A diffusing wave spectroscopy study of pharmaceutical emulsions for physical stability assessment

Emulsions are broadly used in pharmaceutics either as intermediate products or as final dosage forms. Such disperse systems are only kinetically stabilized and therefore early detection of physical instability is highly desirable. This work employed diffusing wave spectroscopy (DWS) to study a series of model emulsions that were categorized, based on their composition, as either "simple" or "complex". DWS data were compared with results of droplet size imaging, apparent viscosity obtained by microfluidics, and near-infrared (NIR) analytical centrifugation. A mathematical model of the droplet mean square displacement (MSD) was modified by us regarding improved fitting of experimental data. Although the emulsions showed different types of instability like creaming and sedimentation, a good rank correlation was found between the DWS parameters and results from the comparative stability methods. Our findings indicate that DWS provides a highly attractive method for stability analysis of pharmaceutical emulsions because it requires only low sample volumes, is rapid and non-invasive. The proposed data modeling provides the means for a better understanding of emulsion microstructure that in turn will help designing quality into pharmaceutical dispersions.

Injectable lipid emulsions-advancements, opportunities and challenges

Injectable lipid emulsions, for decades, have been clinically used as an energy source for hospitalized patients by providing essential fatty acids and vitamins. Recent interest in utilizing lipid emulsions for delivering lipid soluble therapeutic agents, intravenously, has been continuously growing due to the biocompatible nature of the lipid-based delivery systems. Advancements in the area of novel lipids (olive oil and fish oil) have opened a new area for future clinical application of lipid-based injectable delivery systems that may provide a better safety profile over traditionally used long- and medium-chain triglycerides to critically ill patients. Formulation components and process parameters play critical role in the success of lipid injectable emulsions as drug delivery vehicles and hence need to be well integrated in the formulation development strategies. Physico-chemical properties of active therapeutic agents significantly impact pharmacokinetics and tissue disposition following intravenous administration of drug-containing lipid emulsion and hence need special attention while selecting such delivery vehicles. In summary, this review provides a broad overview of recent advancements in the field of novel lipids, opportunities for intravenous drug delivery, and challenges associated with injectable lipid emulsions.

1-O-alkylglycerol stabilized carbamazepine intravenous o/w nanoemulsions for drug targeting in mice

Carbamazepine (CBZ) is used in the treatment of generalized tonic clonic and partial seizures. In seizure disorder the focal point of treatment is brain. At present no commercial parenteral formulation of CBZ is available. We developed o/w nanoemulsions of CBZ stabilized by 1-O-alkylglycerol/lecithin for intravenous administration and evaluated the brain targeting potential of these formulations. The nanoemulsions were characterized for globule size, zeta potential (ZP), CBZ content and in vivo tissue distribution in mice. The in vivo data revealed a significant uptake of CBZ in all tissues. Among the nanoemulsions, 1-O-decylglycerol stabilized system showed significantly higher tissue levels and availability of CBZ. Particularly for this system 2.37 times higher brain availability and a brain/serum concentration ratio of 3.0 at 30 min is an important finding. This indicates the brain targeting potential. A systematic formulation development of CBZ nanoemulsions employing 1-O-alkylglycerols might pave way to achieve selective brain delivery of this important antiepileptic drug.