The novel formulation design of self-emulsifying drug delivery systems (SEDDS) type O/W microemulsion I: enhancing effects on oral bioavailability of poorly water soluble compounds in rats and beagle dogs

Physiologically Based Pharmacokinetic Models Predicting Renal and Hepatic Concentrations of Industrial Chemicals after Virtual Oral Doses in Rats

Recently developed high-throughput in vitro assays in combination with computational models could provide alternatives to animal testing. The purpose of the present study was to model the plasma, hepatic, and renal pharmacokinetics of approximately 150 structurally varied types of drugs, food components, and industrial chemicals after virtual external oral dosing in rats and to determine the relationship between the simulated internal concentrations in tissue/plasma and their lowest-observed-effect levels. The model parameters were based on rat plasma data from the literature and empirically determined pharmacokinetics measured after oral administrations to rats carried out to evaluate hepatotoxic or nephrotic potentials. To ensure that the analyzed substances exhibited a broad diversity of chemical structures, their structure-based location in the chemical space underwent projection onto a two-dimensional plane, as reported previously, using generative topographic mapping. A high-throughput in silico one-compartment model and a physiologically based pharmacokinetic (PBPK) model consisting of chemical receptor (gut), metabolizing (liver), central (main), and excreting (kidney) compartments were developed in parallel. For 159 disparate chemicals, the maximum plasma concentrations and the areas under the concentration-time curves obtained by one-compartment models and modified simple PBPK models were closely correlated. However, there were differences between the PBPK modeled and empirically obtained hepatic/renal concentrations and plasma maximal concentrations/areas under the concentration-time curves of the 159 chemicals. For a few compounds, the lowest-observed-effect levels were available for hepatotoxicity and nephrotoxicity in the Hazard Evaluation Support System Integrated Platform in Japan. The areas under the renal or hepatic concentration-time curves estimated using PBPK modeling were inversely associated with these lowest-observed-effect levels. Using PBPK forward dosimetry could provide the plasma/tissue concentrations of drugs and chemicals after oral dosing, thereby facilitating estimates of nephrotoxic or hepatotoxic potential as a part of the risk assessment.

In vitro evaluation of a self-emulsifying drug delivery system (SEDDS) for nasal administration of dimenhydrinate

The objective of the study was the development and in vitro characterization of a self-emulsifying drug delivery system (SEDDS) for the nasal application of dimenhydrinate. Final composition of SEDDS was established based on drug solubility and stability studies. Dimenhydrinate was loaded into the SEDDS pre-concentrates to 7.5% (m/v). The droplet size of the final SEDDS formulations was in a range between 60 and 220 nm. Permeability, as well as tissue toxicity, of the formulations was investigated using bovine nasal mucosa. Enhancement in permeation up to 2.8-fold compared to pure dimenhydrinate was confirmed. Furthermore, toxicity studies did not reveal any serious tissue damages related to the SEDDS. Additionally, irritation potential of SEDDS was evaluated in ciliary beat frequency measurements. Incorporation of dimenhydrinate into SEDDS might therefore be considered as a promising approach within the field of nasal delivery of antiemetics by utilizing permeation enhancement strategy.

Nanostructuring Biomaterials with Specific Activities towards Digestive Enzymes for Controlled Gastrointestinal Absorption of Lipophilic Bioactive Molecules

This review describes the development of novel lipid-based biomaterials that modulate fat digestion for the enhanced uptake of encapsulated lipophilic bioactive compounds (e.g. drugs and vitamins). Specific focus is directed towards analysing how key material characteristics affect the biological function of digestive lipases and manipulate lipolytic digestion. The mechanism of lipase action is a complex, interfacial process, whereby hydrolysis can be controlled by the ability for lipase to access and adsorb to the lipid-in-water interface. However, significant conjecture exists within the literature regarding parameters that influence the activities of digestive lipases. Important findings from recent investigations that strategically examined the interplay between the interfacial composition of the lipid microenvironment and lipolysis kinetics in simulated biophysical environments are presented. The correlation between lipolysis and the rate of solubilisation and absorption of lipophilic compounds in the gastrointestinal tract (GIT) is detailed. Greater insights into the mechanism of lipase action have provided a new approach for designing colloidal carriers that orally deliver poorly soluble compounds, directly impacting the pharmaceutical and food industries.

Multifaceted applications of bile salts in pharmacy: an emphasis on nanomedicine

The human body has long provided pharmaceutical science with biomaterials of interesting applications. Bile salts (BSs) are biomaterials reminiscent of traditional surfactants with peculiar structure and self-assembled topologies. In the pharmaceutical field, BSs were employed on the basis of two different concepts. The first concept exploited BSs' metabolic and homeostatic functions in disease modulation, whereas the second one utilized BSs' potential to modify drug-delivery characteristics, which recently involved nanotechnology. This review is the first to gather major pharmaceutical applications of BSs from endogenous organotropism up to integration into nanomedicine, with a greater focus on the latter domain. Endogenous applications highlighted the role of BS in modulating hypercholesterolemia and cancer therapy in view of enterohepatic circulation. In addition, recent BS-integrated nanomedicines have been surveyed, chiefly size-tunable cholate nanoparticles, BS-lecithin mixed micelles, bilosomes, probilosomes, and surface-engineered bilosomes. A greater emphasis has been laid on nanosystems for vaccine and cancer therapy. The comparative advantages of BS-integrated nanomedicines over conventional nanocarriers have been noted. Paradoxical effects, current pitfalls, future perspectives, and opinions have also been outlined.

Strategies for oral delivery and mitochondrial targeting of CoQ10

Coenzyme Q10 (CoQ10), also known as ubiquinone or ubidecarenone, is a powerful, endogenously produced, intracellularly existing lipophilic antioxidant. It combats reactive oxygen species (ROS) known to be responsible for a variety of human pathological conditions. Its target site is the inner mitochondrial membrane (IMM) of each cell. In case of deficiency and/or aging, CoQ10 oral supplementation is warranted. However, CoQ10 has low oral bioavailability due to its lipophilic nature, large molecular weight, regional differences in its gastrointestinal permeability and involvement of multitransporters. Intracellular delivery and mitochondrial target ability issues pose additional hurdles. To maximize CoQ10 delivery to its biopharmaceutical target, numerous approaches have been undertaken. The review summaries the current research on CoQ10 bioavailability and highlights the headways to obtain a satisfactory intracellular and targeted mitochondrial delivery. Unresolved questions and research gaps were identified to bring this promising natural product to the forefront of therapeutic agents for treatment of different pathologies.

Toward the establishment of standardized in vitro tests for lipid-based formulations, part 6: effects of varying pancreatin and calcium levels

The impact of pancreatin and calcium addition on a wide array of lipid-based formulations (LBFs) during in vitro lipolysis, with regard to digestion rates and distribution of the model drug danazol, was investigated. Pancreatin primarily affected the extent of digestion, leaving drug distribution somewhat unaffected. Calcium only affected the extent of digestion slightly but had a major influence on drug distribution, with more drug precipitating at higher calcium levels. This is likely to be caused by a combination of removal of lipolysis products from solution by the formation of calcium soaps and calcium precipitating with bile acids, events known to reduce the solubilizing capacity of LBFs dispersed in biorelevant media. Further, during the digestion of hydrophilic LBFs, like IIIA-LC, the un-ionized-ionized ratio of free fatty acids (FFA) remained unchanged at physiological calcium levels. This makes the titration curves at pH 6.5 representable for digestion. However, caution should be taken when interpreting lipolysis curves of lipophilic LBFs, like I-LC, at pH 6.5, at physiological levels of calcium (1.4 mM); un-ionized-ionized ratio of FFA might change during digestion, rendering the lipolysis curve at pH 6.5 non-representable for the total digestion. The ratio of un-ionized-ionized FFAs can be maintained during digestion by applying non-physiological levels of calcium, resulting in a modified drug distribution with increased drug precipitation. However, as the main objective of the in vitro digestion model is to evaluate drug distribution, which is believed to have an impact on bioavailability in vivo, a physiological level (1.4 mM) of calcium is preferred.

Bile salts and their importance for drug absorption

Bile salts are present in the intestines of humans as well as the animals used during the development of pharmaceutical products. This review provides a short introduction into the physical chemical properties of bile salts, a description of the bile concentration and composition of bile in different animal species and an overview of the literature investigating the influence of bile salts on the in vivo performance of different compounds and drug formulations. Generally, there is a positive effect on bioavailability when bile is present in the gastro-intestinal tract, independent of the formulation systems, e.g. suspensions, solutions, cyclodextrin complexes or lipid based formulations, but a few exceptions have also been reported.

Development and evaluation of a novel microemulsion formulation of elacridar to improve its bioavailability

The study objective was to develop a formulation of elacridar to overcome its dissolution-rate-limited bioavailability. Elacridar is a P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) inhibitor that has been used to improve the brain distribution of drugs that are substrates of P-gp and BCRP. The chronic use of elacridar is restricted because of the poor solubility leading to poor oral bioavailability. A microemulsion formulation using Cremophor EL, Carbitol, and Captex 355 (6:3:1) was developed. The elacridar microemulsion was effective in the inhibition of P-gp and Bcrp in Madin-Darby canine kidney II-transfected cells. Friend Leukemia Virus Strain B (FVB) mice were used to determine the bioavailability of elacridar after a 10 mg/kg dose of elacridar in the microemulsion, intraperitoneally (i.p.) and orally (p.o.); and the absolute bioavailability was determined to be 1.3 and 0.47, respectively. Coadministration of elacridar microemulsion i.p. with p.o. erlotinib in FVB mice improved the erlotinib brain penetration threefold. The current study shows that a microemulsion formulation of elacridar is effective in improving the bioavailability of elacridar and is an effective inhibitor of P-gp and Bcrp, in vitro and in vivo. It offers an alternative to the suspension and allows a decrease in the dose required to achieve a significant inhibitory effect at the blood-brain barrier.

Molecular dynamics simulations of functional group effects on solvation thermodynamics of model solutes in decane and tricaprylin

Triglycerides and related fatty acid esters constitute a large percentage of the lipid excipients employed in the development of lipid-based drug formulations. Computer simulations can provide useful information on the structural, dynamic, and thermodynamic properties of these systems and may ultimately be valuable in predicting relative drug solubilities in lipid vehicles. This study utilized all-atom molecular dynamics simulations to explore the solvation of several model solutes in lipid vehicles. First, a combined thermodynamic perturbation and integration approach was employed to calculate functional group contributions to the free energy of transfer from n-decane to tricaprylin for a set of polar substituents attached to the 9-position of anthracene. A scaling factor of 0.79 for all atomic charges in the dry lipid (where the unscaled charges were obtained at the level of the HF/6-31G* basis set) was necessary in order to match the calculated group contributions to the free energies of transfer with their experimental values at 37 degrees C. A second set of simulations was performed in water-saturated tricaprylin containing a single molecule of benzamide to explore the state of organization of solvent molecules, the distribution of water molecules, and the local environment surrounding the solute. Radial distribution functions revealed evidence of local structure in the liquid triglyceride. The dissolved water was found to exist approximately 50% as monomers and 50% as self-associated species. Substantial hydrogen-bonding of benzamide with ester carbonyl oxygen atoms was observed.

What determines drug solubility in lipid vehicles: is it predictable?

Lipid-based drug delivery systems are of increasing interest to the pharmaceutical scientist because of their potential to solubilize drug molecules that may be otherwise difficult to develop. The ability to predict lipid solubility is an important step in being able to identify the right excipients to solubilize and formulate drugs in lipid formulations. However, predicting lipid solubility is complicated by the fact that interfacial effects may play a dominant role in these mixtures and the solubility may be affected by the microstructure (microemulsions, emulsions, oily solutions, etc.), as well as by the physicochemical properties of the oil, surfactant, co-solvent, and the drug. This review illustrates the fundamental factors that govern solubility in lipid mixtures and discusses models built at varying levels of sophistication to estimate the solubility. Examples from the literature are presented that demonstrate the application of these models, how their choice is related to the drug/lipid employed, and the challenges involved in solubility prediction. New data on the role water plays in altering lipid solubility, not only through its interaction with the solute, but also by changing the structure of lipids by promoting lipid organization are highlighted. The available data demonstrate that a rational understanding of solubilization in lipids is a worthwhile pursuit and models to predict at least the relative solubility from chemical structure have potential. Prediction of absolute solubility is more difficult as it requires knowledge of the drug's escaping tendency from the crystalline state. In recent years, it has become amply clear that for polar solutes, specific interactions are a critical factor governing solubility. Methods that can better take into account the specific as well as non-specific interactions between the solute and solvent, and the lipid microstructure, hold considerable promise for the future.

Enhancing intestinal drug solubilisation using lipid-based delivery systems

Lipid-based delivery systems are finding increasing application in the oral delivery of poorly water-soluble, lipophilic drugs. Whilst lipidic dose forms may improve oral bioavailability via several mechanisms, enhancement of gastrointestinal solubilisation remains argueably the most important method of absorption enhancement. This review firstly describes the mechanistic rationale which underpins the use of lipid-based delivery systems to enhance drug solubilisation and briefly reviews the available literature describing increases in oral bioavailability after the administration of lipid solution, suspension and self-emulsifying formulations. The use of in vitro methods including dispersion tests and more complex models of in vitro lipolysis as indicators of potential in vivo performance are subsequently described, with particular focus on recent data which suggests that the digestion of surfactants present in lipid-based formulations may impact on formulation performance. Finally, a series of seven guiding principles for formulation design of lipid-based delivery systems are suggested based on an analysis of recent data generated in our laboratories and elsewhere.

Design of potent amorphous drug nanoparticles for rapid generation of highly supersaturated media

Controlled precipitation produced aqueous nanoparticle suspensions of a poorly water soluble drug, itraconazole (ITZ), in an amorphous state, despite unusually high potencies (drug weight/total weight) of up to 94%. Adsorption of the amphiphilic stabilizer hydroxypropylmethylcellulose (HPMC) at the particle-aqueous solution interface arrested particle growth, producing surface areas from 13 to 51 m(2)/g. Dissolution of the particles in acidic media yielded high plateau levels in supersaturation up to 90 times the equilibrium solubility. The degree of supersaturation increased with particle curvature, as characterized by the surface area and described qualitatively by the Kelvin equation. A thermodynamic analysis indicated HPMC maintained amorphous ITZ in the solid phase with a fugacity 90 times the crystalline value, while it did not influence the fugacity of ITZ in the aqueous phase. High surface areas led to more rapid and levels of supersaturation higher than those seen for low-surface area solid dispersions, which undergo crystallization during slow dissolution. The rapid generation of high levels of supersaturation with potent amorphous nanoparticles, containing small amounts of stabilizers oriented at the particle surface, offers new opportunities for improving bioavailability of poorly water soluble drugs.

The novel formulation design of self-emulsifying drug delivery systems (SEDDS) type O/W microemulsion III: the permeation mechanism of a poorly water soluble drug entrapped O/W microemulsion in rat isolated intestinal membrane by the Ussing chamber method

We used ibuprofen as a poorly water soluble model drug, to examine the influence of bile salts and mucin layers on the permeability of that entrapped in an O/W microemulsion, in a rat isolated intestinal membrane by the Ussing chamber method. Under the presence of 3 kinds of the primary bile salts such a sodium taurocholate, etc., or a secondary bile salt such a sodium taurochenodeoxycholate at 0.01 mmol/L concentration, a significant difference was not demonstrated in the permeation clearance of the ibuprofen entrapped O/W microemulsion, as compared with the case without the bile salts. Thus, the bile salts did not have a remarkable influence on the permeability of the drug entrapped in the O/W microemulsion, and it was verified that this O/W microemulsion was hardly influenced by the flow of the bile secretion. On the other hand, when N-acetyl-L-cysteine (NAC) with the removal ability of a mucin layer was combined with the ibuprofen entrapped O/W microemulsion at the concentration of 3 and 10 mmol/L, it was shown that the permeation clearance of free ibuprofen did not decrease, but that of ibuprofen entrapped in the O/W microemulsion decreased with the increase of the NAC concentration. Therefore, it is confirmed that the mucin layer participates in the permeability of the drug entrapped in the O/W microemulsion. From these results, the mechanism in which the drug entrapped in the O/W microemulsion is released in a mucin layer, without passing through the route of the mixed micelle formation by bile, thereafter the drug permeates an intestinal membrane, is supposed.

The Novel Formulation Design of Self-emulsifying Drug Delivery Systems (SEDDS) Type O/W Microemulsion II: Stable Gastrointestinal Absorption of a Poorly Water Soluble New Compound, ER-1258 in Bile-fistula Rats

The stabilization effect of the novel self-emulsifying drug delivery systems (SEDDS) type O/W microemulsion on the gastrointestinal absorption of a poorly water soluble new compound, ER-1258 was examined by bile-fistula model rats. In the components of this formulation, medium chain fatty acid triglyceride (MCT), diglyceryl monooleate (DGMO-C), polyoxyethylene hydrogenated castor oil 40 (HCO-40) and ethanol were used as an oil, a lipophilic surfactant, a hydrophilic surfactant and a solubilizer at the mixture ratio of 25/5/45/25 w/w%, respectively. The ratios of AUC in the non-treated rats to that in the bile-fistula rats were 5.1, 12.1 and 3.0 for the suspension, the oily solution and the SEDDS type O/W microemulsion, respectively. The risk from which the difference between individuals of the compound absorption amounts resulting from the flow of the bile secretion serves as the maximum was high in order of oily solution>suspension>SEDDS type O/W microemulsion. Therefore, it was verified that the SEDDS type O/W microemulsion was able to reduce this risk, compared with the other formulations. When short chain fatty acid triglyceride (Triacetin) was used as an oil, the similar effect was demonstrated in the formulation composed of sorbitan sesquioleate (SO-15) as a lipophilic surfactant and polyoxyethylene hydrogenated castor oil 60 (HCO-60) or polyoxyethylene 20 sorbitan monooleate (TO-10M) as a hydrophilic surfactant.