Use of biorelevant dissolution media in dissolution tests as a predictive method of oral bioavailability

Abstract Dissolution is a key step in the uptake of oral drugs. In order to compare the behaviour of the dissolution of two formulations, the dissolution profile test was used. This assay must be discriminative and should mimic in vivo conditions. Many dissolution media described in pharmacopoeias are not predictive of bioavailability. Due to this, biorelevant media are used as an alternative to solve this problem. The objective of this work is to evaluate the relevance of biorelevant dissolution media to predict in vivo drug dissolution. For this, a bibliographic search was carried out in scientific databases. The search was first performed for articles verifying the physicochemical properties of human gastrointestinal fluids. Subsequently, a comparison was made between the properties of gastrointestinal fluids and those of biorelevant and pharmacopoeial media. Finally, the results of bioequivalence studies and dissolution profile tests in biorelevant media described in the literature were compared. The results revealed that there are a few publications that have analysed some physicochemical properties of gastrointestinal fluids. In addition, high variability was observed for some properties. Regarding the comparison of these properties with pharmacopoeial media and biorelevant media, the analysis showed that the biorelevant media are more similar to gastrointestinal fluids than the pharmacopoeial media. Finally, the in vitro dissolution profile results were similar to the results obtained in vivo. Thus, biorelevant media may be useful for analysing dissolution profiles.

Formulation and stability studies of metformin hydrochloride in a controlled porosity osmotic pump system

This study was designed to formulate, for the first time, metformin hydrochloride (MH, 850 mg/tablet) as a controlledporosity osmotic pump (CPOP) system to achieve zero-order release pattern. MH core tablet was coated with celluloseacetate membrane containing PEG 400. The effect of different percentages and molecular weights of polyethyleneoxide (PEO, 900K and 4M) in tablet core was studied. The United States Pharmacopeia (USP) apparatus II andphosphate buffer pH 6.8 were used for the release studies; meanwhile, a promising formula was tested in biorelevantmedia. The stability of some selected formulations was carried out for 6 months, at bench and accelerated conditions.Evaluation included: MH content, Differential scanning calorimetry (DSC), Scanning electron microscopy (SEM),drug release, and kinetics. Results revealed that increasing PEO percentage within the core decreased MH release.SEM verified formation of pores in the membrane that accounts for MH release. Almost all stored tablets werestable for all studied parameters. MH endothermic peak maintained its position and energy of enthalpy on storageas confirmed by DSC. MH release rate from a promising formula, following zero-order release model, increased by28% in biorelevant media compared to phosphate buffer. Subsequently, in vitro release in biorelevant media could beemployed as a tool to anticipate in vivo tone of CPOP formulations

Análisis comparativo de la cinética de liberación de diclofenaco sódico a partir de matrices hidrofílicas en medios de disolución convencionales y biorrelevantes / A comparative analysis of the release kinetics of sodium diclofenac from hydrophilic matrices in conventional dissolution media and biorelevant media is carried out

Se utilizaron dos polímeros hidrofílicos comúnmente empleados en la formulación de matrices de liberación extendida, hidroxipropil-metil-celulosa (HPMC, hipromelosa) y óxido de polietileno (PEO), junto con celulosa microcristalina y lactosa, con el objetivo de estudiar la cinética de liberación del diclofenaco sódico en los aparatos II y III de la USP, en un medio de disolución compendial y en medios biorrelevantes. La cinética de liberación predominante en el aparato II fue uno y en el aparato III, cero. El valor de las constantes n y k aplicando la ley del exponente, indicaron tanto para el aparato II como para el III, que no se presenta el efecto "burst" y que el mecanismo predominante en la liberación del fármaco, es la relajación y la erosión del polímero. Los resultados sugieren que la metodología de disolución en un medio biorrelevante es apropiada para discriminar entre formulaciones y para predecir el desempeño in vivo de tabletas de liberación extendida de diclofenaco sódico.

Two hydrophilic polymers commonly employed on the development of extended release products, hydroxypropyl-methyl-cellulose (HPMC, hypromellose) and polyethylene oxide (PEO) were formulated with microcrystalline cellulose or lactose in order to investigate the release kinetics of sodium diclofenac on USP apparatus II and III using a compendial or biorelevant media, respectively. The dominant release kinetic on apparatus II was first order and zero on apparatus III. The values of the kinetic constant (k) and the release exponent (n) from the Power Law Model indicated that there was no burst effect in none of the studied formulations, relaxation and polymer erosion was the dominant mechanism of drug release in both methods. The results suggest that biorelevant dissolution methodology is appropriate for the discrimination of formulations and prediction of in vivo performance of MR diclofenac sodium matrices.