Pharmacoscintigraphy studies to assess the feasibility of a controlled release formulation of ziprasidone.

Ziprasidone, like many BCS Class II drugs with low intrinsic solubility and a strong tendency to crystallize from supersaturated solutions, presents significant technical challenges when developing an oral controlled release dosage form. In order to achieve acceptable bioavailability and prolonged exposures for once-daily dosing, good colonic absorption and a reliable controlled release (CR) technology are necessary. To this end, a novel solubilized drug form--coated crystals made by spray drying (CCSD), was formulated and progressed into human clinical studies. This report describes studies of colonic absorption for the CCSD using the Enterion™ capsule and a pharmacoscintigraphy study in which the CCSD was orally administered via a radiolabelled osmotic tablet formulation. These studies demonstrated that the probability of achieving the required drug solubilization in the colon with the CCSD concept and thereby the desired once daily pharmacokinetic profile was extremely low.

Solid nanocrystalline dispersions of ziprasidone with enhanced bioavailability in the fasted state.

Reducing the absorption difference between fed and fasted states is an important goal in the development of pharmaceutical dosage forms. The goal of this work was to develop and characterize a solid nanocrystalline dispersion (SNCD) to improve the oral absorption of ziprasidone in the fasted state, thereby reducing the food effect observed for the commercial formulation. A solution of ziprasidone hydrochloride and the polymer hydroxypropyl methylcellulose acetate succinate (HPMCAS) was spray-dried to form a solid amorphous spray-dried dispersion (SDD), which was then exposed to a controlled temperature and relative humidity (RH) to yield the ziprasidone SNCD. The SNCD was characterized using powder X-ray diffraction, thermal analysis, microscopy, and in vitro dissolution testing. These tools indicate the SNCD consists of a high-energy crystalline form of ziprasidone in domains approximately 100 nm in diameter but with crystal grain sizes on the order of 20 nm. The SNCD was dosed orally in capsules to beagle dogs. Pharmacokinetic studies showed complete fasted-state absorption of ziprasidone, achieving the desired improvement in the fed/fasted ratio.

In vitro and in vivo characterization of amorphous, nanocrystalline, and crystalline ziprasidone formulations.

Ziprasidone, commercially available as Geodon capsules, is an atypical antipsychotic used in the treatment of schizophrenia and bipolar disorder. It is a BCS Class II drug that shows up to a 2-fold increase in absorption in the presence of food. Because compliance is a major issue in this patient population, we developed and characterized solubilized formulations of ziprasidone in an effort to improve absorption in the fasted state, thereby resulting in a reduced food effect. Three formulations utilizing solubilization technologies were studied: (1) an amorphous inclusion complex of ziprasidone mesylate and a cyclodextrin, (2) a nanosuspension of crystalline ziprasidone free base, and (3) jet-milled ziprasidone HCl coated crystals made by spray drying (CCSD) the drug with hypromellose acetate succinate. The formulations were characterized by in vitro methods appropriate to each particular solubilization technology. These studies confirmed that ziprasidone mesylate - cyclodextrin was an amorphous inclusion complex with enhanced dissolution rates. The ziprasidone free base crystalline nanosuspension showed a mean particle size of 274 nm and a monomodal particle size distribution. In a membrane permeation test, the CCSD showed a 1.5-fold higher initial flux compared to crystalline ziprasidone HCl. The three formulations were administered to fasted beagle dogs and their pharmacokinetics compared to Geodon capsules administered in the fed state. The amorphous complex and the nanosuspension showed increased absorption in the fasted state, indicating that solubilized formulations of ziprasidone have the potential to reduce the food effect in humans.

DNA-Based Assembly of Gold Nanocrystals.

Specific, designed, nonperiodic arrangements of gold nanocrystals that are 5 and 10 nm in diameter can be prepared with double-stranded DNA serving as a template (see drawing; A' and B' denote oligonucleotide sequences complementary to sequences A and B). The methods described should be applicable to nanocrystals composed of various materials.