Parenteral water/oil emulsions containing hydrophilic compounds with enhanced in vivo retention: formulation, rheological characterisation and study of in vivo fate using whole body gamma-scintigraphy

Lipid emulsions in clinical nutrition: Enteral and parenteral nutrition

Clinical nutrition emulsions are important products that can be life-saving for many patients suffering from gastrointestinal tract disorders, swallowing impairment, cancer, liver diseases, and many other clinical conditions. The transfer of lipids to the human body can be either intravenously (Parenteral Nutrition, PN) or through the gastrointestinal tract (Enteral Nutrition, EN). PN emulsions are considered pharmaceuticals and thus regulated accordingly. On the other hand, EN emulsions are classified as Food for Specific Medical Purposes (FSMP) and do not follow pharmaceutical regulations. Regarding product design, PN emulsions must follow theoretical emulsion formulation and production aspects, but special requirements regarding droplet size distribution must be followed to comply with national pharmacopeia monographs. Furthermore, a full clinical program on clinical evidence to prove safety and efficacy must be provided for marketing approval. On the contrary, EN emulsions require limited clinical evidence to substantiate health or clinical benefits. A short introduction to clinical nutrition with a focus on lipid emulsions is presented in this chapter. Furthermore, a general overview of the composition and main ingredients of clinical nutrition lipid emulsions is reviewed. Main clinical aspects are also mentioned here, highlighting the difficulties of clinically proving the efficacy of these products. The manufacturing and control of clinical nutrition emulsions are also reviewed, focusing on PN products and the main regulatory requirements related to the safety of these intravenous emulsions. Finally, stability and physicochemical properties are reviewed, and examples of commercially available products are used to illustrate these properties linked to the stability of these products. Lipids in clinical nutrition is a moving field and we do hope this chapter may remain a valuable source to understand newly emerging research on this topic.

Formation of W/O emulsion using hydrophilic nanoparticles by three-phase emulsification and its energetic analysis

In this study, we investigated the characteristics of water-in-oil (W/O) emulsions formed by hydrophilic nanoparticles in three-phase emulsification and discussed their stability by performing an energy analysis. W/O emulsions prepared using the three-phase emulsification method are stable in several systems, even in those with a high internal-phase ratio of water up to 85 wt%. Hydrophilic nanoparticles can exist in the internal water phase independently, and the emulsifying action does not depend on the concentration of nanoparticles or the state of the internal water phase. The energy analysis of the model, in which nanoparticles partially penetrate from the aqueous phase to the oil phase, suggests that hydrophilic nanoparticles can form W/O emulsions. It was also found that the entropy change based on the hydrophobic hydration around the nanoparticles was the main driving force for the nanoparticles to partially penetrate the oil phase.

Pharmacokinetics of Long-Acting Aqueous Nano-/Microsuspensions After Intramuscular Administration in Different Animal Species and Humans-a Review

Formulating aqueous suspensions is an attractive strategy to incorporate poorly water-soluble drugs, where the drug release can be tailored to maintain desired release profiles of several weeks to months after parenteral (i.e., intramuscular or subcutaneous) administration. A sustained drug release can be desirable to combat chronic diseases by overcoming pill fatigue of a daily oral intake, hence, improving patient compliance. Although the marketed aqueous suspensions for intramuscular injection efficiently relieve the daily pill burden in chronic diseases, the exact drug release mechanisms remain to be fully unraveled. The in vivo drug release and subsequent absorption to the systemic circulation are influenced by a plethora of variables, resulting in a complex in vivo behavior of aqueous suspensions after intramuscular administration. A better understanding of the factors influencing the in vivo performance of aqueous suspensions could advance their drug development. An overview of the potential influential variables on the drug release after intramuscular injection of aqueous suspensions is provided with, where possible, available pharmacokinetic parameters in humans or other species derived from literature, patents, and clinical trials. These variables can be categorized into drug substance and formulation properties, administration site properties, and the host response towards drug particles. Based on the findings, the most critical factors are particle size, dose level, stabilizing excipient, drug lipophilicity, gender, body mass index, and host response.

Allogeneic Bone Impregnated with Biodegradable Depot Delivery Systems for the Local Treatment of Joint Replacement Infections: An In Vitro Study

Although progress is evident in the effective treatment of joint replacement-related infections, it still remains a serious issue in orthopedics. As an example, the local application of antibiotics-impregnated bone grafts supplies the high drug levels without systemic side effects. However, antibiotics in the powder or solution form could be a risk for local toxicity and do not allow sustained drug release. The present study evaluated the use of an antibiotic gel, a water-in-oil emulsion, and a PLGA microparticulate solid dispersion as depot delivery systems impregnating bone grafts for the treatment of joint replacement-related infections. The results of rheological and bioadhesive tests revealed the suitability of these formulations for the impregnation of bone grafts. Moreover, no negative effect on proliferation and viability of bone marrow mesenchymal stem cells was detected. An ex vivo dissolution test of vancomycin hydrochloride and gentamicin sulphate from the impregnated bone grafts showed a reduced burst and prolonged drug release. The PLGA-based formulation proved to be particularly promising, as one-day burst release drugs was only 15% followed with sustained antibiotics release with zero-order kinetics. The results of this study will be the basis for the development of a new product in the Tissue Section of the University Hospital for the treatment of bone defects and infections of joint replacements.

A novel oil-based suspension of a micro-environmental, pH-modifying solid dispersion for parenteral delivery: Formulation and stability evaluation

The objective of this study was to evaluate a novel oil-based suspension as a potential parenteral drug delivery system for drugs with poor water solubility. Most of the new active pharmaceutical ingredients are weak acid or basic drugs with pH-dependent solubility. To limit this dependence, use of micro-environmental pH-modifying solid dispersions (micro pHm SD) has been proved to increase the bioavailability of these drugs. Toltrazuril (TOL), a weakly acidic drug with poor aqueous and pH-dependent solubility, was studied as a model drug. Recently, studies on TOL with focus on the parenteral injection are rarely to find in the literature. A novel parenteral oil-based TOL suspension was prepared containing TOL micro pHm SD (TSD) powders suspended in oil-based vehicles and the optimal formulation was screened. The stability of this formulation was assessed considering particle size distribution, settling volume ratio, redispersibility, thermal stability, and drug content. The optimized white oil-based TOL pHm SD suspension (W-TSDS) showed significant improved stability and shear-thinning behavior. In particular, fumed silica as suspending agent positively influenced the physical stability of the formulation. Furthermore, W-TSDS showed good injectability using 21 G needles and more rapid and sustained drug release compared to TSD powders in vitro. In the in vivo safety evaluation, W-TSDS showed good histocompatibility in rabbits injected subcutaneously or intramuscularly. We believe these findings provide an alternative choice of dosage form for the delivery of new active pharmaceutical ingredients.

Modeling the Time Course of the Tissue Responses to Intramuscular Long-acting Paliperidone Palmitate Nano-/Microcrystals and Polystyrene Microspheres in the Rat

Long-acting injectable (LAI) drug suspensions consist of drug nano-/microcrystals suspended in an aqueous vehicle and enable prolonged therapeutic drug exposure up to several months. The examination of injection site reactions (ISRs) to the intramuscular (IM) injection of LAI suspensions is relevant not only from a safety perspective but also for the understanding of the pharmacokinetics. The aim of this study was to perform a multilevel temporal characterization of the local and lymphatic histopathological/immunological alterations triggered by the IM injection of an LAI paliperidone palmitate suspension and an analog polystyrene suspension in rats and identify critical time points and parameters with regard to the host response. The ISRs showed a moderate to marked chronic granulomatous inflammation, which was mediated by multiple cyto-/chemokines, including interleukin-1β, monocyte Chemoattractant Protein-1, and vascular endothelial growth factor. Lymphatic uptake and lymph node retention of nano-/microparticles were observed, but the contribution to the drug absorption was negligible. A simple image analysis procedure and empirical model were proposed for the accurate evaluation of the depot geometry, cell infiltration, and vascularization. This study was designed as a reference for the evaluation and comparison of future LAIs and to support the mechanistic modeling of the formulation–physiology interplay regulating the drug absorption from LAIs.

Formulation and in vitro and in vivo characterization of a phenytoin self-emulsifying drug delivery system (SEDDS)

The aim of this study is to develop and characterize a self-emulsifying drug delivery system (SEDDS) of phenytoin, and to compare its relative bioavailability to a commercially available suspension. Four phenytoin SEDDS were prepared and evaluated. Following emulsification, the optimized formula was selected to have the smallest mean particle size and the highest absolute zeta potential, which should yield the formation of a stable emulsion. Its dissolution characteristics were superior to the other SEDDS formulas. In vivo and in vitro tests were run to compare the optimized formula, SEDDS II, to a commercially available Dilantin suspension. The in vitro dissolution indicated a significant improvement in phenytoin release characteristics. The in vivo study using male rats showed a clear enhancement in phenytoin oral absorption from SEDDS compared to Dilantin suspension. The area under the curve AUC((-10min-->10h)) of phenytoin after SEDDS administration increased by 2.3 times compared to Dilantin (p<0.05), and the rate of absorption of phenytoin was significantly faster from the SEDDS. The concentration after 30min (C(30min)) of SEDDS administration was 4.9 times higher than C(30min) after Dilantin administration (p<0.05). A sustained effect of phenytoin in plasma was also observed. After 12 weeks storage, SEDDS II was found to be chemically and physically stable under stressed conditions.

Antiviral peptides targeting the west nile virus envelope protein

West Nile virus (WNV) can cause fatal murine and human encephalitis. The viral envelope protein interacts with host cells. A murine brain cDNA phage display library was therefore probed with WNV envelope protein, resulting in the identification of several adherent peptides. Of these, peptide 1 prevented WNV infection in vitro with a 50% inhibition concentration of 67 muM and also inhibited infection of a related flavivirus, dengue virus. Peptide 9, a derivative of peptide 1, was a particularly potent inhibitor of WNV in vitro, with a 50% inhibition concentration of 2.6 muM. Moreover, mice challenged with WNV that had been incubated with peptide 9 had reduced viremia and fatality compared with control animals. Peptide 9 penetrated the murine blood-brain barrier and was found in the brain parenchyma, implying that it may have antiviral activity in the central nervous system. These short peptides serve as the basis for developing new therapeutics for West Nile encephalitis and, potentially, other flaviviruses.

Strategies to improve plasma half life time of peptide and protein drugs

Due to the obvious advantages of long-acting peptide and protein drugs, strategies to prolong plasma half life time of such compounds are highly on demand. Short plasma half life times are commonly due to fast renal clearance as well as to enzymatic degradation occurring during systemic circulation. Modifications of the peptide/protein can lead to prolonged plasma half life times. By shortening the overall amino acid amount of somatostatin and replacing L: -analogue amino acids with D: -amino acids, plasma half life time of the derivate octreotide was 1.5 hours in comparison to only few minutes of somatostatin. A PEG(2,40 K) conjugate of INF-alpha-2b exhibited a 330-fold prolonged plasma half life time compared to the native protein. It was the aim of this review to provide an overview of possible strategies to prolong plasma half life time such as modification of N- and C-terminus or PEGylation as well as methods to evaluate the effectiveness of drug modifications. Furthermore, fundamental data about most important proteolytic enzymes of human blood, liver and kidney as well as their cleavage specificity and inhibitors for them are provided in order to predict enzymatic cleavage of peptide and protein drugs during systemic circulation.

Protein drug stability: a formulation challenge

The increasing use of recombinantly expressed therapeutic proteins in the pharmaceutical industry has highlighted issues such as their stability during long-term storage and means of efficacious delivery that avoid adverse immunogenic side effects. Controlled chemical modifications, such as substitutions, acylation and PEGylation, have fulfilled some but not all of their promises, while hydrogels and lipid-based formulations could well be developed into generic delivery systems. Strategies to curb the aggregation and misfolding of proteins during storage are likely to benefit from the recent surge of interest in protein fibrillation. This might in turn lead to generally accepted guidelines and tests to avoid unforeseen adverse effects in drug delivery.

Sustained release veterinary parenteral products

Controlled release parenteral dosage forms have application in veterinary medicine. Systems that minimize the need for repeated injections while achieving therapeutic effects for extended periods offer benefits that make commercial development of these products desirable. While some products have already found commercial success, others will result from application of new controlled release technologies. This review highlights the formulation and technology challenges in developing some of these controlled release technologies into products. Further, examples of application of controlled release technologies in the veterinary field are discussed.

Sustained elevated plasma aprotinin concentration in mice following intraperitoneal injections of w/o emulsions incorporating aprotinin

This study was initiated to test the feasibility of w/o emulsions as a sustained release system for aprotinin following intraperitoneal injection in mice. The emulsion was well tolerated in mice and sustained release was observed over a period of 96 h. The time for maximum plasma concentration of aprotinin was 10 min and 12 h after injection of a control solution and the emulsion dosage form, respectively. Furthermore, the hemolytic activity of the emulsion constituents was low indicating a low acute toxicological potential of the emulsion. The present study also showed that the lipolytic activity in peritoneal exudate from mice is important for the clearance of oily vehicles from the peritoneal cavity with lipolytic rate constants ranging from 50 to 130 nmol free fatty acid released/min/mg exudate protein at 37 degrees C, pH 8.5. It was concluded that the w/o emulsion was well suited to provide sustained elevated plasma aprotinin concentrations in mice.