To maintain antimicrobial activity, frequent administration of conventional formulations of many antibiotics with short half-life is necessary. Otherwise, concentration under MIC occurs frequently in the course of anti-infective treatment, which induces antibiotic resistance. By maintaining a constant plasma drug concentration over MIC for a prolonged period, extended-release dosage forms maximize the therapeutic effect of antibiotics while minimizing antibiotic resistance. Another undoubted advantage of extended-release formulation is improved patient compliance. For better release properties, many materials have been introduced into the matrix and coating extended-release system in the past few years. Materials that have been widely used in industry are hydrophilic matrix materials such as hydroxypropylmethylcellulose. The excellent biocompatibility and extensive laboratory studies provide biodegradable polymers great potential for industrial applications. In addition, it seems like the researches on tailored materials that are obtained by chemical modification of the existing materials or combination of different carriers in physical mixtures have a long way to go. Meanwhile, with the development of polymers and inorganic porous nanocarriers, nanotechnology is applied increasingly for the extended delivery of antibiotics. This review highlights the development of materials used in extended-release formulation and nanoparticles for antibiotic delivery. We also provide an overview of the antibiotic extended-release products that have provided clinical benefit or are undergoing the clinical trial.

Solid dispersions are a useful approach to improve the dissolution rate and bioavailability of poorly water-soluble active pharmaceutical ingredients (APIs). The aim of this study was to improve the physicochemical properties and bioavailability of a poorly water-soluble aprepitant by preparation of solid dispersions. The solid dispersions were characterized by dissolution, FTIR, XRPD, DSC, SEM and pharmacokinetic studies in rats. The dissolution rate of the aprepitant was significantly increased by solid dispersions, and XRD, DSC, and SEM analysis indicated that the aprepitant existed in an amorphous form within the solid dispersions. The result of dissolution study showed that the dissolution rate of SDs was nearly five-fold faster than aprepitant. FTIR spectrometry suggested the presence of intermolecular hydrogen bonds between the aprepitant and polymer. Pharmacokinetic studies in rats indicated that the degree drug absorption was comparable with that of Emend ® . Aprepitant exists in an amorphous state in solid dispersions and the solid dispersions can markedly improve the dissolution and oral bioavailability of the aprepitant. The AUC0-t of the SDs was 2.4-fold that of the aprepitant. In addition, the method and its associated techniques are very easy to carry out.

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Two types of CDDS, prepared herein by means of the regular coating technique, are able to achieve site-specific drug delivery targeting at colon following oral administration, and provide a promising strategy to control drug release targeting the desired lower gastrointestinal region.

Abstract. Tetrandrine (TET) is a poorly water-soluble bisbenzylisoquinoline alkaloid. In this study, TET solid lipid nanoparticles (SLNs) were prepared by a melt-emulsification and ultrasonication technique. Precirol ® ATO 5, glyceryl monostearate, and stearic acid were used as the lipid matrix for the SLNs, while Lipoid E80, Pluronic F68, and sodium deoxycholate were used as emulsifying and stabilizing agents. The physicochemical characteristics of the TET-SLNs were investigated when it was found that the mean particle size and zeta potential of the TET-SLNs were 134±1.3 nm and −53.8±1.7 mV, respectively, and the entrapment efficiency (EE) was 89.57%±0.39%. Differential scanning calorimetry indicated that TET was in an amorphous state in SLNs. TET-SLNs exhibited a higher release rate at a lower pH and a lower release rate at a higher pH. The release pattern of the TET-SLNs followed the Weibull model. The pharmacokinetics of TET-SLNs after intravenous administration to male rats was studied. TET-SLN resulted in a higher plasma concentration and lower clearance. The biodistribution study indicated that TET-SLN showed a high uptake in reticuloendothelial system organs. In conclusion, TET-SLNs with a small particle size, and high EE, can be produced by the method described in this study. The SLN system is a promising approach for the intravenous delivery of tetrandrine.

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