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Type III lipid-based formulations (LBFs) combine poorly water-soluble drugs with oils, surfactants, and cosolvents to deliver the drugs into the systemic circulation. However, the solubility of the drug can be influenced by the colloidal phases formed in the gastrointestinal tract as the formulation is dispersed and makes contact with bile and other materials present within the GI tract. Thus, an understanding of the phase behavior of LBFs in the gut is critical for designing efficient LBFs. Molecular dynamics (MD) simulation is a powerful tool for the study of colloidal systems. In this study, we modeled the internal structures of five type III LBFs of loratadine containing poly(ethylene oxide) nonionic surfactants polysorbate 80 and polyoxyl hydrogenated castor oil (Kolliphor RH40) using long-timescale MD simulations (0.4–1.7 μs). We also conducted experimental investigations (dilution of formulations with water) including commercial Claritin liquid softgel capsules. The simulations show that LBFs form continuous phase, water-swollen reverse micelles, and bicontinuous and phase-separated systems at different dilutions, which correlate with the experimental observations. This study supports the use of MD simulation as a predictive tool to determine the fate of LBFs composed of medium-chain lipids, polyethylene oxide surfactants, and polymers.

The scientific rationale for selection of the surfactant type during oral formulation development requires an in-depth understanding of the interplay between surfactant characteristics and biopharmaceutical factors. Currently, however, there is a lack of comprehensive knowledge of how surfactant properties, such as hydrophilic–lipophilic balance (HLB), digestibility, and fatty acid (FA) chain length, translate into in vivoperformance. In the present study, the relationship between surfactant properties, in vitrocharacteristics, and in vivobioavailability was systematically evaluated. An in vitrolipolysis model was used to study the digestibility of a variety of nonionic surfactants. Eight surfactants and one surfactant mixture were selected for further analysis using the model poorly water-soluble drug nilotinib. In vitrolipolysis of all nilotinib formulations was performed, followed by an in vivopharmacokinetic evaluation in rats. The in vitrolipolysis studies showed that medium-chain FA-based surfactants were more readily digested compared to long-chain surfactants. The in vivostudy demonstrated that a Tween 20 formulation significantly enhanced the absolute bioavailability of nilotinib up to 5.2-fold relative to an aqueous suspension. In general, surfactants that were highly digestible in vitrotended to display higher bioavailability of nilotinib in vivo. The bioavailability may additionally be related to the FA chain length of digestible surfactants with an improved exposure in the case of medium-chain FA-based surfactants. There was no apparent relationship between the HLB value of surfactants and the in vivobioavailability of nilotinib. The impact of this study’s findings suggests that when designing surfactant-based formulations to enhance oral bioavailability of the poorly water-soluble drug nilotinib, highly digestible, medium chain-based surfactants are preferred. Additionally, for low-permeability drugs such as nilotinib, which is subject to efflux by intestinal P-glycoprotein, the biopharmaceutical effects of surfactants merit further consideration.

Labrasol®and Gelucire®44/14 are lipid-based excipients used for the oral drug delivery of poorly water-soluble drugs. These macrogolglycerides are composed of acylglycerols and PEG esters, potential substrates of digestive lipases. We developed an in vitro method to simulate the gastrointestinal lipolysis of these excipients and to evaluate the impact of lipolysis in vivo. At the end of the gastric phase, the composition of both excipients was significantly modified underlining the importance of gastric lipolysis in vivo. We also studied the influence of excipients’ lipolysis on the solubilization of a poorly water-soluble drug, cinnarizine, in aqueous phase. Gastrointestinal lipolysis of Labrasol®was a prerequisite to maintain cinnarizine in aqueous solution, whereas the lipolysis of Gelucire®44/14 did not affect the cinnarizine solubilization.

Gelucire®44/14, a lauroyl polyoxylglycerides obtained by polyglycolysis of hydrogenated coconut oil with PEG-32, is used to increase the oral bioavailability of poorly-water soluble drugs. It is a solid dispersion composed of a PEG ester fraction under a lamellar phase of 120 Å with a helical conformation and an acylglycerol fraction under a hexagonal packing. This excipient spontaneously evolves to its most stable phase of 120 Å after storage at 25 °C for 21 hours leading to physically stable formulations. Gelucire®44/14 is a hydrophilic system that hydrates and swells in contact with water and forms cubic mesophases before complete erosion/emulsification. It is also lipolyzed by various enzymes such as gastric lipase or carboxyl ester hydrolase. After an in vitro gastrointestinal lipolysis simulation, the main components remaining are mono and diesters of PEG-32. These amphiphilic metabolites can explain the beneficial role of Gelucire®44/14 on the solubility of poorly-water soluble drugs such as cinnarizine even after partial lipolysis of the lipid-based system. Finally that excipient can also increase the bioavailability of active substances by interacting with enterocyte-based proteins like P-glycoprotein or cytochromes P450.

The objective of this study was to evaluate the use of glyceryl behenate as a plasticizer and release modifier in solid dispersion systems containing itraconazole and carbamazepine. Amorphous solid dispersions of high molecular weight polyvinylpyrrolidone were prepared by hot-melt extrusion, the processing of which was improved by the inclusion of glyceryl behenate. Dispersions were milled and subsequently compressed into tablets. Solid dispersions were also prepared by KinetiSol Dispersing, which allowed for the manufacture of monolithic tablets of the same composition and shape as compressed tablets. Tablets without glyceryl behenate and all compressed tablets were observed to have an incomplete release profile likely due to drug crystallization within the tablet as this occurred at conditions in which dissolution concentrations were below saturation. Monolithic tablets formulated to be more hydrophobic, by including glyceryl behenate, allowed for sustained release below and above saturation conditions.

The LFCS Consortium was established to develop standardized in vitrotests for lipid-based formulations (LBFs) and to examine the utility of these tests to probe the fundamental mechanisms that underlie LBF performance. In this publication, the impact of bile salt (sodium taurodeoxycholate, NaTDC) concentration and drug loading on the ability of a range of representative LBFs to generate and sustain drug solubilization and supersaturation during in vitrodigestion testing has been explored and a common driver of the potential for drug precipitation identified. Danazol was used as a model poorly water-soluble drug throughout. In general, increasing NaTDC concentrations increased the digestion of the most lipophilic LBFs and promoted lipid (and drug) trafficking from poorly dispersed oil phases to the aqueous colloidal phase (APDIGEST). High NaTDC concentrations showed some capacity to reduce drug precipitation, although, at NaTDC concentrations ≥3 mM, NaTDC effects on either digestion or drug solubilization were modest. In contrast, increasing drug load had a marked impact on drug solubilization. For LBFs containing long-chain lipids, drug precipitation was limited even at drug loads approaching saturation in the formulation and concentrations of solubilized drug in APDIGESTincreased with increased drug load. For LBFs containing medium-chain lipids, however, significant precipitation was evident, especially at higher drug loads. Across all formulations a remarkably consistent trend emerged such that the likelihood of precipitation was almost entirely dependent on the maximum supersaturation ratio (SRM) attained on initiation of digestion. SRMdefines the supersaturation “pressure” in the system and is calculated from the maximum attainable concentration in the APDIGEST(assuming zero precipitation), divided by the solubility of the drug in the colloidal phases formed post digestion. For LBFs where phase separation of oil phases did not occur, a threshold value for SRMwas evident, regardless of formulation composition and drug solubilization reduced markedly above SRM> 2.5. The threshold SRMmay prove to be an effective tool in discriminating between LBFs based on performance.

The bile salt-stimulated lipase or carboxyl ester hydrolase (CEH) is a non-specific enzyme secreted by the exocrine pancreas and mammary glands. Recently we demonstrated that PEG esters were good substrates for CEH as it exhibited the highest specific activity ever recorded for this enzyme on PEG-8 monocaprylate. The aim of this study was to develop a specific and sensitive method for assaying CEH in biological samples in which several lipases are contained. Eight different PEG-n mono and dicaprylates with ethylene oxide units ranging from n= 6 to 32 were tested using the pH-stat technique. PEG-20 dicaprylate was the best substrate to discriminate CEH from other digestive lipases. Since pancreatic lipase related-protein 2 (PLRP2) was also found to display a significant activity on PEG-20 dicaprylate, experiments were designed to optimize the specificity of the assay for CEH. The main parameters for increasing CEH activity, while reducing that of PLRP2, were the pH and the concentration of bile salts. A linear relationship between the enzyme activity and the mass of CEH was established. The specificity of this assay was validated using gastrointestinal fluids containing CEH, PLRP2, gastric and pancreatic lipases.

The aim of the study was to develop a protocol to encapsulate lipidized-peptides in Nanostructured Lipid Carrier (NLC) by High Pressure Homogenization (HPH) for oral delivery. The impact of composition, pressure and number of cycles on particle size, polydispersity index (PDI), and stability was studied. The lipophilicity of two model peptides, Desmopressin (DES) and Leuprolide (LEU) was increased by formation of a Hydrophobic Ion Pair (HIP) with sodium docusate. The precipitation efficiency was 94.96 ± 0.27% and 99.92 ± 0.08% respectively. Their solubility was evaluated in lipidic excipients. NLC were formed by pre-emulsion and HPH at 70 °C. Blank NLC of 95 ± 3 nm with a PDI of 0.14 ± 0.01 were obtained using 10% (w/v) Precirol®ATO5, 4% Kolliphor®RH40 and 5% Capryol™90. The particles were obtained after 3 min pre-emulsion at 11 000 rpm followed by 5 cycles at 500 bar on Microfluidizer® at 70 °C and finally 10 min in at 4 °C under stirring. The complexes were successfully encapsulated in the developed NLC. HPLC analysis attested that peptides were not degraded by the process. The encapsulation efficiency (EE) was highly dependent on the Log P of the HIP with an EE of 10.7 ± 2.2% for DES-docusate HIP (log P = 0.5) and 84.7 ± 2.0% for LEU-docusate HIP (log P = 3).