Novel Extended-Release Multiple-Unit System of Imidafenacin Prepared by Fluid-Bed Coating Technique.

The objective of this study was to formulate once-a-day extended-release (ER) pellet system of imidafenacin (IDN), a recently approved urinary antispasmodic agent with twice-a-day dosing regimen. The sugar sphere pellets were firstly layered with IDN and hypromellose and then coated with Eudragit RS (copolymers of acrylic and methacrylic acid esters), employed as a release modifier, using a fluid-bed coater. Solid-state characterizations using solid-state X-ray diffraction and differential scanning calorimeter indicated that the antispasmodic agent was homogeneously layered onto the pellets in an amorphous state. Drug release from multiple-unit ER system was effectively retarded in proportion to the amount of Eudragit RS in the outer layer, with a high correlation value above 0.86. In a pharmacokinetic evaluation in beagle dogs, the plasma concentration profile of IDN was markedly protracted by ER pellets, exhibiting delayed the time needed to reach the maximum drug concentration and the elimination half-life in plasma, compared to the commercial immediate release form (Uritos® tablet, Kyorin Pharmaceutical Co., Ltd., Japan). Therefore, the novel ER pellets can be a promising tool for oral IDN therapy, providing a once-a-day dosing regimen, and thus, improving patient compliance.

Surface-Modification of RIPL Peptide-Conjugated Liposomes to Achieve Steric Stabilization and pH Sensitivity.

We have previously demonstrated that RIPL peptide-conjugated liposomes (RIPL-L) exhibited high hepsin (HPN) selectivity and enhanced intracellular drug delivery. In this study, surface modification of RIPL-L was performed to reduce plasma protein adsorption and off-target effects. For steric stabilization, distearoyl phosphatidylethanolamine (DSPE)-polyethylene glycol (PEG)2000 was used (5% molar ratio to total lipid) to prepare PEG-RIPL-L. Further, pH-sensitive oligopeptides [(HD)4 or (HE)4] were coupled to shield the RIPL polyarginine moiety, yielding (HD)4/PEG-RIPL-L and (HE)4/PEG-RIPL-L. All liposomal vesicles had a narrow and homogenous size distribution of approximately 140­150 nm, with zeta potentials varying from −15 to 36 mV. Increased plasma stability was observed upon quantifying the protein adsorbed onto liposomes by using a micro bicinchoninic acid assay. The (HD)4- and (HE)4-coupling capacity of PEG-RIPL-L was investigated by measuring the amount of oligopeptide involved in transient ionic complexation (TIC-oligopep) and zeta potential changes. As the molar ratio of (HD)4 and (HE)4 increased, TIC-oligopep increased and zeta potential decreased. (HE)4/PEG-RIPL-L were pH-sensitive, producing 1.6-fold greater cellular uptake of FITC-dextran by LNCaP cells at pH 6.8 than at pH 7.4. This result suggested that (HE)4/PEG-RIPL-L might provide a sterically stabilized, pH-sensitive drug carrier for HPN-specific cancer targeting.

Formulation and in vivo pharmacokinetic evaluation of ethyl cellulose-coated sustained release multiple-unit system of tacrolimus.

A novel once-a-day sustained-release (SR) system of tacrolimus (FK506), a poorly water-soluble immunosuppressive agent, was designed employing ethyl cellulose (EC) polymer as release retardant. Drug (5 mg) was layered onto sugar spheres (518.3 mg) with hypromellose (5 mg), to transform the drug from a crystalline to an amorphous form. Subsequently, the drug-layered pellets were recoated with EC polymer (0.5-1.5 mg) using a fluid bed granulator. Drug release from the reservoir-type pellets was markedly impeded by the outer EC-based coating layer (EC 1 mg), displaying about 60% of drug release after 8 h, regardless of the acidity of the media. In an in vivo pharmacokinetic study in fasted Cynomolgus monkeys, the drug level in blood was gradually increased over 4.7 h and high drug concentration was maintained until 24 h, with an elimination half-life of 16.6 h. There were no statistical differences between the novel SR pellets and the recently marketed SR capsule (Advagraf®, Astellas Pharma, Japan) in terms of maximum blood concentration, area under the curve, and half-life values, in both fasted and fed states. Therefore, the novel EC-coated pellets are expected to be bioequivalent to the commercial SR capsule, providing a once-daily dosing regimen in patients with allogenic rejection.