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

Variations in gastrointestinal lipases, pH and bile acid levels with food intake, age and diseases: Possible impact on oral lipid-based drug delivery systems

The lipids and some surfactants present in oral lipid-based drug delivery systems are potential substrates for the various lipases involved in gastrointestinal (GI) lipolysis. The levels of these enzymes, together with pH and biliairy secretion, are important parameters that condition the fate of lipid-based formulations (LBF) and the dispersion, solubilization and absorption of lipophilic drugs in the GI tract. Since in vitro methods of digestion are now combined with dissolution assays for a better assessment of LBF performance, it is essential to have a basic knowledge on lipase, pH and bile acid (BA) levels in vivo to develop relevant in vitro models. While these parameters and their variations in healthy subjects are today well documented, in vivo data on specific populations (age groups, patients with various diseases, patients with treatment affecting GI tract parameters, …) are scarce and obtaining them from clinical studies is sometimes difficult due to ethical limitations. Here we collected some in vivo data already available on the levels of digestive lipases, gastric and intestinal pH, and BAs at various ages and in patients with exocrine pancreatic insufficiency, a pathological situation that leads to drastic changes in GI tract parameters and impacts pharmacological treatments.

Influence of drug load and physical form of cinnarizine in new SNEDDS dosing regimens: in vivo and in vitro evaluations

The aim of this work was to evaluate the influence of drug load and physical form of cinnarizine (CIN) in self-nanoemulsifying drug delivery systems (SNEDDS) on absorption in rats. Further, the predictivity of the dynamic in vitro lipolysis model was evaluated. The following dosing regimens were assessed: (1) CIN dissolved in SNEDDS at 80% of equilibrium solubility (S_eq) (SNEDDS 80%); (2) supersaturated SNEDDS with CIN dissolved at 200% S_eq (super-SNEDDS solution); (3) SNEDDS suspension with CIN added at 200% S_eq (CIN partially dissolved and partially suspended) (super-SNEDDS suspension); (4) drug-free SNEDDS co-dosed with aqueous CIN suspension (Chasing principle), and (5) CIN aqueous suspension. The CIN dose was kept constant for all dosing regimens. Therefore, the super-SNEDDS solution and super-SNEDDS suspension contained 2.5-fold less SNEDDS pre-concentrate than SNEDDS 80% and the Chasing principle. In vivo, a higher AUC after dosing CIN in SNEDDS 80% and the Chasing principle was obtained when compared to the super-SNEDDS solution, super-SNEDDS suspension, and aqueous suspension. In vitro, a higher extent of CIN in the aqueous phase was observed for all SNEDDS-containing dosing regimens, compared to the aqueous suspension. Since the drug level in the aqueous phase is traditionally considered as the fraction available for absorption, a lack of in vitro-in vivo relation was observed. This study revealed that the physical form of CIN in the current SNEDDS does not affect CIN absorption and solubilization, whereas the drug load, or amount of co-dosed lipid, significantly influenced CIN bioavailability.

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.

The utility of self-emulsifying oil formulation to improve the poor solubility of the anti HIV drug CSIC

Background

CSIC (5-chloro-3-phenylsulfonylindole-2-carboxamide), a non-nucleoside reverse transcriptase inhibitor (NNRTI) has not been advanced as a therapeutic anti-HIV candidate drug due to its low aqueous solubility and poor bioavailability.

Objective

The objective of this work was to formulate CSIC into self-emulsifying oil formulations for the purpose of improving its aqueous solubility and evaluating in vitro antiretroviral activity.

Methods

CSIC self-emulsifying oil formulations (SEFs) were formulated and evaluated for droplet size, zeta potential, polydispersity index (PDI), viscosity, emulsification time, stability and bioactivity.

Results

Results showed significantly improved solubility of CSIC in the SEFs.The concentration of co-surfactant affected the droplet size, zeta potential and polydispersity index. In vitro bioactivity studies showed that the CSIC SEFs retained full anti-HIV activity.

Conclusion

The in vitro data from this first attempt to formulate CSIC SEFs suggest that improvement on the aqueous solubility of CSIC through this delivery system may accentuate its antiretroviral effectiveness in vivo via bioavailability enhancement. The formulation is therefore intended as an oral anti-HIV agent for prophylactic and therapeutic uses.

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.

SNEDDS Containing Poorly Water Soluble Cinnarizine; Development and in Vitro Characterization of Dispersion, Digestion and Solubilization

Self-Nanoemulsifying Drug Delivery Systems (SNEDDSs) were developed using well-defined excipients with the objective of mimicking digested SNEDDSs without the use of enzymes and in vitro lipolysis models and thereby enabling studies of the morphology and size of nanoemulsions as well as digested nanoemulsions by Cryo-TEM imaging and Dynamic Light Scattering. Four SNEDDSs (I-IV) were developed. Going from SNEDDS I to IV lipid content and solubility of the model drug cinnarizine decreased, which was also the case for dispersion time and droplet size. Droplet size of all SNEDDS was evaluated at 1% (w/w) dispersion under different conditions. Cinnarizine incorporation increased the droplet size of SNEDDSs I and II whereas for SNEDDSs III and IV no difference was observed. At low pH cinnarizine had no effect on droplet size, probably due to increased aqueous solubility and partitioning into the aqueous phase. Dispersion of the SNEDDSs in Simulated Intestinal Media (SIM) containing bile salts and phospholipids resulted in a decrease in droplet size for all SNEDDS, as compared to dispersion in buffer. Increasing the bile salt/phospholipid content in the SIM decreased the droplet sizes further. Mimicked digested SNEDDS with highest lipid content (I and II) formed smaller nanoemulsion droplet sizes upon dispersion in SIM, whereas droplet size from III and IV were virtually unchanged by digestion. Increasing the bile acid/phosphatidylcholine content in the SIM generally decreased droplet size, due to the solubilizing power of the endogenous surfactants. Digestion of SNEDDSs II resulted in formation of vesicles or micelles in fasted and fed state SIM, respectively. The developed and characterized SNEDDS provide for a better knowledge of the colloid phases generated during digestion of SNEDDS and therefore will enable studies that may yield a more detailed understanding of SNEDDS performance.

Polymeric nanocapsules with SEDDS oil-core for the controlled and enhanced oral absorption of cyclosporine

Self-microemulsifying drug delivery system (SEDDS) cored-polymeric nanocapsules (NC) were fabricated using emulsion diffusion method for the controlled oral absorption of the poorly water soluble drug, cyclosporine. Poly-dl-lactide (PDLLA) was used as the shell-forming polymer. The NCs in different polymer/oil ratios (from 25/125 to 125/125) were prepared following a solvent-diffusion method. Especially, the SEDDS oil-core compositions, which can form microemulsions on dispersion, were selected based on a pseudo-phase diagram study and further optimized based on the solubility and permeability studies. The prepared NCs were with a mean diameter of 150-220 nm and 9.4-4.5% w/w drug loading. In vivo study in rats showed that the optimized NC(50/125) and NC(100/125) released the drug in controlled way as well as enhanced the bioavailability significantly with AUC(0-24h) values of 14880.3±1470.6 and 12657.8±754.5 ng h/ml, respectively, compared to that of SEDDS-core solution (9878.9±409.6 ng h/ml). Moreover it was observed that the NCs maintained blood concentration of cyclosporine (>500 ng/ml) for 14-20 h but in the case of control formulation it was only 7.33 h. Our results suggest that the prepared NCs could be a potential carrier for the oral controlled release formulation of cyclosporine.

Effect of bile on the oral absorption of halofantrine in polyethylene glycol 400 and polysorbate 80 formulations dosed to bile duct cannulated rats

Objectives

The aim of this study was to examine the effects of bile on the oral absorption of the poorly water-soluble compound, halofantrine, when administered to rats in vehicles consisting of the co-solvent polyethylene glycol 400 (PEG 400) alone or in mixtures with the surfactant polysorbate 80 (PS 80) (95 : 5; 85 : 15; 75 : 25 PEG 400 : PS 80).

Methods

Halofantrine (17.5 mg/kg) was administered to bile duct cannulated (BDC) and sham-operated rats in a fixed vehicle volume of 5 ml/kg.

Key findings

The bioavailability of halofantrine was significantly lower in BDC rats when dosed with 0–5% PS 80 in PEG 400 compared with BDC rats dosed with >15% PS 80. Increasing the concentration of PS 80 to 15–100% eliminated this difference. A possible explanation for the lower bioavailability of halofantrine in BDC rats when dosed in pure PEG 400 could be the dilution of the vehicle by intestinal fluids, decreased transit time and precipitation in the gastrointestinal tract upon dilution of PEG 400.

Conclusions

The addition of PS 80 to the formulation increased its solubilising power upon dilution and may have inhibited precipitation and substituted the absence of bile above a certain level. Adjusting the level of surfactant in drug formulations could therefore be used to minimise variability in the bioavailability from co-solvent systems based upon differences in bile concentration between individuals.

An updated and simplified method for bile duct cannulation of rats

The single bile duct cannulated rat model was used for short-term intestinal absorption studies. Rats were randomly assigned to three groups: (A) bile duct cannulated, (B) control laparotomy and (C) no treatment. The body weight and health of the rats were monitored before and until day 5 after surgery, while bile flow was measured in group A on day 2. On the fifth day, tail vein blood was harvested, and alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and total bilirubin were quantified. Analysis of variance showed no significant difference between the groups for these parameters. This study demonstrated the suitability of a surgical rat model feasible for evaluation of the impact of bile in pharmacokinetic studies.

Microemulsions as carriers for drugs and nutraceuticals

Microemulsions are potentially excellent carriers for bioactive molecules. They offer the advantage of spontaneous formation, ease of manufacture, thermodynamic stability, and improved solubilization of bioactive materials. This review explores some of the new trends in microemulsion research through analysis of some representative studies. The solubilization of different classic drugs, peptides, and nutraceuticals in various oral microemulsion compositions and microstructures was reviewed. It was found that even W/O microemulsions, which are expected to break upon dilution in the digestive tract, increase the permeability and bioavailability of drugs. Thus, it seems that component selection (the use of molecules that can act as permeability enhancers) is of great importance. Structures such as self-microemulsifying drug delivery systems (SMEDDS), W/O, bicontinuous, and O/W microemulsions, were closely examined, and their potential to serve as drug carriers was evaluated. It seems that for microemulsion systems to be used as vehicles for bioactive materials, the formulations should be based on SMEEDS, which form O/W upon dilution to a specific water content. U-type microemulsions are actually an improved SMEDDS formulation, capable of being diluted with any given water concentration. Much research is being conducted on microemulsion microstructure since there is an obvious direct connection between the microstructure, solubilization capacity, and bioavailability of the active molecules.

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.