Solubility of Pharmaceutical Ingredients in Natural Edible Oils.

Natural edible oils (NEOs) are common excipients for lipid-based formulations. Many of them are complex mixtures comprising hundreds of different triglycerides (TGs). One major challenge in developing lipid-based formulations is the variety in NEO compositions affecting the solubility of active pharmaceutical ingredients. In this work, solubilities of indomethacin (IND), ibuprofen (IBU), and fenofibrate (FFB) in soybean oil and in coconut oil were measured via differential scanning calorimetry, high-performance liquid chromatography, and Raman spectroscopy. Furthermore, this work proposes an approach that mimics NEOs using one key TG and models the API solubilities in these NEOs based on perturbed-chain statistical associating fluid theory (PC-SAFT). Key TGs were determined using the 1,2,3-random hypothesis, and PC-SAFT parameters were estimated via a group-contribution method. Using the proposed approach, the solubility of IBU and FFB was modeled in soybean oil and coconut oil. Furthermore, the solubilities of five more APIs (IND, cinnarizine, naproxen, griseofulvin, and felodipine) were modeled in soybean oil. All modeling results were found in very good agreement with the experimental data. The influence of different NEO kinds on API solubility was examined by comparing FFB and IBU solubilities in soybean oil and refined coconut oil. PC-SAFT was thus found to allow assessing the batch-to-batch consistency of NEO batches in silico.

Suitability of Artificial Membranes in Lipolysis-Permeation Assays of Oral Lipid-Based Formulations.

PURPOSE: To evaluate the performance of artificial membranes in in vitro lipolysis-permeation assays useful for absorption studies of drugs loaded in lipid-based formulations (LBFs). METHODS: Polycarbonate as well as PVDF filters were treated with hexadecane, or lecithin in n-dodecane solution (LiDo) to form artificial membranes. They were thereafter used as absorption membranes separating two compartments mimicking the luminal and serosal side of the intestine in vitro. Membranes were subjected to dispersions of an LBF that had been digested by porcine pancreatin and spiked with the membrane integrity marker Lucifer Yellow (LY). Three fenofibrate-loaded LBFs were used to explore the in vivo relevance of the assay. RESULTS: Of the explored artificial membranes, only LiDo applied to PVDF was compatible with lipolysis by porcine pancreatin. Formulation ranking based on mass transfer in the LiDo model exposed was the same as drug release in single-compartment lipolysis. Ranking based on observed apparent permeability coefficients of fenofibrate with different LBFs were the same as those obtained in a cell-based model. CONCLUSIONS: The LiDo membrane was able to withstand lipolysis for a sufficient assay period. However, the assay with porcine pancreatin as digestive agent did not predict the in vivo ranking of the assayed formulations better than existing methods. Comparison with a Caco-2 based assay method nonetheless indicates that the in vitro in vivo relationship of this cell-free model could be improved with alternative digestive agents.

Preparation of stabilized submicron fenofibrate crystals on niacin as a hydrophilic hydrotropic carrier.

Fenofibrate is antihyperlipidemic which has low and variable oral bioavailability due to erratic dissolution characteristics. Niacin showed a potential atheroprotective effects suggesting possible co-administration with fenofibrate with a potential for development of fixed dose combination. The chemical structure of both drugs highlights the opportunity for interaction upon co-processing due to the existence of complementary hydrogen bonding sites. Accordingly, fenofibrate and niacin were co-processed by wet co-grinding and the resulting product was assessed using scanning electron microscopy, FTIR, thermal analysis and X-ray diffraction in addition to dissolution studies. The instrumental analysis indicated the development of submicron fenofibrate crystals stabilized over the surface of niacin crystals. The developed submicron crystals showed fast dissolution of fenofibrate depending on the relative proportions of fenofibrate to niacin. Co-processing of both drugs at dose ratio which contained higher proportion of niacin resulted in further enhancement in the dissolution rate. This further enhancement was attributed to the hydrotropic effect of niacin which was proved by solubility study in addition to size reduction. This supposition was confirmed from the inferior dissolution of fenofibrate from the physical mixture. The study introduces fenofibrate/niacin as potential fixed dose combination for augmented dissolution rate and pharmacological effects.

A Relative Permittivity Approach for Fast Drug Solubility Screening of Solvents and Excipients in Lipid-Based Delivery.

Drug solubility screening in solvents and lipids is central for the development of lipid-based formulations (LBFs), and any guidance to reduce the experimental workload would be highly desirable. Solubility parameters are interesting as they can be predicted in silico for a drug but they are hardly predictable for complex lipids. This paper uses a new approach to convert an in silico drug solubility parameter to an estimated relative permittivity, εr. Diverse solvents and lipid-based excipients were then experimentally tested for εr and solubility using fenofibrate as model. The typical excipients and solvents used in LBFs showed an εr range of about 2-24, and good solubility of fenofibrate was indeed evidenced in vicinity of its estimated relative permittivity 13.2 ± 2.7. Mixtures of promising excipients were studied subsequently, and the obtained εr was predictable based on the known values of the individual components. The novel permittivity approach has demonstrated its usefulness, it has much potential in early development for ranking of suitable excipients, and it gives an initial orientation to design formulations. Future research may clarify further opportunities and limits of the novel approach for LBFs.

In vitro and in vivo performance of monoacyl phospholipid-based self-emulsifying drug delivery systems.

This study investigates the effect of monoacyl phospholipid incorporation on the in vitro and in vivo performance of self-emulsifying drug delivery systems (SEDDS). Monoacyl phosphatidylcholine (Lipoid S LPC 80 (LPC)) was incorporated into four different fenofibrate (FF)-loaded long-chain SEDDS to investigate the impact of LPC on the emulsion droplet size, extent of digestion, colloidal structure evolution and drug precipitation during in vitro lipolysis simulating human conditions and drug bioavailability in a rat model. The four investigated SEDDS containing long-chain glycerides, polyoxyl 35 castor oil or polyoxyl 8 caprylocaproyl glycerides with or without LPC. In situ synchrotron small/wide-angle X-ray scattering (SAXS/WAXS) was used to simultaneously real-time monitor the kinetics of lamellar phase structure development and FF crystalline precipitation. Adding LPC increased the particle size and polydispersity of the dispersed SEDDS. The two LPC-free SEDDS generated lamellar phase structures (Lα) with d-spacing=4.76nm during digestion. Incorporating LPC into these systems inhibited the formation of lamellar phase structures. The amount of precipitated crystalline FF from the four SEDDS was similar during the first 15min but differed during the last 45min of in vitro digestion. The kinetics of colloidal structure development and FF precipitation was related to the digestion kinetics. The in vivo bioavailability data showed no significant differences between the four SEDDS, which correlates with the in vitro FF precipitation during the first 15min of lipolysis. Thus, the presence of LPC, different emulsion droplet sizes and concentration of lamellar phase structures observed in vitro did not correlate with the FF absorption in rats. The study suggests that later time points of the in vitro lipolysis overestimated FF precipitation in rats because of the high enzyme activity, the lack of gastric and absorption steps, and the low bile salts and phospholipid concentrations of the in vitro model.

Drug release studies from lipid nanoparticles in physiological media by a new DSC method.

Lipid nanoparticles are an interesting parenteral delivery system for poorly water-soluble drugs. In order to approach physiological conditions when conducting release studies from such systems the release media should preferentially contain lipophilic acceptor compartments such as lipoproteins or other colloidal lipophilic components. In practice, drug release studies under such close to physiological conditions may be complicated by the small size of lipid nanoparticles, which is in the same range as that of the potential acceptor particles. This study describes a novel differential scanning calorimetry (DSC) method for drug release measurements which works without separation of donor and acceptor particles. The technique is based on measuring the crystallization temperature of trimyristin nanoparticles by DSC. The crystallization temperature of the nanoparticles decreases proportionally with the amount of active ingredient incorporated and thus increases as a result of drug release. Liquid trimyristin nanoparticles loaded with fenofibrate, orlistat, tocopherol acetate and ubidecarenone were studied in three different release media with increasing complexity and comparability to physiological conditions: a rapeseed oil nanoemulsion, porcine serum and porcine blood. Using the new method, a correlation between release behavior and drug lipophilicity was observed: the higher the logP value of the drug, the slower the release. The extent of drug release was influenced by partition equilibrium as indicated by increased drug release in the rapeseed oil nanoemulsion compared to porcine serum and blood.

Effects of combined dietary supplementation with fenofibrate and Schisandrae Fructus pulp on lipid and glucose levels and liver function in normal and hypercholesterolemic mice.

BACKGROUND: Currently, combined therapy using herbs and synthetic drugs has become a feasible therapeutic intervention against some diseases. The purpose of this study was to assess the effects of supplementation with fenofibrate (FF), a chemical drug used for the treatment of hyperlipidemia, and the aqueous extract of Schisandrae Fructus (SF, a Chinese herb) pulp (AqSF-P) or an SF-related synthetic analog, bicyclol (BY), on serum/hepatic lipid levels and liver status in normal and hypercholesterolemic (HCL) mice. METHODS: Male mice obtained from the Institute of Cancer Research (ICR) were fed on a normal diet (ND) or high cholesterol/bile salt (0.5%/0.15%, w/w) diet (HCBD) containing FF (0.03% or 0.1%, w/w) with or without AqSF-P (0.3%-9.0%, based on crude herbal material, w/w) or BY (0.025%, w/w) for 10 days. Then serum lipid levels and alanine aminotransferase (ALT) activity, as well as hepatic triglyceride (TG), total cholesterol (TC), and glucose levels, were measured. RESULTS: Oral supplementation with FF significantly reduced serum and hepatic TG, TC, and hepatic glucose levels (approximately 79%) in mice fed with ND or HCBD. FF supplementation combined with AqSF-P or BY increased FF-induced reduction in hepatic TC and TG contents in ND-fed mice (up to 67%) and in HCBD-fed mice (up to 54%), when compared with FF supplementation alone. Hepatic glucose-lowering effect of FF was enhanced (up to 19%) by AqSF-P cosupplementation in both normal and HCL mice. FF supplementation enhanced the excretion of fecal TC (by 75%) in mice fed with HCBD. Fecal TC contents were increased by 14%/9% in the combination therapy with FF and AqSF-P in ND-/HCBD-fed mice. Serum ALT activity was elevated by 45% in HCBD-fed mice. FF caused a significant increase in ALT activity by 198% and 120% in normal and HCL mice, respectively. BY markedly attenuated the ALT activity by 54% in mice fed with ND supplemented with 0.1% FF and by 42% in mice fed with HCBD supplemented with 0.03% FF. CONCLUSION: AqSF-P cosupplementation augmented the hepatic lipid-/glucose-lowering effects of FF. BY ameliorated FF-induced liver injury in normal and HCL mice.

Preparation and characterization of fenofibrate-loaded nanostructured lipid carriers for oral bioavailability enhancement.

The aim of this study is to investigate the potential of nanostructured lipid carriers (NLCs) in improving the oral bioavailability of a lipid lowering agent, fenofibrate (FEN). FEN-loaded NLCs (FEN-NLCs) were prepared by hot homogenization followed by an ultrasonication method using Compritol 888 ATO as a solid lipid, Labrafil M 1944CS as a liquid lipid, and soya lecithin and Tween 80 as emulsifiers. NLCs were characterized in terms of particle size and zeta potential, surface morphology, encapsulation efficiency, and physical state properties. Bioavailability studies were carried out in rats by oral administration of FEN-NLC. NLCs exhibited a spherical shape with a small particle size (84.9 ± 4.9 nm). The drug entrapment efficiency was 99% with a loading capacity of 9.93 ± 0.01% (w/w). Biphasic drug release manner with a burst release initially, followed by prolonged release was depicted for in vitro drug release studies. After oral administration of the FEN-NLC, drug concentration in plasma and AUCt-∞ was fourfold higher, respectively, compared to the free FEN suspension. According to these results, FEN-NLC could be a potential delivery system for improvement of loading capacity and control of drug release, thus prolonging drug action time in the body and enhancing the bioavailability.

How do in-vitro release profiles of nanosuspensions from Alzet® pumps correspond to the in-vivo situation? A case study on radiolabeled fenofibrate.

In research and development sufficiently high and constant plasma levels of drug candidates are often requested, but simple solutions of hydrophobic drugs delivered from the commonly used micro-osmotic pumps cannot meet these demands. Nanosuspensions released from implanted osmotic devices can be a strategy to overcome this challenge but little is known about their pharmacokinetic behavior after subcutaneous application. In the current study, four different nanosuspension formulations containing iodinated fenofibrate were prepared, physicochemically characterized and investigated concerning their in-vitro release kinetics from osmotic pumps. One nanosuspension of lower viscosity exhibited thereby an unexpectedly first order release kinetics, whereas the higher viscous counterpart was released in the expected zero-order manner. To assess the relation of the in-vitro release kinetics to the in-vivo fate of nanosuspensions, various [(131)I] iodinated fenofibrate formulations were subcutaneously applied to mice. The biodistribution was followed by means of γ-scintigraphy and γ-scintillation. Two different nanosuspensions released from osmotic pumps were compared to bolus injections of a nanosuspension and an organic drug solution. The distribution and elimination of the bolus injected drug solution were almost completed within 48h. In contrast, a long lasting (>1week) depot at the injection site was formed by the bolus injected nanosuspension. Ex vivo examination of the organs showed a sustained, but exponential decrease of the radiolabel concentration. More constant drug levels in the organs were achieved within the nanosuspensions released from osmotic pumps. The organ levels of [(131)I] labeled fenofibrate were found to be more constant in case of the pump with the higher viscous nanosuspension in contrast to the lower viscous counterpart. However, the very different release profiles of the lower and higher viscous nanosuspension observed in-vitro were not observed in-vivo, as both pumps showed zero order release. In conclusion, nanosuspensions of poorly soluble compounds released from subcutaneously implanted osmotic pumps can be a suitable approach in pharmacokinetic studies. Although the in-vivo release of nanosuspensions differed in the expected release profile from the in-vitro test results, these in-vitro release tests present a valuable tool for the pre-selection of suitable nanosuspension candidates.

Formulation and optimization of fenofibrate lipospheres using Taguchi's experimental design.

Fenofibrate lipospheres were prepared by the melt dispersion technique. Critical parameters influencing particle size and entrapment efficiency were optimized by applying the L9 Taguchi experimental design. Entrapment efficiency of up to 87 % was obtained for the optimized formulation on increasing olive oil up to 30 % in the lipid carrier. Particle size analysis by microscopy and SEM revealed narrow particle size distribution and formation of discrete lipospheres of superior morphology. In vitro dissolution data best fitted the Higuchi model, indicating diffusion controlled release from porous lipid matrices. Prolonged release was obtained from stearic acid-olive oil lipospheres compared to cetyl alcohol-olive oil lipospheres due to the relatively hydrophobic matrix formed by stearic acid. Lipid lowering studies in Triton induced hyperlipidemia rat model demonstrated higher lipid lowering ability for fenofibrate lipospheres compared to the commercial product and plain drug.

Optimization of self nanoemulsifying drug delivery system for poorly water-soluble drug using response surface methodology.

There is an increasing interest on self-nanoemulsifying drug delivery system (SNEDDS) for oral delivery of poorly water-soluble drugs. However, development of SNEDDS is often driven by empiric, pseudo-ternary diagrams and solubility of drugs, and it is lacking a systematic approach for evaluating impact of excipients on the performance of formulations as well as the fate of drug. The aim of this study was to rationalize the SNEDDS development procedure and to get a better understanding on the role of excipients on the SNEDDS. The formulations consist of soybean oil or rapeseed oil, Cremophor(®) RH40, Maisine™ 35-1 and ethanol. Response surface methodology (RSM) was used in the development of SNEDDS. Significant advantages of RSM were found in reducing the work load and determining the impact of excipients on formulation characteristics. The most significant factor in influencing droplet size was the co-surfactant Maisine™ 35-1, the droplet size increased with increasing concentration of Maisine™ 35-1. It suggests that Maisine™ 35-1 has double functions in the SNEDDS; it functions as co-surfactant to improve the emulsification of oil, meanwhile it also works as the oil phase and results in larger droplets. A significant reduction in droplet size was interestingly observed when fenofibrate was loaded in the vehicles, probably due to the surface activity of fenofibrate, promoting the self-emulsifying process. It was evident that drug precipitation during lipolysis was not affected by the level of co-solvent ethanol in the formulation, while it had pronounced impact on drug solubilization during the initial dispersion stage.

In vitro digestion testing of lipid-based delivery systems: calcium ions combine with fatty acids liberated from triglyceride rich lipid solutions to form soaps and reduce the solubilization capacity of colloidal digestion products.

In vitro digestion testing is of practical importance to predict the fate of drugs administered in lipid-based delivery systems. Calcium ions are often added to digestion media to increase the extent of digestion of long-chain triglycerides (LCTs), but the effects they have on phase behaviour of the products of digestion, and consequent drug solubilization, are not well understood. This study investigates the effect of calcium and bile salt concentrations on the rate and extent of in vitro digestion of soybean oil, as well as the solubilizing capacity of the digestion products for two poorly water-soluble drugs, fenofibrate and danazol. In the presence of higher concentrations of calcium ions, the solubilization capacities of the digests were reduced for both drugs. This effect is attributed to the formation of insoluble calcium soaps, visible as precipitates during the digestions. This reduces the availability of liberated fatty acids to form mixed micelles and vesicles, thereby reducing drug solubilization. The use of high calcium concentrations does indeed force in vitro digestion of LCTs but may overestimate the extent of drug precipitation that occurs within the intestinal lumen.

A novel nanomatrix system consisted of colloidal silica and pH-sensitive polymethylacrylate improves the oral bioavailability of fenofibrate.

A novel solid particle system with a nanomatrix structure and without surfactant for the oral delivery of insoluble drugs was prepared. This used a combination of pH-sensitive polymethylacrylate and nano-porous silica, in order to improve the drug absorption using only pharmaceutical excipients and a relative simple process. The in vitro drug dissolution and in vivo oral bioavailability of this formulation, using fenofibrate as the model drug, were compared with other reference formulations such as a suspension, micronized formulation or self microemulsion drug delivery system (SMEDDS). The supersaturation stabilizing effect of different polymers was evaluated and the physicochemical characterization of the optimal formulation was conducted by SEM, TEM, surface area analysis, DSC, and XRD. The optimized formulation prepared with polymethylacrylate (Eudragit®L100-55) and silica (Sylysia®350) markedly improved the drug dissolution compared with other reference preparations and displayed a comparative oral bioavailability to the SMEDDS. Fenofibrate existed in a molecular or amorphous state in the nanomatrix, and this state was maintained for up to 1year, without obvious changes in drug release and absorption. In conclusion, the nanomatrix formulation described here is a promising system to enhance the oral bioavailability of water-insoluble drugs.

The conflict between in vitro release studies in human biorelevant media and the in vivo exposure in rats of the lipophilic compound fenofibrate.

The performance of four different lipid-based (Tween 80-Captex 200P, Tween 80-Capmul MCM, Tween 80-Caprol 3GO and Tween 80-soybean oil) and one commercially available micronized formulation (Lipanthyl Micronized(®)) of the lipophilic compound fenofibrate was compared in vitro in various biorelevant media and in vivo in rats. In simulated gastric fluid without pepsin (SGF(sp)) and fasted state simulated intestinal fluid (FaSSIF), only Tween 80-Captex 200P system resulted in a stable fenofibrate concentration, but no supersaturation was obtained. The other three lipid based systems created fenofibrate supersaturation; however they did not maintain it. In fed state simulated intestinal fluid (FeSSIF), all lipid-based formulations resulted in complete dissolution of fenofibrate during the experiment, which represented a supersaturated state for Tween 80-Capmul MCM and Tween 80-Caprol 3GO systems. In both FaSSIF and FeSSIF, all lipid-based formulations yielded a higher fenofibrate concentration than the micronized formulation. Contrary to the in vitro results, no significant difference in the in vivo performance was observed among the four tested lipid-based formulations both in the fasted and the fed states. The in vivo performance of all lipid-based formulations was better than that of Lipanthyl Micronized(®), in the fasted as well as in the fed state. The fact that for the lipid based systems the in vitro differences in pharmaceutical performance were not translated into in vivo differences can be attributed to the continuous excretion of bile in the gastrointestinal tract of rats, causing enhanced solubilizing capacity for lipophilic drugs. This study clearly points to the conflicting situation that might arise during the preclinical phase of the development of lipid based formulations of lipophilic drugs as the performance of such systems is very often evaluated by both in vitro release studies in human biorelevant media as well as in vivo studies in rats. Care must be taken to select a relevant animal model.

Catalytic ozonation of fenofibric acid over alumina-supported manganese oxide.

The catalytic ozonation of fenofibric acid was studied using activated alumina and alumina-supported manganese oxide in a semicontinuous reactor. The rate constants at 20°C for the non-catalytic reaction of fenofibric acid with ozone and hydroxyl radicals were 3.43±0.20 M(-1) s(-1) and (6.55±0.33)×10(9) M(-1) s(-1), respectively. The kinetic constant for the catalytic reaction between fenofibric acid and hydroxyl radicals did not differ significantly from that of homogeneous ozonation, either using Al(2)O(3) or MnO(x)/Al(2)O(3). The results showed a considerable increase in the generation of hydroxyl radicals due to the use of catalysts even in the case of catalytic runs performed using a real wastewater matrix. Both catalysts promoted the decomposition of ozone in homogeneous phase, but the higher production of hydroxyl radicals corresponded to the catalyst with more activity in terms of ozone decomposition. We did not find evidence of the catalysts having any effect on rate constants, which suggests that the reaction may not involve the adsorption of organics on catalyst surface.