A novel pH-dependent gradient-release delivery system for nitrendipine: I. Manufacturing, evaluation in vitro and bioavailability in healthy dogs

Preparation and evaluation of Vinpocetine self-emulsifying pH gradient release pellets

The main objective of this study was to develop a pH gradient release pellet with self-emulsifying drug delivery system (SEDDS), which could not only improve the oral bioavailability of Vinpocetine (VIN), a poor soluble drug, but reduce the fluctuation of plasma concentration. First, the liquid VIN SEDDS formulation was prepared. Then the self-emulsifying pH gradient release pellets were prepared by extrusion spheronization technique, and formulation consisted by the liquid SEDDS, absorbent (colloidal silicon dioxide), penetration enhancer (sodium chloride), microcrystalline cellulose, ethyl alcohol, and three coating materials (HPMC, Eudragit L30D55, Eudragit FS30D) were eventually selected. Three kinds of coated pellets were mixed in capsules with the mass ratio of 1:1:1. The release curves of capsules were investigated in vitro under the simulated gastrointestinal conditions. In addition, the oral bioavailability and pharmacokinetics of VIN self-emulsifying pH gradient release pellets, commercial tablets and liquid VIN SEDDS were evaluated in Beagle dogs. The oral bioavailability of self-emulsifying pH gradient release pellets was about 149.8% of commercial VIN tablets, and it was about 86% of liquid VIN SEDDS, but there were no significant difference between liquid SEDDS and self-emulsifying pH gradient release pellets. In conclusion, the self-emulsifying pH gradient release pellets could significantly enhance the absorption of VIN and effectively achieve a pH gradient release. And the self-emulsifying pH gradient release pellet was a promising method to improve bioavailability of insoluble drugs.

Aerosol-Assisted Fast Formulating Uniform Pharmaceutical Polymer Microparticles with Variable Properties toward pH-Sensitive Controlled Drug Release

Microencapsulation is highly attractive for oral drug delivery. Microparticles are a common form of drug carrier for this purpose. There is still a high demand on efficient methods to fabricate microparticles with uniform sizes and well-controlled particle properties. In this paper, uniform hydroxypropyl methylcellulose phthalate (HPMCP)-based pharmaceutical microparticles loaded with either hydrophobic or hydrophilic model drugs have been directly formulated by using a unique aerosol technique, i.e., the microfluidic spray drying technology. A series of microparticles of controllable particle sizes, shapes, and structures are fabricated by tuning the solvent composition and drying temperature. It is found that a more volatile solvent and a higher drying temperature can result in fast evaporation rates to form microparticles of larger lateral size, more irregular shape, and denser matrix. The nature of the model drugs also plays an important role in determining particle properties. The drug release behaviors of the pharmaceutical microparticles are dependent on their structural properties and the nature of a specific drug, as well as sensitive to the pH value of the release medium. Most importantly, drugs in the microparticles obtained by using a more volatile solvent or a higher drying temperature can be well protected from degradation in harsh simulated gastric fluids due to the dense structures of the microparticles, while they can be fast-released in simulated intestinal fluids through particle dissolution. These pharmaceutical microparticles are potentially useful for site-specific (enteric) delivery of orally-administered drugs.

Stability of poly(epsilon-caprolactone) microparticles containing Brucella ovis antigens as a vaccine delivery system against brucellosis

In previous works, our research group has successfully proved the use of subcellular vaccines based on poly(epsilon-caprolactone) (PEC) microparticles containing an antigenic extract of Brucella ovis (HS) against experimental brucellosis in both mice and rams. However, the successful exploitation of pharmaceutical products, and therefore of this product as veterinary vaccine, requires preservation of both biological activity and native structure in all steps of development from purification to storage. In this context, we have carried out an accelerated stability study to evaluate the relative stability of HS when loading in PEC microparticles. For this purpose, freeze-dried microparticles were stored at 40 +/- 1 degrees C and 75% RH as a preliminary analysis of a stability testing. The results showed that both physico-chemical (size, morphology, antigen content, release profile) and biological (integrity and antigenicity of the HS) properties were preserved after 6 months of storage. On the contrary, after 1 year of storage, the HS release profile was dramatically affected probably due to a progressive loss of the polymer microstructure. In addition, the degradation and loss of the antigenicity of the HS components was also evident by SDS-PAGE and immunoblotting analysis. In fact, after 12 months of storage, only the integrity and antigenicity of two of the major protective proteins of the HS antigenic complex were preserved.

Design and optimization of mefloquine hydrochloride microparticles for bitter taste masking

The objective of the present investigation was to reduce the bitterness with improved dissolution, in acidic medium (pH 1.2), of mefloquine hydrochloride (MFL). Microparticles were prepared by coacervation method using Eudragit E (EE) as polymer and sodium hydroxide as precipitant. A 3(2) full factorial design was used for optimization wherein the drug concentration (A) and polymer concentration (B) were selected as independent variables and the bitterness score, particle size and dissolution at various pH were selected as the dependent variables. The desirability function approach has been employed in order to find the best compromise between the different experimental responses. The model is further cross validated for bias. The optimized microparticles were characterized by FT-IR, DSC, XRPD and SEM. Bitterness score was evaluated by human gustatory sensation test. Multiple linear regression analysis revealed that the reduced bitterness of MFL can be obtained by controlling the dissolution of microparticles at pH 6.8 and increasing the EE concentration. The increase in polymer concentration leads to reduction in dissolution of microparticles at pH > 5 due to its insolubility. However the dissolution studies at pH 1.2 demonstrated enhanced dissolution of MFL from microparticles might be due to the high porosity of the microparticles, hydrophilic nature of the EE, and improved wettability, provided by the dissolved EE. The bitterness score of microparticles was decreased to zero compared to 3+ of pure ARM. In conclusion the bitterness of MFL was reduced with improved dissolution at acidic pH.