Combining lipid based drug delivery and amorphous solid dispersions for improved oral drug absorption of a poorly water-soluble drug.

Two widely applied enabling drug delivery approaches, self-nanoemulsifying drug delivery systems (SNEDDS) and amorphous solid dispersions (ASD), were combined, with the aim of enhancing physical stability, solubilization and absorption of the model drug ritonavir. Ritonavir was loaded at a concentration above its saturation solubility (Seq) in the SNEDDS (superSNEDDS, 250% of Seq). An ASD of ritonavir with polyvinylpyrrolidone-vinyl acetate copolymers (Kollidon® VA64) was prepared by ball milling. Relevant control formulations, which include conventional SNEDDS (90% of Seq), superSNEDDS with a physical mix of Kollidon® VA64 and ritonavir (superSNEDDS+PM) and an aqueous suspension of ritonavir were used. A pharmacokinetic (PK) study in rats was performed to assess the relative bioavailability of ritonavir after oral administration. This was followed by evaluating the formulations in a novel two-step in vitro lipolysis model simulating rat gastric and intestinal conditions. The addition of a ritonavir containing ASD to superSNEDDS increased the degree of supersaturation from 250% to 275% Seq in the superSNEDDS and the physical stability (absence of drug recrystallization) of the system from 48 h to 1 month under ambient conditions. The PK study in rats displayed significantly higher Cmax and AUC0-7h (3-fold increase) and faster Tmax for superSNEDDS+ASD compared to the conventional SNEDDS whilst containing 3 times less lipid than the latter. Furthermore, superSNEDDS+ASD were able to keep the drug solubilised during in vitro lipolysis to the same degree as the conventional SNEDDS. These findings suggest that dissolving an ASD in a superSNEDDS can contribute to the development of novel oral delivery systems with increased bioavailability for poorly water-soluble drugs.

Production and characterization of anisotropic particles from biodegradable materials.

In recent years, production and characterization of anisotropic particles has become of interest in a wide range of scientific fields including polymer chemistry, drug delivery, electronics, energy, and nanotechnology. In this work, we demonstrate a novel formulation for production of anisotropic particles via an internal phase separation of biodegradable components. Specifically, binary mixtures of biodegradable polymers poly(lactic-co-glycolic acid), polycaprolactone, and biodegradable lipid Precirol (glyceryl palmitostearate) were dissolved in dichloromethane, emulsified, and prepared into anisotropic particles using a modified solvent evaporation technique. During the slow evaporation process the components self-assembled into anisotropic particles with distinct morphologies. Polymer/polymer formulations resulted in compartmentalized anisotropic heterodimer particles, while polymer/lipid combinations yielded "ice cream cone" shaped particles. It was found that addition of certain active pharmaceuticals resulted in an altered, pox-like segregation at the particle surface of polymer/polymer formulations. The anisotropic nature of the particles was subsequently characterized using optical microscopy, scanning electron microscopy, zeta potential, electrophoresis, and X-ray diffraction. Successful formulations presented here may potentially be employed as multicompartmental drug carriers with staggered drug release rates or alternatively as a colloidal excipient for an arsenal of pharmaceutical applications.

Atomistic simulation study of surfactant and polymer interactions on the surface of a fenofibrate crystal.

It is currently of great interest to the pharmaceutical industry to control the size and agglomeration of nano- and micro-particles for the enhancement of drug delivery. Typically, surfactants and polymers are used as additives to interact with and stabilize the growing crystal surface, thus controlling size and agglomeration; however, selection is traditionally done empirically or using heuristics. The objective of this study was to use molecular dynamic simulations to investigate and predict additive interactions, and thus, evaluate the stabilization potential of individual and multiple additives on the surface of the model drug fenofibrate. Non-ionic surfactant Tween 80, anionic surfactant sodium dodecyl sulfate (SDS), and polymers hydroxypropyl methylcellulose (HPMC) and Pullulan were evaluated individually on three distinct crystal surfaces [(001), (010), (100)], as well as in surfactant-polymer combinations. HPMC was determined to have the strongest interaction with the surfaces of the fenofibrate crystal, and therefore, was predicted to be the most effective individual additive. A mixture of HPMC with SDS was determined to be the most effective mixture of additives, and more effective than HPMC alone, indicating a synergistic effect. The predictions of mixed additives indicated a relative order of effectiveness as follows: HPMC-SDS>HPMC-Tween 80>Pullulan-Tween 80>Pullulan-SDS. The simulations were subsequently validated by an anti-solvent crystallization of fenofibrate where it was found that HPMC individually, and a mixture of HPMC-SDS, produced the smallest and most stable crystals, as measured by laser diffraction; this, in combination with measurements of the crystal growth rate in the presence and absence of additives confirmed the results of the simulations.