellar formulation was higher (1.08 ± 0.1 µg/ml) compared to the cefotaxime-3α,7α-dihydroxy-12-keto-5β-cholanate complex (0.69 ± 0.1 µg/ml) and cefotaxime in aqueous solution (0.52 ± 0.1 µg/ml). Similarly, the mean values for area under the plasma concentration-time curve extrapolated to infinity (AUC_0-∞) of cefotaxime in the mixed micellar formulation was higher (3.89 ± 0.9 μg·h/mL) compared to the cefotaxime-3α,7α-dihydroxy-12-keto-5β-cholanate complex (1.52 ± 0.2 μg·h/mL) and cefotaxime in aqueous solution (1.03 ± 0.4 μg·h/mL), respectively.

CONCLUSION

The mixed micellar formulation was able to increase the oral bioavailability of the BCS Class III drug cefotaxime up to fourfold by enhancing drug permeation through the mucosal membrane of the small intestine.

Clouding phenomenon in amphiphilic systems: A review of five decades

Phase separation in amphiphilic systems is an important phenomenon. The temperature at which an amphiphilic solution phase separates is known as Cloud Point (CP). This article reviews in detail the process of phase separation in various amphiphiles (surfactants, polymers and drugs) and effect of different classes of additives on the CP of these amphiphilic systems. Ions affect the CP of drugs in a different way: kosmotropes and hard bases decrease while chaotropes and soft bases increase the CP of nonionic and cationic surfactants. Anionic surfactants show CP in presence of quaternary salts only. Thus, depending upon the nature and concentration of additive, the CP of an amphiphilic system gets increased or decreased and, hence, properties of the system may be tuned as per the need and use. A system with CP at high concentration can be made to phase separate at lower concentration by simply introducing an appropriate additive in it. This makes the system cost effective. On the other hand, if not required, a low CP can be enhanced with the help of another type of a suitable additive.

Comparison of bile salt/phosphatidylcholine mixed micelles in solubilization to sterols and stability

Androst-3β,5α,6β-triol (Triol) is a promising neuroprotective agent, but its poor solubility restricts its development into parenteral preparations. In this study, Triol is significantly solubilized by bile salt/phosphatidylcholine mixed micelles (BS/PC-MM). All BS/PC-MM systems are tested to remarkably improve the drug solubility with various stabilities after drug loading. Among them, the sodium glycocholate (SGC)/egg phosphatidylcholine (EPC) system with 2:1 ratio in weight and the total concentration of SGC and EPC of 100 mg/mL is proved to produce stable mixed micelles with high drug loading. It is found that the stability of drug-loaded mixed micelles is quite different, which might be related to the change in critical micelle concentration (CMC) after incorporating drugs. SGC/EPC and SGC/soya phosphatidylcholine (SPC) remain transparent under accelerated conditions and manifest a decreased CMC (dropping from 0.105 to 0.056 mg/mL and from 0.067 to 0.024 mg/mL, respectively). In contrast, swine bile acid-sodium salt (SBA-Na)/PC and sodium deoxycholate (SDC)/PC are accompanied by drug precipitation and reached the maximum CMC on the first and the third days, respectively. Interestingly, the variation of CMC under accelerated testing conditions highly matches the drug-precipitating event in the primary stability experiment. In brief, the bile salt/phosphatidylcholine system exists as a potential strategy of improving sterol drug solubility. CMC variation under accelerated testing conditions might be a simple and easy method to predict the stability of drug-loaded mixed micelles.

Ginsenoside Rg3 bile salt-phosphatidylcholine-based mixed micelles: design, characterization, and evaluation

20(R)-Ginsenoside Rg3 (G-Rg3) has good inhibition of tumor angiogenesis and anti-tumor effect. However, its poor aqueous solubility and liposolubility are not ideal for clinical applications. In this study, a G-Rg3 bile salt-phosphatidylcholine-based mixed micelle system (BS-PC-MMS) was prepared. The optimization of G-Rg3 BS-PC-MMS was carried out using response surface methodology based on a central composite design. The encapsulation efficiency (EE) and light transmission (LT) of the optimized formulation were 90.69±2.54% and 99.10±3.12%, respectively. The average particle size of micelles was 20 nm. To increase the stability of G-Rg3 BS-PC-MMS, the lyophilized formulation of micelles was prepared. The G-Rg3 BS-PC-MMS did not produce hemolysis of erythrocytes within a certain concentration range and exhibited a good inhibition of tumor cells. The chick embryo chorioallantoic membrane assay results showed that the G-Rg3 BS-PC-MMS significantly inhibited angiogenesis. The G-Rg3 BS-PC-MMS is thus shown to be a safe, stable, and promising drug delivery system.

Solubilization and Interaction Studies of Bile Salts with Surfactants and Drugs: a Review

In this review, bile salt, bile salt-surfactant, and bile salt-drug interactions and their solubilization studies are mainly focused. Usefulness of bile salts in digestion, absorption, and excretion of various compounds and their rare properties in ordering the shape and size of the micelles owing to the presence of hydrophobic and hydrophilic faces are taken into consideration while compiling this review. Bile salts as potential bio-surfactants to solubilize drugs of interest are also highlighted. This review will give an insight into the selection of drugs in different applications as their properties get modified by interaction with bile salts, thus influencing their solution behavior which, in turn, modifies the phase-forming behavior, microemulsion, and clouding phenomenon, besides solubilization. Finally, their future perspectives are taken into consideration to assess their possible uses as bio-surfactants without side effects to human beings.

Micellization and adsorption behaviour of bile salt systems

Variation of enthalpy change with concentration of binary bile salt mixture.

Mixed nanomicelles loaded with thymopeptides-sodium deoxycholate/phospholipid improve drug absorption

AIM

To improve the absorption of thymopeptides (TH) by preparing sodium deoxycholate/phospholipid-mixed nanomicelles (SDC/PL-MMs).

METHODS

TH-SDC/PL-MMs were prepared by a film dispersion method, and then evaluated using photon correlation spectroscopy (PCS), zeta potential measurement, as well as their physical stability after storage for several days. Furthermore, in situ intestinal single-pass perfusion experiments and pharmacodynamics in immunodeficient mice were performed to make a comparison with TH powders and the control drug in absorption properties.

RESULTS

A narrow size distribution of nanomicelles, with a mean particle size of (149 ± 8.32) nm and a zeta potential of (-31.05 ± 2.52) mV, was obtained. The in situ intestine perfusion experiments demonstrated a significant advantage in absorption characteristics for TH compared to the other formulations, and oral administration of TH-SDC/PL-MMs potentiated an equivalent effect with i.h. TH in pharmacodynamic studies in immunodeficient mice.

CONCLUSIONS

TH-SDC/PL-MMs prepared by a film dispersion method are able to improve the absorption of TH. SDC/PL-MMs might be a good approach for the more effective delivery of drugs like TH.

Subcutaneously injected ivermectin-loaded mixed micelles: formulation, pharmacokinetics and local irritation study

Clinical application of ivermectin (IVM) is limited by several unfavorable properties, induced by its insolubility in water. Slight differences in formulation may change the plasma pharmacokinetics and efficacy. In this study, an IVM-loaded Soy phosphatidylcholine-sodium deoxycholate mixed micelles (IVM-SPC-SDC-MMs) were developed to improve its aqueous solubility, aiming to make it more applicable for clinical use. First, IVM-SPC-SDC-MMs were prepared using the co-precipitation method. After formulation optimization, the particle size was 9.46 ± 0.16 nm according to dynamic light scattering. The water solubility of IVM in SPC-SDC-MMs (4.79 ± 0.02 mg/mL) was improved by 1200-fold, comparing with free IVM (0.004 mg/mL). After subcutaneous administration, the pharmacokinetic study showed that IVM-SPC-SDC-MMs and commercially available IVM injection were bioequivalent. Also, the local irritation study confirmed that IVM-SPC-SDC-MMs reduced side reactions of the commercially available IVM injection. These results indicated that IVM-SPC-SDC-MMs represented a promising new drug formulation suitable for subcutaneous delivery of IVM.

Application of spray granulation for conversion of mixed phospholipid-bile salt micelles to dry powder form: influence of drug hydrophobicity on nanoparticle reagglomeration

The aim of this study was to investigate the feasibility of using spray granulation as a drying method to convert phospholipid (PL)-sodium deoxycholate (SDC)-mixed micelles (MMs) containing a water-insoluble drug to a solid dosage form and to evaluate how drugs with significantly different physicochemical properties affect the spray granulation process and subsequent in vitro and in vivo processes. Cucurbitacin B (Cu B) and glycyrrhizin (GL) were used as the model drugs. After spray granulation, the dried Cu B-PL/SDC-MM powder was completely redispersible within 15 minutes in vitro. Meanwhile, the area under the curve during 24 hours (AUC_0–24) and peak serum concentration from the dried powder were significantly (P<0.05) lower than the values from Cu B-PL/SDC-MMs in vivo. However, a better result was obtained for GL, ie, the drug was redispersed completely within 5 minutes in vitro. Further, absorption from the dried GL-PL/SDC-MM powder was increased to the same level as that for GL-PL/SDC-MMs in vivo compared with the control group. The difference in these results can be found in Cu B and GL. Cu B nanoparticles reagglomerated when released, resulting in slower redispersibility and less absorption compared with the original PL-SDC-MMs. However, no agglomeration or delay was observed for GL. A possible explanation is the difference in surface hydrophobicity between Cu B and GL. The results of this study not only show that spray granulation is an effective drying technique that can complement spray-drying and freeze-drying, but also confirm that the physicochemical properties of a drug have a significant influence on the in vitro and in vivo performance of the dried powder obtained after spray granulation.

Two-channel dansyl/tryptophan emitters with a cholic acid bridge as reporters for local hydrophobicity within supramolecular systems based on bile salts

Simultaneous emission from the Trp and Dns fluorophores of linked dyads in biomimetic media is quenched by iodide anions with rate constants that depend on the local hydrophobicity.

Antinuclear antibodies with nucleosome-restricted specificity for targeted delivery of chemotherapeutic agents

Circulating antinuclear autoantibodies (ANAs) are well known to accompany various pathological conditions and can be artificially induced by immunization. Research and clinical data permit us to hypothesize a definite connection between cancer and ANAs. Based on the available data, my group's research suggested that exogenous ANAs may be used as anticancer therapeutics. Among these ANAs, nucleosome-specific ANAs may be particularly useful. Advances in cancer immunotherapy with monoclonal antibodies re-emphasized the role of humoral immunity in neoplasia control. The development of a universal antibody targeting diverse cancers is of clear importance. We showed that certain natural ANAs recognize the surface of numerous tumor cells but not normal cells via cell surface-bound nucleosomes originating from the apoptotically dying neighboring tumor cells, mediate antibody-dependent cellular cytotoxicity of tumor cells in vitro and inhibit the development of murine tumor in syngeneic mice. A single monoclonal antinuclear nucleosome-specific autoantibody, mAb 2C5, specifically recognizes multiple unrelated human tumor cell lines and accumulates at a high tumor-to-normal cell ratio in various human tumors in nude mice. Immunotherapy with mAb 2C5 resulted in significant suppression of the growth of several human tumors. In addition, mAb 2C5, when used in subtherapeutic quantities, can serve as a highly efficient specific ligand to target various drug- or diagnostic agent-loaded pharmaceutical nanocarriers, such as liposomes and polymeric micelles, to various tumors. Here, the data (accumulated predominantly in our laboratory over several years) on mAb 2C5-mediated tumor targeting of chemotherapeutic agents is reviewed.

Improvement of oral bioavailability of glycyrrhizin by sodium deoxycholate/phospholipid-mixed nanomicelles

Glycyrrhizin (GL), extracted from the Glycyrrhiza glabra L., is active triterpenoid saponin components. However, due to its impermeability across the gastrointestinal mucosa, oral bioavailability of the drug was relatively low. To improve its oral bioavailability, formulation of GL as sodium deoxycholate/phospholipid-mixed nanomicelles (SDC/PL-MMs) has been performed in this study. GL-SDC/PL-MMs were produced by a film dispersion method and then investigated using photon correlation spectroscopy (PCS), zeta potential measurement, as well as its physical stability after storage for 10, 20, 30, 60, 90 and 120 days. To verify the theoretical hypothesis, pharmacokinetics and pharmacodynamic studies based on carbon tetrachloride (CCl(4))-induced acute liver injury was investigated. Results showed that a narrow size distributed nanomicelles with a mean particle size of 82.99 ± 7.5 nm and a zeta potential of -32.23 ± 1.05 mV was obtained. In the pharmacokinetics, GL-SDC/PL-MMs show a significant superiority in AUC(0-t), C(max) and other pharmacokinetic parameters compared with the control group. In the pharmacodynamic studies, compared with the bifendate control group, GL-SDC/PL-MMs showed an equivalent effect in reducing alanine aminotransferase (ALT), aspartate aminotransferase (AST) and improving the pathological changes of liver tissue. These results revealed that SDC/PL-MMs could enhance GL absorption in gastrointestinal tract and pharmacodynamic effect in the treatment of acute liver injury caused by CCl(4), and SDC/PL-MMs might be a good choice for oral delivery of poor bioavailability drug like GL.

A self-assembled nanodelivery system enhances the oral bioavailability of daidzein: in vitro characteristics and in vivo performance

AIM

A self-assembled nano-based delivery system was designed and developed to increase the oral bioavailability of poor hydrophilic and lipophilic daidzein.

METHODS

Daidzein was firstly combined with lecithin to form the daidzein-lecithin complex, then self-assembled into micelles (DLMs) with lecithin and sodium bile. The physiochemical properties and intestinal absorption of DLMs were characterized, and the pharmacokinetic behavior was evaluated in rats.

RESULTS

DLMs exhibited nanometer-sized particles. DLMs were mainly distributed in the stomach and proximal intestine after oral administration. The intestinal absorption of DLMs was significantly improved, and DLMs could be absorbed via both endocytosis and passive transport. The AUC(0-t) value of daidzein in rats treated with DLMs was ninefold greater than that of free daidzein suspension.

CONCLUSION

The presented delivery system could provide a new promising strategy for enhancing the oral bioavailability of drugs with poor hydrophilicity and lipophilicity.

Mixed micelles loaded with silybin-polyene phosphatidylcholine complex improve drug solubility

AIM

To prepare a novel formulation of phosphatidylcholine (PC)-bile salts (BS)-mixed micelles (MMs) loaded with silybin (SLB)-PC complex for parenteral applications.

METHODS

SLB-PC-BS-MMs were prepared using the co-precipitation method. Differential scanning calorimetry (DSC) analysis was used to confirm the formation of the complex and several parameters were optimized to obtain a high quality formulation. The water-solubility, drug loading, particle size, zeta potential, morphology and in vivo properties of the SLB-PC-BS-MMs were determined.

RESULTS

The solubility of SLB in water was increased from 40.83 ± 1.18 μg/mL to 10.14 ± 0.36 mg/mL with a high drug loading (DL) of 14.43% ± 0.44% under optimized conditions. The SLB-PC-BS-MMs were observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) and showed spherical shapes. The particle size and zeta potential, as measured by photon correlation spectroscopy (PCS), were about 30 ± 4.8 nm and -39 ± 5.0 mV, respectively. In vivo studies showed that incorporation of the SLB-PC complex into PC-BS-MMs led to a prolonged circulation time of the drug.

CONCLUSION

This novel formulation appears to be a good candidate for drug substances that exhibit poor solubility for parenteral administration.

Solubilization and Pharmacokinetic Behaviors of Sodium Cholate/Lecithin-Mixed Micelles Containing Cyclosporine A

The purpose of this study was to investigate the solubilization capacity of sodium cholate/lecithin-mixed micelles and to evaluate the potential of mixed micelles as a carrier of cyclosporine A for intravenous infusion. The mixed micelles were prepared by coprecipitation technique. The formulation components and preparation procedures, which may affect the solubilization of cyclosporine A, were studied. The dilution stability of cyclosporine A-containing mixed micelles was investigated. Pharmacokinetic behaviors of mixed micelles in rabbits after intravenous infusion were compared with Sandimmun. Results showed the strategies to increase the solubility of cyclosporine A include lowering the molar ratio of sodium cholate to lecithin, increasing the concentration of lecithin, and reducing the ionic strength of the dispersion medium and temperature. The largest solubility was found to be 5.42 +/- 0.16 mg/ml. The leakage of mixed micelles in 5% glucose (5.84%) was much less than that in saline solution (36.7%). The relative bioavailability of mixed micelles versus Sandimmun was 112 +/- 20%, and statistical analysis demonstrated both preparations were bioequivalent. Sodium cholate/lecithin-mixed micelles are promising carriers in the intravenous delivery of cyclosporine A, considering their capability of large-scale production and low-toxic property.

Role of nanotechnology in pharmaceutical product development

A number of new molecular entities (NMEs) selected for full-scale development based on their safety and pharmacological data suffer from undesirable physicochemical and biopharmaceutical properties, which lead to poor pharmacokinetics and distribution after in vivo administration. An optimization of the preformulation studies to develop a dosage form with proper drug delivery system to achieve desirable pharmacokinetic and toxicological properties can aid in the accelerated development of these NMEs into therapies. Nanoparticulate drug delivery systems show a promising approach to obtain desirable druglike properties by altering the biopharmaceutics and pharmacokinetics properties of the molecule. Apart from the advantages of enhancing potential for systemic administration, nanoparticulate drug delivery systems can also be used for site-specific delivery, thus alleviating unwanted toxicity due to nonspecific distribution, improve patient compliance, and provide favorable clinical outcomes. This review summarizes some of the parameters and approaches that can be used to evaluate nanoparticulate drug delivery systems in early stages of formulation development.

The study of the influence of surfactant charge on alkaline hydrolysis reactions of acetylsalicylic acid (ASA) and triflusal (TFL) using spectrophotometric methods

In this research, the effects of micellar systems on alkaline hydrolysis reactions of acetylsalicylic acid (ASA) and triflusal (TFL) were found to be dependant upon the surfactant charge within the micelle. In cationic micelles, there is a catalytic effect at low concentrations of surfactant. However, this reaction is inhibited at higher surfactant concentrations. In anionic micelles, a catalytic effect occurs, while in zwitterionic and non-ionic micelles there is an inhibitory effect. Such reactions are attributable to changes in reactants on the micellar surface, or to the fact that both reactants are found in different microenvironments. The pseudophase (PS) and ion-exchange (PPIE) models were found to be consistent with the experimental result. Furthermore, the association constants for both drugs could be determined together with micellar rate constants in heterogeneous media.

Action of sodium deoxycholate on subcutaneous human tissue: local and systemic effects

BACKGROUND

Phosphatidylcholine injections have been used as a nonsurgical alternative to the surgical removal of undesired fat. Studies in cell culture suggest that sodium deoxycholate (SD) has a detergent action in fat reduction.

OBJECTIVE

The objective was to study SD in subcutaneous human tissue.

METHODS AND MATERIALS

Thirty volunteers underwent four sessions of subcutaneous abdominal injections of diluted 2.5 or 1% SD stock solutions or placebo. Clinical, hematologic, and ultrasonographic evaluations were performed for 3 months and histology at 3 and 6 months.

RESULTS

Both concentrations of SD induced an inflammatory response at the injection site, with dose-dependent adipocyte lysis. Patients reported mild, localized heat, erythema, swelling, and intense pain. Microscopic evaluation revealed necrosis of adipose tissue with adipocyte lysis, fat dissolution, acute lymphomononuclear inflammatory reaction, and intense phagocytosis of fat cells by macrophages. Fibrosis was observed only at the 6-month biopsy. Nodules at the injection sites, compatible with areas of inflammation, were detected by ultrasonography 2 weeks after the first injection. Placebo injections induced no histologic changes.

CONCLUSIONS

SD induces an inflammatory reaction in subcutaneous human fat and dose-dependent adipocyte lysis with acute pain and fibrosis. No systemic effects were detected. Further studies will establish the best dose-result ratio, frequency of application, and long-term safety.

Medicolegal aspects of tetrazepam metabolism

The benzodiazepine tetrazepam is primarily muscle relaxant with comparably lower central sedating effects and is therefore commonly prescribed for muscle spasms of different origins. To evaluate tetrazepam metabolism, a study was conducted with ten healthy volunteers. Blood and urine samples were regularly collected after the intake of 50 mg tetrazepam. Toxicological analyses revealed that tetrazepam is also metabolized to diazepam and further to nordazepam, which has not yet been reported. Tetrazepam and diazepam could be detected in urine samples at least 72 h after intake, the diazepam concentration being 33% (+/-14% SD), on average, of the tetrazepam concentration. On the basis of three case histories, the importance of the detection of these newly described metabolites is shown as necessary to prevent false accusations and potential negative legal consequences for examined persons.

Thermodynamics of demicellization of mixed micelles composed of sodium oleate and bile salts

Isothermal titration calorimetry (ITC) was used to determine the critical micelle concentration (cmc) and the thermodynamic parameters associated with the demicellization of sodium oleate (NaO) and mixed micelles composed of the bile salt (BS) sodium cholate (NaC) or sodium deoxycholate (NaDC), respectively, and NaO at a molar ratio of 5:2. The influence of the ionic strength (pure water and 0.1 M NaCl at pH 7.5) as well as that of the temperature (10-70 degrees C) were analyzed. For NaO, two cmc's were detected, indicating a two-step aggregation process, whereas only one cmc was observed for the two BSs. A single aggregation mechanism is also evident for the demicellization of mixed micelles (BS/NaO 5:2). Increasing the ionic strength induces the well-known decrease of the cmc. The cmc shows a minimum at room temperature. The cmc(mix) of the mixed micelles was analyzed using models assuming an ideal or nonideal mixing behavior of both detergents. The thermodynamic parameters describing the enthalpy (deltaHdemic), entropy (deltaSdemic), and Gibbs energy change (deltaGdemic), as well as the change in heat capacity (deltaCp,demic) for demicellization, were obtained from one ITC experiment. From the temperature dependence of deltaHdemic, the change of the hydrophobic surface area of the detergents from the micellar into the aqueous phase was derived. In all cases, the deltaCp,demic values are positive. In addition, the temperature dependence of the size of the formed aggregates was studied by dynamic light scattering (DLS). DLS indicated two populations of aggregates in the mixed system, small primary micelles (0.5-2 nm), and larger aggregates with a hydrodynamic radius in the range of 50-150 nm.

Immunomicelles: targeted pharmaceutical carriers for poorly soluble drugs

To prepare immunomicelles, new targeted carriers for poorly soluble pharmaceuticals, a procedure has been developed to chemically attach mAbs to reactive groups incorporated into the corona of polymeric micelles made of polyethylene glycol-phosphatidylethanolamine conjugates. Micelle-attached antibodies retained their ability to specifically interact with their antigens. Immunomicelles with attached antitumor mAb 2C5 effectively recognized and bound various cancer cells in vitro and showed an increased accumulation in experimental tumors in mice when compared with nontargeted micelles. Intravenous administration of tumor-specific 2C5 immunomicelles loaded with a sparingly soluble anticancer agent, taxol, into experimental mice bearing Lewis lung carcinoma resulted in an increased accumulation of taxol in the tumor compared with free taxol or taxol in nontargeted micelles and in enhanced tumor growth inhibition. This family of pharmaceutical carriers can be used for the solubilization and enhanced delivery of poorly soluble drugs to various pathological sites in the body.

Bile salt/lecithin mixed micelles optimized for the solubilization of a poorly soluble steroid molecule using statistical experimental design

Bile salts and lecithin combine physiologically to form mixed micelles which aid the solubilization and absorption of dietary fats and drug molecules. In this series of experiments, we have shown how experimental design procedures aid the optimization of a formulation incorporating a bile salt, lecithin, and water with fluticasone propionate (FP) as the model poorly soluble drug. The initial inclusion of a categorical variable ruled out the use of classic response surface designs; therefore the experimental design was constructed using a d-optimal selection from a candidate set of all possible experimental combinations. A separate 2-factor central composite design was used to determine the optimum lecithin and bile salt concentrations over an extended range after the categorical variable had been eliminated. It has been demonstrated that an increase in either lecithin or cholic acid concentration produces an increase in solubility of FP, while sodium taurocholate appears to depress the solubility of FP compared with the other two bile salts. The increase in solubility associated with the increase in bile salt and lecithin is further demonstrated by a linear relationship between FP solubility and the total lipid in the formulation. The influence of molar ratio of lecithin to bile salt in the formulation is also significant. The physical properties of the mixed micellar system (solution turbidity and viscosity ranking) were used to further discriminate between formulations. The optimization showed that the dominant effect was the lecithin, which improves the solubilizing characteristics of the formulation with increasing concentration. The effect of salt concentration is less marked though slightly quadratic in nature. The overall increase in solubility demonstrated was from <1 microg/mL in water to 205 microg/mL in the optimized mixed micellar system.

Solubilizing potential of submicron emulsions and aqueous dispersions of lecithin

Aqueous lecithin dispersions (WLD, water-lecithin-dispersion) were obtained by dispersing egg lecithin (1.2 or 2.4% w/w) in an isotonic mixture of glycerol and water. The solubilization potential of the pure phospholipid structures was investigated and compared with that of submicron emulsions containing the same amounts of lecithin and 10 or 20% (w/w) of soya-bean oil. The increase in solubility of the investigated lipophilic drugs in WLD was proportional to the lecithin concentration. Concentration of lecithin in the emulsion was the main factor determining solubility of drugs moderately lipophilic (logP below 2.5), while for more lipophilic compounds the presence of oil was a determinant and for such drugs solubility in submicron emulsion was better than in WLD. WLD obtained in a simple technological process may be considered as a carrier particularly for highly lipophilic drugs: solubility of estradiol in this system was 100-fold higher than in water.

Development of a novel parenteral formulation for tetrazepam using a lipid emulsion

A novel parenteral formulation for tetrazepam (10 mg/ml) was developed using lipid emulsions. This formulation utilized a new lipid emulsion formulation, which was developed by changing the polarity of the oil phase. It was found that increasing the polarity of the oil phase resulted in enhanced solubility of tetrazepam. Tetrazepam showed higher solubility in a mixture of castor oil and middle-chain triglycerides (MCTs) (1:1) than in any other oil investigated. This mixture resulted in low interfacial tension and moderate viscosity, which seemed to be the optimum oil phase. In addition, to increase the concentration of tetrazepam, an emulsion formulation containing 30% oil phase was produced and optimized. The drug-free emulsion formulation showed fine particle sizes with an imperceptible change in physicochemical properties after more than 2 years on the shelf. As a result, it was possible to produce a parenteral emulsion formulation containing 10 mg/ml tetrazepam. No change in the physicochemical properties of the emulsion was observed after the addition of tetrazepam. The tetrazepam emulsion showed stable behavior during the autoclaving process and good shelf stability for at least 10 months as well. Tetrazepam itself also displayed good stability during the autoclaving process and also showed good shelf stability in this emulsion formulation.

Surface active drugs: self-association and interaction with membranes and surfactants. Physicochemical and biological aspects

Many pharmacologically active compounds are of amphiphilic (or hydrophobic) nature. As a result, they tend to self-associate and to interact with biological membranes. This review focuses on the self-aggregation properties of drugs, as well as on their interaction with membranes. It is seen that drug-membrane interactions are analogous to the interactions between membranes and classical detergents. Phenomena such as shape changes, vesiculation, membrane disruption, and solubilization have been observed. At the molecular level, these events seem to be modulated by lipid flip-flop and formation of non-bilayer phases. The modulation of physicochemical properties of drugs by self-association and membrane binding is discussed. Pathological consequences of drug-membrane interaction are described. The mechanisms of drug solubilization by surfactants are reviewed from the physicochemical point of view and in relation to drug carrying and absorption by the organism.