In vitro drug release rates from asymmetric-membrane tablet coatings: Prediction of phase-inversion dynamics

Regenerated cellulose capsules for controlled drug delivery: Part IV. In-vitro evaluation of novel self-pore forming regenerated cellulose capsules

In the present work, the release mechanisms of active pharmaceutical ingredients (APIs) enclosed in self-pore forming regenerated cellulose (RC) two-piece hard shell capsules are described. The RC capsules were fabricated using a modified dip-coating approach, which yielded an assembled dosage form that was equivalent in size and shape to a conventional gelatin two-piece hard shell capsule. Drug release characteristics from RC capsules were evaluated using potassium chloride, diphenhydramine hydrochloride, tramadol hydrochloride, niacinamide, acetaminophen and ketoprofen as model APIs. The RC capsules act as a barrier coated reservoir device that releases the enclosed API at a zero order release rate. When comparing all the API's release behavior from RC capsules, a power-law relationship was observed between their zero-order release rates and their respective aqueous solubilities. Osmotic as well as diffusive mechanisms are involved in the release of the enclosed API. The osmotic mechanism's contribution to zero order release rate increases as the aqueous solubility of the tested APIs inside the capsule increases. The osmotic mediated flux and the apparent diffusivity of the APIs through the capsule wall is a competitive process and the osmotic mediated flux of the enclosed API begins to override its diffusivity through the capsule wall as the API solubility increases. This behavior is attributed to the wide range of pore sizes observed in RC membranes, from our prior analysis. The fluid permeability analysis shows that the RC capsules presented in this work may be better suited for osmotic drug delivery applications than conventional encapsulated systems described in the literature.

A novel asymmetric membrane osmotic pump capsule with in situ formed delivery orifices for controlled release of gliclazide solid dispersion system

In this study, a novel asymmetric membrane osmotic pump capsule of gliclazide (GLC) solid dispersion was developed to achieve a controlled drug release. The capsule shells were obtained by wet phase inversion process using cellulose acetate as semi-permeable membrane, glycerol and kolliphor P188 as pore formers, then filled with the mixture of GLC solid dispersion and pH modifiers. Differentiate from the conventional formulations, sodium carbonate was chosen as the osmotic agent and effervescent agent simultaneously to control the drug release, instead of the polymer materials. The ternary solid dispersion of GLC, with polyethylene glycol 6000 and kolliphor P188 as carriers, was prepared by solvent-evaporation method, realizing a 2.09-fold increment in solubility and dissolution rate in comparison with unprocessed GLC. Influence of the composition of the coating solution and pH modifiers on the drug release from the asymmetric membrane capsule (AMC) was investigated. The ultimate cumulative release of the optimal formulation reached 91.32% in an approximately zero-order manner. The osmotic pressure test and dye test were conducted to validate the drug release mechanism from the AMC. The in vivo pharmacokinetic study of the AMC indicated a 102.66±10.95% relative bioavailability compared with the commercial tablet, suggesting the bioequivalence between the two formulations. Consequently, the novel controlled delivery system with combination of solid dispersion and AMC system is capable of providing a satisfactory alternative to release the water-insoluble drugs in a controlled manner.

Controlled porosity osmotic pump system for the delivery of diclofenac sodium: in-vitro and in-vivo evaluation

The objective of this study was to develop controlled porosity osmotic pump (CPOP) tablets of diclofenac sodium (DS). The influence of different cores (polymers and osmogens) and coats (thickness and porosigen content) on DS release were studied. Results revealed that decreasing HPMC viscosity grade from 4000cp (K4M) to 15cp (E15) increased DS release. While increasing the tablet coat thickness decreased DS release. The presence of osmogen increased DS release in the following rank: mannitol > lactose > avicel. There was a direct relationship between increasing PEG-400 in the coating solution and the amount of drug released in all formulations studied, except in one condition. A comparative bioavailability study using a selected CPOP formulation (T) versus the innovator product (R) revealed that CPOP tablet maintained a less fluctuated DS plasma concentration for up to 24 h with a detected mean Cmax of 836.8 ± 142.4 and 445.0 ± 81.0 ng/mL for R and T, respectively. There were no statistically significant differences between R and T, concerning AUC0-24 and AUC0-∞. Moreover, the appearance of the multi-peak phenomenon, which is frequently observed with DS absorption, was found in only 25% of volunteers in case of T versus 75% in case of R.

Phase behavior and rheological properties of polyamine-rich complexes for direct-write assembly

Polyamine-rich complexes are developed for microscale patterning of planar and 3-D structures by direct ink writing. The complexes are formed by mixing poly(allylamine) hydrochloride and poly(acrylic acid) sodium salt in water in a nonstoichiometric ratio. Their phase behavior, rheological properties, and coagulation behavior in alcohol-water reservoirs are characterized. Direct comparisons are made between these complexes, which are based on mixtures of linear polyelectrolytes, and prior observations of complexes composed of linear and highly branched chains. [Gratson, G. M.; Xu, M.; Lewis, J. A. Nature 2004, 428, 386. Gratson, G. M.; Lewis, J. A. Langmuir 2005, 21, 457-464.] The optimal polyamine-rich ink and reservoir compositions are identified for direct-write assembly of wavy, gradient, and 3-D microperiodic architectures.

Effects of surface coating on the controlled release of vitamin B1 from mesoporous silica tablets

The controlled release of vitamin B1 (VB1, thiamine hydrochloride) from mesoporous silica tablets coated with a series of sol-gel coatings was investigated. Tetraethoxysilane (TEOS), n-propyltriethoxysilane (PTES), n-octyltriethoxysilane (OTES), bis(trimethoxysilyl)hexane (TSH), bis(triethoxysilyl)octane (TSO), bis (trimethoxysilylpropyl)amine (TSPA), and bis[(3-trimethoxysilyl)propyl]ethylenediamine (TSPED) were used as precursors for the coatings. The effects of organosilane type and concentration, the number of coatings, drying temperature, and release media on VB1 release from the coated mesoporous silica tablets were comprehensively examined. The TSH, TSO, TSPA, and TSPED coatings were found to be more effective in suppression of release than the other coatings. VB1 release decreases with the increase in the number of coatings and drying temperature. It was found that there is an optimal coating solution concentration for the controlled release. In general, more VB1 is released in 0.01 M HCl solution than in 0.05 M phosphate buffer solution at pH 7.4 because of the electrostatic repulsions between the protonated VB1 cations and the positively charged mesoporous silica carrier/coatings. The experimental results show that drug release can be easily controlled by changing the organosilane type and the number of coating. The method used in this study is an effective and flexible way for controlled release due to the high drug loading and the easy control of release rate.