Modelling of porosity and waterfronts in cellulosic pellets for understanding drug release behavior.

The microstructure of cellulose microcrystalline-Carbopol pellets, prepared under different drying conditions (oven-dried or freeze-dried), was experimentally characterized using mercury intrusion porosimetry and then computationally modelled using Pore-Cor software. Connectivity (mean number of throats per pore), pore skew (sigma), throat skew (q) and correlation level were estimated and simultaneously optimized from the mercury intrusion porosimetry cumulative curves using the Boltzmann-annealed simplex algorithm. Unit cells with percolation properties close to the real ones were generated.

[Renal function evaluation methods in the elderly: reliability and clinical implications].

Chronic renal disease (CRD) is found in a third of the Spanish population aged more than 65 years old. Detection and early treatment would increase survival and help to reduce associated cardiovascular morbidity and mortality as well as the risk of pharmacological iatrogeny. Determination of the glomerular filtration rate has traditionally been considered the best parameter for renal function evaluation, which should not be based exclusively on serum creatinine concentration or creatinine clearance.

Incidence of drying on microstructure and drug release profiles from tablets of MCC-lactose-Carbopol and MCC-dicalcium phosphate-Carbopol pellets.

The influence of intragranular excipients (lactose or dicalcium phosphate) and the drying procedure and conditions (oven-drying and freeze-drying after freezing at -30 or -196 degrees C) on the properties of tablets of MCC-Carbopol pellets was evaluated. The drying procedure caused remarkable differences in pellet size and porosity (freeze-dried pellets were 3-fold more porous than those oven dried). Theophylline release from pellets was completed in less than 30 min and followed first-order kinetics, with a rate closely related to the intragranular porosity.

Microstructural and drug release properties of oven-dried and of slowly or fast frozen freeze-dried MCC-Carbopol pellets.

The influence of the procedure and conditions of drying (oven-drying and freeze-drying after slow or fast freezing) and of the CaCl(2) concentration in the wetting liquid on the physical characteristics and drug release behaviour of microcrystalline cellulose (MCC)-carbopol 40:60 pellets containing theophylline or ketoprofen has been evaluated. The microstructural, morphological and mechanical properties can be modulated, to a large extent, through the control of the drying step and the CaCl(2) proportion. The drying step determines the volumetric contraction of the pellets and, consequently, the porosity parameters.